linux/kernel/cgroup.c
<<
>>
Prefs
   1/*
   2 *  Generic process-grouping system.
   3 *
   4 *  Based originally on the cpuset system, extracted by Paul Menage
   5 *  Copyright (C) 2006 Google, Inc
   6 *
   7 *  Notifications support
   8 *  Copyright (C) 2009 Nokia Corporation
   9 *  Author: Kirill A. Shutemov
  10 *
  11 *  Copyright notices from the original cpuset code:
  12 *  --------------------------------------------------
  13 *  Copyright (C) 2003 BULL SA.
  14 *  Copyright (C) 2004-2006 Silicon Graphics, Inc.
  15 *
  16 *  Portions derived from Patrick Mochel's sysfs code.
  17 *  sysfs is Copyright (c) 2001-3 Patrick Mochel
  18 *
  19 *  2003-10-10 Written by Simon Derr.
  20 *  2003-10-22 Updates by Stephen Hemminger.
  21 *  2004 May-July Rework by Paul Jackson.
  22 *  ---------------------------------------------------
  23 *
  24 *  This file is subject to the terms and conditions of the GNU General Public
  25 *  License.  See the file COPYING in the main directory of the Linux
  26 *  distribution for more details.
  27 */
  28
  29#include <linux/cgroup.h>
  30#include <linux/cred.h>
  31#include <linux/ctype.h>
  32#include <linux/errno.h>
  33#include <linux/fs.h>
  34#include <linux/init_task.h>
  35#include <linux/kernel.h>
  36#include <linux/list.h>
  37#include <linux/mm.h>
  38#include <linux/mutex.h>
  39#include <linux/mount.h>
  40#include <linux/pagemap.h>
  41#include <linux/proc_fs.h>
  42#include <linux/rcupdate.h>
  43#include <linux/sched.h>
  44#include <linux/backing-dev.h>
  45#include <linux/seq_file.h>
  46#include <linux/slab.h>
  47#include <linux/magic.h>
  48#include <linux/spinlock.h>
  49#include <linux/string.h>
  50#include <linux/sort.h>
  51#include <linux/kmod.h>
  52#include <linux/module.h>
  53#include <linux/delayacct.h>
  54#include <linux/cgroupstats.h>
  55#include <linux/hash.h>
  56#include <linux/namei.h>
  57#include <linux/pid_namespace.h>
  58#include <linux/idr.h>
  59#include <linux/vmalloc.h> /* TODO: replace with more sophisticated array */
  60#include <linux/eventfd.h>
  61#include <linux/poll.h>
  62#include <linux/flex_array.h> /* used in cgroup_attach_proc */
  63#include <linux/kthread.h>
  64
  65#include <linux/atomic.h>
  66
  67/* css deactivation bias, makes css->refcnt negative to deny new trygets */
  68#define CSS_DEACT_BIAS          INT_MIN
  69
  70/*
  71 * cgroup_mutex is the master lock.  Any modification to cgroup or its
  72 * hierarchy must be performed while holding it.
  73 *
  74 * cgroup_root_mutex nests inside cgroup_mutex and should be held to modify
  75 * cgroupfs_root of any cgroup hierarchy - subsys list, flags,
  76 * release_agent_path and so on.  Modifying requires both cgroup_mutex and
  77 * cgroup_root_mutex.  Readers can acquire either of the two.  This is to
  78 * break the following locking order cycle.
  79 *
  80 *  A. cgroup_mutex -> cred_guard_mutex -> s_type->i_mutex_key -> namespace_sem
  81 *  B. namespace_sem -> cgroup_mutex
  82 *
  83 * B happens only through cgroup_show_options() and using cgroup_root_mutex
  84 * breaks it.
  85 */
  86static DEFINE_MUTEX(cgroup_mutex);
  87static DEFINE_MUTEX(cgroup_root_mutex);
  88
  89/*
  90 * Generate an array of cgroup subsystem pointers. At boot time, this is
  91 * populated up to CGROUP_BUILTIN_SUBSYS_COUNT, and modular subsystems are
  92 * registered after that. The mutable section of this array is protected by
  93 * cgroup_mutex.
  94 */
  95#define SUBSYS(_x) &_x ## _subsys,
  96static struct cgroup_subsys *subsys[CGROUP_SUBSYS_COUNT] = {
  97#include <linux/cgroup_subsys.h>
  98};
  99
 100#define MAX_CGROUP_ROOT_NAMELEN 64
 101
 102/*
 103 * A cgroupfs_root represents the root of a cgroup hierarchy,
 104 * and may be associated with a superblock to form an active
 105 * hierarchy
 106 */
 107struct cgroupfs_root {
 108        struct super_block *sb;
 109
 110        /*
 111         * The bitmask of subsystems intended to be attached to this
 112         * hierarchy
 113         */
 114        unsigned long subsys_bits;
 115
 116        /* Unique id for this hierarchy. */
 117        int hierarchy_id;
 118
 119        /* The bitmask of subsystems currently attached to this hierarchy */
 120        unsigned long actual_subsys_bits;
 121
 122        /* A list running through the attached subsystems */
 123        struct list_head subsys_list;
 124
 125        /* The root cgroup for this hierarchy */
 126        struct cgroup top_cgroup;
 127
 128        /* Tracks how many cgroups are currently defined in hierarchy.*/
 129        int number_of_cgroups;
 130
 131        /* A list running through the active hierarchies */
 132        struct list_head root_list;
 133
 134        /* All cgroups on this root, cgroup_mutex protected */
 135        struct list_head allcg_list;
 136
 137        /* Hierarchy-specific flags */
 138        unsigned long flags;
 139
 140        /* The path to use for release notifications. */
 141        char release_agent_path[PATH_MAX];
 142
 143        /* The name for this hierarchy - may be empty */
 144        char name[MAX_CGROUP_ROOT_NAMELEN];
 145};
 146
 147/*
 148 * The "rootnode" hierarchy is the "dummy hierarchy", reserved for the
 149 * subsystems that are otherwise unattached - it never has more than a
 150 * single cgroup, and all tasks are part of that cgroup.
 151 */
 152static struct cgroupfs_root rootnode;
 153
 154/*
 155 * cgroupfs file entry, pointed to from leaf dentry->d_fsdata.
 156 */
 157struct cfent {
 158        struct list_head                node;
 159        struct dentry                   *dentry;
 160        struct cftype                   *type;
 161};
 162
 163/*
 164 * CSS ID -- ID per subsys's Cgroup Subsys State(CSS). used only when
 165 * cgroup_subsys->use_id != 0.
 166 */
 167#define CSS_ID_MAX      (65535)
 168struct css_id {
 169        /*
 170         * The css to which this ID points. This pointer is set to valid value
 171         * after cgroup is populated. If cgroup is removed, this will be NULL.
 172         * This pointer is expected to be RCU-safe because destroy()
 173         * is called after synchronize_rcu(). But for safe use, css_is_removed()
 174         * css_tryget() should be used for avoiding race.
 175         */
 176        struct cgroup_subsys_state __rcu *css;
 177        /*
 178         * ID of this css.
 179         */
 180        unsigned short id;
 181        /*
 182         * Depth in hierarchy which this ID belongs to.
 183         */
 184        unsigned short depth;
 185        /*
 186         * ID is freed by RCU. (and lookup routine is RCU safe.)
 187         */
 188        struct rcu_head rcu_head;
 189        /*
 190         * Hierarchy of CSS ID belongs to.
 191         */
 192        unsigned short stack[0]; /* Array of Length (depth+1) */
 193};
 194
 195/*
 196 * cgroup_event represents events which userspace want to receive.
 197 */
 198struct cgroup_event {
 199        /*
 200         * Cgroup which the event belongs to.
 201         */
 202        struct cgroup *cgrp;
 203        /*
 204         * Control file which the event associated.
 205         */
 206        struct cftype *cft;
 207        /*
 208         * eventfd to signal userspace about the event.
 209         */
 210        struct eventfd_ctx *eventfd;
 211        /*
 212         * Each of these stored in a list by the cgroup.
 213         */
 214        struct list_head list;
 215        /*
 216         * All fields below needed to unregister event when
 217         * userspace closes eventfd.
 218         */
 219        poll_table pt;
 220        wait_queue_head_t *wqh;
 221        wait_queue_t wait;
 222        struct work_struct remove;
 223};
 224
 225/* The list of hierarchy roots */
 226
 227static LIST_HEAD(roots);
 228static int root_count;
 229
 230static DEFINE_IDA(hierarchy_ida);
 231static int next_hierarchy_id;
 232static DEFINE_SPINLOCK(hierarchy_id_lock);
 233
 234/* dummytop is a shorthand for the dummy hierarchy's top cgroup */
 235#define dummytop (&rootnode.top_cgroup)
 236
 237/* This flag indicates whether tasks in the fork and exit paths should
 238 * check for fork/exit handlers to call. This avoids us having to do
 239 * extra work in the fork/exit path if none of the subsystems need to
 240 * be called.
 241 */
 242static int need_forkexit_callback __read_mostly;
 243
 244#ifdef CONFIG_PROVE_LOCKING
 245int cgroup_lock_is_held(void)
 246{
 247        return lockdep_is_held(&cgroup_mutex);
 248}
 249#else /* #ifdef CONFIG_PROVE_LOCKING */
 250int cgroup_lock_is_held(void)
 251{
 252        return mutex_is_locked(&cgroup_mutex);
 253}
 254#endif /* #else #ifdef CONFIG_PROVE_LOCKING */
 255
 256EXPORT_SYMBOL_GPL(cgroup_lock_is_held);
 257
 258static int css_unbias_refcnt(int refcnt)
 259{
 260        return refcnt >= 0 ? refcnt : refcnt - CSS_DEACT_BIAS;
 261}
 262
 263/* the current nr of refs, always >= 0 whether @css is deactivated or not */
 264static int css_refcnt(struct cgroup_subsys_state *css)
 265{
 266        int v = atomic_read(&css->refcnt);
 267
 268        return css_unbias_refcnt(v);
 269}
 270
 271/* convenient tests for these bits */
 272inline int cgroup_is_removed(const struct cgroup *cgrp)
 273{
 274        return test_bit(CGRP_REMOVED, &cgrp->flags);
 275}
 276
 277/* bits in struct cgroupfs_root flags field */
 278enum {
 279        ROOT_NOPREFIX, /* mounted subsystems have no named prefix */
 280};
 281
 282static int cgroup_is_releasable(const struct cgroup *cgrp)
 283{
 284        const int bits =
 285                (1 << CGRP_RELEASABLE) |
 286                (1 << CGRP_NOTIFY_ON_RELEASE);
 287        return (cgrp->flags & bits) == bits;
 288}
 289
 290static int notify_on_release(const struct cgroup *cgrp)
 291{
 292        return test_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
 293}
 294
 295static int clone_children(const struct cgroup *cgrp)
 296{
 297        return test_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
 298}
 299
 300/*
 301 * for_each_subsys() allows you to iterate on each subsystem attached to
 302 * an active hierarchy
 303 */
 304#define for_each_subsys(_root, _ss) \
 305list_for_each_entry(_ss, &_root->subsys_list, sibling)
 306
 307/* for_each_active_root() allows you to iterate across the active hierarchies */
 308#define for_each_active_root(_root) \
 309list_for_each_entry(_root, &roots, root_list)
 310
 311static inline struct cgroup *__d_cgrp(struct dentry *dentry)
 312{
 313        return dentry->d_fsdata;
 314}
 315
 316static inline struct cfent *__d_cfe(struct dentry *dentry)
 317{
 318        return dentry->d_fsdata;
 319}
 320
 321static inline struct cftype *__d_cft(struct dentry *dentry)
 322{
 323        return __d_cfe(dentry)->type;
 324}
 325
 326/* the list of cgroups eligible for automatic release. Protected by
 327 * release_list_lock */
 328static LIST_HEAD(release_list);
 329static DEFINE_RAW_SPINLOCK(release_list_lock);
 330static void cgroup_release_agent(struct work_struct *work);
 331static DECLARE_WORK(release_agent_work, cgroup_release_agent);
 332static void check_for_release(struct cgroup *cgrp);
 333
 334/* Link structure for associating css_set objects with cgroups */
 335struct cg_cgroup_link {
 336        /*
 337         * List running through cg_cgroup_links associated with a
 338         * cgroup, anchored on cgroup->css_sets
 339         */
 340        struct list_head cgrp_link_list;
 341        struct cgroup *cgrp;
 342        /*
 343         * List running through cg_cgroup_links pointing at a
 344         * single css_set object, anchored on css_set->cg_links
 345         */
 346        struct list_head cg_link_list;
 347        struct css_set *cg;
 348};
 349
 350/* The default css_set - used by init and its children prior to any
 351 * hierarchies being mounted. It contains a pointer to the root state
 352 * for each subsystem. Also used to anchor the list of css_sets. Not
 353 * reference-counted, to improve performance when child cgroups
 354 * haven't been created.
 355 */
 356
 357static struct css_set init_css_set;
 358static struct cg_cgroup_link init_css_set_link;
 359
 360static int cgroup_init_idr(struct cgroup_subsys *ss,
 361                           struct cgroup_subsys_state *css);
 362
 363/* css_set_lock protects the list of css_set objects, and the
 364 * chain of tasks off each css_set.  Nests outside task->alloc_lock
 365 * due to cgroup_iter_start() */
 366static DEFINE_RWLOCK(css_set_lock);
 367static int css_set_count;
 368
 369/*
 370 * hash table for cgroup groups. This improves the performance to find
 371 * an existing css_set. This hash doesn't (currently) take into
 372 * account cgroups in empty hierarchies.
 373 */
 374#define CSS_SET_HASH_BITS       7
 375#define CSS_SET_TABLE_SIZE      (1 << CSS_SET_HASH_BITS)
 376static struct hlist_head css_set_table[CSS_SET_TABLE_SIZE];
 377
 378static struct hlist_head *css_set_hash(struct cgroup_subsys_state *css[])
 379{
 380        int i;
 381        int index;
 382        unsigned long tmp = 0UL;
 383
 384        for (i = 0; i < CGROUP_SUBSYS_COUNT; i++)
 385                tmp += (unsigned long)css[i];
 386        tmp = (tmp >> 16) ^ tmp;
 387
 388        index = hash_long(tmp, CSS_SET_HASH_BITS);
 389
 390        return &css_set_table[index];
 391}
 392
 393/* We don't maintain the lists running through each css_set to its
 394 * task until after the first call to cgroup_iter_start(). This
 395 * reduces the fork()/exit() overhead for people who have cgroups
 396 * compiled into their kernel but not actually in use */
 397static int use_task_css_set_links __read_mostly;
 398
 399static void __put_css_set(struct css_set *cg, int taskexit)
 400{
 401        struct cg_cgroup_link *link;
 402        struct cg_cgroup_link *saved_link;
 403        /*
 404         * Ensure that the refcount doesn't hit zero while any readers
 405         * can see it. Similar to atomic_dec_and_lock(), but for an
 406         * rwlock
 407         */
 408        if (atomic_add_unless(&cg->refcount, -1, 1))
 409                return;
 410        write_lock(&css_set_lock);
 411        if (!atomic_dec_and_test(&cg->refcount)) {
 412                write_unlock(&css_set_lock);
 413                return;
 414        }
 415
 416        /* This css_set is dead. unlink it and release cgroup refcounts */
 417        hlist_del(&cg->hlist);
 418        css_set_count--;
 419
 420        list_for_each_entry_safe(link, saved_link, &cg->cg_links,
 421                                 cg_link_list) {
 422                struct cgroup *cgrp = link->cgrp;
 423                list_del(&link->cg_link_list);
 424                list_del(&link->cgrp_link_list);
 425                if (atomic_dec_and_test(&cgrp->count) &&
 426                    notify_on_release(cgrp)) {
 427                        if (taskexit)
 428                                set_bit(CGRP_RELEASABLE, &cgrp->flags);
 429                        check_for_release(cgrp);
 430                }
 431
 432                kfree(link);
 433        }
 434
 435        write_unlock(&css_set_lock);
 436        kfree_rcu(cg, rcu_head);
 437}
 438
 439/*
 440 * refcounted get/put for css_set objects
 441 */
 442static inline void get_css_set(struct css_set *cg)
 443{
 444        atomic_inc(&cg->refcount);
 445}
 446
 447static inline void put_css_set(struct css_set *cg)
 448{
 449        __put_css_set(cg, 0);
 450}
 451
 452static inline void put_css_set_taskexit(struct css_set *cg)
 453{
 454        __put_css_set(cg, 1);
 455}
 456
 457/*
 458 * compare_css_sets - helper function for find_existing_css_set().
 459 * @cg: candidate css_set being tested
 460 * @old_cg: existing css_set for a task
 461 * @new_cgrp: cgroup that's being entered by the task
 462 * @template: desired set of css pointers in css_set (pre-calculated)
 463 *
 464 * Returns true if "cg" matches "old_cg" except for the hierarchy
 465 * which "new_cgrp" belongs to, for which it should match "new_cgrp".
 466 */
 467static bool compare_css_sets(struct css_set *cg,
 468                             struct css_set *old_cg,
 469                             struct cgroup *new_cgrp,
 470                             struct cgroup_subsys_state *template[])
 471{
 472        struct list_head *l1, *l2;
 473
 474        if (memcmp(template, cg->subsys, sizeof(cg->subsys))) {
 475                /* Not all subsystems matched */
 476                return false;
 477        }
 478
 479        /*
 480         * Compare cgroup pointers in order to distinguish between
 481         * different cgroups in heirarchies with no subsystems. We
 482         * could get by with just this check alone (and skip the
 483         * memcmp above) but on most setups the memcmp check will
 484         * avoid the need for this more expensive check on almost all
 485         * candidates.
 486         */
 487
 488        l1 = &cg->cg_links;
 489        l2 = &old_cg->cg_links;
 490        while (1) {
 491                struct cg_cgroup_link *cgl1, *cgl2;
 492                struct cgroup *cg1, *cg2;
 493
 494                l1 = l1->next;
 495                l2 = l2->next;
 496                /* See if we reached the end - both lists are equal length. */
 497                if (l1 == &cg->cg_links) {
 498                        BUG_ON(l2 != &old_cg->cg_links);
 499                        break;
 500                } else {
 501                        BUG_ON(l2 == &old_cg->cg_links);
 502                }
 503                /* Locate the cgroups associated with these links. */
 504                cgl1 = list_entry(l1, struct cg_cgroup_link, cg_link_list);
 505                cgl2 = list_entry(l2, struct cg_cgroup_link, cg_link_list);
 506                cg1 = cgl1->cgrp;
 507                cg2 = cgl2->cgrp;
 508                /* Hierarchies should be linked in the same order. */
 509                BUG_ON(cg1->root != cg2->root);
 510
 511                /*
 512                 * If this hierarchy is the hierarchy of the cgroup
 513                 * that's changing, then we need to check that this
 514                 * css_set points to the new cgroup; if it's any other
 515                 * hierarchy, then this css_set should point to the
 516                 * same cgroup as the old css_set.
 517                 */
 518                if (cg1->root == new_cgrp->root) {
 519                        if (cg1 != new_cgrp)
 520                                return false;
 521                } else {
 522                        if (cg1 != cg2)
 523                                return false;
 524                }
 525        }
 526        return true;
 527}
 528
 529/*
 530 * find_existing_css_set() is a helper for
 531 * find_css_set(), and checks to see whether an existing
 532 * css_set is suitable.
 533 *
 534 * oldcg: the cgroup group that we're using before the cgroup
 535 * transition
 536 *
 537 * cgrp: the cgroup that we're moving into
 538 *
 539 * template: location in which to build the desired set of subsystem
 540 * state objects for the new cgroup group
 541 */
 542static struct css_set *find_existing_css_set(
 543        struct css_set *oldcg,
 544        struct cgroup *cgrp,
 545        struct cgroup_subsys_state *template[])
 546{
 547        int i;
 548        struct cgroupfs_root *root = cgrp->root;
 549        struct hlist_head *hhead;
 550        struct hlist_node *node;
 551        struct css_set *cg;
 552
 553        /*
 554         * Build the set of subsystem state objects that we want to see in the
 555         * new css_set. while subsystems can change globally, the entries here
 556         * won't change, so no need for locking.
 557         */
 558        for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
 559                if (root->subsys_bits & (1UL << i)) {
 560                        /* Subsystem is in this hierarchy. So we want
 561                         * the subsystem state from the new
 562                         * cgroup */
 563                        template[i] = cgrp->subsys[i];
 564                } else {
 565                        /* Subsystem is not in this hierarchy, so we
 566                         * don't want to change the subsystem state */
 567                        template[i] = oldcg->subsys[i];
 568                }
 569        }
 570
 571        hhead = css_set_hash(template);
 572        hlist_for_each_entry(cg, node, hhead, hlist) {
 573                if (!compare_css_sets(cg, oldcg, cgrp, template))
 574                        continue;
 575
 576                /* This css_set matches what we need */
 577                return cg;
 578        }
 579
 580        /* No existing cgroup group matched */
 581        return NULL;
 582}
 583
 584static void free_cg_links(struct list_head *tmp)
 585{
 586        struct cg_cgroup_link *link;
 587        struct cg_cgroup_link *saved_link;
 588
 589        list_for_each_entry_safe(link, saved_link, tmp, cgrp_link_list) {
 590                list_del(&link->cgrp_link_list);
 591                kfree(link);
 592        }
 593}
 594
 595/*
 596 * allocate_cg_links() allocates "count" cg_cgroup_link structures
 597 * and chains them on tmp through their cgrp_link_list fields. Returns 0 on
 598 * success or a negative error
 599 */
 600static int allocate_cg_links(int count, struct list_head *tmp)
 601{
 602        struct cg_cgroup_link *link;
 603        int i;
 604        INIT_LIST_HEAD(tmp);
 605        for (i = 0; i < count; i++) {
 606                link = kmalloc(sizeof(*link), GFP_KERNEL);
 607                if (!link) {
 608                        free_cg_links(tmp);
 609                        return -ENOMEM;
 610                }
 611                list_add(&link->cgrp_link_list, tmp);
 612        }
 613        return 0;
 614}
 615
 616/**
 617 * link_css_set - a helper function to link a css_set to a cgroup
 618 * @tmp_cg_links: cg_cgroup_link objects allocated by allocate_cg_links()
 619 * @cg: the css_set to be linked
 620 * @cgrp: the destination cgroup
 621 */
 622static void link_css_set(struct list_head *tmp_cg_links,
 623                         struct css_set *cg, struct cgroup *cgrp)
 624{
 625        struct cg_cgroup_link *link;
 626
 627        BUG_ON(list_empty(tmp_cg_links));
 628        link = list_first_entry(tmp_cg_links, struct cg_cgroup_link,
 629                                cgrp_link_list);
 630        link->cg = cg;
 631        link->cgrp = cgrp;
 632        atomic_inc(&cgrp->count);
 633        list_move(&link->cgrp_link_list, &cgrp->css_sets);
 634        /*
 635         * Always add links to the tail of the list so that the list
 636         * is sorted by order of hierarchy creation
 637         */
 638        list_add_tail(&link->cg_link_list, &cg->cg_links);
 639}
 640
 641/*
 642 * find_css_set() takes an existing cgroup group and a
 643 * cgroup object, and returns a css_set object that's
 644 * equivalent to the old group, but with the given cgroup
 645 * substituted into the appropriate hierarchy. Must be called with
 646 * cgroup_mutex held
 647 */
 648static struct css_set *find_css_set(
 649        struct css_set *oldcg, struct cgroup *cgrp)
 650{
 651        struct css_set *res;
 652        struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT];
 653
 654        struct list_head tmp_cg_links;
 655
 656        struct hlist_head *hhead;
 657        struct cg_cgroup_link *link;
 658
 659        /* First see if we already have a cgroup group that matches
 660         * the desired set */
 661        read_lock(&css_set_lock);
 662        res = find_existing_css_set(oldcg, cgrp, template);
 663        if (res)
 664                get_css_set(res);
 665        read_unlock(&css_set_lock);
 666
 667        if (res)
 668                return res;
 669
 670        res = kmalloc(sizeof(*res), GFP_KERNEL);
 671        if (!res)
 672                return NULL;
 673
 674        /* Allocate all the cg_cgroup_link objects that we'll need */
 675        if (allocate_cg_links(root_count, &tmp_cg_links) < 0) {
 676                kfree(res);
 677                return NULL;
 678        }
 679
 680        atomic_set(&res->refcount, 1);
 681        INIT_LIST_HEAD(&res->cg_links);
 682        INIT_LIST_HEAD(&res->tasks);
 683        INIT_HLIST_NODE(&res->hlist);
 684
 685        /* Copy the set of subsystem state objects generated in
 686         * find_existing_css_set() */
 687        memcpy(res->subsys, template, sizeof(res->subsys));
 688
 689        write_lock(&css_set_lock);
 690        /* Add reference counts and links from the new css_set. */
 691        list_for_each_entry(link, &oldcg->cg_links, cg_link_list) {
 692                struct cgroup *c = link->cgrp;
 693                if (c->root == cgrp->root)
 694                        c = cgrp;
 695                link_css_set(&tmp_cg_links, res, c);
 696        }
 697
 698        BUG_ON(!list_empty(&tmp_cg_links));
 699
 700        css_set_count++;
 701
 702        /* Add this cgroup group to the hash table */
 703        hhead = css_set_hash(res->subsys);
 704        hlist_add_head(&res->hlist, hhead);
 705
 706        write_unlock(&css_set_lock);
 707
 708        return res;
 709}
 710
 711/*
 712 * Return the cgroup for "task" from the given hierarchy. Must be
 713 * called with cgroup_mutex held.
 714 */
 715static struct cgroup *task_cgroup_from_root(struct task_struct *task,
 716                                            struct cgroupfs_root *root)
 717{
 718        struct css_set *css;
 719        struct cgroup *res = NULL;
 720
 721        BUG_ON(!mutex_is_locked(&cgroup_mutex));
 722        read_lock(&css_set_lock);
 723        /*
 724         * No need to lock the task - since we hold cgroup_mutex the
 725         * task can't change groups, so the only thing that can happen
 726         * is that it exits and its css is set back to init_css_set.
 727         */
 728        css = task->cgroups;
 729        if (css == &init_css_set) {
 730                res = &root->top_cgroup;
 731        } else {
 732                struct cg_cgroup_link *link;
 733                list_for_each_entry(link, &css->cg_links, cg_link_list) {
 734                        struct cgroup *c = link->cgrp;
 735                        if (c->root == root) {
 736                                res = c;
 737                                break;
 738                        }
 739                }
 740        }
 741        read_unlock(&css_set_lock);
 742        BUG_ON(!res);
 743        return res;
 744}
 745
 746/*
 747 * There is one global cgroup mutex. We also require taking
 748 * task_lock() when dereferencing a task's cgroup subsys pointers.
 749 * See "The task_lock() exception", at the end of this comment.
 750 *
 751 * A task must hold cgroup_mutex to modify cgroups.
 752 *
 753 * Any task can increment and decrement the count field without lock.
 754 * So in general, code holding cgroup_mutex can't rely on the count
 755 * field not changing.  However, if the count goes to zero, then only
 756 * cgroup_attach_task() can increment it again.  Because a count of zero
 757 * means that no tasks are currently attached, therefore there is no
 758 * way a task attached to that cgroup can fork (the other way to
 759 * increment the count).  So code holding cgroup_mutex can safely
 760 * assume that if the count is zero, it will stay zero. Similarly, if
 761 * a task holds cgroup_mutex on a cgroup with zero count, it
 762 * knows that the cgroup won't be removed, as cgroup_rmdir()
 763 * needs that mutex.
 764 *
 765 * The fork and exit callbacks cgroup_fork() and cgroup_exit(), don't
 766 * (usually) take cgroup_mutex.  These are the two most performance
 767 * critical pieces of code here.  The exception occurs on cgroup_exit(),
 768 * when a task in a notify_on_release cgroup exits.  Then cgroup_mutex
 769 * is taken, and if the cgroup count is zero, a usermode call made
 770 * to the release agent with the name of the cgroup (path relative to
 771 * the root of cgroup file system) as the argument.
 772 *
 773 * A cgroup can only be deleted if both its 'count' of using tasks
 774 * is zero, and its list of 'children' cgroups is empty.  Since all
 775 * tasks in the system use _some_ cgroup, and since there is always at
 776 * least one task in the system (init, pid == 1), therefore, top_cgroup
 777 * always has either children cgroups and/or using tasks.  So we don't
 778 * need a special hack to ensure that top_cgroup cannot be deleted.
 779 *
 780 *      The task_lock() exception
 781 *
 782 * The need for this exception arises from the action of
 783 * cgroup_attach_task(), which overwrites one tasks cgroup pointer with
 784 * another.  It does so using cgroup_mutex, however there are
 785 * several performance critical places that need to reference
 786 * task->cgroup without the expense of grabbing a system global
 787 * mutex.  Therefore except as noted below, when dereferencing or, as
 788 * in cgroup_attach_task(), modifying a task'ss cgroup pointer we use
 789 * task_lock(), which acts on a spinlock (task->alloc_lock) already in
 790 * the task_struct routinely used for such matters.
 791 *
 792 * P.S.  One more locking exception.  RCU is used to guard the
 793 * update of a tasks cgroup pointer by cgroup_attach_task()
 794 */
 795
 796/**
 797 * cgroup_lock - lock out any changes to cgroup structures
 798 *
 799 */
 800void cgroup_lock(void)
 801{
 802        mutex_lock(&cgroup_mutex);
 803}
 804EXPORT_SYMBOL_GPL(cgroup_lock);
 805
 806/**
 807 * cgroup_unlock - release lock on cgroup changes
 808 *
 809 * Undo the lock taken in a previous cgroup_lock() call.
 810 */
 811void cgroup_unlock(void)
 812{
 813        mutex_unlock(&cgroup_mutex);
 814}
 815EXPORT_SYMBOL_GPL(cgroup_unlock);
 816
 817/*
 818 * A couple of forward declarations required, due to cyclic reference loop:
 819 * cgroup_mkdir -> cgroup_create -> cgroup_populate_dir ->
 820 * cgroup_add_file -> cgroup_create_file -> cgroup_dir_inode_operations
 821 * -> cgroup_mkdir.
 822 */
 823
 824static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode);
 825static struct dentry *cgroup_lookup(struct inode *, struct dentry *, struct nameidata *);
 826static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);
 827static int cgroup_populate_dir(struct cgroup *cgrp);
 828static const struct inode_operations cgroup_dir_inode_operations;
 829static const struct file_operations proc_cgroupstats_operations;
 830
 831static struct backing_dev_info cgroup_backing_dev_info = {
 832        .name           = "cgroup",
 833        .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK,
 834};
 835
 836static int alloc_css_id(struct cgroup_subsys *ss,
 837                        struct cgroup *parent, struct cgroup *child);
 838
 839static struct inode *cgroup_new_inode(umode_t mode, struct super_block *sb)
 840{
 841        struct inode *inode = new_inode(sb);
 842
 843        if (inode) {
 844                inode->i_ino = get_next_ino();
 845                inode->i_mode = mode;
 846                inode->i_uid = current_fsuid();
 847                inode->i_gid = current_fsgid();
 848                inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 849                inode->i_mapping->backing_dev_info = &cgroup_backing_dev_info;
 850        }
 851        return inode;
 852}
 853
 854/*
 855 * Call subsys's pre_destroy handler.
 856 * This is called before css refcnt check.
 857 */
 858static int cgroup_call_pre_destroy(struct cgroup *cgrp)
 859{
 860        struct cgroup_subsys *ss;
 861        int ret = 0;
 862
 863        for_each_subsys(cgrp->root, ss) {
 864                if (!ss->pre_destroy)
 865                        continue;
 866
 867                ret = ss->pre_destroy(cgrp);
 868                if (ret) {
 869                        /* ->pre_destroy() failure is being deprecated */
 870                        WARN_ON_ONCE(!ss->__DEPRECATED_clear_css_refs);
 871                        break;
 872                }
 873        }
 874
 875        return ret;
 876}
 877
 878static void cgroup_diput(struct dentry *dentry, struct inode *inode)
 879{
 880        /* is dentry a directory ? if so, kfree() associated cgroup */
 881        if (S_ISDIR(inode->i_mode)) {
 882                struct cgroup *cgrp = dentry->d_fsdata;
 883                struct cgroup_subsys *ss;
 884                BUG_ON(!(cgroup_is_removed(cgrp)));
 885                /* It's possible for external users to be holding css
 886                 * reference counts on a cgroup; css_put() needs to
 887                 * be able to access the cgroup after decrementing
 888                 * the reference count in order to know if it needs to
 889                 * queue the cgroup to be handled by the release
 890                 * agent */
 891                synchronize_rcu();
 892
 893                mutex_lock(&cgroup_mutex);
 894                /*
 895                 * Release the subsystem state objects.
 896                 */
 897                for_each_subsys(cgrp->root, ss)
 898                        ss->destroy(cgrp);
 899
 900                cgrp->root->number_of_cgroups--;
 901                mutex_unlock(&cgroup_mutex);
 902
 903                /*
 904                 * Drop the active superblock reference that we took when we
 905                 * created the cgroup
 906                 */
 907                deactivate_super(cgrp->root->sb);
 908
 909                /*
 910                 * if we're getting rid of the cgroup, refcount should ensure
 911                 * that there are no pidlists left.
 912                 */
 913                BUG_ON(!list_empty(&cgrp->pidlists));
 914
 915                kfree_rcu(cgrp, rcu_head);
 916        } else {
 917                struct cfent *cfe = __d_cfe(dentry);
 918                struct cgroup *cgrp = dentry->d_parent->d_fsdata;
 919
 920                WARN_ONCE(!list_empty(&cfe->node) &&
 921                          cgrp != &cgrp->root->top_cgroup,
 922                          "cfe still linked for %s\n", cfe->type->name);
 923                kfree(cfe);
 924        }
 925        iput(inode);
 926}
 927
 928static int cgroup_delete(const struct dentry *d)
 929{
 930        return 1;
 931}
 932
 933static void remove_dir(struct dentry *d)
 934{
 935        struct dentry *parent = dget(d->d_parent);
 936
 937        d_delete(d);
 938        simple_rmdir(parent->d_inode, d);
 939        dput(parent);
 940}
 941
 942static int cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
 943{
 944        struct cfent *cfe;
 945
 946        lockdep_assert_held(&cgrp->dentry->d_inode->i_mutex);
 947        lockdep_assert_held(&cgroup_mutex);
 948
 949        list_for_each_entry(cfe, &cgrp->files, node) {
 950                struct dentry *d = cfe->dentry;
 951
 952                if (cft && cfe->type != cft)
 953                        continue;
 954
 955                dget(d);
 956                d_delete(d);
 957                simple_unlink(cgrp->dentry->d_inode, d);
 958                list_del_init(&cfe->node);
 959                dput(d);
 960
 961                return 0;
 962        }
 963        return -ENOENT;
 964}
 965
 966static void cgroup_clear_directory(struct dentry *dir)
 967{
 968        struct cgroup *cgrp = __d_cgrp(dir);
 969
 970        while (!list_empty(&cgrp->files))
 971                cgroup_rm_file(cgrp, NULL);
 972}
 973
 974/*
 975 * NOTE : the dentry must have been dget()'ed
 976 */
 977static void cgroup_d_remove_dir(struct dentry *dentry)
 978{
 979        struct dentry *parent;
 980
 981        cgroup_clear_directory(dentry);
 982
 983        parent = dentry->d_parent;
 984        spin_lock(&parent->d_lock);
 985        spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
 986        list_del_init(&dentry->d_u.d_child);
 987        spin_unlock(&dentry->d_lock);
 988        spin_unlock(&parent->d_lock);
 989        remove_dir(dentry);
 990}
 991
 992/*
 993 * A queue for waiters to do rmdir() cgroup. A tasks will sleep when
 994 * cgroup->count == 0 && list_empty(&cgroup->children) && subsys has some
 995 * reference to css->refcnt. In general, this refcnt is expected to goes down
 996 * to zero, soon.
 997 *
 998 * CGRP_WAIT_ON_RMDIR flag is set under cgroup's inode->i_mutex;
 999 */
1000static DECLARE_WAIT_QUEUE_HEAD(cgroup_rmdir_waitq);
1001
1002static void cgroup_wakeup_rmdir_waiter(struct cgroup *cgrp)
1003{
1004        if (unlikely(test_and_clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags)))
1005                wake_up_all(&cgroup_rmdir_waitq);
1006}
1007
1008void cgroup_exclude_rmdir(struct cgroup_subsys_state *css)
1009{
1010        css_get(css);
1011}
1012
1013void cgroup_release_and_wakeup_rmdir(struct cgroup_subsys_state *css)
1014{
1015        cgroup_wakeup_rmdir_waiter(css->cgroup);
1016        css_put(css);
1017}
1018
1019/*
1020 * Call with cgroup_mutex held. Drops reference counts on modules, including
1021 * any duplicate ones that parse_cgroupfs_options took. If this function
1022 * returns an error, no reference counts are touched.
1023 */
1024static int rebind_subsystems(struct cgroupfs_root *root,
1025                              unsigned long final_bits)
1026{
1027        unsigned long added_bits, removed_bits;
1028        struct cgroup *cgrp = &root->top_cgroup;
1029        int i;
1030
1031        BUG_ON(!mutex_is_locked(&cgroup_mutex));
1032        BUG_ON(!mutex_is_locked(&cgroup_root_mutex));
1033
1034        removed_bits = root->actual_subsys_bits & ~final_bits;
1035        added_bits = final_bits & ~root->actual_subsys_bits;
1036        /* Check that any added subsystems are currently free */
1037        for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1038                unsigned long bit = 1UL << i;
1039                struct cgroup_subsys *ss = subsys[i];
1040                if (!(bit & added_bits))
1041                        continue;
1042                /*
1043                 * Nobody should tell us to do a subsys that doesn't exist:
1044                 * parse_cgroupfs_options should catch that case and refcounts
1045                 * ensure that subsystems won't disappear once selected.
1046                 */
1047                BUG_ON(ss == NULL);
1048                if (ss->root != &rootnode) {
1049                        /* Subsystem isn't free */
1050                        return -EBUSY;
1051                }
1052        }
1053
1054        /* Currently we don't handle adding/removing subsystems when
1055         * any child cgroups exist. This is theoretically supportable
1056         * but involves complex error handling, so it's being left until
1057         * later */
1058        if (root->number_of_cgroups > 1)
1059                return -EBUSY;
1060
1061        /* Process each subsystem */
1062        for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1063                struct cgroup_subsys *ss = subsys[i];
1064                unsigned long bit = 1UL << i;
1065                if (bit & added_bits) {
1066                        /* We're binding this subsystem to this hierarchy */
1067                        BUG_ON(ss == NULL);
1068                        BUG_ON(cgrp->subsys[i]);
1069                        BUG_ON(!dummytop->subsys[i]);
1070                        BUG_ON(dummytop->subsys[i]->cgroup != dummytop);
1071                        mutex_lock(&ss->hierarchy_mutex);
1072                        cgrp->subsys[i] = dummytop->subsys[i];
1073                        cgrp->subsys[i]->cgroup = cgrp;
1074                        list_move(&ss->sibling, &root->subsys_list);
1075                        ss->root = root;
1076                        if (ss->bind)
1077                                ss->bind(cgrp);
1078                        mutex_unlock(&ss->hierarchy_mutex);
1079                        /* refcount was already taken, and we're keeping it */
1080                } else if (bit & removed_bits) {
1081                        /* We're removing this subsystem */
1082                        BUG_ON(ss == NULL);
1083                        BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]);
1084                        BUG_ON(cgrp->subsys[i]->cgroup != cgrp);
1085                        mutex_lock(&ss->hierarchy_mutex);
1086                        if (ss->bind)
1087                                ss->bind(dummytop);
1088                        dummytop->subsys[i]->cgroup = dummytop;
1089                        cgrp->subsys[i] = NULL;
1090                        subsys[i]->root = &rootnode;
1091                        list_move(&ss->sibling, &rootnode.subsys_list);
1092                        mutex_unlock(&ss->hierarchy_mutex);
1093                        /* subsystem is now free - drop reference on module */
1094                        module_put(ss->module);
1095                } else if (bit & final_bits) {
1096                        /* Subsystem state should already exist */
1097                        BUG_ON(ss == NULL);
1098                        BUG_ON(!cgrp->subsys[i]);
1099                        /*
1100                         * a refcount was taken, but we already had one, so
1101                         * drop the extra reference.
1102                         */
1103                        module_put(ss->module);
1104#ifdef CONFIG_MODULE_UNLOAD
1105                        BUG_ON(ss->module && !module_refcount(ss->module));
1106#endif
1107                } else {
1108                        /* Subsystem state shouldn't exist */
1109                        BUG_ON(cgrp->subsys[i]);
1110                }
1111        }
1112        root->subsys_bits = root->actual_subsys_bits = final_bits;
1113        synchronize_rcu();
1114
1115        return 0;
1116}
1117
1118static int cgroup_show_options(struct seq_file *seq, struct dentry *dentry)
1119{
1120        struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
1121        struct cgroup_subsys *ss;
1122
1123        mutex_lock(&cgroup_root_mutex);
1124        for_each_subsys(root, ss)
1125                seq_printf(seq, ",%s", ss->name);
1126        if (test_bit(ROOT_NOPREFIX, &root->flags))
1127                seq_puts(seq, ",noprefix");
1128        if (strlen(root->release_agent_path))
1129                seq_printf(seq, ",release_agent=%s", root->release_agent_path);
1130        if (clone_children(&root->top_cgroup))
1131                seq_puts(seq, ",clone_children");
1132        if (strlen(root->name))
1133                seq_printf(seq, ",name=%s", root->name);
1134        mutex_unlock(&cgroup_root_mutex);
1135        return 0;
1136}
1137
1138struct cgroup_sb_opts {
1139        unsigned long subsys_bits;
1140        unsigned long flags;
1141        char *release_agent;
1142        bool clone_children;
1143        char *name;
1144        /* User explicitly requested empty subsystem */
1145        bool none;
1146
1147        struct cgroupfs_root *new_root;
1148
1149};
1150
1151/*
1152 * Convert a hierarchy specifier into a bitmask of subsystems and flags. Call
1153 * with cgroup_mutex held to protect the subsys[] array. This function takes
1154 * refcounts on subsystems to be used, unless it returns error, in which case
1155 * no refcounts are taken.
1156 */
1157static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
1158{
1159        char *token, *o = data;
1160        bool all_ss = false, one_ss = false;
1161        unsigned long mask = (unsigned long)-1;
1162        int i;
1163        bool module_pin_failed = false;
1164
1165        BUG_ON(!mutex_is_locked(&cgroup_mutex));
1166
1167#ifdef CONFIG_CPUSETS
1168        mask = ~(1UL << cpuset_subsys_id);
1169#endif
1170
1171        memset(opts, 0, sizeof(*opts));
1172
1173        while ((token = strsep(&o, ",")) != NULL) {
1174                if (!*token)
1175                        return -EINVAL;
1176                if (!strcmp(token, "none")) {
1177                        /* Explicitly have no subsystems */
1178                        opts->none = true;
1179                        continue;
1180                }
1181                if (!strcmp(token, "all")) {
1182                        /* Mutually exclusive option 'all' + subsystem name */
1183                        if (one_ss)
1184                                return -EINVAL;
1185                        all_ss = true;
1186                        continue;
1187                }
1188                if (!strcmp(token, "noprefix")) {
1189                        set_bit(ROOT_NOPREFIX, &opts->flags);
1190                        continue;
1191                }
1192                if (!strcmp(token, "clone_children")) {
1193                        opts->clone_children = true;
1194                        continue;
1195                }
1196                if (!strncmp(token, "release_agent=", 14)) {
1197                        /* Specifying two release agents is forbidden */
1198                        if (opts->release_agent)
1199                                return -EINVAL;
1200                        opts->release_agent =
1201                                kstrndup(token + 14, PATH_MAX - 1, GFP_KERNEL);
1202                        if (!opts->release_agent)
1203                                return -ENOMEM;
1204                        continue;
1205                }
1206                if (!strncmp(token, "name=", 5)) {
1207                        const char *name = token + 5;
1208                        /* Can't specify an empty name */
1209                        if (!strlen(name))
1210                                return -EINVAL;
1211                        /* Must match [\w.-]+ */
1212                        for (i = 0; i < strlen(name); i++) {
1213                                char c = name[i];
1214                                if (isalnum(c))
1215                                        continue;
1216                                if ((c == '.') || (c == '-') || (c == '_'))
1217                                        continue;
1218                                return -EINVAL;
1219                        }
1220                        /* Specifying two names is forbidden */
1221                        if (opts->name)
1222                                return -EINVAL;
1223                        opts->name = kstrndup(name,
1224                                              MAX_CGROUP_ROOT_NAMELEN - 1,
1225                                              GFP_KERNEL);
1226                        if (!opts->name)
1227                                return -ENOMEM;
1228
1229                        continue;
1230                }
1231
1232                for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1233                        struct cgroup_subsys *ss = subsys[i];
1234                        if (ss == NULL)
1235                                continue;
1236                        if (strcmp(token, ss->name))
1237                                continue;
1238                        if (ss->disabled)
1239                                continue;
1240
1241                        /* Mutually exclusive option 'all' + subsystem name */
1242                        if (all_ss)
1243                                return -EINVAL;
1244                        set_bit(i, &opts->subsys_bits);
1245                        one_ss = true;
1246
1247                        break;
1248                }
1249                if (i == CGROUP_SUBSYS_COUNT)
1250                        return -ENOENT;
1251        }
1252
1253        /*
1254         * If the 'all' option was specified select all the subsystems,
1255         * otherwise if 'none', 'name=' and a subsystem name options
1256         * were not specified, let's default to 'all'
1257         */
1258        if (all_ss || (!one_ss && !opts->none && !opts->name)) {
1259                for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1260                        struct cgroup_subsys *ss = subsys[i];
1261                        if (ss == NULL)
1262                                continue;
1263                        if (ss->disabled)
1264                                continue;
1265                        set_bit(i, &opts->subsys_bits);
1266                }
1267        }
1268
1269        /* Consistency checks */
1270
1271        /*
1272         * Option noprefix was introduced just for backward compatibility
1273         * with the old cpuset, so we allow noprefix only if mounting just
1274         * the cpuset subsystem.
1275         */
1276        if (test_bit(ROOT_NOPREFIX, &opts->flags) &&
1277            (opts->subsys_bits & mask))
1278                return -EINVAL;
1279
1280
1281        /* Can't specify "none" and some subsystems */
1282        if (opts->subsys_bits && opts->none)
1283                return -EINVAL;
1284
1285        /*
1286         * We either have to specify by name or by subsystems. (So all
1287         * empty hierarchies must have a name).
1288         */
1289        if (!opts->subsys_bits && !opts->name)
1290                return -EINVAL;
1291
1292        /*
1293         * Grab references on all the modules we'll need, so the subsystems
1294         * don't dance around before rebind_subsystems attaches them. This may
1295         * take duplicate reference counts on a subsystem that's already used,
1296         * but rebind_subsystems handles this case.
1297         */
1298        for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
1299                unsigned long bit = 1UL << i;
1300
1301                if (!(bit & opts->subsys_bits))
1302                        continue;
1303                if (!try_module_get(subsys[i]->module)) {
1304                        module_pin_failed = true;
1305                        break;
1306                }
1307        }
1308        if (module_pin_failed) {
1309                /*
1310                 * oops, one of the modules was going away. this means that we
1311                 * raced with a module_delete call, and to the user this is
1312                 * essentially a "subsystem doesn't exist" case.
1313                 */
1314                for (i--; i >= CGROUP_BUILTIN_SUBSYS_COUNT; i--) {
1315                        /* drop refcounts only on the ones we took */
1316                        unsigned long bit = 1UL << i;
1317
1318                        if (!(bit & opts->subsys_bits))
1319                                continue;
1320                        module_put(subsys[i]->module);
1321                }
1322                return -ENOENT;
1323        }
1324
1325        return 0;
1326}
1327
1328static void drop_parsed_module_refcounts(unsigned long subsys_bits)
1329{
1330        int i;
1331        for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
1332                unsigned long bit = 1UL << i;
1333
1334                if (!(bit & subsys_bits))
1335                        continue;
1336                module_put(subsys[i]->module);
1337        }
1338}
1339
1340static int cgroup_remount(struct super_block *sb, int *flags, char *data)
1341{
1342        int ret = 0;
1343        struct cgroupfs_root *root = sb->s_fs_info;
1344        struct cgroup *cgrp = &root->top_cgroup;
1345        struct cgroup_sb_opts opts;
1346
1347        mutex_lock(&cgrp->dentry->d_inode->i_mutex);
1348        mutex_lock(&cgroup_mutex);
1349        mutex_lock(&cgroup_root_mutex);
1350
1351        /* See what subsystems are wanted */
1352        ret = parse_cgroupfs_options(data, &opts);
1353        if (ret)
1354                goto out_unlock;
1355
1356        /* See feature-removal-schedule.txt */
1357        if (opts.subsys_bits != root->actual_subsys_bits || opts.release_agent)
1358                pr_warning("cgroup: option changes via remount are deprecated (pid=%d comm=%s)\n",
1359                           task_tgid_nr(current), current->comm);
1360
1361        /* Don't allow flags or name to change at remount */
1362        if (opts.flags != root->flags ||
1363            (opts.name && strcmp(opts.name, root->name))) {
1364                ret = -EINVAL;
1365                drop_parsed_module_refcounts(opts.subsys_bits);
1366                goto out_unlock;
1367        }
1368
1369        ret = rebind_subsystems(root, opts.subsys_bits);
1370        if (ret) {
1371                drop_parsed_module_refcounts(opts.subsys_bits);
1372                goto out_unlock;
1373        }
1374
1375        /* clear out any existing files and repopulate subsystem files */
1376        cgroup_clear_directory(cgrp->dentry);
1377        cgroup_populate_dir(cgrp);
1378
1379        if (opts.release_agent)
1380                strcpy(root->release_agent_path, opts.release_agent);
1381 out_unlock:
1382        kfree(opts.release_agent);
1383        kfree(opts.name);
1384        mutex_unlock(&cgroup_root_mutex);
1385        mutex_unlock(&cgroup_mutex);
1386        mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
1387        return ret;
1388}
1389
1390static const struct super_operations cgroup_ops = {
1391        .statfs = simple_statfs,
1392        .drop_inode = generic_delete_inode,
1393        .show_options = cgroup_show_options,
1394        .remount_fs = cgroup_remount,
1395};
1396
1397static void init_cgroup_housekeeping(struct cgroup *cgrp)
1398{
1399        INIT_LIST_HEAD(&cgrp->sibling);
1400        INIT_LIST_HEAD(&cgrp->children);
1401        INIT_LIST_HEAD(&cgrp->files);
1402        INIT_LIST_HEAD(&cgrp->css_sets);
1403        INIT_LIST_HEAD(&cgrp->release_list);
1404        INIT_LIST_HEAD(&cgrp->pidlists);
1405        mutex_init(&cgrp->pidlist_mutex);
1406        INIT_LIST_HEAD(&cgrp->event_list);
1407        spin_lock_init(&cgrp->event_list_lock);
1408}
1409
1410static void init_cgroup_root(struct cgroupfs_root *root)
1411{
1412        struct cgroup *cgrp = &root->top_cgroup;
1413
1414        INIT_LIST_HEAD(&root->subsys_list);
1415        INIT_LIST_HEAD(&root->root_list);
1416        INIT_LIST_HEAD(&root->allcg_list);
1417        root->number_of_cgroups = 1;
1418        cgrp->root = root;
1419        cgrp->top_cgroup = cgrp;
1420        list_add_tail(&cgrp->allcg_node, &root->allcg_list);
1421        init_cgroup_housekeeping(cgrp);
1422}
1423
1424static bool init_root_id(struct cgroupfs_root *root)
1425{
1426        int ret = 0;
1427
1428        do {
1429                if (!ida_pre_get(&hierarchy_ida, GFP_KERNEL))
1430                        return false;
1431                spin_lock(&hierarchy_id_lock);
1432                /* Try to allocate the next unused ID */
1433                ret = ida_get_new_above(&hierarchy_ida, next_hierarchy_id,
1434                                        &root->hierarchy_id);
1435                if (ret == -ENOSPC)
1436                        /* Try again starting from 0 */
1437                        ret = ida_get_new(&hierarchy_ida, &root->hierarchy_id);
1438                if (!ret) {
1439                        next_hierarchy_id = root->hierarchy_id + 1;
1440                } else if (ret != -EAGAIN) {
1441                        /* Can only get here if the 31-bit IDR is full ... */
1442                        BUG_ON(ret);
1443                }
1444                spin_unlock(&hierarchy_id_lock);
1445        } while (ret);
1446        return true;
1447}
1448
1449static int cgroup_test_super(struct super_block *sb, void *data)
1450{
1451        struct cgroup_sb_opts *opts = data;
1452        struct cgroupfs_root *root = sb->s_fs_info;
1453
1454        /* If we asked for a name then it must match */
1455        if (opts->name && strcmp(opts->name, root->name))
1456                return 0;
1457
1458        /*
1459         * If we asked for subsystems (or explicitly for no
1460         * subsystems) then they must match
1461         */
1462        if ((opts->subsys_bits || opts->none)
1463            && (opts->subsys_bits != root->subsys_bits))
1464                return 0;
1465
1466        return 1;
1467}
1468
1469static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
1470{
1471        struct cgroupfs_root *root;
1472
1473        if (!opts->subsys_bits && !opts->none)
1474                return NULL;
1475
1476        root = kzalloc(sizeof(*root), GFP_KERNEL);
1477        if (!root)
1478                return ERR_PTR(-ENOMEM);
1479
1480        if (!init_root_id(root)) {
1481                kfree(root);
1482                return ERR_PTR(-ENOMEM);
1483        }
1484        init_cgroup_root(root);
1485
1486        root->subsys_bits = opts->subsys_bits;
1487        root->flags = opts->flags;
1488        if (opts->release_agent)
1489                strcpy(root->release_agent_path, opts->release_agent);
1490        if (opts->name)
1491                strcpy(root->name, opts->name);
1492        if (opts->clone_children)
1493                set_bit(CGRP_CLONE_CHILDREN, &root->top_cgroup.flags);
1494        return root;
1495}
1496
1497static void cgroup_drop_root(struct cgroupfs_root *root)
1498{
1499        if (!root)
1500                return;
1501
1502        BUG_ON(!root->hierarchy_id);
1503        spin_lock(&hierarchy_id_lock);
1504        ida_remove(&hierarchy_ida, root->hierarchy_id);
1505        spin_unlock(&hierarchy_id_lock);
1506        kfree(root);
1507}
1508
1509static int cgroup_set_super(struct super_block *sb, void *data)
1510{
1511        int ret;
1512        struct cgroup_sb_opts *opts = data;
1513
1514        /* If we don't have a new root, we can't set up a new sb */
1515        if (!opts->new_root)
1516                return -EINVAL;
1517
1518        BUG_ON(!opts->subsys_bits && !opts->none);
1519
1520        ret = set_anon_super(sb, NULL);
1521        if (ret)
1522                return ret;
1523
1524        sb->s_fs_info = opts->new_root;
1525        opts->new_root->sb = sb;
1526
1527        sb->s_blocksize = PAGE_CACHE_SIZE;
1528        sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
1529        sb->s_magic = CGROUP_SUPER_MAGIC;
1530        sb->s_op = &cgroup_ops;
1531
1532        return 0;
1533}
1534
1535static int cgroup_get_rootdir(struct super_block *sb)
1536{
1537        static const struct dentry_operations cgroup_dops = {
1538                .d_iput = cgroup_diput,
1539                .d_delete = cgroup_delete,
1540        };
1541
1542        struct inode *inode =
1543                cgroup_new_inode(S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR, sb);
1544
1545        if (!inode)
1546                return -ENOMEM;
1547
1548        inode->i_fop = &simple_dir_operations;
1549        inode->i_op = &cgroup_dir_inode_operations;
1550        /* directories start off with i_nlink == 2 (for "." entry) */
1551        inc_nlink(inode);
1552        sb->s_root = d_make_root(inode);
1553        if (!sb->s_root)
1554                return -ENOMEM;
1555        /* for everything else we want ->d_op set */
1556        sb->s_d_op = &cgroup_dops;
1557        return 0;
1558}
1559
1560static struct dentry *cgroup_mount(struct file_system_type *fs_type,
1561                         int flags, const char *unused_dev_name,
1562                         void *data)
1563{
1564        struct cgroup_sb_opts opts;
1565        struct cgroupfs_root *root;
1566        int ret = 0;
1567        struct super_block *sb;
1568        struct cgroupfs_root *new_root;
1569        struct inode *inode;
1570
1571        /* First find the desired set of subsystems */
1572        mutex_lock(&cgroup_mutex);
1573        ret = parse_cgroupfs_options(data, &opts);
1574        mutex_unlock(&cgroup_mutex);
1575        if (ret)
1576                goto out_err;
1577
1578        /*
1579         * Allocate a new cgroup root. We may not need it if we're
1580         * reusing an existing hierarchy.
1581         */
1582        new_root = cgroup_root_from_opts(&opts);
1583        if (IS_ERR(new_root)) {
1584                ret = PTR_ERR(new_root);
1585                goto drop_modules;
1586        }
1587        opts.new_root = new_root;
1588
1589        /* Locate an existing or new sb for this hierarchy */
1590        sb = sget(fs_type, cgroup_test_super, cgroup_set_super, &opts);
1591        if (IS_ERR(sb)) {
1592                ret = PTR_ERR(sb);
1593                cgroup_drop_root(opts.new_root);
1594                goto drop_modules;
1595        }
1596
1597        root = sb->s_fs_info;
1598        BUG_ON(!root);
1599        if (root == opts.new_root) {
1600                /* We used the new root structure, so this is a new hierarchy */
1601                struct list_head tmp_cg_links;
1602                struct cgroup *root_cgrp = &root->top_cgroup;
1603                struct cgroupfs_root *existing_root;
1604                const struct cred *cred;
1605                int i;
1606
1607                BUG_ON(sb->s_root != NULL);
1608
1609                ret = cgroup_get_rootdir(sb);
1610                if (ret)
1611                        goto drop_new_super;
1612                inode = sb->s_root->d_inode;
1613
1614                mutex_lock(&inode->i_mutex);
1615                mutex_lock(&cgroup_mutex);
1616                mutex_lock(&cgroup_root_mutex);
1617
1618                /* Check for name clashes with existing mounts */
1619                ret = -EBUSY;
1620                if (strlen(root->name))
1621                        for_each_active_root(existing_root)
1622                                if (!strcmp(existing_root->name, root->name))
1623                                        goto unlock_drop;
1624
1625                /*
1626                 * We're accessing css_set_count without locking
1627                 * css_set_lock here, but that's OK - it can only be
1628                 * increased by someone holding cgroup_lock, and
1629                 * that's us. The worst that can happen is that we
1630                 * have some link structures left over
1631                 */
1632                ret = allocate_cg_links(css_set_count, &tmp_cg_links);
1633                if (ret)
1634                        goto unlock_drop;
1635
1636                ret = rebind_subsystems(root, root->subsys_bits);
1637                if (ret == -EBUSY) {
1638                        free_cg_links(&tmp_cg_links);
1639                        goto unlock_drop;
1640                }
1641                /*
1642                 * There must be no failure case after here, since rebinding
1643                 * takes care of subsystems' refcounts, which are explicitly
1644                 * dropped in the failure exit path.
1645                 */
1646
1647                /* EBUSY should be the only error here */
1648                BUG_ON(ret);
1649
1650                list_add(&root->root_list, &roots);
1651                root_count++;
1652
1653                sb->s_root->d_fsdata = root_cgrp;
1654                root->top_cgroup.dentry = sb->s_root;
1655
1656                /* Link the top cgroup in this hierarchy into all
1657                 * the css_set objects */
1658                write_lock(&css_set_lock);
1659                for (i = 0; i < CSS_SET_TABLE_SIZE; i++) {
1660                        struct hlist_head *hhead = &css_set_table[i];
1661                        struct hlist_node *node;
1662                        struct css_set *cg;
1663
1664                        hlist_for_each_entry(cg, node, hhead, hlist)
1665                                link_css_set(&tmp_cg_links, cg, root_cgrp);
1666                }
1667                write_unlock(&css_set_lock);
1668
1669                free_cg_links(&tmp_cg_links);
1670
1671                BUG_ON(!list_empty(&root_cgrp->sibling));
1672                BUG_ON(!list_empty(&root_cgrp->children));
1673                BUG_ON(root->number_of_cgroups != 1);
1674
1675                cred = override_creds(&init_cred);
1676                cgroup_populate_dir(root_cgrp);
1677                revert_creds(cred);
1678                mutex_unlock(&cgroup_root_mutex);
1679                mutex_unlock(&cgroup_mutex);
1680                mutex_unlock(&inode->i_mutex);
1681        } else {
1682                /*
1683                 * We re-used an existing hierarchy - the new root (if
1684                 * any) is not needed
1685                 */
1686                cgroup_drop_root(opts.new_root);
1687                /* no subsys rebinding, so refcounts don't change */
1688                drop_parsed_module_refcounts(opts.subsys_bits);
1689        }
1690
1691        kfree(opts.release_agent);
1692        kfree(opts.name);
1693        return dget(sb->s_root);
1694
1695 unlock_drop:
1696        mutex_unlock(&cgroup_root_mutex);
1697        mutex_unlock(&cgroup_mutex);
1698        mutex_unlock(&inode->i_mutex);
1699 drop_new_super:
1700        deactivate_locked_super(sb);
1701 drop_modules:
1702        drop_parsed_module_refcounts(opts.subsys_bits);
1703 out_err:
1704        kfree(opts.release_agent);
1705        kfree(opts.name);
1706        return ERR_PTR(ret);
1707}
1708
1709static void cgroup_kill_sb(struct super_block *sb) {
1710        struct cgroupfs_root *root = sb->s_fs_info;
1711        struct cgroup *cgrp = &root->top_cgroup;
1712        int ret;
1713        struct cg_cgroup_link *link;
1714        struct cg_cgroup_link *saved_link;
1715
1716        BUG_ON(!root);
1717
1718        BUG_ON(root->number_of_cgroups != 1);
1719        BUG_ON(!list_empty(&cgrp->children));
1720        BUG_ON(!list_empty(&cgrp->sibling));
1721
1722        mutex_lock(&cgroup_mutex);
1723        mutex_lock(&cgroup_root_mutex);
1724
1725        /* Rebind all subsystems back to the default hierarchy */
1726        ret = rebind_subsystems(root, 0);
1727        /* Shouldn't be able to fail ... */
1728        BUG_ON(ret);
1729
1730        /*
1731         * Release all the links from css_sets to this hierarchy's
1732         * root cgroup
1733         */
1734        write_lock(&css_set_lock);
1735
1736        list_for_each_entry_safe(link, saved_link, &cgrp->css_sets,
1737                                 cgrp_link_list) {
1738                list_del(&link->cg_link_list);
1739                list_del(&link->cgrp_link_list);
1740                kfree(link);
1741        }
1742        write_unlock(&css_set_lock);
1743
1744        if (!list_empty(&root->root_list)) {
1745                list_del(&root->root_list);
1746                root_count--;
1747        }
1748
1749        mutex_unlock(&cgroup_root_mutex);
1750        mutex_unlock(&cgroup_mutex);
1751
1752        kill_litter_super(sb);
1753        cgroup_drop_root(root);
1754}
1755
1756static struct file_system_type cgroup_fs_type = {
1757        .name = "cgroup",
1758        .mount = cgroup_mount,
1759        .kill_sb = cgroup_kill_sb,
1760};
1761
1762static struct kobject *cgroup_kobj;
1763
1764/**
1765 * cgroup_path - generate the path of a cgroup
1766 * @cgrp: the cgroup in question
1767 * @buf: the buffer to write the path into
1768 * @buflen: the length of the buffer
1769 *
1770 * Called with cgroup_mutex held or else with an RCU-protected cgroup
1771 * reference.  Writes path of cgroup into buf.  Returns 0 on success,
1772 * -errno on error.
1773 */
1774int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
1775{
1776        char *start;
1777        struct dentry *dentry = rcu_dereference_check(cgrp->dentry,
1778                                                      cgroup_lock_is_held());
1779
1780        if (!dentry || cgrp == dummytop) {
1781                /*
1782                 * Inactive subsystems have no dentry for their root
1783                 * cgroup
1784                 */
1785                strcpy(buf, "/");
1786                return 0;
1787        }
1788
1789        start = buf + buflen;
1790
1791        *--start = '\0';
1792        for (;;) {
1793                int len = dentry->d_name.len;
1794
1795                if ((start -= len) < buf)
1796                        return -ENAMETOOLONG;
1797                memcpy(start, dentry->d_name.name, len);
1798                cgrp = cgrp->parent;
1799                if (!cgrp)
1800                        break;
1801
1802                dentry = rcu_dereference_check(cgrp->dentry,
1803                                               cgroup_lock_is_held());
1804                if (!cgrp->parent)
1805                        continue;
1806                if (--start < buf)
1807                        return -ENAMETOOLONG;
1808                *start = '/';
1809        }
1810        memmove(buf, start, buf + buflen - start);
1811        return 0;
1812}
1813EXPORT_SYMBOL_GPL(cgroup_path);
1814
1815/*
1816 * Control Group taskset
1817 */
1818struct task_and_cgroup {
1819        struct task_struct      *task;
1820        struct cgroup           *cgrp;
1821        struct css_set          *cg;
1822};
1823
1824struct cgroup_taskset {
1825        struct task_and_cgroup  single;
1826        struct flex_array       *tc_array;
1827        int                     tc_array_len;
1828        int                     idx;
1829        struct cgroup           *cur_cgrp;
1830};
1831
1832/**
1833 * cgroup_taskset_first - reset taskset and return the first task
1834 * @tset: taskset of interest
1835 *
1836 * @tset iteration is initialized and the first task is returned.
1837 */
1838struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset)
1839{
1840        if (tset->tc_array) {
1841                tset->idx = 0;
1842                return cgroup_taskset_next(tset);
1843        } else {
1844                tset->cur_cgrp = tset->single.cgrp;
1845                return tset->single.task;
1846        }
1847}
1848EXPORT_SYMBOL_GPL(cgroup_taskset_first);
1849
1850/**
1851 * cgroup_taskset_next - iterate to the next task in taskset
1852 * @tset: taskset of interest
1853 *
1854 * Return the next task in @tset.  Iteration must have been initialized
1855 * with cgroup_taskset_first().
1856 */
1857struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset)
1858{
1859        struct task_and_cgroup *tc;
1860
1861        if (!tset->tc_array || tset->idx >= tset->tc_array_len)
1862                return NULL;
1863
1864        tc = flex_array_get(tset->tc_array, tset->idx++);
1865        tset->cur_cgrp = tc->cgrp;
1866        return tc->task;
1867}
1868EXPORT_SYMBOL_GPL(cgroup_taskset_next);
1869
1870/**
1871 * cgroup_taskset_cur_cgroup - return the matching cgroup for the current task
1872 * @tset: taskset of interest
1873 *
1874 * Return the cgroup for the current (last returned) task of @tset.  This
1875 * function must be preceded by either cgroup_taskset_first() or
1876 * cgroup_taskset_next().
1877 */
1878struct cgroup *cgroup_taskset_cur_cgroup(struct cgroup_taskset *tset)
1879{
1880        return tset->cur_cgrp;
1881}
1882EXPORT_SYMBOL_GPL(cgroup_taskset_cur_cgroup);
1883
1884/**
1885 * cgroup_taskset_size - return the number of tasks in taskset
1886 * @tset: taskset of interest
1887 */
1888int cgroup_taskset_size(struct cgroup_taskset *tset)
1889{
1890        return tset->tc_array ? tset->tc_array_len : 1;
1891}
1892EXPORT_SYMBOL_GPL(cgroup_taskset_size);
1893
1894
1895/*
1896 * cgroup_task_migrate - move a task from one cgroup to another.
1897 *
1898 * 'guarantee' is set if the caller promises that a new css_set for the task
1899 * will already exist. If not set, this function might sleep, and can fail with
1900 * -ENOMEM. Must be called with cgroup_mutex and threadgroup locked.
1901 */
1902static void cgroup_task_migrate(struct cgroup *cgrp, struct cgroup *oldcgrp,
1903                                struct task_struct *tsk, struct css_set *newcg)
1904{
1905        struct css_set *oldcg;
1906
1907        /*
1908         * We are synchronized through threadgroup_lock() against PF_EXITING
1909         * setting such that we can't race against cgroup_exit() changing the
1910         * css_set to init_css_set and dropping the old one.
1911         */
1912        WARN_ON_ONCE(tsk->flags & PF_EXITING);
1913        oldcg = tsk->cgroups;
1914
1915        task_lock(tsk);
1916        rcu_assign_pointer(tsk->cgroups, newcg);
1917        task_unlock(tsk);
1918
1919        /* Update the css_set linked lists if we're using them */
1920        write_lock(&css_set_lock);
1921        if (!list_empty(&tsk->cg_list))
1922                list_move(&tsk->cg_list, &newcg->tasks);
1923        write_unlock(&css_set_lock);
1924
1925        /*
1926         * We just gained a reference on oldcg by taking it from the task. As
1927         * trading it for newcg is protected by cgroup_mutex, we're safe to drop
1928         * it here; it will be freed under RCU.
1929         */
1930        put_css_set(oldcg);
1931
1932        set_bit(CGRP_RELEASABLE, &oldcgrp->flags);
1933}
1934
1935/**
1936 * cgroup_attach_task - attach task 'tsk' to cgroup 'cgrp'
1937 * @cgrp: the cgroup the task is attaching to
1938 * @tsk: the task to be attached
1939 *
1940 * Call with cgroup_mutex and threadgroup locked. May take task_lock of
1941 * @tsk during call.
1942 */
1943int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
1944{
1945        int retval = 0;
1946        struct cgroup_subsys *ss, *failed_ss = NULL;
1947        struct cgroup *oldcgrp;
1948        struct cgroupfs_root *root = cgrp->root;
1949        struct cgroup_taskset tset = { };
1950        struct css_set *newcg;
1951
1952        /* @tsk either already exited or can't exit until the end */
1953        if (tsk->flags & PF_EXITING)
1954                return -ESRCH;
1955
1956        /* Nothing to do if the task is already in that cgroup */
1957        oldcgrp = task_cgroup_from_root(tsk, root);
1958        if (cgrp == oldcgrp)
1959                return 0;
1960
1961        tset.single.task = tsk;
1962        tset.single.cgrp = oldcgrp;
1963
1964        for_each_subsys(root, ss) {
1965                if (ss->can_attach) {
1966                        retval = ss->can_attach(cgrp, &tset);
1967                        if (retval) {
1968                                /*
1969                                 * Remember on which subsystem the can_attach()
1970                                 * failed, so that we only call cancel_attach()
1971                                 * against the subsystems whose can_attach()
1972                                 * succeeded. (See below)
1973                                 */
1974                                failed_ss = ss;
1975                                goto out;
1976                        }
1977                }
1978        }
1979
1980        newcg = find_css_set(tsk->cgroups, cgrp);
1981        if (!newcg) {
1982                retval = -ENOMEM;
1983                goto out;
1984        }
1985
1986        cgroup_task_migrate(cgrp, oldcgrp, tsk, newcg);
1987
1988        for_each_subsys(root, ss) {
1989                if (ss->attach)
1990                        ss->attach(cgrp, &tset);
1991        }
1992
1993        synchronize_rcu();
1994
1995        /*
1996         * wake up rmdir() waiter. the rmdir should fail since the cgroup
1997         * is no longer empty.
1998         */
1999        cgroup_wakeup_rmdir_waiter(cgrp);
2000out:
2001        if (retval) {
2002                for_each_subsys(root, ss) {
2003                        if (ss == failed_ss)
2004                                /*
2005                                 * This subsystem was the one that failed the
2006                                 * can_attach() check earlier, so we don't need
2007                                 * to call cancel_attach() against it or any
2008                                 * remaining subsystems.
2009                                 */
2010                                break;
2011                        if (ss->cancel_attach)
2012                                ss->cancel_attach(cgrp, &tset);
2013                }
2014        }
2015        return retval;
2016}
2017
2018/**
2019 * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
2020 * @from: attach to all cgroups of a given task
2021 * @tsk: the task to be attached
2022 */
2023int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
2024{
2025        struct cgroupfs_root *root;
2026        int retval = 0;
2027
2028        cgroup_lock();
2029        for_each_active_root(root) {
2030                struct cgroup *from_cg = task_cgroup_from_root(from, root);
2031
2032                retval = cgroup_attach_task(from_cg, tsk);
2033                if (retval)
2034                        break;
2035        }
2036        cgroup_unlock();
2037
2038        return retval;
2039}
2040EXPORT_SYMBOL_GPL(cgroup_attach_task_all);
2041
2042/**
2043 * cgroup_attach_proc - attach all threads in a threadgroup to a cgroup
2044 * @cgrp: the cgroup to attach to
2045 * @leader: the threadgroup leader task_struct of the group to be attached
2046 *
2047 * Call holding cgroup_mutex and the group_rwsem of the leader. Will take
2048 * task_lock of each thread in leader's threadgroup individually in turn.
2049 */
2050static int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
2051{
2052        int retval, i, group_size;
2053        struct cgroup_subsys *ss, *failed_ss = NULL;
2054        /* guaranteed to be initialized later, but the compiler needs this */
2055        struct cgroupfs_root *root = cgrp->root;
2056        /* threadgroup list cursor and array */
2057        struct task_struct *tsk;
2058        struct task_and_cgroup *tc;
2059        struct flex_array *group;
2060        struct cgroup_taskset tset = { };
2061
2062        /*
2063         * step 0: in order to do expensive, possibly blocking operations for
2064         * every thread, we cannot iterate the thread group list, since it needs
2065         * rcu or tasklist locked. instead, build an array of all threads in the
2066         * group - group_rwsem prevents new threads from appearing, and if
2067         * threads exit, this will just be an over-estimate.
2068         */
2069        group_size = get_nr_threads(leader);
2070        /* flex_array supports very large thread-groups better than kmalloc. */
2071        group = flex_array_alloc(sizeof(*tc), group_size, GFP_KERNEL);
2072        if (!group)
2073                return -ENOMEM;
2074        /* pre-allocate to guarantee space while iterating in rcu read-side. */
2075        retval = flex_array_prealloc(group, 0, group_size - 1, GFP_KERNEL);
2076        if (retval)
2077                goto out_free_group_list;
2078
2079        tsk = leader;
2080        i = 0;
2081        /*
2082         * Prevent freeing of tasks while we take a snapshot. Tasks that are
2083         * already PF_EXITING could be freed from underneath us unless we
2084         * take an rcu_read_lock.
2085         */
2086        rcu_read_lock();
2087        do {
2088                struct task_and_cgroup ent;
2089
2090                /* @tsk either already exited or can't exit until the end */
2091                if (tsk->flags & PF_EXITING)
2092                        continue;
2093
2094                /* as per above, nr_threads may decrease, but not increase. */
2095                BUG_ON(i >= group_size);
2096                ent.task = tsk;
2097                ent.cgrp = task_cgroup_from_root(tsk, root);
2098                /* nothing to do if this task is already in the cgroup */
2099                if (ent.cgrp == cgrp)
2100                        continue;
2101                /*
2102                 * saying GFP_ATOMIC has no effect here because we did prealloc
2103                 * earlier, but it's good form to communicate our expectations.
2104                 */
2105                retval = flex_array_put(group, i, &ent, GFP_ATOMIC);
2106                BUG_ON(retval != 0);
2107                i++;
2108        } while_each_thread(leader, tsk);
2109        rcu_read_unlock();
2110        /* remember the number of threads in the array for later. */
2111        group_size = i;
2112        tset.tc_array = group;
2113        tset.tc_array_len = group_size;
2114
2115        /* methods shouldn't be called if no task is actually migrating */
2116        retval = 0;
2117        if (!group_size)
2118                goto out_free_group_list;
2119
2120        /*
2121         * step 1: check that we can legitimately attach to the cgroup.
2122         */
2123        for_each_subsys(root, ss) {
2124                if (ss->can_attach) {
2125                        retval = ss->can_attach(cgrp, &tset);
2126                        if (retval) {
2127                                failed_ss = ss;
2128                                goto out_cancel_attach;
2129                        }
2130                }
2131        }
2132
2133        /*
2134         * step 2: make sure css_sets exist for all threads to be migrated.
2135         * we use find_css_set, which allocates a new one if necessary.
2136         */
2137        for (i = 0; i < group_size; i++) {
2138                tc = flex_array_get(group, i);
2139                tc->cg = find_css_set(tc->task->cgroups, cgrp);
2140                if (!tc->cg) {
2141                        retval = -ENOMEM;
2142                        goto out_put_css_set_refs;
2143                }
2144        }
2145
2146        /*
2147         * step 3: now that we're guaranteed success wrt the css_sets,
2148         * proceed to move all tasks to the new cgroup.  There are no
2149         * failure cases after here, so this is the commit point.
2150         */
2151        for (i = 0; i < group_size; i++) {
2152                tc = flex_array_get(group, i);
2153                cgroup_task_migrate(cgrp, tc->cgrp, tc->task, tc->cg);
2154        }
2155        /* nothing is sensitive to fork() after this point. */
2156
2157        /*
2158         * step 4: do subsystem attach callbacks.
2159         */
2160        for_each_subsys(root, ss) {
2161                if (ss->attach)
2162                        ss->attach(cgrp, &tset);
2163        }
2164
2165        /*
2166         * step 5: success! and cleanup
2167         */
2168        synchronize_rcu();
2169        cgroup_wakeup_rmdir_waiter(cgrp);
2170        retval = 0;
2171out_put_css_set_refs:
2172        if (retval) {
2173                for (i = 0; i < group_size; i++) {
2174                        tc = flex_array_get(group, i);
2175                        if (!tc->cg)
2176                                break;
2177                        put_css_set(tc->cg);
2178                }
2179        }
2180out_cancel_attach:
2181        if (retval) {
2182                for_each_subsys(root, ss) {
2183                        if (ss == failed_ss)
2184                                break;
2185                        if (ss->cancel_attach)
2186                                ss->cancel_attach(cgrp, &tset);
2187                }
2188        }
2189out_free_group_list:
2190        flex_array_free(group);
2191        return retval;
2192}
2193
2194/*
2195 * Find the task_struct of the task to attach by vpid and pass it along to the
2196 * function to attach either it or all tasks in its threadgroup. Will lock
2197 * cgroup_mutex and threadgroup; may take task_lock of task.
2198 */
2199static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
2200{
2201        struct task_struct *tsk;
2202        const struct cred *cred = current_cred(), *tcred;
2203        int ret;
2204
2205        if (!cgroup_lock_live_group(cgrp))
2206                return -ENODEV;
2207
2208retry_find_task:
2209        rcu_read_lock();
2210        if (pid) {
2211                tsk = find_task_by_vpid(pid);
2212                if (!tsk) {
2213                        rcu_read_unlock();
2214                        ret= -ESRCH;
2215                        goto out_unlock_cgroup;
2216                }
2217                /*
2218                 * even if we're attaching all tasks in the thread group, we
2219                 * only need to check permissions on one of them.
2220                 */
2221                tcred = __task_cred(tsk);
2222                if (!uid_eq(cred->euid, GLOBAL_ROOT_UID) &&
2223                    !uid_eq(cred->euid, tcred->uid) &&
2224                    !uid_eq(cred->euid, tcred->suid)) {
2225                        rcu_read_unlock();
2226                        ret = -EACCES;
2227                        goto out_unlock_cgroup;
2228                }
2229        } else
2230                tsk = current;
2231
2232        if (threadgroup)
2233                tsk = tsk->group_leader;
2234
2235        /*
2236         * Workqueue threads may acquire PF_THREAD_BOUND and become
2237         * trapped in a cpuset, or RT worker may be born in a cgroup
2238         * with no rt_runtime allocated.  Just say no.
2239         */
2240        if (tsk == kthreadd_task || (tsk->flags & PF_THREAD_BOUND)) {
2241                ret = -EINVAL;
2242                rcu_read_unlock();
2243                goto out_unlock_cgroup;
2244        }
2245
2246        get_task_struct(tsk);
2247        rcu_read_unlock();
2248
2249        threadgroup_lock(tsk);
2250        if (threadgroup) {
2251                if (!thread_group_leader(tsk)) {
2252                        /*
2253                         * a race with de_thread from another thread's exec()
2254                         * may strip us of our leadership, if this happens,
2255                         * there is no choice but to throw this task away and
2256                         * try again; this is
2257                         * "double-double-toil-and-trouble-check locking".
2258                         */
2259                        threadgroup_unlock(tsk);
2260                        put_task_struct(tsk);
2261                        goto retry_find_task;
2262                }
2263                ret = cgroup_attach_proc(cgrp, tsk);
2264        } else
2265                ret = cgroup_attach_task(cgrp, tsk);
2266        threadgroup_unlock(tsk);
2267
2268        put_task_struct(tsk);
2269out_unlock_cgroup:
2270        cgroup_unlock();
2271        return ret;
2272}
2273
2274static int cgroup_tasks_write(struct cgroup *cgrp, struct cftype *cft, u64 pid)
2275{
2276        return attach_task_by_pid(cgrp, pid, false);
2277}
2278
2279static int cgroup_procs_write(struct cgroup *cgrp, struct cftype *cft, u64 tgid)
2280{
2281        return attach_task_by_pid(cgrp, tgid, true);
2282}
2283
2284/**
2285 * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive.
2286 * @cgrp: the cgroup to be checked for liveness
2287 *
2288 * On success, returns true; the lock should be later released with
2289 * cgroup_unlock(). On failure returns false with no lock held.
2290 */
2291bool cgroup_lock_live_group(struct cgroup *cgrp)
2292{
2293        mutex_lock(&cgroup_mutex);
2294        if (cgroup_is_removed(cgrp)) {
2295                mutex_unlock(&cgroup_mutex);
2296                return false;
2297        }
2298        return true;
2299}
2300EXPORT_SYMBOL_GPL(cgroup_lock_live_group);
2301
2302static int cgroup_release_agent_write(struct cgroup *cgrp, struct cftype *cft,
2303                                      const char *buffer)
2304{
2305        BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
2306        if (strlen(buffer) >= PATH_MAX)
2307                return -EINVAL;
2308        if (!cgroup_lock_live_group(cgrp))
2309                return -ENODEV;
2310        mutex_lock(&cgroup_root_mutex);
2311        strcpy(cgrp->root->release_agent_path, buffer);
2312        mutex_unlock(&cgroup_root_mutex);
2313        cgroup_unlock();
2314        return 0;
2315}
2316
2317static int cgroup_release_agent_show(struct cgroup *cgrp, struct cftype *cft,
2318                                     struct seq_file *seq)
2319{
2320        if (!cgroup_lock_live_group(cgrp))
2321                return -ENODEV;
2322        seq_puts(seq, cgrp->root->release_agent_path);
2323        seq_putc(seq, '\n');
2324        cgroup_unlock();
2325        return 0;
2326}
2327
2328/* A buffer size big enough for numbers or short strings */
2329#define CGROUP_LOCAL_BUFFER_SIZE 64
2330
2331static ssize_t cgroup_write_X64(struct cgroup *cgrp, struct cftype *cft,
2332                                struct file *file,
2333                                const char __user *userbuf,
2334                                size_t nbytes, loff_t *unused_ppos)
2335{
2336        char buffer[CGROUP_LOCAL_BUFFER_SIZE];
2337        int retval = 0;
2338        char *end;
2339
2340        if (!nbytes)
2341                return -EINVAL;
2342        if (nbytes >= sizeof(buffer))
2343                return -E2BIG;
2344        if (copy_from_user(buffer, userbuf, nbytes))
2345                return -EFAULT;
2346
2347        buffer[nbytes] = 0;     /* nul-terminate */
2348        if (cft->write_u64) {
2349                u64 val = simple_strtoull(strstrip(buffer), &end, 0);
2350                if (*end)
2351                        return -EINVAL;
2352                retval = cft->write_u64(cgrp, cft, val);
2353        } else {
2354                s64 val = simple_strtoll(strstrip(buffer), &end, 0);
2355                if (*end)
2356                        return -EINVAL;
2357                retval = cft->write_s64(cgrp, cft, val);
2358        }
2359        if (!retval)
2360                retval = nbytes;
2361        return retval;
2362}
2363
2364static ssize_t cgroup_write_string(struct cgroup *cgrp, struct cftype *cft,
2365                                   struct file *file,
2366                                   const char __user *userbuf,
2367                                   size_t nbytes, loff_t *unused_ppos)
2368{
2369        char local_buffer[CGROUP_LOCAL_BUFFER_SIZE];
2370        int retval = 0;
2371        size_t max_bytes = cft->max_write_len;
2372        char *buffer = local_buffer;
2373
2374        if (!max_bytes)
2375                max_bytes = sizeof(local_buffer) - 1;
2376        if (nbytes >= max_bytes)
2377                return -E2BIG;
2378        /* Allocate a dynamic buffer if we need one */
2379        if (nbytes >= sizeof(local_buffer)) {
2380                buffer = kmalloc(nbytes + 1, GFP_KERNEL);
2381                if (buffer == NULL)
2382                        return -ENOMEM;
2383        }
2384        if (nbytes && copy_from_user(buffer, userbuf, nbytes)) {
2385                retval = -EFAULT;
2386                goto out;
2387        }
2388
2389        buffer[nbytes] = 0;     /* nul-terminate */
2390        retval = cft->write_string(cgrp, cft, strstrip(buffer));
2391        if (!retval)
2392                retval = nbytes;
2393out:
2394        if (buffer != local_buffer)
2395                kfree(buffer);
2396        return retval;
2397}
2398
2399static ssize_t cgroup_file_write(struct file *file, const char __user *buf,
2400                                                size_t nbytes, loff_t *ppos)
2401{
2402        struct cftype *cft = __d_cft(file->f_dentry);
2403        struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2404
2405        if (cgroup_is_removed(cgrp))
2406                return -ENODEV;
2407        if (cft->write)
2408                return cft->write(cgrp, cft, file, buf, nbytes, ppos);
2409        if (cft->write_u64 || cft->write_s64)
2410                return cgroup_write_X64(cgrp, cft, file, buf, nbytes, ppos);
2411        if (cft->write_string)
2412                return cgroup_write_string(cgrp, cft, file, buf, nbytes, ppos);
2413        if (cft->trigger) {
2414                int ret = cft->trigger(cgrp, (unsigned int)cft->private);
2415                return ret ? ret : nbytes;
2416        }
2417        return -EINVAL;
2418}
2419
2420static ssize_t cgroup_read_u64(struct cgroup *cgrp, struct cftype *cft,
2421                               struct file *file,
2422                               char __user *buf, size_t nbytes,
2423                               loff_t *ppos)
2424{
2425        char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2426        u64 val = cft->read_u64(cgrp, cft);
2427        int len = sprintf(tmp, "%llu\n", (unsigned long long) val);
2428
2429        return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
2430}
2431
2432static ssize_t cgroup_read_s64(struct cgroup *cgrp, struct cftype *cft,
2433                               struct file *file,
2434                               char __user *buf, size_t nbytes,
2435                               loff_t *ppos)
2436{
2437        char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2438        s64 val = cft->read_s64(cgrp, cft);
2439        int len = sprintf(tmp, "%lld\n", (long long) val);
2440
2441        return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
2442}
2443
2444static ssize_t cgroup_file_read(struct file *file, char __user *buf,
2445                                   size_t nbytes, loff_t *ppos)
2446{
2447        struct cftype *cft = __d_cft(file->f_dentry);
2448        struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2449
2450        if (cgroup_is_removed(cgrp))
2451                return -ENODEV;
2452
2453        if (cft->read)
2454                return cft->read(cgrp, cft, file, buf, nbytes, ppos);
2455        if (cft->read_u64)
2456                return cgroup_read_u64(cgrp, cft, file, buf, nbytes, ppos);
2457        if (cft->read_s64)
2458                return cgroup_read_s64(cgrp, cft, file, buf, nbytes, ppos);
2459        return -EINVAL;
2460}
2461
2462/*
2463 * seqfile ops/methods for returning structured data. Currently just
2464 * supports string->u64 maps, but can be extended in future.
2465 */
2466
2467struct cgroup_seqfile_state {
2468        struct cftype *cft;
2469        struct cgroup *cgroup;
2470};
2471
2472static int cgroup_map_add(struct cgroup_map_cb *cb, const char *key, u64 value)
2473{
2474        struct seq_file *sf = cb->state;
2475        return seq_printf(sf, "%s %llu\n", key, (unsigned long long)value);
2476}
2477
2478static int cgroup_seqfile_show(struct seq_file *m, void *arg)
2479{
2480        struct cgroup_seqfile_state *state = m->private;
2481        struct cftype *cft = state->cft;
2482        if (cft->read_map) {
2483                struct cgroup_map_cb cb = {
2484                        .fill = cgroup_map_add,
2485                        .state = m,
2486                };
2487                return cft->read_map(state->cgroup, cft, &cb);
2488        }
2489        return cft->read_seq_string(state->cgroup, cft, m);
2490}
2491
2492static int cgroup_seqfile_release(struct inode *inode, struct file *file)
2493{
2494        struct seq_file *seq = file->private_data;
2495        kfree(seq->private);
2496        return single_release(inode, file);
2497}
2498
2499static const struct file_operations cgroup_seqfile_operations = {
2500        .read = seq_read,
2501        .write = cgroup_file_write,
2502        .llseek = seq_lseek,
2503        .release = cgroup_seqfile_release,
2504};
2505
2506static int cgroup_file_open(struct inode *inode, struct file *file)
2507{
2508        int err;
2509        struct cftype *cft;
2510
2511        err = generic_file_open(inode, file);
2512        if (err)
2513                return err;
2514        cft = __d_cft(file->f_dentry);
2515
2516        if (cft->read_map || cft->read_seq_string) {
2517                struct cgroup_seqfile_state *state =
2518                        kzalloc(sizeof(*state), GFP_USER);
2519                if (!state)
2520                        return -ENOMEM;
2521                state->cft = cft;
2522                state->cgroup = __d_cgrp(file->f_dentry->d_parent);
2523                file->f_op = &cgroup_seqfile_operations;
2524                err = single_open(file, cgroup_seqfile_show, state);
2525                if (err < 0)
2526                        kfree(state);
2527        } else if (cft->open)
2528                err = cft->open(inode, file);
2529        else
2530                err = 0;
2531
2532        return err;
2533}
2534
2535static int cgroup_file_release(struct inode *inode, struct file *file)
2536{
2537        struct cftype *cft = __d_cft(file->f_dentry);
2538        if (cft->release)
2539                return cft->release(inode, file);
2540        return 0;
2541}
2542
2543/*
2544 * cgroup_rename - Only allow simple rename of directories in place.
2545 */
2546static int cgroup_rename(struct inode *old_dir, struct dentry *old_dentry,
2547                            struct inode *new_dir, struct dentry *new_dentry)
2548{
2549        if (!S_ISDIR(old_dentry->d_inode->i_mode))
2550                return -ENOTDIR;
2551        if (new_dentry->d_inode)
2552                return -EEXIST;
2553        if (old_dir != new_dir)
2554                return -EIO;
2555        return simple_rename(old_dir, old_dentry, new_dir, new_dentry);
2556}
2557
2558static const struct file_operations cgroup_file_operations = {
2559        .read = cgroup_file_read,
2560        .write = cgroup_file_write,
2561        .llseek = generic_file_llseek,
2562        .open = cgroup_file_open,
2563        .release = cgroup_file_release,
2564};
2565
2566static const struct inode_operations cgroup_dir_inode_operations = {
2567        .lookup = cgroup_lookup,
2568        .mkdir = cgroup_mkdir,
2569        .rmdir = cgroup_rmdir,
2570        .rename = cgroup_rename,
2571};
2572
2573static struct dentry *cgroup_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
2574{
2575        if (dentry->d_name.len > NAME_MAX)
2576                return ERR_PTR(-ENAMETOOLONG);
2577        d_add(dentry, NULL);
2578        return NULL;
2579}
2580
2581/*
2582 * Check if a file is a control file
2583 */
2584static inline struct cftype *__file_cft(struct file *file)
2585{
2586        if (file->f_dentry->d_inode->i_fop != &cgroup_file_operations)
2587                return ERR_PTR(-EINVAL);
2588        return __d_cft(file->f_dentry);
2589}
2590
2591static int cgroup_create_file(struct dentry *dentry, umode_t mode,
2592                                struct super_block *sb)
2593{
2594        struct inode *inode;
2595
2596        if (!dentry)
2597                return -ENOENT;
2598        if (dentry->d_inode)
2599                return -EEXIST;
2600
2601        inode = cgroup_new_inode(mode, sb);
2602        if (!inode)
2603                return -ENOMEM;
2604
2605        if (S_ISDIR(mode)) {
2606                inode->i_op = &cgroup_dir_inode_operations;
2607                inode->i_fop = &simple_dir_operations;
2608
2609                /* start off with i_nlink == 2 (for "." entry) */
2610                inc_nlink(inode);
2611
2612                /* start with the directory inode held, so that we can
2613                 * populate it without racing with another mkdir */
2614                mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
2615        } else if (S_ISREG(mode)) {
2616                inode->i_size = 0;
2617                inode->i_fop = &cgroup_file_operations;
2618        }
2619        d_instantiate(dentry, inode);
2620        dget(dentry);   /* Extra count - pin the dentry in core */
2621        return 0;
2622}
2623
2624/*
2625 * cgroup_create_dir - create a directory for an object.
2626 * @cgrp: the cgroup we create the directory for. It must have a valid
2627 *        ->parent field. And we are going to fill its ->dentry field.
2628 * @dentry: dentry of the new cgroup
2629 * @mode: mode to set on new directory.
2630 */
2631static int cgroup_create_dir(struct cgroup *cgrp, struct dentry *dentry,
2632                                umode_t mode)
2633{
2634        struct dentry *parent;
2635        int error = 0;
2636
2637        parent = cgrp->parent->dentry;
2638        error = cgroup_create_file(dentry, S_IFDIR | mode, cgrp->root->sb);
2639        if (!error) {
2640                dentry->d_fsdata = cgrp;
2641                inc_nlink(parent->d_inode);
2642                rcu_assign_pointer(cgrp->dentry, dentry);
2643                dget(dentry);
2644        }
2645        dput(dentry);
2646
2647        return error;
2648}
2649
2650/**
2651 * cgroup_file_mode - deduce file mode of a control file
2652 * @cft: the control file in question
2653 *
2654 * returns cft->mode if ->mode is not 0
2655 * returns S_IRUGO|S_IWUSR if it has both a read and a write handler
2656 * returns S_IRUGO if it has only a read handler
2657 * returns S_IWUSR if it has only a write hander
2658 */
2659static umode_t cgroup_file_mode(const struct cftype *cft)
2660{
2661        umode_t mode = 0;
2662
2663        if (cft->mode)
2664                return cft->mode;
2665
2666        if (cft->read || cft->read_u64 || cft->read_s64 ||
2667            cft->read_map || cft->read_seq_string)
2668                mode |= S_IRUGO;
2669
2670        if (cft->write || cft->write_u64 || cft->write_s64 ||
2671            cft->write_string || cft->trigger)
2672                mode |= S_IWUSR;
2673
2674        return mode;
2675}
2676
2677static int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,
2678                           const struct cftype *cft)
2679{
2680        struct dentry *dir = cgrp->dentry;
2681        struct cgroup *parent = __d_cgrp(dir);
2682        struct dentry *dentry;
2683        struct cfent *cfe;
2684        int error;
2685        umode_t mode;
2686        char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
2687
2688        /* does @cft->flags tell us to skip creation on @cgrp? */
2689        if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgrp->parent)
2690                return 0;
2691        if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgrp->parent)
2692                return 0;
2693
2694        if (subsys && !test_bit(ROOT_NOPREFIX, &cgrp->root->flags)) {
2695                strcpy(name, subsys->name);
2696                strcat(name, ".");
2697        }
2698        strcat(name, cft->name);
2699
2700        BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));
2701
2702        cfe = kzalloc(sizeof(*cfe), GFP_KERNEL);
2703        if (!cfe)
2704                return -ENOMEM;
2705
2706        dentry = lookup_one_len(name, dir, strlen(name));
2707        if (IS_ERR(dentry)) {
2708                error = PTR_ERR(dentry);
2709                goto out;
2710        }
2711
2712        mode = cgroup_file_mode(cft);
2713        error = cgroup_create_file(dentry, mode | S_IFREG, cgrp->root->sb);
2714        if (!error) {
2715                cfe->type = (void *)cft;
2716                cfe->dentry = dentry;
2717                dentry->d_fsdata = cfe;
2718                list_add_tail(&cfe->node, &parent->files);
2719                cfe = NULL;
2720        }
2721        dput(dentry);
2722out:
2723        kfree(cfe);
2724        return error;
2725}
2726
2727static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
2728                              const struct cftype cfts[], bool is_add)
2729{
2730        const struct cftype *cft;
2731        int err, ret = 0;
2732
2733        for (cft = cfts; cft->name[0] != '\0'; cft++) {
2734                if (is_add)
2735                        err = cgroup_add_file(cgrp, subsys, cft);
2736                else
2737                        err = cgroup_rm_file(cgrp, cft);
2738                if (err) {
2739                        pr_warning("cgroup_addrm_files: failed to %s %s, err=%d\n",
2740                                   is_add ? "add" : "remove", cft->name, err);
2741                        ret = err;
2742                }
2743        }
2744        return ret;
2745}
2746
2747static DEFINE_MUTEX(cgroup_cft_mutex);
2748
2749static void cgroup_cfts_prepare(void)
2750        __acquires(&cgroup_cft_mutex) __acquires(&cgroup_mutex)
2751{
2752        /*
2753         * Thanks to the entanglement with vfs inode locking, we can't walk
2754         * the existing cgroups under cgroup_mutex and create files.
2755         * Instead, we increment reference on all cgroups and build list of
2756         * them using @cgrp->cft_q_node.  Grab cgroup_cft_mutex to ensure
2757         * exclusive access to the field.
2758         */
2759        mutex_lock(&cgroup_cft_mutex);
2760        mutex_lock(&cgroup_mutex);
2761}
2762
2763static void cgroup_cfts_commit(struct cgroup_subsys *ss,
2764                               const struct cftype *cfts, bool is_add)
2765        __releases(&cgroup_mutex) __releases(&cgroup_cft_mutex)
2766{
2767        LIST_HEAD(pending);
2768        struct cgroup *cgrp, *n;
2769
2770        /* %NULL @cfts indicates abort and don't bother if @ss isn't attached */
2771        if (cfts && ss->root != &rootnode) {
2772                list_for_each_entry(cgrp, &ss->root->allcg_list, allcg_node) {
2773                        dget(cgrp->dentry);
2774                        list_add_tail(&cgrp->cft_q_node, &pending);
2775                }
2776        }
2777
2778        mutex_unlock(&cgroup_mutex);
2779
2780        /*
2781         * All new cgroups will see @cfts update on @ss->cftsets.  Add/rm
2782         * files for all cgroups which were created before.
2783         */
2784        list_for_each_entry_safe(cgrp, n, &pending, cft_q_node) {
2785                struct inode *inode = cgrp->dentry->d_inode;
2786
2787                mutex_lock(&inode->i_mutex);
2788                mutex_lock(&cgroup_mutex);
2789                if (!cgroup_is_removed(cgrp))
2790                        cgroup_addrm_files(cgrp, ss, cfts, is_add);
2791                mutex_unlock(&cgroup_mutex);
2792                mutex_unlock(&inode->i_mutex);
2793
2794                list_del_init(&cgrp->cft_q_node);
2795                dput(cgrp->dentry);
2796        }
2797
2798        mutex_unlock(&cgroup_cft_mutex);
2799}
2800
2801/**
2802 * cgroup_add_cftypes - add an array of cftypes to a subsystem
2803 * @ss: target cgroup subsystem
2804 * @cfts: zero-length name terminated array of cftypes
2805 *
2806 * Register @cfts to @ss.  Files described by @cfts are created for all
2807 * existing cgroups to which @ss is attached and all future cgroups will
2808 * have them too.  This function can be called anytime whether @ss is
2809 * attached or not.
2810 *
2811 * Returns 0 on successful registration, -errno on failure.  Note that this
2812 * function currently returns 0 as long as @cfts registration is successful
2813 * even if some file creation attempts on existing cgroups fail.
2814 */
2815int cgroup_add_cftypes(struct cgroup_subsys *ss, const struct cftype *cfts)
2816{
2817        struct cftype_set *set;
2818
2819        set = kzalloc(sizeof(*set), GFP_KERNEL);
2820        if (!set)
2821                return -ENOMEM;
2822
2823        cgroup_cfts_prepare();
2824        set->cfts = cfts;
2825        list_add_tail(&set->node, &ss->cftsets);
2826        cgroup_cfts_commit(ss, cfts, true);
2827
2828        return 0;
2829}
2830EXPORT_SYMBOL_GPL(cgroup_add_cftypes);
2831
2832/**
2833 * cgroup_rm_cftypes - remove an array of cftypes from a subsystem
2834 * @ss: target cgroup subsystem
2835 * @cfts: zero-length name terminated array of cftypes
2836 *
2837 * Unregister @cfts from @ss.  Files described by @cfts are removed from
2838 * all existing cgroups to which @ss is attached and all future cgroups
2839 * won't have them either.  This function can be called anytime whether @ss
2840 * is attached or not.
2841 *
2842 * Returns 0 on successful unregistration, -ENOENT if @cfts is not
2843 * registered with @ss.
2844 */
2845int cgroup_rm_cftypes(struct cgroup_subsys *ss, const struct cftype *cfts)
2846{
2847        struct cftype_set *set;
2848
2849        cgroup_cfts_prepare();
2850
2851        list_for_each_entry(set, &ss->cftsets, node) {
2852                if (set->cfts == cfts) {
2853                        list_del_init(&set->node);
2854                        cgroup_cfts_commit(ss, cfts, false);
2855                        return 0;
2856                }
2857        }
2858
2859        cgroup_cfts_commit(ss, NULL, false);
2860        return -ENOENT;
2861}
2862
2863/**
2864 * cgroup_task_count - count the number of tasks in a cgroup.
2865 * @cgrp: the cgroup in question
2866 *
2867 * Return the number of tasks in the cgroup.
2868 */
2869int cgroup_task_count(const struct cgroup *cgrp)
2870{
2871        int count = 0;
2872        struct cg_cgroup_link *link;
2873
2874        read_lock(&css_set_lock);
2875        list_for_each_entry(link, &cgrp->css_sets, cgrp_link_list) {
2876                count += atomic_read(&link->cg->refcount);
2877        }
2878        read_unlock(&css_set_lock);
2879        return count;
2880}
2881
2882/*
2883 * Advance a list_head iterator.  The iterator should be positioned at
2884 * the start of a css_set
2885 */
2886static void cgroup_advance_iter(struct cgroup *cgrp,
2887                                struct cgroup_iter *it)
2888{
2889        struct list_head *l = it->cg_link;
2890        struct cg_cgroup_link *link;
2891        struct css_set *cg;
2892
2893        /* Advance to the next non-empty css_set */
2894        do {
2895                l = l->next;
2896                if (l == &cgrp->css_sets) {
2897                        it->cg_link = NULL;
2898                        return;
2899                }
2900                link = list_entry(l, struct cg_cgroup_link, cgrp_link_list);
2901                cg = link->cg;
2902        } while (list_empty(&cg->tasks));
2903        it->cg_link = l;
2904        it->task = cg->tasks.next;
2905}
2906
2907/*
2908 * To reduce the fork() overhead for systems that are not actually
2909 * using their cgroups capability, we don't maintain the lists running
2910 * through each css_set to its tasks until we see the list actually
2911 * used - in other words after the first call to cgroup_iter_start().
2912 */
2913static void cgroup_enable_task_cg_lists(void)
2914{
2915        struct task_struct *p, *g;
2916        write_lock(&css_set_lock);
2917        use_task_css_set_links = 1;
2918        /*
2919         * We need tasklist_lock because RCU is not safe against
2920         * while_each_thread(). Besides, a forking task that has passed
2921         * cgroup_post_fork() without seeing use_task_css_set_links = 1
2922         * is not guaranteed to have its child immediately visible in the
2923         * tasklist if we walk through it with RCU.
2924         */
2925        read_lock(&tasklist_lock);
2926        do_each_thread(g, p) {
2927                task_lock(p);
2928                /*
2929                 * We should check if the process is exiting, otherwise
2930                 * it will race with cgroup_exit() in that the list
2931                 * entry won't be deleted though the process has exited.
2932                 */
2933                if (!(p->flags & PF_EXITING) && list_empty(&p->cg_list))
2934                        list_add(&p->cg_list, &p->cgroups->tasks);
2935                task_unlock(p);
2936        } while_each_thread(g, p);
2937        read_unlock(&tasklist_lock);
2938        write_unlock(&css_set_lock);
2939}
2940
2941void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it)
2942        __acquires(css_set_lock)
2943{
2944        /*
2945         * The first time anyone tries to iterate across a cgroup,
2946         * we need to enable the list linking each css_set to its
2947         * tasks, and fix up all existing tasks.
2948         */
2949        if (!use_task_css_set_links)
2950                cgroup_enable_task_cg_lists();
2951
2952        read_lock(&css_set_lock);
2953        it->cg_link = &cgrp->css_sets;
2954        cgroup_advance_iter(cgrp, it);
2955}
2956
2957struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
2958                                        struct cgroup_iter *it)
2959{
2960        struct task_struct *res;
2961        struct list_head *l = it->task;
2962        struct cg_cgroup_link *link;
2963
2964        /* If the iterator cg is NULL, we have no tasks */
2965        if (!it->cg_link)
2966                return NULL;
2967        res = list_entry(l, struct task_struct, cg_list);
2968        /* Advance iterator to find next entry */
2969        l = l->next;
2970        link = list_entry(it->cg_link, struct cg_cgroup_link, cgrp_link_list);
2971        if (l == &link->cg->tasks) {
2972                /* We reached the end of this task list - move on to
2973                 * the next cg_cgroup_link */
2974                cgroup_advance_iter(cgrp, it);
2975        } else {
2976                it->task = l;
2977        }
2978        return res;
2979}
2980
2981void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it)
2982        __releases(css_set_lock)
2983{
2984        read_unlock(&css_set_lock);
2985}
2986
2987static inline int started_after_time(struct task_struct *t1,
2988                                     struct timespec *time,
2989                                     struct task_struct *t2)
2990{
2991        int start_diff = timespec_compare(&t1->start_time, time);
2992        if (start_diff > 0) {
2993                return 1;
2994        } else if (start_diff < 0) {
2995                return 0;
2996        } else {
2997                /*
2998                 * Arbitrarily, if two processes started at the same
2999                 * time, we'll say that the lower pointer value
3000                 * started first. Note that t2 may have exited by now
3001                 * so this may not be a valid pointer any longer, but
3002                 * that's fine - it still serves to distinguish
3003                 * between two tasks started (effectively) simultaneously.
3004                 */
3005                return t1 > t2;
3006        }
3007}
3008
3009/*
3010 * This function is a callback from heap_insert() and is used to order
3011 * the heap.
3012 * In this case we order the heap in descending task start time.
3013 */
3014static inline int started_after(void *p1, void *p2)
3015{
3016        struct task_struct *t1 = p1;
3017        struct task_struct *t2 = p2;
3018        return started_after_time(t1, &t2->start_time, t2);
3019}
3020
3021/**
3022 * cgroup_scan_tasks - iterate though all the tasks in a cgroup
3023 * @scan: struct cgroup_scanner containing arguments for the scan
3024 *
3025 * Arguments include pointers to callback functions test_task() and
3026 * process_task().
3027 * Iterate through all the tasks in a cgroup, calling test_task() for each,
3028 * and if it returns true, call process_task() for it also.
3029 * The test_task pointer may be NULL, meaning always true (select all tasks).
3030 * Effectively duplicates cgroup_iter_{start,next,end}()
3031 * but does not lock css_set_lock for the call to process_task().
3032 * The struct cgroup_scanner may be embedded in any structure of the caller's
3033 * creation.
3034 * It is guaranteed that process_task() will act on every task that
3035 * is a member of the cgroup for the duration of this call. This
3036 * function may or may not call process_task() for tasks that exit
3037 * or move to a different cgroup during the call, or are forked or
3038 * move into the cgroup during the call.
3039 *
3040 * Note that test_task() may be called with locks held, and may in some
3041 * situations be called multiple times for the same task, so it should
3042 * be cheap.
3043 * If the heap pointer in the struct cgroup_scanner is non-NULL, a heap has been
3044 * pre-allocated and will be used for heap operations (and its "gt" member will
3045 * be overwritten), else a temporary heap will be used (allocation of which
3046 * may cause this function to fail).
3047 */
3048int cgroup_scan_tasks(struct cgroup_scanner *scan)
3049{
3050        int retval, i;
3051        struct cgroup_iter it;
3052        struct task_struct *p, *dropped;
3053        /* Never dereference latest_task, since it's not refcounted */
3054        struct task_struct *latest_task = NULL;
3055        struct ptr_heap tmp_heap;
3056        struct ptr_heap *heap;
3057        struct timespec latest_time = { 0, 0 };
3058
3059        if (scan->heap) {
3060                /* The caller supplied our heap and pre-allocated its memory */
3061                heap = scan->heap;
3062                heap->gt = &started_after;
3063        } else {
3064                /* We need to allocate our own heap memory */
3065                heap = &tmp_heap;
3066                retval = heap_init(heap, PAGE_SIZE, GFP_KERNEL, &started_after);
3067                if (retval)
3068                        /* cannot allocate the heap */
3069                        return retval;
3070        }
3071
3072 again:
3073        /*
3074         * Scan tasks in the cgroup, using the scanner's "test_task" callback
3075         * to determine which are of interest, and using the scanner's
3076         * "process_task" callback to process any of them that need an update.
3077         * Since we don't want to hold any locks during the task updates,
3078         * gather tasks to be processed in a heap structure.
3079         * The heap is sorted by descending task start time.
3080         * If the statically-sized heap fills up, we overflow tasks that
3081         * started later, and in future iterations only consider tasks that
3082         * started after the latest task in the previous pass. This
3083         * guarantees forward progress and that we don't miss any tasks.
3084         */
3085        heap->size = 0;
3086        cgroup_iter_start(scan->cg, &it);
3087        while ((p = cgroup_iter_next(scan->cg, &it))) {
3088                /*
3089                 * Only affect tasks that qualify per the caller's callback,
3090                 * if he provided one
3091                 */
3092                if (scan->test_task && !scan->test_task(p, scan))
3093                        continue;
3094                /*
3095                 * Only process tasks that started after the last task
3096                 * we processed
3097                 */
3098                if (!started_after_time(p, &latest_time, latest_task))
3099                        continue;
3100                dropped = heap_insert(heap, p);
3101                if (dropped == NULL) {
3102                        /*
3103                         * The new task was inserted; the heap wasn't
3104                         * previously full
3105                         */
3106                        get_task_struct(p);
3107                } else if (dropped != p) {
3108                        /*
3109                         * The new task was inserted, and pushed out a
3110                         * different task
3111                         */
3112                        get_task_struct(p);
3113                        put_task_struct(dropped);
3114                }
3115                /*
3116                 * Else the new task was newer than anything already in
3117                 * the heap and wasn't inserted
3118                 */
3119        }
3120        cgroup_iter_end(scan->cg, &it);
3121
3122        if (heap->size) {
3123                for (i = 0; i < heap->size; i++) {
3124                        struct task_struct *q = heap->ptrs[i];
3125                        if (i == 0) {
3126                                latest_time = q->start_time;
3127                                latest_task = q;
3128                        }
3129                        /* Process the task per the caller's callback */
3130                        scan->process_task(q, scan);
3131                        put_task_struct(q);
3132                }
3133                /*
3134                 * If we had to process any tasks at all, scan again
3135                 * in case some of them were in the middle of forking
3136                 * children that didn't get processed.
3137                 * Not the most efficient way to do it, but it avoids
3138                 * having to take callback_mutex in the fork path
3139                 */
3140                goto again;
3141        }
3142        if (heap == &tmp_heap)
3143                heap_free(&tmp_heap);
3144        return 0;
3145}
3146
3147/*
3148 * Stuff for reading the 'tasks'/'procs' files.
3149 *
3150 * Reading this file can return large amounts of data if a cgroup has
3151 * *lots* of attached tasks. So it may need several calls to read(),
3152 * but we cannot guarantee that the information we produce is correct
3153 * unless we produce it entirely atomically.
3154 *
3155 */
3156
3157/* which pidlist file are we talking about? */
3158enum cgroup_filetype {
3159        CGROUP_FILE_PROCS,
3160        CGROUP_FILE_TASKS,
3161};
3162
3163/*
3164 * A pidlist is a list of pids that virtually represents the contents of one
3165 * of the cgroup files ("procs" or "tasks"). We keep a list of such pidlists,
3166 * a pair (one each for procs, tasks) for each pid namespace that's relevant
3167 * to the cgroup.
3168 */
3169struct cgroup_pidlist {
3170        /*
3171         * used to find which pidlist is wanted. doesn't change as long as
3172         * this particular list stays in the list.
3173        */
3174        struct { enum cgroup_filetype type; struct pid_namespace *ns; } key;
3175        /* array of xids */
3176        pid_t *list;
3177        /* how many elements the above list has */
3178        int length;
3179        /* how many files are using the current array */
3180        int use_count;
3181        /* each of these stored in a list by its cgroup */
3182        struct list_head links;
3183        /* pointer to the cgroup we belong to, for list removal purposes */
3184        struct cgroup *owner;
3185        /* protects the other fields */
3186        struct rw_semaphore mutex;
3187};
3188
3189/*
3190 * The following two functions "fix" the issue where there are more pids
3191 * than kmalloc will give memory for; in such cases, we use vmalloc/vfree.
3192 * TODO: replace with a kernel-wide solution to this problem
3193 */
3194#define PIDLIST_TOO_LARGE(c) ((c) * sizeof(pid_t) > (PAGE_SIZE * 2))
3195static void *pidlist_allocate(int count)
3196{
3197        if (PIDLIST_TOO_LARGE(count))
3198                return vmalloc(count * sizeof(pid_t));
3199        else
3200                return kmalloc(count * sizeof(pid_t), GFP_KERNEL);
3201}
3202static void pidlist_free(void *p)
3203{
3204        if (is_vmalloc_addr(p))
3205                vfree(p);
3206        else
3207                kfree(p);
3208}
3209static void *pidlist_resize(void *p, int newcount)
3210{
3211        void *newlist;
3212        /* note: if new alloc fails, old p will still be valid either way */
3213        if (is_vmalloc_addr(p)) {
3214                newlist = vmalloc(newcount * sizeof(pid_t));
3215                if (!newlist)
3216                        return NULL;
3217                memcpy(newlist, p, newcount * sizeof(pid_t));
3218                vfree(p);
3219        } else {
3220                newlist = krealloc(p, newcount * sizeof(pid_t), GFP_KERNEL);
3221        }
3222        return newlist;
3223}
3224
3225/*
3226 * pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
3227 * If the new stripped list is sufficiently smaller and there's enough memory
3228 * to allocate a new buffer, will let go of the unneeded memory. Returns the
3229 * number of unique elements.
3230 */
3231/* is the size difference enough that we should re-allocate the array? */
3232#define PIDLIST_REALLOC_DIFFERENCE(old, new) ((old) - PAGE_SIZE >= (new))
3233static int pidlist_uniq(pid_t **p, int length)
3234{
3235        int src, dest = 1;
3236        pid_t *list = *p;
3237        pid_t *newlist;
3238
3239        /*
3240         * we presume the 0th element is unique, so i starts at 1. trivial
3241         * edge cases first; no work needs to be done for either
3242         */
3243        if (length == 0 || length == 1)
3244                return length;
3245        /* src and dest walk down the list; dest counts unique elements */
3246        for (src = 1; src < length; src++) {
3247                /* find next unique element */
3248                while (list[src] == list[src-1]) {
3249                        src++;
3250                        if (src == length)
3251                                goto after;
3252                }
3253                /* dest always points to where the next unique element goes */
3254                list[dest] = list[src];
3255                dest++;
3256        }
3257after:
3258        /*
3259         * if the length difference is large enough, we want to allocate a
3260         * smaller buffer to save memory. if this fails due to out of memory,
3261         * we'll just stay with what we've got.
3262         */
3263        if (PIDLIST_REALLOC_DIFFERENCE(length, dest)) {
3264                newlist = pidlist_resize(list, dest);
3265                if (newlist)
3266                        *p = newlist;
3267        }
3268        return dest;
3269}
3270
3271static int cmppid(const void *a, const void *b)
3272{
3273        return *(pid_t *)a - *(pid_t *)b;
3274}
3275
3276/*
3277 * find the appropriate pidlist for our purpose (given procs vs tasks)
3278 * returns with the lock on that pidlist already held, and takes care
3279 * of the use count, or returns NULL with no locks held if we're out of
3280 * memory.
3281 */
3282static struct cgroup_pidlist *cgroup_pidlist_find(struct cgroup *cgrp,
3283                                                  enum cgroup_filetype type)
3284{
3285        struct cgroup_pidlist *l;
3286        /* don't need task_nsproxy() if we're looking at ourself */
3287        struct pid_namespace *ns = current->nsproxy->pid_ns;
3288
3289        /*
3290         * We can't drop the pidlist_mutex before taking the l->mutex in case
3291         * the last ref-holder is trying to remove l from the list at the same
3292         * time. Holding the pidlist_mutex precludes somebody taking whichever
3293         * list we find out from under us - compare release_pid_array().
3294         */
3295        mutex_lock(&cgrp->pidlist_mutex);
3296        list_for_each_entry(l, &cgrp->pidlists, links) {
3297                if (l->key.type == type && l->key.ns == ns) {
3298                        /* make sure l doesn't vanish out from under us */
3299                        down_write(&l->mutex);
3300                        mutex_unlock(&cgrp->pidlist_mutex);
3301                        return l;
3302                }
3303        }
3304        /* entry not found; create a new one */
3305        l = kmalloc(sizeof(struct cgroup_pidlist), GFP_KERNEL);
3306        if (!l) {
3307                mutex_unlock(&cgrp->pidlist_mutex);
3308                return l;
3309        }
3310        init_rwsem(&l->mutex);
3311        down_write(&l->mutex);
3312        l->key.type = type;
3313        l->key.ns = get_pid_ns(ns);
3314        l->use_count = 0; /* don't increment here */
3315        l->list = NULL;
3316        l->owner = cgrp;
3317        list_add(&l->links, &cgrp->pidlists);
3318        mutex_unlock(&cgrp->pidlist_mutex);
3319        return l;
3320}
3321
3322/*
3323 * Load a cgroup's pidarray with either procs' tgids or tasks' pids
3324 */
3325static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
3326                              struct cgroup_pidlist **lp)
3327{
3328        pid_t *array;
3329        int length;
3330        int pid, n = 0; /* used for populating the array */
3331        struct cgroup_iter it;
3332        struct task_struct *tsk;
3333        struct cgroup_pidlist *l;
3334
3335        /*
3336         * If cgroup gets more users after we read count, we won't have
3337         * enough space - tough.  This race is indistinguishable to the
3338         * caller from the case that the additional cgroup users didn't
3339         * show up until sometime later on.
3340         */
3341        length = cgroup_task_count(cgrp);
3342        array = pidlist_allocate(length);
3343        if (!array)
3344                return -ENOMEM;
3345        /* now, populate the array */
3346        cgroup_iter_start(cgrp, &it);
3347        while ((tsk = cgroup_iter_next(cgrp, &it))) {
3348                if (unlikely(n == length))
3349                        break;
3350                /* get tgid or pid for procs or tasks file respectively */
3351                if (type == CGROUP_FILE_PROCS)
3352                        pid = task_tgid_vnr(tsk);
3353                else
3354                        pid = task_pid_vnr(tsk);
3355                if (pid > 0) /* make sure to only use valid results */
3356                        array[n++] = pid;
3357        }
3358        cgroup_iter_end(cgrp, &it);
3359        length = n;
3360        /* now sort & (if procs) strip out duplicates */
3361        sort(array, length, sizeof(pid_t), cmppid, NULL);
3362        if (type == CGROUP_FILE_PROCS)
3363                length = pidlist_uniq(&array, length);
3364        l = cgroup_pidlist_find(cgrp, type);
3365        if (!l) {
3366                pidlist_free(array);
3367                return -ENOMEM;
3368        }
3369        /* store array, freeing old if necessary - lock already held */
3370        pidlist_free(l->list);
3371        l->list = array;
3372        l->length = length;
3373        l->use_count++;
3374        up_write(&l->mutex);
3375        *lp = l;
3376        return 0;
3377}
3378
3379/**
3380 * cgroupstats_build - build and fill cgroupstats
3381 * @stats: cgroupstats to fill information into
3382 * @dentry: A dentry entry belonging to the cgroup for which stats have
3383 * been requested.
3384 *
3385 * Build and fill cgroupstats so that taskstats can export it to user
3386 * space.
3387 */
3388int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
3389{
3390        int ret = -EINVAL;
3391        struct cgroup *cgrp;
3392        struct cgroup_iter it;
3393        struct task_struct *tsk;
3394
3395        /*
3396         * Validate dentry by checking the superblock operations,
3397         * and make sure it's a directory.
3398         */
3399        if (dentry->d_sb->s_op != &cgroup_ops ||
3400            !S_ISDIR(dentry->d_inode->i_mode))
3401                 goto err;
3402
3403        ret = 0;
3404        cgrp = dentry->d_fsdata;
3405
3406        cgroup_iter_start(cgrp, &it);
3407        while ((tsk = cgroup_iter_next(cgrp, &it))) {
3408                switch (tsk->state) {
3409                case TASK_RUNNING:
3410                        stats->nr_running++;
3411                        break;
3412                case TASK_INTERRUPTIBLE:
3413                        stats->nr_sleeping++;
3414                        break;
3415                case TASK_UNINTERRUPTIBLE:
3416                        stats->nr_uninterruptible++;
3417                        break;
3418                case TASK_STOPPED:
3419                        stats->nr_stopped++;
3420                        break;
3421                default:
3422                        if (delayacct_is_task_waiting_on_io(tsk))
3423                                stats->nr_io_wait++;
3424                        break;
3425                }
3426        }
3427        cgroup_iter_end(cgrp, &it);
3428
3429err:
3430        return ret;
3431}
3432
3433
3434/*
3435 * seq_file methods for the tasks/procs files. The seq_file position is the
3436 * next pid to display; the seq_file iterator is a pointer to the pid
3437 * in the cgroup->l->list array.
3438 */
3439
3440static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
3441{
3442        /*
3443         * Initially we receive a position value that corresponds to
3444         * one more than the last pid shown (or 0 on the first call or
3445         * after a seek to the start). Use a binary-search to find the
3446         * next pid to display, if any
3447         */
3448        struct cgroup_pidlist *l = s->private;
3449        int index = 0, pid = *pos;
3450        int *iter;
3451
3452        down_read(&l->mutex);
3453        if (pid) {
3454                int end = l->length;
3455
3456                while (index < end) {
3457                        int mid = (index + end) / 2;
3458                        if (l->list[mid] == pid) {
3459                                index = mid;
3460                                break;
3461                        } else if (l->list[mid] <= pid)
3462                                index = mid + 1;
3463                        else
3464                                end = mid;
3465                }
3466        }
3467        /* If we're off the end of the array, we're done */
3468        if (index >= l->length)
3469                return NULL;
3470        /* Update the abstract position to be the actual pid that we found */
3471        iter = l->list + index;
3472        *pos = *iter;
3473        return iter;
3474}
3475
3476static void cgroup_pidlist_stop(struct seq_file *s, void *v)
3477{
3478        struct cgroup_pidlist *l = s->private;
3479        up_read(&l->mutex);
3480}
3481
3482static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
3483{
3484        struct cgroup_pidlist *l = s->private;
3485        pid_t *p = v;
3486        pid_t *end = l->list + l->length;
3487        /*
3488         * Advance to the next pid in the array. If this goes off the
3489         * end, we're done
3490         */
3491        p++;
3492        if (p >= end) {
3493                return NULL;
3494        } else {
3495                *pos = *p;
3496                return p;
3497        }
3498}
3499
3500static int cgroup_pidlist_show(struct seq_file *s, void *v)
3501{
3502        return seq_printf(s, "%d\n", *(int *)v);
3503}
3504
3505/*
3506 * seq_operations functions for iterating on pidlists through seq_file -
3507 * independent of whether it's tasks or procs
3508 */
3509static const struct seq_operations cgroup_pidlist_seq_operations = {
3510        .start = cgroup_pidlist_start,
3511        .stop = cgroup_pidlist_stop,
3512        .next = cgroup_pidlist_next,
3513        .show = cgroup_pidlist_show,
3514};
3515
3516static void cgroup_release_pid_array(struct cgroup_pidlist *l)
3517{
3518        /*
3519         * the case where we're the last user of this particular pidlist will
3520         * have us remove it from the cgroup's list, which entails taking the
3521         * mutex. since in pidlist_find the pidlist->lock depends on cgroup->
3522         * pidlist_mutex, we have to take pidlist_mutex first.
3523         */
3524        mutex_lock(&l->owner->pidlist_mutex);
3525        down_write(&l->mutex);
3526        BUG_ON(!l->use_count);
3527        if (!--l->use_count) {
3528                /* we're the last user if refcount is 0; remove and free */
3529                list_del(&l->links);
3530                mutex_unlock(&l->owner->pidlist_mutex);
3531                pidlist_free(l->list);
3532                put_pid_ns(l->key.ns);
3533                up_write(&l->mutex);
3534                kfree(l);
3535                return;
3536        }
3537        mutex_unlock(&l->owner->pidlist_mutex);
3538        up_write(&l->mutex);
3539}
3540
3541static int cgroup_pidlist_release(struct inode *inode, struct file *file)
3542{
3543        struct cgroup_pidlist *l;
3544        if (!(file->f_mode & FMODE_READ))
3545                return 0;
3546        /*
3547         * the seq_file will only be initialized if the file was opened for
3548         * reading; hence we check if it's not null only in that case.
3549         */
3550        l = ((struct seq_file *)file->private_data)->private;
3551        cgroup_release_pid_array(l);
3552        return seq_release(inode, file);
3553}
3554
3555static const struct file_operations cgroup_pidlist_operations = {
3556        .read = seq_read,
3557        .llseek = seq_lseek,
3558        .write = cgroup_file_write,
3559        .release = cgroup_pidlist_release,
3560};
3561
3562/*
3563 * The following functions handle opens on a file that displays a pidlist
3564 * (tasks or procs). Prepare an array of the process/thread IDs of whoever's
3565 * in the cgroup.
3566 */
3567/* helper function for the two below it */
3568static int cgroup_pidlist_open(struct file *file, enum cgroup_filetype type)
3569{
3570        struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
3571        struct cgroup_pidlist *l;
3572        int retval;
3573
3574        /* Nothing to do for write-only files */
3575        if (!(file->f_mode & FMODE_READ))
3576                return 0;
3577
3578        /* have the array populated */
3579        retval = pidlist_array_load(cgrp, type, &l);
3580        if (retval)
3581                return retval;
3582        /* configure file information */
3583        file->f_op = &cgroup_pidlist_operations;
3584
3585        retval = seq_open(file, &cgroup_pidlist_seq_operations);
3586        if (retval) {
3587                cgroup_release_pid_array(l);
3588                return retval;
3589        }
3590        ((struct seq_file *)file->private_data)->private = l;
3591        return 0;
3592}
3593static int cgroup_tasks_open(struct inode *unused, struct file *file)
3594{
3595        return cgroup_pidlist_open(file, CGROUP_FILE_TASKS);
3596}
3597static int cgroup_procs_open(struct inode *unused, struct file *file)
3598{
3599        return cgroup_pidlist_open(file, CGROUP_FILE_PROCS);
3600}
3601
3602static u64 cgroup_read_notify_on_release(struct cgroup *cgrp,
3603                                            struct cftype *cft)
3604{
3605        return notify_on_release(cgrp);
3606}
3607
3608static int cgroup_write_notify_on_release(struct cgroup *cgrp,
3609                                          struct cftype *cft,
3610                                          u64 val)
3611{
3612        clear_bit(CGRP_RELEASABLE, &cgrp->flags);
3613        if (val)
3614                set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
3615        else
3616                clear_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
3617        return 0;
3618}
3619
3620/*
3621 * Unregister event and free resources.
3622 *
3623 * Gets called from workqueue.
3624 */
3625static void cgroup_event_remove(struct work_struct *work)
3626{
3627        struct cgroup_event *event = container_of(work, struct cgroup_event,
3628                        remove);
3629        struct cgroup *cgrp = event->cgrp;
3630
3631        event->cft->unregister_event(cgrp, event->cft, event->eventfd);
3632
3633        eventfd_ctx_put(event->eventfd);
3634        kfree(event);
3635        dput(cgrp->dentry);
3636}
3637
3638/*
3639 * Gets called on POLLHUP on eventfd when user closes it.
3640 *
3641 * Called with wqh->lock held and interrupts disabled.
3642 */
3643static int cgroup_event_wake(wait_queue_t *wait, unsigned mode,
3644                int sync, void *key)
3645{
3646        struct cgroup_event *event = container_of(wait,
3647                        struct cgroup_event, wait);
3648        struct cgroup *cgrp = event->cgrp;
3649        unsigned long flags = (unsigned long)key;
3650
3651        if (flags & POLLHUP) {
3652                __remove_wait_queue(event->wqh, &event->wait);
3653                spin_lock(&cgrp->event_list_lock);
3654                list_del(&event->list);
3655                spin_unlock(&cgrp->event_list_lock);
3656                /*
3657                 * We are in atomic context, but cgroup_event_remove() may
3658                 * sleep, so we have to call it in workqueue.
3659                 */
3660                schedule_work(&event->remove);
3661        }
3662
3663        return 0;
3664}
3665
3666static void cgroup_event_ptable_queue_proc(struct file *file,
3667                wait_queue_head_t *wqh, poll_table *pt)
3668{
3669        struct cgroup_event *event = container_of(pt,
3670                        struct cgroup_event, pt);
3671
3672        event->wqh = wqh;
3673        add_wait_queue(wqh, &event->wait);
3674}
3675
3676/*
3677 * Parse input and register new cgroup event handler.
3678 *
3679 * Input must be in format '<event_fd> <control_fd> <args>'.
3680 * Interpretation of args is defined by control file implementation.
3681 */
3682static int cgroup_write_event_control(struct cgroup *cgrp, struct cftype *cft,
3683                                      const char *buffer)
3684{
3685        struct cgroup_event *event = NULL;
3686        unsigned int efd, cfd;
3687        struct file *efile = NULL;
3688        struct file *cfile = NULL;
3689        char *endp;
3690        int ret;
3691
3692        efd = simple_strtoul(buffer, &endp, 10);
3693        if (*endp != ' ')
3694                return -EINVAL;
3695        buffer = endp + 1;
3696
3697        cfd = simple_strtoul(buffer, &endp, 10);
3698        if ((*endp != ' ') && (*endp != '\0'))
3699                return -EINVAL;
3700        buffer = endp + 1;
3701
3702        event = kzalloc(sizeof(*event), GFP_KERNEL);
3703        if (!event)
3704                return -ENOMEM;
3705        event->cgrp = cgrp;
3706        INIT_LIST_HEAD(&event->list);
3707        init_poll_funcptr(&event->pt, cgroup_event_ptable_queue_proc);
3708        init_waitqueue_func_entry(&event->wait, cgroup_event_wake);
3709        INIT_WORK(&event->remove, cgroup_event_remove);
3710
3711        efile = eventfd_fget(efd);
3712        if (IS_ERR(efile)) {
3713                ret = PTR_ERR(efile);
3714                goto fail;
3715        }
3716
3717        event->eventfd = eventfd_ctx_fileget(efile);
3718        if (IS_ERR(event->eventfd)) {
3719                ret = PTR_ERR(event->eventfd);
3720                goto fail;
3721        }
3722
3723        cfile = fget(cfd);
3724        if (!cfile) {
3725                ret = -EBADF;
3726                goto fail;
3727        }
3728
3729        /* the process need read permission on control file */
3730        /* AV: shouldn't we check that it's been opened for read instead? */
3731        ret = inode_permission(cfile->f_path.dentry->d_inode, MAY_READ);
3732        if (ret < 0)
3733                goto fail;
3734
3735        event->cft = __file_cft(cfile);
3736        if (IS_ERR(event->cft)) {
3737                ret = PTR_ERR(event->cft);
3738                goto fail;
3739        }
3740
3741        if (!event->cft->register_event || !event->cft->unregister_event) {
3742                ret = -EINVAL;
3743                goto fail;
3744        }
3745
3746        ret = event->cft->register_event(cgrp, event->cft,
3747                        event->eventfd, buffer);
3748        if (ret)
3749                goto fail;
3750
3751        if (efile->f_op->poll(efile, &event->pt) & POLLHUP) {
3752                event->cft->unregister_event(cgrp, event->cft, event->eventfd);
3753                ret = 0;
3754                goto fail;
3755        }
3756
3757        /*
3758         * Events should be removed after rmdir of cgroup directory, but before
3759         * destroying subsystem state objects. Let's take reference to cgroup
3760         * directory dentry to do that.
3761         */
3762        dget(cgrp->dentry);
3763
3764        spin_lock(&cgrp->event_list_lock);
3765        list_add(&event->list, &cgrp->event_list);
3766        spin_unlock(&cgrp->event_list_lock);
3767
3768        fput(cfile);
3769        fput(efile);
3770
3771        return 0;
3772
3773fail:
3774        if (cfile)
3775                fput(cfile);
3776
3777        if (event && event->eventfd && !IS_ERR(event->eventfd))
3778                eventfd_ctx_put(event->eventfd);
3779
3780        if (!IS_ERR_OR_NULL(efile))
3781                fput(efile);
3782
3783        kfree(event);
3784
3785        return ret;
3786}
3787
3788static u64 cgroup_clone_children_read(struct cgroup *cgrp,
3789                                    struct cftype *cft)
3790{
3791        return clone_children(cgrp);
3792}
3793
3794static int cgroup_clone_children_write(struct cgroup *cgrp,
3795                                     struct cftype *cft,
3796                                     u64 val)
3797{
3798        if (val)
3799                set_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
3800        else
3801                clear_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
3802        return 0;
3803}
3804
3805/*
3806 * for the common functions, 'private' gives the type of file
3807 */
3808/* for hysterical raisins, we can't put this on the older files */
3809#define CGROUP_FILE_GENERIC_PREFIX "cgroup."
3810static struct cftype files[] = {
3811        {
3812                .name = "tasks",
3813                .open = cgroup_tasks_open,
3814                .write_u64 = cgroup_tasks_write,
3815                .release = cgroup_pidlist_release,
3816                .mode = S_IRUGO | S_IWUSR,
3817        },
3818        {
3819                .name = CGROUP_FILE_GENERIC_PREFIX "procs",
3820                .open = cgroup_procs_open,
3821                .write_u64 = cgroup_procs_write,
3822                .release = cgroup_pidlist_release,
3823                .mode = S_IRUGO | S_IWUSR,
3824        },
3825        {
3826                .name = "notify_on_release",
3827                .read_u64 = cgroup_read_notify_on_release,
3828                .write_u64 = cgroup_write_notify_on_release,
3829        },
3830        {
3831                .name = CGROUP_FILE_GENERIC_PREFIX "event_control",
3832                .write_string = cgroup_write_event_control,
3833                .mode = S_IWUGO,
3834        },
3835        {
3836                .name = "cgroup.clone_children",
3837                .read_u64 = cgroup_clone_children_read,
3838                .write_u64 = cgroup_clone_children_write,
3839        },
3840        {
3841                .name = "release_agent",
3842                .flags = CFTYPE_ONLY_ON_ROOT,
3843                .read_seq_string = cgroup_release_agent_show,
3844                .write_string = cgroup_release_agent_write,
3845                .max_write_len = PATH_MAX,
3846        },
3847        { }     /* terminate */
3848};
3849
3850static int cgroup_populate_dir(struct cgroup *cgrp)
3851{
3852        int err;
3853        struct cgroup_subsys *ss;
3854
3855        err = cgroup_addrm_files(cgrp, NULL, files, true);
3856        if (err < 0)
3857                return err;
3858
3859        /* process cftsets of each subsystem */
3860        for_each_subsys(cgrp->root, ss) {
3861                struct cftype_set *set;
3862
3863                list_for_each_entry(set, &ss->cftsets, node)
3864                        cgroup_addrm_files(cgrp, ss, set->cfts, true);
3865        }
3866
3867        /* This cgroup is ready now */
3868        for_each_subsys(cgrp->root, ss) {
3869                struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
3870                /*
3871                 * Update id->css pointer and make this css visible from
3872                 * CSS ID functions. This pointer will be dereferened
3873                 * from RCU-read-side without locks.
3874                 */
3875                if (css->id)
3876                        rcu_assign_pointer(css->id->css, css);
3877        }
3878
3879        return 0;
3880}
3881
3882static void css_dput_fn(struct work_struct *work)
3883{
3884        struct cgroup_subsys_state *css =
3885                container_of(work, struct cgroup_subsys_state, dput_work);
3886        struct dentry *dentry = css->cgroup->dentry;
3887        struct super_block *sb = dentry->d_sb;
3888
3889        atomic_inc(&sb->s_active);
3890        dput(dentry);
3891        deactivate_super(sb);
3892}
3893
3894static void init_cgroup_css(struct cgroup_subsys_state *css,
3895                               struct cgroup_subsys *ss,
3896                               struct cgroup *cgrp)
3897{
3898        css->cgroup = cgrp;
3899        atomic_set(&css->refcnt, 1);
3900        css->flags = 0;
3901        css->id = NULL;
3902        if (cgrp == dummytop)
3903                set_bit(CSS_ROOT, &css->flags);
3904        BUG_ON(cgrp->subsys[ss->subsys_id]);
3905        cgrp->subsys[ss->subsys_id] = css;
3906
3907        /*
3908         * If !clear_css_refs, css holds an extra ref to @cgrp->dentry
3909         * which is put on the last css_put().  dput() requires process
3910         * context, which css_put() may be called without.  @css->dput_work
3911         * will be used to invoke dput() asynchronously from css_put().
3912         */
3913        INIT_WORK(&css->dput_work, css_dput_fn);
3914        if (ss->__DEPRECATED_clear_css_refs)
3915                set_bit(CSS_CLEAR_CSS_REFS, &css->flags);
3916}
3917
3918static void cgroup_lock_hierarchy(struct cgroupfs_root *root)
3919{
3920        /* We need to take each hierarchy_mutex in a consistent order */
3921        int i;
3922
3923        /*
3924         * No worry about a race with rebind_subsystems that might mess up the
3925         * locking order, since both parties are under cgroup_mutex.
3926         */
3927        for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
3928                struct cgroup_subsys *ss = subsys[i];
3929                if (ss == NULL)
3930                        continue;
3931                if (ss->root == root)
3932                        mutex_lock(&ss->hierarchy_mutex);
3933        }
3934}
3935
3936static void cgroup_unlock_hierarchy(struct cgroupfs_root *root)
3937{
3938        int i;
3939
3940        for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
3941                struct cgroup_subsys *ss = subsys[i];
3942                if (ss == NULL)
3943                        continue;
3944                if (ss->root == root)
3945                        mutex_unlock(&ss->hierarchy_mutex);
3946        }
3947}
3948
3949/*
3950 * cgroup_create - create a cgroup
3951 * @parent: cgroup that will be parent of the new cgroup
3952 * @dentry: dentry of the new cgroup
3953 * @mode: mode to set on new inode
3954 *
3955 * Must be called with the mutex on the parent inode held
3956 */
3957static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
3958                             umode_t mode)
3959{
3960        struct cgroup *cgrp;
3961        struct cgroupfs_root *root = parent->root;
3962        int err = 0;
3963        struct cgroup_subsys *ss;
3964        struct super_block *sb = root->sb;
3965
3966        cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
3967        if (!cgrp)
3968                return -ENOMEM;
3969
3970        /* Grab a reference on the superblock so the hierarchy doesn't
3971         * get deleted on unmount if there are child cgroups.  This
3972         * can be done outside cgroup_mutex, since the sb can't
3973         * disappear while someone has an open control file on the
3974         * fs */
3975        atomic_inc(&sb->s_active);
3976
3977        mutex_lock(&cgroup_mutex);
3978
3979        init_cgroup_housekeeping(cgrp);
3980
3981        cgrp->parent = parent;
3982        cgrp->root = parent->root;
3983        cgrp->top_cgroup = parent->top_cgroup;
3984
3985        if (notify_on_release(parent))
3986                set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
3987
3988        if (clone_children(parent))
3989                set_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
3990
3991        for_each_subsys(root, ss) {
3992                struct cgroup_subsys_state *css = ss->create(cgrp);
3993
3994                if (IS_ERR(css)) {
3995                        err = PTR_ERR(css);
3996                        goto err_destroy;
3997                }
3998                init_cgroup_css(css, ss, cgrp);
3999                if (ss->use_id) {
4000                        err = alloc_css_id(ss, parent, cgrp);
4001                        if (err)
4002                                goto err_destroy;
4003                }
4004                /* At error, ->destroy() callback has to free assigned ID. */
4005                if (clone_children(parent) && ss->post_clone)
4006                        ss->post_clone(cgrp);
4007        }
4008
4009        cgroup_lock_hierarchy(root);
4010        list_add(&cgrp->sibling, &cgrp->parent->children);
4011        cgroup_unlock_hierarchy(root);
4012        root->number_of_cgroups++;
4013
4014        err = cgroup_create_dir(cgrp, dentry, mode);
4015        if (err < 0)
4016                goto err_remove;
4017
4018        /* If !clear_css_refs, each css holds a ref to the cgroup's dentry */
4019        for_each_subsys(root, ss)
4020                if (!ss->__DEPRECATED_clear_css_refs)
4021                        dget(dentry);
4022
4023        /* The cgroup directory was pre-locked for us */
4024        BUG_ON(!mutex_is_locked(&cgrp->dentry->d_inode->i_mutex));
4025
4026        list_add_tail(&cgrp->allcg_node, &root->allcg_list);
4027
4028        err = cgroup_populate_dir(cgrp);
4029        /* If err < 0, we have a half-filled directory - oh well ;) */
4030
4031        mutex_unlock(&cgroup_mutex);
4032        mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
4033
4034        return 0;
4035
4036 err_remove:
4037
4038        cgroup_lock_hierarchy(root);
4039        list_del(&cgrp->sibling);
4040        cgroup_unlock_hierarchy(root);
4041        root->number_of_cgroups--;
4042
4043 err_destroy:
4044
4045        for_each_subsys(root, ss) {
4046                if (cgrp->subsys[ss->subsys_id])
4047                        ss->destroy(cgrp);
4048        }
4049
4050        mutex_unlock(&cgroup_mutex);
4051
4052        /* Release the reference count that we took on the superblock */
4053        deactivate_super(sb);
4054
4055        kfree(cgrp);
4056        return err;
4057}
4058
4059static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
4060{
4061        struct cgroup *c_parent = dentry->d_parent->d_fsdata;
4062
4063        /* the vfs holds inode->i_mutex already */
4064        return cgroup_create(c_parent, dentry, mode | S_IFDIR);
4065}
4066
4067/*
4068 * Check the reference count on each subsystem. Since we already
4069 * established that there are no tasks in the cgroup, if the css refcount
4070 * is also 1, then there should be no outstanding references, so the
4071 * subsystem is safe to destroy. We scan across all subsystems rather than
4072 * using the per-hierarchy linked list of mounted subsystems since we can
4073 * be called via check_for_release() with no synchronization other than
4074 * RCU, and the subsystem linked list isn't RCU-safe.
4075 */
4076static int cgroup_has_css_refs(struct cgroup *cgrp)
4077{
4078        int i;
4079
4080        /*
4081         * We won't need to lock the subsys array, because the subsystems
4082         * we're concerned about aren't going anywhere since our cgroup root
4083         * has a reference on them.
4084         */
4085        for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4086                struct cgroup_subsys *ss = subsys[i];
4087                struct cgroup_subsys_state *css;
4088
4089                /* Skip subsystems not present or not in this hierarchy */
4090                if (ss == NULL || ss->root != cgrp->root)
4091                        continue;
4092
4093                css = cgrp->subsys[ss->subsys_id];
4094                /*
4095                 * When called from check_for_release() it's possible
4096                 * that by this point the cgroup has been removed
4097                 * and the css deleted. But a false-positive doesn't
4098                 * matter, since it can only happen if the cgroup
4099                 * has been deleted and hence no longer needs the
4100                 * release agent to be called anyway.
4101                 */
4102                if (css && css_refcnt(css) > 1)
4103                        return 1;
4104        }
4105        return 0;
4106}
4107
4108/*
4109 * Atomically mark all (or else none) of the cgroup's CSS objects as
4110 * CSS_REMOVED. Return true on success, or false if the cgroup has
4111 * busy subsystems. Call with cgroup_mutex held
4112 *
4113 * Depending on whether a subsys has __DEPRECATED_clear_css_refs set or
4114 * not, cgroup removal behaves differently.
4115 *
4116 * If clear is set, css refcnt for the subsystem should be zero before
4117 * cgroup removal can be committed.  This is implemented by
4118 * CGRP_WAIT_ON_RMDIR and retry logic around ->pre_destroy(), which may be
4119 * called multiple times until all css refcnts reach zero and is allowed to
4120 * veto removal on any invocation.  This behavior is deprecated and will be
4121 * removed as soon as the existing user (memcg) is updated.
4122 *
4123 * If clear is not set, each css holds an extra reference to the cgroup's
4124 * dentry and cgroup removal proceeds regardless of css refs.
4125 * ->pre_destroy() will be called at least once and is not allowed to fail.
4126 * On the last put of each css, whenever that may be, the extra dentry ref
4127 * is put so that dentry destruction happens only after all css's are
4128 * released.
4129 */
4130static int cgroup_clear_css_refs(struct cgroup *cgrp)
4131{
4132        struct cgroup_subsys *ss;
4133        unsigned long flags;
4134        bool failed = false;
4135
4136        local_irq_save(flags);
4137
4138        /*
4139         * Block new css_tryget() by deactivating refcnt.  If all refcnts
4140         * for subsystems w/ clear_css_refs set were 1 at the moment of
4141         * deactivation, we succeeded.
4142         */
4143        for_each_subsys(cgrp->root, ss) {
4144                struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
4145
4146                WARN_ON(atomic_read(&css->refcnt) < 0);
4147                atomic_add(CSS_DEACT_BIAS, &css->refcnt);
4148
4149                if (ss->__DEPRECATED_clear_css_refs)
4150                        failed |= css_refcnt(css) != 1;
4151        }
4152
4153        /*
4154         * If succeeded, set REMOVED and put all the base refs; otherwise,
4155         * restore refcnts to positive values.  Either way, all in-progress
4156         * css_tryget() will be released.
4157         */
4158        for_each_subsys(cgrp->root, ss) {
4159                struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
4160
4161                if (!failed) {
4162                        set_bit(CSS_REMOVED, &css->flags);
4163                        css_put(css);
4164                } else {
4165                        atomic_sub(CSS_DEACT_BIAS, &css->refcnt);
4166                }
4167        }
4168
4169        local_irq_restore(flags);
4170        return !failed;
4171}
4172
4173static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
4174{
4175        struct cgroup *cgrp = dentry->d_fsdata;
4176        struct dentry *d;
4177        struct cgroup *parent;
4178        DEFINE_WAIT(wait);
4179        struct cgroup_event *event, *tmp;
4180        int ret;
4181
4182        /* the vfs holds both inode->i_mutex already */
4183again:
4184        mutex_lock(&cgroup_mutex);
4185        if (atomic_read(&cgrp->count) != 0) {
4186                mutex_unlock(&cgroup_mutex);
4187                return -EBUSY;
4188        }
4189        if (!list_empty(&cgrp->children)) {
4190                mutex_unlock(&cgroup_mutex);
4191                return -EBUSY;
4192        }
4193        mutex_unlock(&cgroup_mutex);
4194
4195        /*
4196         * In general, subsystem has no css->refcnt after pre_destroy(). But
4197         * in racy cases, subsystem may have to get css->refcnt after
4198         * pre_destroy() and it makes rmdir return with -EBUSY. This sometimes
4199         * make rmdir return -EBUSY too often. To avoid that, we use waitqueue
4200         * for cgroup's rmdir. CGRP_WAIT_ON_RMDIR is for synchronizing rmdir
4201         * and subsystem's reference count handling. Please see css_get/put
4202         * and css_tryget() and cgroup_wakeup_rmdir_waiter() implementation.
4203         */
4204        set_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
4205
4206        /*
4207         * Call pre_destroy handlers of subsys. Notify subsystems
4208         * that rmdir() request comes.
4209         */
4210        ret = cgroup_call_pre_destroy(cgrp);
4211        if (ret) {
4212                clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
4213                return ret;
4214        }
4215
4216        mutex_lock(&cgroup_mutex);
4217        parent = cgrp->parent;
4218        if (atomic_read(&cgrp->count) || !list_empty(&cgrp->children)) {
4219                clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
4220                mutex_unlock(&cgroup_mutex);
4221                return -EBUSY;
4222        }
4223        prepare_to_wait(&cgroup_rmdir_waitq, &wait, TASK_INTERRUPTIBLE);
4224        if (!cgroup_clear_css_refs(cgrp)) {
4225                mutex_unlock(&cgroup_mutex);
4226                /*
4227                 * Because someone may call cgroup_wakeup_rmdir_waiter() before
4228                 * prepare_to_wait(), we need to check this flag.
4229                 */
4230                if (test_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags))
4231                        schedule();
4232                finish_wait(&cgroup_rmdir_waitq, &wait);
4233                clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
4234                if (signal_pending(current))
4235                        return -EINTR;
4236                goto again;
4237        }
4238        /* NO css_tryget() can success after here. */
4239        finish_wait(&cgroup_rmdir_waitq, &wait);
4240        clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
4241
4242        raw_spin_lock(&release_list_lock);
4243        set_bit(CGRP_REMOVED, &cgrp->flags);
4244        if (!list_empty(&cgrp->release_list))
4245                list_del_init(&cgrp->release_list);
4246        raw_spin_unlock(&release_list_lock);
4247
4248        cgroup_lock_hierarchy(cgrp->root);
4249        /* delete this cgroup from parent->children */
4250        list_del_init(&cgrp->sibling);
4251        cgroup_unlock_hierarchy(cgrp->root);
4252
4253        list_del_init(&cgrp->allcg_node);
4254
4255        d = dget(cgrp->dentry);
4256
4257        cgroup_d_remove_dir(d);
4258        dput(d);
4259
4260        set_bit(CGRP_RELEASABLE, &parent->flags);
4261        check_for_release(parent);
4262
4263        /*
4264         * Unregister events and notify userspace.
4265         * Notify userspace about cgroup removing only after rmdir of cgroup
4266         * directory to avoid race between userspace and kernelspace
4267         */
4268        spin_lock(&cgrp->event_list_lock);
4269        list_for_each_entry_safe(event, tmp, &cgrp->event_list, list) {
4270                list_del(&event->list);
4271                remove_wait_queue(event->wqh, &event->wait);
4272                eventfd_signal(event->eventfd, 1);
4273                schedule_work(&event->remove);
4274        }
4275        spin_unlock(&cgrp->event_list_lock);
4276
4277        mutex_unlock(&cgroup_mutex);
4278        return 0;
4279}
4280
4281static void __init_or_module cgroup_init_cftsets(struct cgroup_subsys *ss)
4282{
4283        INIT_LIST_HEAD(&ss->cftsets);
4284
4285        /*
4286         * base_cftset is embedded in subsys itself, no need to worry about
4287         * deregistration.
4288         */
4289        if (ss->base_cftypes) {
4290                ss->base_cftset.cfts = ss->base_cftypes;
4291                list_add_tail(&ss->base_cftset.node, &ss->cftsets);
4292        }
4293}
4294
4295static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
4296{
4297        struct cgroup_subsys_state *css;
4298
4299        printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
4300
4301        /* init base cftset */
4302        cgroup_init_cftsets(ss);
4303
4304        /* Create the top cgroup state for this subsystem */
4305        list_add(&ss->sibling, &rootnode.subsys_list);
4306        ss->root = &rootnode;
4307        css = ss->create(dummytop);
4308        /* We don't handle early failures gracefully */
4309        BUG_ON(IS_ERR(css));
4310        init_cgroup_css(css, ss, dummytop);
4311
4312        /* Update the init_css_set to contain a subsys
4313         * pointer to this state - since the subsystem is
4314         * newly registered, all tasks and hence the
4315         * init_css_set is in the subsystem's top cgroup. */
4316        init_css_set.subsys[ss->subsys_id] = dummytop->subsys[ss->subsys_id];
4317
4318        need_forkexit_callback |= ss->fork || ss->exit;
4319
4320        /* At system boot, before all subsystems have been
4321         * registered, no tasks have been forked, so we don't
4322         * need to invoke fork callbacks here. */
4323        BUG_ON(!list_empty(&init_task.tasks));
4324
4325        mutex_init(&ss->hierarchy_mutex);
4326        lockdep_set_class(&ss->hierarchy_mutex, &ss->subsys_key);
4327        ss->active = 1;
4328
4329        /* this function shouldn't be used with modular subsystems, since they
4330         * need to register a subsys_id, among other things */
4331        BUG_ON(ss->module);
4332}
4333
4334/**
4335 * cgroup_load_subsys: load and register a modular subsystem at runtime
4336 * @ss: the subsystem to load
4337 *
4338 * This function should be called in a modular subsystem's initcall. If the
4339 * subsystem is built as a module, it will be assigned a new subsys_id and set
4340 * up for use. If the subsystem is built-in anyway, work is delegated to the
4341 * simpler cgroup_init_subsys.
4342 */
4343int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
4344{
4345        int i;
4346        struct cgroup_subsys_state *css;
4347
4348        /* check name and function validity */
4349        if (ss->name == NULL || strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN ||
4350            ss->create == NULL || ss->destroy == NULL)
4351                return -EINVAL;
4352
4353        /*
4354         * we don't support callbacks in modular subsystems. this check is
4355         * before the ss->module check for consistency; a subsystem that could
4356         * be a module should still have no callbacks even if the user isn't
4357         * compiling it as one.
4358         */
4359        if (ss->fork || ss->exit)
4360                return -EINVAL;
4361
4362        /*
4363         * an optionally modular subsystem is built-in: we want to do nothing,
4364         * since cgroup_init_subsys will have already taken care of it.
4365         */
4366        if (ss->module == NULL) {
4367                /* a few sanity checks */
4368                BUG_ON(ss->subsys_id >= CGROUP_BUILTIN_SUBSYS_COUNT);
4369                BUG_ON(subsys[ss->subsys_id] != ss);
4370                return 0;
4371        }
4372
4373        /* init base cftset */
4374        cgroup_init_cftsets(ss);
4375
4376        /*
4377         * need to register a subsys id before anything else - for example,
4378         * init_cgroup_css needs it.
4379         */
4380        mutex_lock(&cgroup_mutex);
4381        /* find the first empty slot in the array */
4382        for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
4383                if (subsys[i] == NULL)
4384                        break;
4385        }
4386        if (i == CGROUP_SUBSYS_COUNT) {
4387                /* maximum number of subsystems already registered! */
4388                mutex_unlock(&cgroup_mutex);
4389                return -EBUSY;
4390        }
4391        /* assign ourselves the subsys_id */
4392        ss->subsys_id = i;
4393        subsys[i] = ss;
4394
4395        /*
4396         * no ss->create seems to need anything important in the ss struct, so
4397         * this can happen first (i.e. before the rootnode attachment).
4398         */
4399        css = ss->create(dummytop);
4400        if (IS_ERR(css)) {
4401                /* failure case - need to deassign the subsys[] slot. */
4402                subsys[i] = NULL;
4403                mutex_unlock(&cgroup_mutex);
4404                return PTR_ERR(css);
4405        }
4406
4407        list_add(&ss->sibling, &rootnode.subsys_list);
4408        ss->root = &rootnode;
4409
4410        /* our new subsystem will be attached to the dummy hierarchy. */
4411        init_cgroup_css(css, ss, dummytop);
4412        /* init_idr must be after init_cgroup_css because it sets css->id. */
4413        if (ss->use_id) {
4414                int ret = cgroup_init_idr(ss, css);
4415                if (ret) {
4416                        dummytop->subsys[ss->subsys_id] = NULL;
4417                        ss->destroy(dummytop);
4418                        subsys[i] = NULL;
4419                        mutex_unlock(&cgroup_mutex);
4420                        return ret;
4421                }
4422        }
4423
4424        /*
4425         * Now we need to entangle the css into the existing css_sets. unlike
4426         * in cgroup_init_subsys, there are now multiple css_sets, so each one
4427         * will need a new pointer to it; done by iterating the css_set_table.
4428         * furthermore, modifying the existing css_sets will corrupt the hash
4429         * table state, so each changed css_set will need its hash recomputed.
4430         * this is all done under the css_set_lock.
4431         */
4432        write_lock(&css_set_lock);
4433        for (i = 0; i < CSS_SET_TABLE_SIZE; i++) {
4434                struct css_set *cg;
4435                struct hlist_node *node, *tmp;
4436                struct hlist_head *bucket = &css_set_table[i], *new_bucket;
4437
4438                hlist_for_each_entry_safe(cg, node, tmp, bucket, hlist) {
4439                        /* skip entries that we already rehashed */
4440                        if (cg->subsys[ss->subsys_id])
4441                                continue;
4442                        /* remove existing entry */
4443                        hlist_del(&cg->hlist);
4444                        /* set new value */
4445                        cg->subsys[ss->subsys_id] = css;
4446                        /* recompute hash and restore entry */
4447                        new_bucket = css_set_hash(cg->subsys);
4448                        hlist_add_head(&cg->hlist, new_bucket);
4449                }
4450        }
4451        write_unlock(&css_set_lock);
4452
4453        mutex_init(&ss->hierarchy_mutex);
4454        lockdep_set_class(&ss->hierarchy_mutex, &ss->subsys_key);
4455        ss->active = 1;
4456
4457        /* success! */
4458        mutex_unlock(&cgroup_mutex);
4459        return 0;
4460}
4461EXPORT_SYMBOL_GPL(cgroup_load_subsys);
4462
4463/**
4464 * cgroup_unload_subsys: unload a modular subsystem
4465 * @ss: the subsystem to unload
4466 *
4467 * This function should be called in a modular subsystem's exitcall. When this
4468 * function is invoked, the refcount on the subsystem's module will be 0, so
4469 * the subsystem will not be attached to any hierarchy.
4470 */
4471void cgroup_unload_subsys(struct cgroup_subsys *ss)
4472{
4473        struct cg_cgroup_link *link;
4474        struct hlist_head *hhead;
4475
4476        BUG_ON(ss->module == NULL);
4477
4478        /*
4479         * we shouldn't be called if the subsystem is in use, and the use of
4480         * try_module_get in parse_cgroupfs_options should ensure that it
4481         * doesn't start being used while we're killing it off.
4482         */
4483        BUG_ON(ss->root != &rootnode);
4484
4485        mutex_lock(&cgroup_mutex);
4486        /* deassign the subsys_id */
4487        BUG_ON(ss->subsys_id < CGROUP_BUILTIN_SUBSYS_COUNT);
4488        subsys[ss->subsys_id] = NULL;
4489
4490        /* remove subsystem from rootnode's list of subsystems */
4491        list_del_init(&ss->sibling);
4492
4493        /*
4494         * disentangle the css from all css_sets attached to the dummytop. as
4495         * in loading, we need to pay our respects to the hashtable gods.
4496         */
4497        write_lock(&css_set_lock);
4498        list_for_each_entry(link, &dummytop->css_sets, cgrp_link_list) {
4499                struct css_set *cg = link->cg;
4500
4501                hlist_del(&cg->hlist);
4502                BUG_ON(!cg->subsys[ss->subsys_id]);
4503                cg->subsys[ss->subsys_id] = NULL;
4504                hhead = css_set_hash(cg->subsys);
4505                hlist_add_head(&cg->hlist, hhead);
4506        }
4507        write_unlock(&css_set_lock);
4508
4509        /*
4510         * remove subsystem's css from the dummytop and free it - need to free
4511         * before marking as null because ss->destroy needs the cgrp->subsys
4512         * pointer to find their state. note that this also takes care of
4513         * freeing the css_id.
4514         */
4515        ss->destroy(dummytop);
4516        dummytop->subsys[ss->subsys_id] = NULL;
4517
4518        mutex_unlock(&cgroup_mutex);
4519}
4520EXPORT_SYMBOL_GPL(cgroup_unload_subsys);
4521
4522/**
4523 * cgroup_init_early - cgroup initialization at system boot
4524 *
4525 * Initialize cgroups at system boot, and initialize any
4526 * subsystems that request early init.
4527 */
4528int __init cgroup_init_early(void)
4529{
4530        int i;
4531        atomic_set(&init_css_set.refcount, 1);
4532        INIT_LIST_HEAD(&init_css_set.cg_links);
4533        INIT_LIST_HEAD(&init_css_set.tasks);
4534        INIT_HLIST_NODE(&init_css_set.hlist);
4535        css_set_count = 1;
4536        init_cgroup_root(&rootnode);
4537        root_count = 1;
4538        init_task.cgroups = &init_css_set;
4539
4540        init_css_set_link.cg = &init_css_set;
4541        init_css_set_link.cgrp = dummytop;
4542        list_add(&init_css_set_link.cgrp_link_list,
4543                 &rootnode.top_cgroup.css_sets);
4544        list_add(&init_css_set_link.cg_link_list,
4545                 &init_css_set.cg_links);
4546
4547        for (i = 0; i < CSS_SET_TABLE_SIZE; i++)
4548                INIT_HLIST_HEAD(&css_set_table[i]);
4549
4550        /* at bootup time, we don't worry about modular subsystems */
4551        for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4552                struct cgroup_subsys *ss = subsys[i];
4553
4554                BUG_ON(!ss->name);
4555                BUG_ON(strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN);
4556                BUG_ON(!ss->create);
4557                BUG_ON(!ss->destroy);
4558                if (ss->subsys_id != i) {
4559                        printk(KERN_ERR "cgroup: Subsys %s id == %d\n",
4560                               ss->name, ss->subsys_id);
4561                        BUG();
4562                }
4563
4564                if (ss->early_init)
4565                        cgroup_init_subsys(ss);
4566        }
4567        return 0;
4568}
4569
4570/**
4571 * cgroup_init - cgroup initialization
4572 *
4573 * Register cgroup filesystem and /proc file, and initialize
4574 * any subsystems that didn't request early init.
4575 */
4576int __init cgroup_init(void)
4577{
4578        int err;
4579        int i;
4580        struct hlist_head *hhead;
4581
4582        err = bdi_init(&cgroup_backing_dev_info);
4583        if (err)
4584                return err;
4585
4586        /* at bootup time, we don't worry about modular subsystems */
4587        for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4588                struct cgroup_subsys *ss = subsys[i];
4589                if (!ss->early_init)
4590                        cgroup_init_subsys(ss);
4591                if (ss->use_id)
4592                        cgroup_init_idr(ss, init_css_set.subsys[ss->subsys_id]);
4593        }
4594
4595        /* Add init_css_set to the hash table */
4596        hhead = css_set_hash(init_css_set.subsys);
4597        hlist_add_head(&init_css_set.hlist, hhead);
4598        BUG_ON(!init_root_id(&rootnode));
4599
4600        cgroup_kobj = kobject_create_and_add("cgroup", fs_kobj);
4601        if (!cgroup_kobj) {
4602                err = -ENOMEM;
4603                goto out;
4604        }
4605
4606        err = register_filesystem(&cgroup_fs_type);
4607        if (err < 0) {
4608                kobject_put(cgroup_kobj);
4609                goto out;
4610        }
4611
4612        proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations);
4613
4614out:
4615        if (err)
4616                bdi_destroy(&cgroup_backing_dev_info);
4617
4618        return err;
4619}
4620
4621/*
4622 * proc_cgroup_show()
4623 *  - Print task's cgroup paths into seq_file, one line for each hierarchy
4624 *  - Used for /proc/<pid>/cgroup.
4625 *  - No need to task_lock(tsk) on this tsk->cgroup reference, as it
4626 *    doesn't really matter if tsk->cgroup changes after we read it,
4627 *    and we take cgroup_mutex, keeping cgroup_attach_task() from changing it
4628 *    anyway.  No need to check that tsk->cgroup != NULL, thanks to
4629 *    the_top_cgroup_hack in cgroup_exit(), which sets an exiting tasks
4630 *    cgroup to top_cgroup.
4631 */
4632
4633/* TODO: Use a proper seq_file iterator */
4634static int proc_cgroup_show(struct seq_file *m, void *v)
4635{
4636        struct pid *pid;
4637        struct task_struct *tsk;
4638        char *buf;
4639        int retval;
4640        struct cgroupfs_root *root;
4641
4642        retval = -ENOMEM;
4643        buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
4644        if (!buf)
4645                goto out;
4646
4647        retval = -ESRCH;
4648        pid = m->private;
4649        tsk = get_pid_task(pid, PIDTYPE_PID);
4650        if (!tsk)
4651                goto out_free;
4652
4653        retval = 0;
4654
4655        mutex_lock(&cgroup_mutex);
4656
4657        for_each_active_root(root) {
4658                struct cgroup_subsys *ss;
4659                struct cgroup *cgrp;
4660                int count = 0;
4661
4662                seq_printf(m, "%d:", root->hierarchy_id);
4663                for_each_subsys(root, ss)
4664                        seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
4665                if (strlen(root->name))
4666                        seq_printf(m, "%sname=%s", count ? "," : "",
4667                                   root->name);
4668                seq_putc(m, ':');
4669                cgrp = task_cgroup_from_root(tsk, root);
4670                retval = cgroup_path(cgrp, buf, PAGE_SIZE);
4671                if (retval < 0)
4672                        goto out_unlock;
4673                seq_puts(m, buf);
4674                seq_putc(m, '\n');
4675        }
4676
4677out_unlock:
4678        mutex_unlock(&cgroup_mutex);
4679        put_task_struct(tsk);
4680out_free:
4681        kfree(buf);
4682out:
4683        return retval;
4684}
4685
4686static int cgroup_open(struct inode *inode, struct file *file)
4687{
4688        struct pid *pid = PROC_I(inode)->pid;
4689        return single_open(file, proc_cgroup_show, pid);
4690}
4691
4692const struct file_operations proc_cgroup_operations = {
4693        .open           = cgroup_open,
4694        .read           = seq_read,
4695        .llseek         = seq_lseek,
4696        .release        = single_release,
4697};
4698
4699/* Display information about each subsystem and each hierarchy */
4700static int proc_cgroupstats_show(struct seq_file *m, void *v)
4701{
4702        int i;
4703
4704        seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
4705        /*
4706         * ideally we don't want subsystems moving around while we do this.
4707         * cgroup_mutex is also necessary to guarantee an atomic snapshot of
4708         * subsys/hierarchy state.
4709         */
4710        mutex_lock(&cgroup_mutex);
4711        for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4712                struct cgroup_subsys *ss = subsys[i];
4713                if (ss == NULL)
4714                        continue;
4715                seq_printf(m, "%s\t%d\t%d\t%d\n",
4716                           ss->name, ss->root->hierarchy_id,
4717                           ss->root->number_of_cgroups, !ss->disabled);
4718        }
4719        mutex_unlock(&cgroup_mutex);
4720        return 0;
4721}
4722
4723static int cgroupstats_open(struct inode *inode, struct file *file)
4724{
4725        return single_open(file, proc_cgroupstats_show, NULL);
4726}
4727
4728static const struct file_operations proc_cgroupstats_operations = {
4729        .open = cgroupstats_open,
4730        .read = seq_read,
4731        .llseek = seq_lseek,
4732        .release = single_release,
4733};
4734
4735/**
4736 * cgroup_fork - attach newly forked task to its parents cgroup.
4737 * @child: pointer to task_struct of forking parent process.
4738 *
4739 * Description: A task inherits its parent's cgroup at fork().
4740 *
4741 * A pointer to the shared css_set was automatically copied in
4742 * fork.c by dup_task_struct().  However, we ignore that copy, since
4743 * it was not made under the protection of RCU, cgroup_mutex or
4744 * threadgroup_change_begin(), so it might no longer be a valid
4745 * cgroup pointer.  cgroup_attach_task() might have already changed
4746 * current->cgroups, allowing the previously referenced cgroup
4747 * group to be removed and freed.
4748 *
4749 * Outside the pointer validity we also need to process the css_set
4750 * inheritance between threadgoup_change_begin() and
4751 * threadgoup_change_end(), this way there is no leak in any process
4752 * wide migration performed by cgroup_attach_proc() that could otherwise
4753 * miss a thread because it is too early or too late in the fork stage.
4754 *
4755 * At the point that cgroup_fork() is called, 'current' is the parent
4756 * task, and the passed argument 'child' points to the child task.
4757 */
4758void cgroup_fork(struct task_struct *child)
4759{
4760        /*
4761         * We don't need to task_lock() current because current->cgroups
4762         * can't be changed concurrently here. The parent obviously hasn't
4763         * exited and called cgroup_exit(), and we are synchronized against
4764         * cgroup migration through threadgroup_change_begin().
4765         */
4766        child->cgroups = current->cgroups;
4767        get_css_set(child->cgroups);
4768        INIT_LIST_HEAD(&child->cg_list);
4769}
4770
4771/**
4772 * cgroup_fork_callbacks - run fork callbacks
4773 * @child: the new task
4774 *
4775 * Called on a new task very soon before adding it to the
4776 * tasklist. No need to take any locks since no-one can
4777 * be operating on this task.
4778 */
4779void cgroup_fork_callbacks(struct task_struct *child)
4780{
4781        if (need_forkexit_callback) {
4782                int i;
4783                /*
4784                 * forkexit callbacks are only supported for builtin
4785                 * subsystems, and the builtin section of the subsys array is
4786                 * immutable, so we don't need to lock the subsys array here.
4787                 */
4788                for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4789                        struct cgroup_subsys *ss = subsys[i];
4790                        if (ss->fork)
4791                                ss->fork(child);
4792                }
4793        }
4794}
4795
4796/**
4797 * cgroup_post_fork - called on a new task after adding it to the task list
4798 * @child: the task in question
4799 *
4800 * Adds the task to the list running through its css_set if necessary.
4801 * Has to be after the task is visible on the task list in case we race
4802 * with the first call to cgroup_iter_start() - to guarantee that the
4803 * new task ends up on its list.
4804 */
4805void cgroup_post_fork(struct task_struct *child)
4806{
4807        /*
4808         * use_task_css_set_links is set to 1 before we walk the tasklist
4809         * under the tasklist_lock and we read it here after we added the child
4810         * to the tasklist under the tasklist_lock as well. If the child wasn't
4811         * yet in the tasklist when we walked through it from
4812         * cgroup_enable_task_cg_lists(), then use_task_css_set_links value
4813         * should be visible now due to the paired locking and barriers implied
4814         * by LOCK/UNLOCK: it is written before the tasklist_lock unlock
4815         * in cgroup_enable_task_cg_lists() and read here after the tasklist_lock
4816         * lock on fork.
4817         */
4818        if (use_task_css_set_links) {
4819                write_lock(&css_set_lock);
4820                if (list_empty(&child->cg_list)) {
4821                        /*
4822                         * It's safe to use child->cgroups without task_lock()
4823                         * here because we are protected through
4824                         * threadgroup_change_begin() against concurrent
4825                         * css_set change in cgroup_task_migrate(). Also
4826                         * the task can't exit at that point until
4827                         * wake_up_new_task() is called, so we are protected
4828                         * against cgroup_exit() setting child->cgroup to
4829                         * init_css_set.
4830                         */
4831                        list_add(&child->cg_list, &child->cgroups->tasks);
4832                }
4833                write_unlock(&css_set_lock);
4834        }
4835}
4836/**
4837 * cgroup_exit - detach cgroup from exiting task
4838 * @tsk: pointer to task_struct of exiting process
4839 * @run_callback: run exit callbacks?
4840 *
4841 * Description: Detach cgroup from @tsk and release it.
4842 *
4843 * Note that cgroups marked notify_on_release force every task in
4844 * them to take the global cgroup_mutex mutex when exiting.
4845 * This could impact scaling on very large systems.  Be reluctant to
4846 * use notify_on_release cgroups where very high task exit scaling
4847 * is required on large systems.
4848 *
4849 * the_top_cgroup_hack:
4850 *
4851 *    Set the exiting tasks cgroup to the root cgroup (top_cgroup).
4852 *
4853 *    We call cgroup_exit() while the task is still competent to
4854 *    handle notify_on_release(), then leave the task attached to the
4855 *    root cgroup in each hierarchy for the remainder of its exit.
4856 *
4857 *    To do this properly, we would increment the reference count on
4858 *    top_cgroup, and near the very end of the kernel/exit.c do_exit()
4859 *    code we would add a second cgroup function call, to drop that
4860 *    reference.  This would just create an unnecessary hot spot on
4861 *    the top_cgroup reference count, to no avail.
4862 *
4863 *    Normally, holding a reference to a cgroup without bumping its
4864 *    count is unsafe.   The cgroup could go away, or someone could
4865 *    attach us to a different cgroup, decrementing the count on
4866 *    the first cgroup that we never incremented.  But in this case,
4867 *    top_cgroup isn't going away, and either task has PF_EXITING set,
4868 *    which wards off any cgroup_attach_task() attempts, or task is a failed
4869 *    fork, never visible to cgroup_attach_task.
4870 */
4871void cgroup_exit(struct task_struct *tsk, int run_callbacks)
4872{
4873        struct css_set *cg;
4874        int i;
4875
4876        /*
4877         * Unlink from the css_set task list if necessary.
4878         * Optimistically check cg_list before taking
4879         * css_set_lock
4880         */
4881        if (!list_empty(&tsk->cg_list)) {
4882                write_lock(&css_set_lock);
4883                if (!list_empty(&tsk->cg_list))
4884                        list_del_init(&tsk->cg_list);
4885                write_unlock(&css_set_lock);
4886        }
4887
4888        /* Reassign the task to the init_css_set. */
4889        task_lock(tsk);
4890        cg = tsk->cgroups;
4891        tsk->cgroups = &init_css_set;
4892
4893        if (run_callbacks && need_forkexit_callback) {
4894                /*
4895                 * modular subsystems can't use callbacks, so no need to lock
4896                 * the subsys array
4897                 */
4898                for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4899                        struct cgroup_subsys *ss = subsys[i];
4900                        if (ss->exit) {
4901                                struct cgroup *old_cgrp =
4902                                        rcu_dereference_raw(cg->subsys[i])->cgroup;
4903                                struct cgroup *cgrp = task_cgroup(tsk, i);
4904                                ss->exit(cgrp, old_cgrp, tsk);
4905                        }
4906                }
4907        }
4908        task_unlock(tsk);
4909
4910        if (cg)
4911                put_css_set_taskexit(cg);
4912}
4913
4914/**
4915 * cgroup_is_descendant - see if @cgrp is a descendant of @task's cgrp
4916 * @cgrp: the cgroup in question
4917 * @task: the task in question
4918 *
4919 * See if @cgrp is a descendant of @task's cgroup in the appropriate
4920 * hierarchy.
4921 *
4922 * If we are sending in dummytop, then presumably we are creating
4923 * the top cgroup in the subsystem.
4924 *
4925 * Called only by the ns (nsproxy) cgroup.
4926 */
4927int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task)
4928{
4929        int ret;
4930        struct cgroup *target;
4931
4932        if (cgrp == dummytop)
4933                return 1;
4934
4935        target = task_cgroup_from_root(task, cgrp->root);
4936        while (cgrp != target && cgrp!= cgrp->top_cgroup)
4937                cgrp = cgrp->parent;
4938        ret = (cgrp == target);
4939        return ret;
4940}
4941
4942static void check_for_release(struct cgroup *cgrp)
4943{
4944        /* All of these checks rely on RCU to keep the cgroup
4945         * structure alive */
4946        if (cgroup_is_releasable(cgrp) && !atomic_read(&cgrp->count)
4947            && list_empty(&cgrp->children) && !cgroup_has_css_refs(cgrp)) {
4948                /* Control Group is currently removeable. If it's not
4949                 * already queued for a userspace notification, queue
4950                 * it now */
4951                int need_schedule_work = 0;
4952                raw_spin_lock(&release_list_lock);
4953                if (!cgroup_is_removed(cgrp) &&
4954                    list_empty(&cgrp->release_list)) {
4955                        list_add(&cgrp->release_list, &release_list);
4956                        need_schedule_work = 1;
4957                }
4958                raw_spin_unlock(&release_list_lock);
4959                if (need_schedule_work)
4960                        schedule_work(&release_agent_work);
4961        }
4962}
4963
4964/* Caller must verify that the css is not for root cgroup */
4965bool __css_tryget(struct cgroup_subsys_state *css)
4966{
4967        do {
4968                int v = css_refcnt(css);
4969
4970                if (atomic_cmpxchg(&css->refcnt, v, v + 1) == v)
4971                        return true;
4972                cpu_relax();
4973        } while (!test_bit(CSS_REMOVED, &css->flags));
4974
4975        return false;
4976}
4977EXPORT_SYMBOL_GPL(__css_tryget);
4978
4979/* Caller must verify that the css is not for root cgroup */
4980void __css_put(struct cgroup_subsys_state *css)
4981{
4982        struct cgroup *cgrp = css->cgroup;
4983        int v;
4984
4985        rcu_read_lock();
4986        v = css_unbias_refcnt(atomic_dec_return(&css->refcnt));
4987
4988        switch (v) {
4989        case 1:
4990                if (notify_on_release(cgrp)) {
4991                        set_bit(CGRP_RELEASABLE, &cgrp->flags);
4992                        check_for_release(cgrp);
4993                }
4994                cgroup_wakeup_rmdir_waiter(cgrp);
4995                break;
4996        case 0:
4997                if (!test_bit(CSS_CLEAR_CSS_REFS, &css->flags))
4998                        schedule_work(&css->dput_work);
4999                break;
5000        }
5001        rcu_read_unlock();
5002}
5003EXPORT_SYMBOL_GPL(__css_put);
5004
5005/*
5006 * Notify userspace when a cgroup is released, by running the
5007 * configured release agent with the name of the cgroup (path
5008 * relative to the root of cgroup file system) as the argument.
5009 *
5010 * Most likely, this user command will try to rmdir this cgroup.
5011 *
5012 * This races with the possibility that some other task will be
5013 * attached to this cgroup before it is removed, or that some other
5014 * user task will 'mkdir' a child cgroup of this cgroup.  That's ok.
5015 * The presumed 'rmdir' will fail quietly if this cgroup is no longer
5016 * unused, and this cgroup will be reprieved from its death sentence,
5017 * to continue to serve a useful existence.  Next time it's released,
5018 * we will get notified again, if it still has 'notify_on_release' set.
5019 *
5020 * The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
5021 * means only wait until the task is successfully execve()'d.  The
5022 * separate release agent task is forked by call_usermodehelper(),
5023 * then control in this thread returns here, without waiting for the
5024 * release agent task.  We don't bother to wait because the caller of
5025 * this routine has no use for the exit status of the release agent
5026 * task, so no sense holding our caller up for that.
5027 */
5028static void cgroup_release_agent(struct work_struct *work)
5029{
5030        BUG_ON(work != &release_agent_work);
5031        mutex_lock(&cgroup_mutex);
5032        raw_spin_lock(&release_list_lock);
5033        while (!list_empty(&release_list)) {
5034                char *argv[3], *envp[3];
5035                int i;
5036                char *pathbuf = NULL, *agentbuf = NULL;
5037                struct cgroup *cgrp = list_entry(release_list.next,
5038                                                    struct cgroup,
5039                                                    release_list);
5040                list_del_init(&cgrp->release_list);
5041                raw_spin_unlock(&release_list_lock);
5042                pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
5043                if (!pathbuf)
5044                        goto continue_free;
5045                if (cgroup_path(cgrp, pathbuf, PAGE_SIZE) < 0)
5046                        goto continue_free;
5047                agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
5048                if (!agentbuf)
5049                        goto continue_free;
5050
5051                i = 0;
5052                argv[i++] = agentbuf;
5053                argv[i++] = pathbuf;
5054                argv[i] = NULL;
5055
5056                i = 0;
5057                /* minimal command environment */
5058                envp[i++] = "HOME=/";
5059                envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
5060                envp[i] = NULL;
5061
5062                /* Drop the lock while we invoke the usermode helper,
5063                 * since the exec could involve hitting disk and hence
5064                 * be a slow process */
5065                mutex_unlock(&cgroup_mutex);
5066                call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
5067                mutex_lock(&cgroup_mutex);
5068 continue_free:
5069                kfree(pathbuf);
5070                kfree(agentbuf);
5071                raw_spin_lock(&release_list_lock);
5072        }
5073        raw_spin_unlock(&release_list_lock);
5074        mutex_unlock(&cgroup_mutex);
5075}
5076
5077static int __init cgroup_disable(char *str)
5078{
5079        int i;
5080        char *token;
5081
5082        while ((token = strsep(&str, ",")) != NULL) {
5083                if (!*token)
5084                        continue;
5085                /*
5086                 * cgroup_disable, being at boot time, can't know about module
5087                 * subsystems, so we don't worry about them.
5088                 */
5089                for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
5090                        struct cgroup_subsys *ss = subsys[i];
5091
5092                        if (!strcmp(token, ss->name)) {
5093                                ss->disabled = 1;
5094                                printk(KERN_INFO "Disabling %s control group"
5095                                        " subsystem\n", ss->name);
5096                                break;
5097                        }
5098                }
5099        }
5100        return 1;
5101}
5102__setup("cgroup_disable=", cgroup_disable);
5103
5104/*
5105 * Functons for CSS ID.
5106 */
5107
5108/*
5109 *To get ID other than 0, this should be called when !cgroup_is_removed().
5110 */
5111unsigned short css_id(struct cgroup_subsys_state *css)
5112{
5113        struct css_id *cssid;
5114
5115        /*
5116         * This css_id() can return correct value when somone has refcnt
5117         * on this or this is under rcu_read_lock(). Once css->id is allocated,
5118         * it's unchanged until freed.
5119         */
5120        cssid = rcu_dereference_check(css->id, css_refcnt(css));
5121
5122        if (cssid)
5123                return cssid->id;
5124        return 0;
5125}
5126EXPORT_SYMBOL_GPL(css_id);
5127
5128unsigned short css_depth(struct cgroup_subsys_state *css)
5129{
5130        struct css_id *cssid;
5131
5132        cssid = rcu_dereference_check(css->id, css_refcnt(css));
5133
5134        if (cssid)
5135                return cssid->depth;
5136        return 0;
5137}
5138EXPORT_SYMBOL_GPL(css_depth);
5139
5140/**
5141 *  css_is_ancestor - test "root" css is an ancestor of "child"
5142 * @child: the css to be tested.
5143 * @root: the css supporsed to be an ancestor of the child.
5144 *
5145 * Returns true if "root" is an ancestor of "child" in its hierarchy. Because
5146 * this function reads css->id, the caller must hold rcu_read_lock().
5147 * But, considering usual usage, the csses should be valid objects after test.
5148 * Assuming that the caller will do some action to the child if this returns
5149 * returns true, the caller must take "child";s reference count.
5150 * If "child" is valid object and this returns true, "root" is valid, too.
5151 */
5152
5153bool css_is_ancestor(struct cgroup_subsys_state *child,
5154                    const struct cgroup_subsys_state *root)
5155{
5156        struct css_id *child_id;
5157        struct css_id *root_id;
5158
5159        child_id  = rcu_dereference(child->id);
5160        if (!child_id)
5161                return false;
5162        root_id = rcu_dereference(root->id);
5163        if (!root_id)
5164                return false;
5165        if (child_id->depth < root_id->depth)
5166                return false;
5167        if (child_id->stack[root_id->depth] != root_id->id)
5168                return false;
5169        return true;
5170}
5171
5172void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css)
5173{
5174        struct css_id *id = css->id;
5175        /* When this is called before css_id initialization, id can be NULL */
5176        if (!id)
5177                return;
5178
5179        BUG_ON(!ss->use_id);
5180
5181        rcu_assign_pointer(id->css, NULL);
5182        rcu_assign_pointer(css->id, NULL);
5183        spin_lock(&ss->id_lock);
5184        idr_remove(&ss->idr, id->id);
5185        spin_unlock(&ss->id_lock);
5186        kfree_rcu(id, rcu_head);
5187}
5188EXPORT_SYMBOL_GPL(free_css_id);
5189
5190/*
5191 * This is called by init or create(). Then, calls to this function are
5192 * always serialized (By cgroup_mutex() at create()).
5193 */
5194
5195static struct css_id *get_new_cssid(struct cgroup_subsys *ss, int depth)
5196{
5197        struct css_id *newid;
5198        int myid, error, size;
5199
5200        BUG_ON(!ss->use_id);
5201
5202        size = sizeof(*newid) + sizeof(unsigned short) * (depth + 1);
5203        newid = kzalloc(size, GFP_KERNEL);
5204        if (!newid)
5205                return ERR_PTR(-ENOMEM);
5206        /* get id */
5207        if (unlikely(!idr_pre_get(&ss->idr, GFP_KERNEL))) {
5208                error = -ENOMEM;
5209                goto err_out;
5210        }
5211        spin_lock(&ss->id_lock);
5212        /* Don't use 0. allocates an ID of 1-65535 */
5213        error = idr_get_new_above(&ss->idr, newid, 1, &myid);
5214        spin_unlock(&ss->id_lock);
5215
5216        /* Returns error when there are no free spaces for new ID.*/
5217        if (error) {
5218                error = -ENOSPC;
5219                goto err_out;
5220        }
5221        if (myid > CSS_ID_MAX)
5222                goto remove_idr;
5223
5224        newid->id = myid;
5225        newid->depth = depth;
5226        return newid;
5227remove_idr:
5228        error = -ENOSPC;
5229        spin_lock(&ss->id_lock);
5230        idr_remove(&ss->idr, myid);
5231        spin_unlock(&ss->id_lock);
5232err_out:
5233        kfree(newid);
5234        return ERR_PTR(error);
5235
5236}
5237
5238static int __init_or_module cgroup_init_idr(struct cgroup_subsys *ss,
5239                                            struct cgroup_subsys_state *rootcss)
5240{
5241        struct css_id *newid;
5242
5243        spin_lock_init(&ss->id_lock);
5244        idr_init(&ss->idr);
5245
5246        newid = get_new_cssid(ss, 0);
5247        if (IS_ERR(newid))
5248                return PTR_ERR(newid);
5249
5250        newid->stack[0] = newid->id;
5251        newid->css = rootcss;
5252        rootcss->id = newid;
5253        return 0;
5254}
5255
5256static int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *parent,
5257                        struct cgroup *child)
5258{
5259        int subsys_id, i, depth = 0;
5260        struct cgroup_subsys_state *parent_css, *child_css;
5261        struct css_id *child_id, *parent_id;
5262
5263        subsys_id = ss->subsys_id;
5264        parent_css = parent->subsys[subsys_id];
5265        child_css = child->subsys[subsys_id];
5266        parent_id = parent_css->id;
5267        depth = parent_id->depth + 1;
5268
5269        child_id = get_new_cssid(ss, depth);
5270        if (IS_ERR(child_id))
5271                return PTR_ERR(child_id);
5272
5273        for (i = 0; i < depth; i++)
5274                child_id->stack[i] = parent_id->stack[i];
5275        child_id->stack[depth] = child_id->id;
5276        /*
5277         * child_id->css pointer will be set after this cgroup is available
5278         * see cgroup_populate_dir()
5279         */
5280        rcu_assign_pointer(child_css->id, child_id);
5281
5282        return 0;
5283}
5284
5285/**
5286 * css_lookup - lookup css by id
5287 * @ss: cgroup subsys to be looked into.
5288 * @id: the id
5289 *
5290 * Returns pointer to cgroup_subsys_state if there is valid one with id.
5291 * NULL if not. Should be called under rcu_read_lock()
5292 */
5293struct cgroup_subsys_state *css_lookup(struct cgroup_subsys *ss, int id)
5294{
5295        struct css_id *cssid = NULL;
5296
5297        BUG_ON(!ss->use_id);
5298        cssid = idr_find(&ss->idr, id);
5299
5300        if (unlikely(!cssid))
5301                return NULL;
5302
5303        return rcu_dereference(cssid->css);
5304}
5305EXPORT_SYMBOL_GPL(css_lookup);
5306
5307/**
5308 * css_get_next - lookup next cgroup under specified hierarchy.
5309 * @ss: pointer to subsystem
5310 * @id: current position of iteration.
5311 * @root: pointer to css. search tree under this.
5312 * @foundid: position of found object.
5313 *
5314 * Search next css under the specified hierarchy of rootid. Calling under
5315 * rcu_read_lock() is necessary. Returns NULL if it reaches the end.
5316 */
5317struct cgroup_subsys_state *
5318css_get_next(struct cgroup_subsys *ss, int id,
5319             struct cgroup_subsys_state *root, int *foundid)
5320{
5321        struct cgroup_subsys_state *ret = NULL;
5322        struct css_id *tmp;
5323        int tmpid;
5324        int rootid = css_id(root);
5325        int depth = css_depth(root);
5326
5327        if (!rootid)
5328                return NULL;
5329
5330        BUG_ON(!ss->use_id);
5331        WARN_ON_ONCE(!rcu_read_lock_held());
5332
5333        /* fill start point for scan */
5334        tmpid = id;
5335        while (1) {
5336                /*
5337                 * scan next entry from bitmap(tree), tmpid is updated after
5338                 * idr_get_next().
5339                 */
5340                tmp = idr_get_next(&ss->idr, &tmpid);
5341                if (!tmp)
5342                        break;
5343                if (tmp->depth >= depth && tmp->stack[depth] == rootid) {
5344                        ret = rcu_dereference(tmp->css);
5345                        if (ret) {
5346                                *foundid = tmpid;
5347                                break;
5348                        }
5349                }
5350                /* continue to scan from next id */
5351                tmpid = tmpid + 1;
5352        }
5353        return ret;
5354}
5355
5356/*
5357 * get corresponding css from file open on cgroupfs directory
5358 */
5359struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id)
5360{
5361        struct cgroup *cgrp;
5362        struct inode *inode;
5363        struct cgroup_subsys_state *css;
5364
5365        inode = f->f_dentry->d_inode;
5366        /* check in cgroup filesystem dir */
5367        if (inode->i_op != &cgroup_dir_inode_operations)
5368                return ERR_PTR(-EBADF);
5369
5370        if (id < 0 || id >= CGROUP_SUBSYS_COUNT)
5371                return ERR_PTR(-EINVAL);
5372
5373        /* get cgroup */
5374        cgrp = __d_cgrp(f->f_dentry);
5375        css = cgrp->subsys[id];
5376        return css ? css : ERR_PTR(-ENOENT);
5377}
5378
5379#ifdef CONFIG_CGROUP_DEBUG
5380static struct cgroup_subsys_state *debug_create(struct cgroup *cont)
5381{
5382        struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);
5383
5384        if (!css)
5385                return ERR_PTR(-ENOMEM);
5386
5387        return css;
5388}
5389
5390static void debug_destroy(struct cgroup *cont)
5391{
5392        kfree(cont->subsys[debug_subsys_id]);
5393}
5394
5395static u64 cgroup_refcount_read(struct cgroup *cont, struct cftype *cft)
5396{
5397        return atomic_read(&cont->count);
5398}
5399
5400static u64 debug_taskcount_read(struct cgroup *cont, struct cftype *cft)
5401{
5402        return cgroup_task_count(cont);
5403}
5404
5405static u64 current_css_set_read(struct cgroup *cont, struct cftype *cft)
5406{
5407        return (u64)(unsigned long)current->cgroups;
5408}
5409
5410static u64 current_css_set_refcount_read(struct cgroup *cont,
5411                                           struct cftype *cft)
5412{
5413        u64 count;
5414
5415        rcu_read_lock();
5416        count = atomic_read(&current->cgroups->refcount);
5417        rcu_read_unlock();
5418        return count;
5419}
5420
5421static int current_css_set_cg_links_read(struct cgroup *cont,
5422                                         struct cftype *cft,
5423                                         struct seq_file *seq)
5424{
5425        struct cg_cgroup_link *link;
5426        struct css_set *cg;
5427
5428        read_lock(&css_set_lock);
5429        rcu_read_lock();
5430        cg = rcu_dereference(current->cgroups);
5431        list_for_each_entry(link, &cg->cg_links, cg_link_list) {
5432                struct cgroup *c = link->cgrp;
5433                const char *name;
5434
5435                if (c->dentry)
5436                        name = c->dentry->d_name.name;
5437                else
5438                        name = "?";
5439                seq_printf(seq, "Root %d group %s\n",
5440                           c->root->hierarchy_id, name);
5441        }
5442        rcu_read_unlock();
5443        read_unlock(&css_set_lock);
5444        return 0;
5445}
5446
5447#define MAX_TASKS_SHOWN_PER_CSS 25
5448static int cgroup_css_links_read(struct cgroup *cont,
5449                                 struct cftype *cft,
5450                                 struct seq_file *seq)
5451{
5452        struct cg_cgroup_link *link;
5453
5454        read_lock(&css_set_lock);
5455        list_for_each_entry(link, &cont->css_sets, cgrp_link_list) {
5456                struct css_set *cg = link->cg;
5457                struct task_struct *task;
5458                int count = 0;
5459                seq_printf(seq, "css_set %p\n", cg);
5460                list_for_each_entry(task, &cg->tasks, cg_list) {
5461                        if (count++ > MAX_TASKS_SHOWN_PER_CSS) {
5462                                seq_puts(seq, "  ...\n");
5463                                break;
5464                        } else {
5465                                seq_printf(seq, "  task %d\n",
5466                                           task_pid_vnr(task));
5467                        }
5468                }
5469        }
5470        read_unlock(&css_set_lock);
5471        return 0;
5472}
5473
5474static u64 releasable_read(struct cgroup *cgrp, struct cftype *cft)
5475{
5476        return test_bit(CGRP_RELEASABLE, &cgrp->flags);
5477}
5478
5479static struct cftype debug_files[] =  {
5480        {
5481                .name = "cgroup_refcount",
5482                .read_u64 = cgroup_refcount_read,
5483        },
5484        {
5485                .name = "taskcount",
5486                .read_u64 = debug_taskcount_read,
5487        },
5488
5489        {
5490                .name = "current_css_set",
5491                .read_u64 = current_css_set_read,
5492        },
5493
5494        {
5495                .name = "current_css_set_refcount",
5496                .read_u64 = current_css_set_refcount_read,
5497        },
5498
5499        {
5500                .name = "current_css_set_cg_links",
5501                .read_seq_string = current_css_set_cg_links_read,
5502        },
5503
5504        {
5505                .name = "cgroup_css_links",
5506                .read_seq_string = cgroup_css_links_read,
5507        },
5508
5509        {
5510                .name = "releasable",
5511                .read_u64 = releasable_read,
5512        },
5513
5514        { }     /* terminate */
5515};
5516
5517struct cgroup_subsys debug_subsys = {
5518        .name = "debug",
5519        .create = debug_create,
5520        .destroy = debug_destroy,
5521        .subsys_id = debug_subsys_id,
5522        .base_cftypes = debug_files,
5523};
5524#endif /* CONFIG_CGROUP_DEBUG */
5525
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.