linux/fs/cachefiles/namei.c
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   1/* CacheFiles path walking and related routines
   2 *
   3 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   4 * Written by David Howells (dhowells@redhat.com)
   5 *
   6 * This program is free software; you can redistribute it and/or
   7 * modify it under the terms of the GNU General Public Licence
   8 * as published by the Free Software Foundation; either version
   9 * 2 of the Licence, or (at your option) any later version.
  10 */
  11
  12#include <linux/module.h>
  13#include <linux/sched.h>
  14#include <linux/file.h>
  15#include <linux/fs.h>
  16#include <linux/fsnotify.h>
  17#include <linux/quotaops.h>
  18#include <linux/xattr.h>
  19#include <linux/mount.h>
  20#include <linux/namei.h>
  21#include <linux/security.h>
  22#include <linux/slab.h>
  23#include "internal.h"
  24
  25#define CACHEFILES_KEYBUF_SIZE 512
  26
  27/*
  28 * dump debugging info about an object
  29 */
  30static noinline
  31void __cachefiles_printk_object(struct cachefiles_object *object,
  32                                const char *prefix,
  33                                u8 *keybuf)
  34{
  35        struct fscache_cookie *cookie;
  36        unsigned keylen, loop;
  37
  38        printk(KERN_ERR "%sobject: OBJ%x\n",
  39               prefix, object->fscache.debug_id);
  40        printk(KERN_ERR "%sobjstate=%s fl=%lx wbusy=%x ev=%lx[%lx]\n",
  41               prefix, object->fscache.state->name,
  42               object->fscache.flags, work_busy(&object->fscache.work),
  43               object->fscache.events, object->fscache.event_mask);
  44        printk(KERN_ERR "%sops=%u inp=%u exc=%u\n",
  45               prefix, object->fscache.n_ops, object->fscache.n_in_progress,
  46               object->fscache.n_exclusive);
  47        printk(KERN_ERR "%sparent=%p\n",
  48               prefix, object->fscache.parent);
  49
  50        spin_lock(&object->fscache.lock);
  51        cookie = object->fscache.cookie;
  52        if (cookie) {
  53                printk(KERN_ERR "%scookie=%p [pr=%p nd=%p fl=%lx]\n",
  54                       prefix,
  55                       object->fscache.cookie,
  56                       object->fscache.cookie->parent,
  57                       object->fscache.cookie->netfs_data,
  58                       object->fscache.cookie->flags);
  59                if (keybuf)
  60                        keylen = cookie->def->get_key(cookie->netfs_data, keybuf,
  61                                                      CACHEFILES_KEYBUF_SIZE);
  62                else
  63                        keylen = 0;
  64        } else {
  65                printk(KERN_ERR "%scookie=NULL\n", prefix);
  66                keylen = 0;
  67        }
  68        spin_unlock(&object->fscache.lock);
  69
  70        if (keylen) {
  71                printk(KERN_ERR "%skey=[%u] '", prefix, keylen);
  72                for (loop = 0; loop < keylen; loop++)
  73                        printk("%02x", keybuf[loop]);
  74                printk("'\n");
  75        }
  76}
  77
  78/*
  79 * dump debugging info about a pair of objects
  80 */
  81static noinline void cachefiles_printk_object(struct cachefiles_object *object,
  82                                              struct cachefiles_object *xobject)
  83{
  84        u8 *keybuf;
  85
  86        keybuf = kmalloc(CACHEFILES_KEYBUF_SIZE, GFP_NOIO);
  87        if (object)
  88                __cachefiles_printk_object(object, "", keybuf);
  89        if (xobject)
  90                __cachefiles_printk_object(xobject, "x", keybuf);
  91        kfree(keybuf);
  92}
  93
  94/*
  95 * mark the owner of a dentry, if there is one, to indicate that that dentry
  96 * has been preemptively deleted
  97 * - the caller must hold the i_mutex on the dentry's parent as required to
  98 *   call vfs_unlink(), vfs_rmdir() or vfs_rename()
  99 */
 100static void cachefiles_mark_object_buried(struct cachefiles_cache *cache,
 101                                          struct dentry *dentry)
 102{
 103        struct cachefiles_object *object;
 104        struct rb_node *p;
 105
 106        _enter(",'%*.*s'",
 107               dentry->d_name.len, dentry->d_name.len, dentry->d_name.name);
 108
 109        write_lock(&cache->active_lock);
 110
 111        p = cache->active_nodes.rb_node;
 112        while (p) {
 113                object = rb_entry(p, struct cachefiles_object, active_node);
 114                if (object->dentry > dentry)
 115                        p = p->rb_left;
 116                else if (object->dentry < dentry)
 117                        p = p->rb_right;
 118                else
 119                        goto found_dentry;
 120        }
 121
 122        write_unlock(&cache->active_lock);
 123        _leave(" [no owner]");
 124        return;
 125
 126        /* found the dentry for  */
 127found_dentry:
 128        kdebug("preemptive burial: OBJ%x [%s] %p",
 129               object->fscache.debug_id,
 130               object->fscache.state->name,
 131               dentry);
 132
 133        if (fscache_object_is_live(&object->fscache)) {
 134                printk(KERN_ERR "\n");
 135                printk(KERN_ERR "CacheFiles: Error:"
 136                       " Can't preemptively bury live object\n");
 137                cachefiles_printk_object(object, NULL);
 138        } else if (test_and_set_bit(CACHEFILES_OBJECT_BURIED, &object->flags)) {
 139                printk(KERN_ERR "CacheFiles: Error:"
 140                       " Object already preemptively buried\n");
 141        }
 142
 143        write_unlock(&cache->active_lock);
 144        _leave(" [owner marked]");
 145}
 146
 147/*
 148 * record the fact that an object is now active
 149 */
 150static int cachefiles_mark_object_active(struct cachefiles_cache *cache,
 151                                         struct cachefiles_object *object)
 152{
 153        struct cachefiles_object *xobject;
 154        struct rb_node **_p, *_parent = NULL;
 155        struct dentry *dentry;
 156
 157        _enter(",%p", object);
 158
 159try_again:
 160        write_lock(&cache->active_lock);
 161
 162        if (test_and_set_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags)) {
 163                printk(KERN_ERR "CacheFiles: Error: Object already active\n");
 164                cachefiles_printk_object(object, NULL);
 165                BUG();
 166        }
 167
 168        dentry = object->dentry;
 169        _p = &cache->active_nodes.rb_node;
 170        while (*_p) {
 171                _parent = *_p;
 172                xobject = rb_entry(_parent,
 173                                   struct cachefiles_object, active_node);
 174
 175                ASSERT(xobject != object);
 176
 177                if (xobject->dentry > dentry)
 178                        _p = &(*_p)->rb_left;
 179                else if (xobject->dentry < dentry)
 180                        _p = &(*_p)->rb_right;
 181                else
 182                        goto wait_for_old_object;
 183        }
 184
 185        rb_link_node(&object->active_node, _parent, _p);
 186        rb_insert_color(&object->active_node, &cache->active_nodes);
 187
 188        write_unlock(&cache->active_lock);
 189        _leave(" = 0");
 190        return 0;
 191
 192        /* an old object from a previous incarnation is hogging the slot - we
 193         * need to wait for it to be destroyed */
 194wait_for_old_object:
 195        if (fscache_object_is_live(&object->fscache)) {
 196                printk(KERN_ERR "\n");
 197                printk(KERN_ERR "CacheFiles: Error:"
 198                       " Unexpected object collision\n");
 199                cachefiles_printk_object(object, xobject);
 200                BUG();
 201        }
 202        atomic_inc(&xobject->usage);
 203        write_unlock(&cache->active_lock);
 204
 205        if (test_bit(CACHEFILES_OBJECT_ACTIVE, &xobject->flags)) {
 206                wait_queue_head_t *wq;
 207
 208                signed long timeout = 60 * HZ;
 209                wait_queue_t wait;
 210                bool requeue;
 211
 212                /* if the object we're waiting for is queued for processing,
 213                 * then just put ourselves on the queue behind it */
 214                if (work_pending(&xobject->fscache.work)) {
 215                        _debug("queue OBJ%x behind OBJ%x immediately",
 216                               object->fscache.debug_id,
 217                               xobject->fscache.debug_id);
 218                        goto requeue;
 219                }
 220
 221                /* otherwise we sleep until either the object we're waiting for
 222                 * is done, or the fscache_object is congested */
 223                wq = bit_waitqueue(&xobject->flags, CACHEFILES_OBJECT_ACTIVE);
 224                init_wait(&wait);
 225                requeue = false;
 226                do {
 227                        prepare_to_wait(wq, &wait, TASK_UNINTERRUPTIBLE);
 228                        if (!test_bit(CACHEFILES_OBJECT_ACTIVE, &xobject->flags))
 229                                break;
 230
 231                        requeue = fscache_object_sleep_till_congested(&timeout);
 232                } while (timeout > 0 && !requeue);
 233                finish_wait(wq, &wait);
 234
 235                if (requeue &&
 236                    test_bit(CACHEFILES_OBJECT_ACTIVE, &xobject->flags)) {
 237                        _debug("queue OBJ%x behind OBJ%x after wait",
 238                               object->fscache.debug_id,
 239                               xobject->fscache.debug_id);
 240                        goto requeue;
 241                }
 242
 243                if (timeout <= 0) {
 244                        printk(KERN_ERR "\n");
 245                        printk(KERN_ERR "CacheFiles: Error: Overlong"
 246                               " wait for old active object to go away\n");
 247                        cachefiles_printk_object(object, xobject);
 248                        goto requeue;
 249                }
 250        }
 251
 252        ASSERT(!test_bit(CACHEFILES_OBJECT_ACTIVE, &xobject->flags));
 253
 254        cache->cache.ops->put_object(&xobject->fscache);
 255        goto try_again;
 256
 257requeue:
 258        clear_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags);
 259        cache->cache.ops->put_object(&xobject->fscache);
 260        _leave(" = -ETIMEDOUT");
 261        return -ETIMEDOUT;
 262}
 263
 264/*
 265 * delete an object representation from the cache
 266 * - file backed objects are unlinked
 267 * - directory backed objects are stuffed into the graveyard for userspace to
 268 *   delete
 269 * - unlocks the directory mutex
 270 */
 271static int cachefiles_bury_object(struct cachefiles_cache *cache,
 272                                  struct dentry *dir,
 273                                  struct dentry *rep,
 274                                  bool preemptive)
 275{
 276        struct dentry *grave, *trap;
 277        struct path path, path_to_graveyard;
 278        char nbuffer[8 + 8 + 1];
 279        int ret;
 280
 281        _enter(",'%*.*s','%*.*s'",
 282               dir->d_name.len, dir->d_name.len, dir->d_name.name,
 283               rep->d_name.len, rep->d_name.len, rep->d_name.name);
 284
 285        _debug("remove %p from %p", rep, dir);
 286
 287        /* non-directories can just be unlinked */
 288        if (!S_ISDIR(rep->d_inode->i_mode)) {
 289                _debug("unlink stale object");
 290
 291                path.mnt = cache->mnt;
 292                path.dentry = dir;
 293                ret = security_path_unlink(&path, rep);
 294                if (ret < 0) {
 295                        cachefiles_io_error(cache, "Unlink security error");
 296                } else {
 297                        ret = vfs_unlink(dir->d_inode, rep);
 298
 299                        if (preemptive)
 300                                cachefiles_mark_object_buried(cache, rep);
 301                }
 302
 303                mutex_unlock(&dir->d_inode->i_mutex);
 304
 305                if (ret == -EIO)
 306                        cachefiles_io_error(cache, "Unlink failed");
 307
 308                _leave(" = %d", ret);
 309                return ret;
 310        }
 311
 312        /* directories have to be moved to the graveyard */
 313        _debug("move stale object to graveyard");
 314        mutex_unlock(&dir->d_inode->i_mutex);
 315
 316try_again:
 317        /* first step is to make up a grave dentry in the graveyard */
 318        sprintf(nbuffer, "%08x%08x",
 319                (uint32_t) get_seconds(),
 320                (uint32_t) atomic_inc_return(&cache->gravecounter));
 321
 322        /* do the multiway lock magic */
 323        trap = lock_rename(cache->graveyard, dir);
 324
 325        /* do some checks before getting the grave dentry */
 326        if (rep->d_parent != dir) {
 327                /* the entry was probably culled when we dropped the parent dir
 328                 * lock */
 329                unlock_rename(cache->graveyard, dir);
 330                _leave(" = 0 [culled?]");
 331                return 0;
 332        }
 333
 334        if (!S_ISDIR(cache->graveyard->d_inode->i_mode)) {
 335                unlock_rename(cache->graveyard, dir);
 336                cachefiles_io_error(cache, "Graveyard no longer a directory");
 337                return -EIO;
 338        }
 339
 340        if (trap == rep) {
 341                unlock_rename(cache->graveyard, dir);
 342                cachefiles_io_error(cache, "May not make directory loop");
 343                return -EIO;
 344        }
 345
 346        if (d_mountpoint(rep)) {
 347                unlock_rename(cache->graveyard, dir);
 348                cachefiles_io_error(cache, "Mountpoint in cache");
 349                return -EIO;
 350        }
 351
 352        grave = lookup_one_len(nbuffer, cache->graveyard, strlen(nbuffer));
 353        if (IS_ERR(grave)) {
 354                unlock_rename(cache->graveyard, dir);
 355
 356                if (PTR_ERR(grave) == -ENOMEM) {
 357                        _leave(" = -ENOMEM");
 358                        return -ENOMEM;
 359                }
 360
 361                cachefiles_io_error(cache, "Lookup error %ld",
 362                                    PTR_ERR(grave));
 363                return -EIO;
 364        }
 365
 366        if (grave->d_inode) {
 367                unlock_rename(cache->graveyard, dir);
 368                dput(grave);
 369                grave = NULL;
 370                cond_resched();
 371                goto try_again;
 372        }
 373
 374        if (d_mountpoint(grave)) {
 375                unlock_rename(cache->graveyard, dir);
 376                dput(grave);
 377                cachefiles_io_error(cache, "Mountpoint in graveyard");
 378                return -EIO;
 379        }
 380
 381        /* target should not be an ancestor of source */
 382        if (trap == grave) {
 383                unlock_rename(cache->graveyard, dir);
 384                dput(grave);
 385                cachefiles_io_error(cache, "May not make directory loop");
 386                return -EIO;
 387        }
 388
 389        /* attempt the rename */
 390        path.mnt = cache->mnt;
 391        path.dentry = dir;
 392        path_to_graveyard.mnt = cache->mnt;
 393        path_to_graveyard.dentry = cache->graveyard;
 394        ret = security_path_rename(&path, rep, &path_to_graveyard, grave);
 395        if (ret < 0) {
 396                cachefiles_io_error(cache, "Rename security error %d", ret);
 397        } else {
 398                ret = vfs_rename(dir->d_inode, rep,
 399                                 cache->graveyard->d_inode, grave);
 400                if (ret != 0 && ret != -ENOMEM)
 401                        cachefiles_io_error(cache,
 402                                            "Rename failed with error %d", ret);
 403
 404                if (preemptive)
 405                        cachefiles_mark_object_buried(cache, rep);
 406        }
 407
 408        unlock_rename(cache->graveyard, dir);
 409        dput(grave);
 410        _leave(" = 0");
 411        return 0;
 412}
 413
 414/*
 415 * delete an object representation from the cache
 416 */
 417int cachefiles_delete_object(struct cachefiles_cache *cache,
 418                             struct cachefiles_object *object)
 419{
 420        struct dentry *dir;
 421        int ret;
 422
 423        _enter(",OBJ%x{%p}", object->fscache.debug_id, object->dentry);
 424
 425        ASSERT(object->dentry);
 426        ASSERT(object->dentry->d_inode);
 427        ASSERT(object->dentry->d_parent);
 428
 429        dir = dget_parent(object->dentry);
 430
 431        mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_PARENT);
 432
 433        if (test_bit(CACHEFILES_OBJECT_BURIED, &object->flags)) {
 434                /* object allocation for the same key preemptively deleted this
 435                 * object's file so that it could create its own file */
 436                _debug("object preemptively buried");
 437                mutex_unlock(&dir->d_inode->i_mutex);
 438                ret = 0;
 439        } else {
 440                /* we need to check that our parent is _still_ our parent - it
 441                 * may have been renamed */
 442                if (dir == object->dentry->d_parent) {
 443                        ret = cachefiles_bury_object(cache, dir,
 444                                                     object->dentry, false);
 445                } else {
 446                        /* it got moved, presumably by cachefilesd culling it,
 447                         * so it's no longer in the key path and we can ignore
 448                         * it */
 449                        mutex_unlock(&dir->d_inode->i_mutex);
 450                        ret = 0;
 451                }
 452        }
 453
 454        dput(dir);
 455        _leave(" = %d", ret);
 456        return ret;
 457}
 458
 459/*
 460 * walk from the parent object to the child object through the backing
 461 * filesystem, creating directories as we go
 462 */
 463int cachefiles_walk_to_object(struct cachefiles_object *parent,
 464                              struct cachefiles_object *object,
 465                              const char *key,
 466                              struct cachefiles_xattr *auxdata)
 467{
 468        struct cachefiles_cache *cache;
 469        struct dentry *dir, *next = NULL;
 470        struct path path;
 471        unsigned long start;
 472        const char *name;
 473        int ret, nlen;
 474
 475        _enter("OBJ%x{%p},OBJ%x,%s,",
 476               parent->fscache.debug_id, parent->dentry,
 477               object->fscache.debug_id, key);
 478
 479        cache = container_of(parent->fscache.cache,
 480                             struct cachefiles_cache, cache);
 481        path.mnt = cache->mnt;
 482
 483        ASSERT(parent->dentry);
 484        ASSERT(parent->dentry->d_inode);
 485
 486        if (!(S_ISDIR(parent->dentry->d_inode->i_mode))) {
 487                // TODO: convert file to dir
 488                _leave("looking up in none directory");
 489                return -ENOBUFS;
 490        }
 491
 492        dir = dget(parent->dentry);
 493
 494advance:
 495        /* attempt to transit the first directory component */
 496        name = key;
 497        nlen = strlen(key);
 498
 499        /* key ends in a double NUL */
 500        key = key + nlen + 1;
 501        if (!*key)
 502                key = NULL;
 503
 504lookup_again:
 505        /* search the current directory for the element name */
 506        _debug("lookup '%s'", name);
 507
 508        mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_PARENT);
 509
 510        start = jiffies;
 511        next = lookup_one_len(name, dir, nlen);
 512        cachefiles_hist(cachefiles_lookup_histogram, start);
 513        if (IS_ERR(next))
 514                goto lookup_error;
 515
 516        _debug("next -> %p %s", next, next->d_inode ? "positive" : "negative");
 517
 518        if (!key)
 519                object->new = !next->d_inode;
 520
 521        /* if this element of the path doesn't exist, then the lookup phase
 522         * failed, and we can release any readers in the certain knowledge that
 523         * there's nothing for them to actually read */
 524        if (!next->d_inode)
 525                fscache_object_lookup_negative(&object->fscache);
 526
 527        /* we need to create the object if it's negative */
 528        if (key || object->type == FSCACHE_COOKIE_TYPE_INDEX) {
 529                /* index objects and intervening tree levels must be subdirs */
 530                if (!next->d_inode) {
 531                        ret = cachefiles_has_space(cache, 1, 0);
 532                        if (ret < 0)
 533                                goto create_error;
 534
 535                        path.dentry = dir;
 536                        ret = security_path_mkdir(&path, next, 0);
 537                        if (ret < 0)
 538                                goto create_error;
 539                        start = jiffies;
 540                        ret = vfs_mkdir(dir->d_inode, next, 0);
 541                        cachefiles_hist(cachefiles_mkdir_histogram, start);
 542                        if (ret < 0)
 543                                goto create_error;
 544
 545                        ASSERT(next->d_inode);
 546
 547                        _debug("mkdir -> %p{%p{ino=%lu}}",
 548                               next, next->d_inode, next->d_inode->i_ino);
 549
 550                } else if (!S_ISDIR(next->d_inode->i_mode)) {
 551                        kerror("inode %lu is not a directory",
 552                               next->d_inode->i_ino);
 553                        ret = -ENOBUFS;
 554                        goto error;
 555                }
 556
 557        } else {
 558                /* non-index objects start out life as files */
 559                if (!next->d_inode) {
 560                        ret = cachefiles_has_space(cache, 1, 0);
 561                        if (ret < 0)
 562                                goto create_error;
 563
 564                        path.dentry = dir;
 565                        ret = security_path_mknod(&path, next, S_IFREG, 0);
 566                        if (ret < 0)
 567                                goto create_error;
 568                        start = jiffies;
 569                        ret = vfs_create(dir->d_inode, next, S_IFREG, true);
 570                        cachefiles_hist(cachefiles_create_histogram, start);
 571                        if (ret < 0)
 572                                goto create_error;
 573
 574                        ASSERT(next->d_inode);
 575
 576                        _debug("create -> %p{%p{ino=%lu}}",
 577                               next, next->d_inode, next->d_inode->i_ino);
 578
 579                } else if (!S_ISDIR(next->d_inode->i_mode) &&
 580                           !S_ISREG(next->d_inode->i_mode)
 581                           ) {
 582                        kerror("inode %lu is not a file or directory",
 583                               next->d_inode->i_ino);
 584                        ret = -ENOBUFS;
 585                        goto error;
 586                }
 587        }
 588
 589        /* process the next component */
 590        if (key) {
 591                _debug("advance");
 592                mutex_unlock(&dir->d_inode->i_mutex);
 593                dput(dir);
 594                dir = next;
 595                next = NULL;
 596                goto advance;
 597        }
 598
 599        /* we've found the object we were looking for */
 600        object->dentry = next;
 601
 602        /* if we've found that the terminal object exists, then we need to
 603         * check its attributes and delete it if it's out of date */
 604        if (!object->new) {
 605                _debug("validate '%*.*s'",
 606                       next->d_name.len, next->d_name.len, next->d_name.name);
 607
 608                ret = cachefiles_check_object_xattr(object, auxdata);
 609                if (ret == -ESTALE) {
 610                        /* delete the object (the deleter drops the directory
 611                         * mutex) */
 612                        object->dentry = NULL;
 613
 614                        ret = cachefiles_bury_object(cache, dir, next, true);
 615                        dput(next);
 616                        next = NULL;
 617
 618                        if (ret < 0)
 619                                goto delete_error;
 620
 621                        _debug("redo lookup");
 622                        goto lookup_again;
 623                }
 624        }
 625
 626        /* note that we're now using this object */
 627        ret = cachefiles_mark_object_active(cache, object);
 628
 629        mutex_unlock(&dir->d_inode->i_mutex);
 630        dput(dir);
 631        dir = NULL;
 632
 633        if (ret == -ETIMEDOUT)
 634                goto mark_active_timed_out;
 635
 636        _debug("=== OBTAINED_OBJECT ===");
 637
 638        if (object->new) {
 639                /* attach data to a newly constructed terminal object */
 640                ret = cachefiles_set_object_xattr(object, auxdata);
 641                if (ret < 0)
 642                        goto check_error;
 643        } else {
 644                /* always update the atime on an object we've just looked up
 645                 * (this is used to keep track of culling, and atimes are only
 646                 * updated by read, write and readdir but not lookup or
 647                 * open) */
 648                path.dentry = next;
 649                touch_atime(&path);
 650        }
 651
 652        /* open a file interface onto a data file */
 653        if (object->type != FSCACHE_COOKIE_TYPE_INDEX) {
 654                if (S_ISREG(object->dentry->d_inode->i_mode)) {
 655                        const struct address_space_operations *aops;
 656
 657                        ret = -EPERM;
 658                        aops = object->dentry->d_inode->i_mapping->a_ops;
 659                        if (!aops->bmap)
 660                                goto check_error;
 661
 662                        object->backer = object->dentry;
 663                } else {
 664                        BUG(); // TODO: open file in data-class subdir
 665                }
 666        }
 667
 668        object->new = 0;
 669        fscache_obtained_object(&object->fscache);
 670
 671        _leave(" = 0 [%lu]", object->dentry->d_inode->i_ino);
 672        return 0;
 673
 674create_error:
 675        _debug("create error %d", ret);
 676        if (ret == -EIO)
 677                cachefiles_io_error(cache, "Create/mkdir failed");
 678        goto error;
 679
 680mark_active_timed_out:
 681        _debug("mark active timed out");
 682        goto release_dentry;
 683
 684check_error:
 685        _debug("check error %d", ret);
 686        write_lock(&cache->active_lock);
 687        rb_erase(&object->active_node, &cache->active_nodes);
 688        clear_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags);
 689        wake_up_bit(&object->flags, CACHEFILES_OBJECT_ACTIVE);
 690        write_unlock(&cache->active_lock);
 691release_dentry:
 692        dput(object->dentry);
 693        object->dentry = NULL;
 694        goto error_out;
 695
 696delete_error:
 697        _debug("delete error %d", ret);
 698        goto error_out2;
 699
 700lookup_error:
 701        _debug("lookup error %ld", PTR_ERR(next));
 702        ret = PTR_ERR(next);
 703        if (ret == -EIO)
 704                cachefiles_io_error(cache, "Lookup failed");
 705        next = NULL;
 706error:
 707        mutex_unlock(&dir->d_inode->i_mutex);
 708        dput(next);
 709error_out2:
 710        dput(dir);
 711error_out:
 712        _leave(" = error %d", -ret);
 713        return ret;
 714}
 715
 716/*
 717 * get a subdirectory
 718 */
 719struct dentry *cachefiles_get_directory(struct cachefiles_cache *cache,
 720                                        struct dentry *dir,
 721                                        const char *dirname)
 722{
 723        struct dentry *subdir;
 724        unsigned long start;
 725        struct path path;
 726        int ret;
 727
 728        _enter(",,%s", dirname);
 729
 730        /* search the current directory for the element name */
 731        mutex_lock(&dir->d_inode->i_mutex);
 732
 733        start = jiffies;
 734        subdir = lookup_one_len(dirname, dir, strlen(dirname));
 735        cachefiles_hist(cachefiles_lookup_histogram, start);
 736        if (IS_ERR(subdir)) {
 737                if (PTR_ERR(subdir) == -ENOMEM)
 738                        goto nomem_d_alloc;
 739                goto lookup_error;
 740        }
 741
 742        _debug("subdir -> %p %s",
 743               subdir, subdir->d_inode ? "positive" : "negative");
 744
 745        /* we need to create the subdir if it doesn't exist yet */
 746        if (!subdir->d_inode) {
 747                ret = cachefiles_has_space(cache, 1, 0);
 748                if (ret < 0)
 749                        goto mkdir_error;
 750
 751                _debug("attempt mkdir");
 752
 753                path.mnt = cache->mnt;
 754                path.dentry = dir;
 755                ret = security_path_mkdir(&path, subdir, 0700);
 756                if (ret < 0)
 757                        goto mkdir_error;
 758                ret = vfs_mkdir(dir->d_inode, subdir, 0700);
 759                if (ret < 0)
 760                        goto mkdir_error;
 761
 762                ASSERT(subdir->d_inode);
 763
 764                _debug("mkdir -> %p{%p{ino=%lu}}",
 765                       subdir,
 766                       subdir->d_inode,
 767                       subdir->d_inode->i_ino);
 768        }
 769
 770        mutex_unlock(&dir->d_inode->i_mutex);
 771
 772        /* we need to make sure the subdir is a directory */
 773        ASSERT(subdir->d_inode);
 774
 775        if (!S_ISDIR(subdir->d_inode->i_mode)) {
 776                kerror("%s is not a directory", dirname);
 777                ret = -EIO;
 778                goto check_error;
 779        }
 780
 781        ret = -EPERM;
 782        if (!subdir->d_inode->i_op ||
 783            !subdir->d_inode->i_op->setxattr ||
 784            !subdir->d_inode->i_op->getxattr ||
 785            !subdir->d_inode->i_op->lookup ||
 786            !subdir->d_inode->i_op->mkdir ||
 787            !subdir->d_inode->i_op->create ||
 788            !subdir->d_inode->i_op->rename ||
 789            !subdir->d_inode->i_op->rmdir ||
 790            !subdir->d_inode->i_op->unlink)
 791                goto check_error;
 792
 793        _leave(" = [%lu]", subdir->d_inode->i_ino);
 794        return subdir;
 795
 796check_error:
 797        dput(subdir);
 798        _leave(" = %d [check]", ret);
 799        return ERR_PTR(ret);
 800
 801mkdir_error:
 802        mutex_unlock(&dir->d_inode->i_mutex);
 803        dput(subdir);
 804        kerror("mkdir %s failed with error %d", dirname, ret);
 805        return ERR_PTR(ret);
 806
 807lookup_error:
 808        mutex_unlock(&dir->d_inode->i_mutex);
 809        ret = PTR_ERR(subdir);
 810        kerror("Lookup %s failed with error %d", dirname, ret);
 811        return ERR_PTR(ret);
 812
 813nomem_d_alloc:
 814        mutex_unlock(&dir->d_inode->i_mutex);
 815        _leave(" = -ENOMEM");
 816        return ERR_PTR(-ENOMEM);
 817}
 818
 819/*
 820 * find out if an object is in use or not
 821 * - if finds object and it's not in use:
 822 *   - returns a pointer to the object and a reference on it
 823 *   - returns with the directory locked
 824 */
 825static struct dentry *cachefiles_check_active(struct cachefiles_cache *cache,
 826                                              struct dentry *dir,
 827                                              char *filename)
 828{
 829        struct cachefiles_object *object;
 830        struct rb_node *_n;
 831        struct dentry *victim;
 832        unsigned long start;
 833        int ret;
 834
 835        //_enter(",%*.*s/,%s",
 836        //       dir->d_name.len, dir->d_name.len, dir->d_name.name, filename);
 837
 838        /* look up the victim */
 839        mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_PARENT);
 840
 841        start = jiffies;
 842        victim = lookup_one_len(filename, dir, strlen(filename));
 843        cachefiles_hist(cachefiles_lookup_histogram, start);
 844        if (IS_ERR(victim))
 845                goto lookup_error;
 846
 847        //_debug("victim -> %p %s",
 848        //       victim, victim->d_inode ? "positive" : "negative");
 849
 850        /* if the object is no longer there then we probably retired the object
 851         * at the netfs's request whilst the cull was in progress
 852         */
 853        if (!victim->d_inode) {
 854                mutex_unlock(&dir->d_inode->i_mutex);
 855                dput(victim);
 856                _leave(" = -ENOENT [absent]");
 857                return ERR_PTR(-ENOENT);
 858        }
 859
 860        /* check to see if we're using this object */
 861        read_lock(&cache->active_lock);
 862
 863        _n = cache->active_nodes.rb_node;
 864
 865        while (_n) {
 866                object = rb_entry(_n, struct cachefiles_object, active_node);
 867
 868                if (object->dentry > victim)
 869                        _n = _n->rb_left;
 870                else if (object->dentry < victim)
 871                        _n = _n->rb_right;
 872                else
 873                        goto object_in_use;
 874        }
 875
 876        read_unlock(&cache->active_lock);
 877
 878        //_leave(" = %p", victim);
 879        return victim;
 880
 881object_in_use:
 882        read_unlock(&cache->active_lock);
 883        mutex_unlock(&dir->d_inode->i_mutex);
 884        dput(victim);
 885        //_leave(" = -EBUSY [in use]");
 886        return ERR_PTR(-EBUSY);
 887
 888lookup_error:
 889        mutex_unlock(&dir->d_inode->i_mutex);
 890        ret = PTR_ERR(victim);
 891        if (ret == -ENOENT) {
 892                /* file or dir now absent - probably retired by netfs */
 893                _leave(" = -ESTALE [absent]");
 894                return ERR_PTR(-ESTALE);
 895        }
 896
 897        if (ret == -EIO) {
 898                cachefiles_io_error(cache, "Lookup failed");
 899        } else if (ret != -ENOMEM) {
 900                kerror("Internal error: %d", ret);
 901                ret = -EIO;
 902        }
 903
 904        _leave(" = %d", ret);
 905        return ERR_PTR(ret);
 906}
 907
 908/*
 909 * cull an object if it's not in use
 910 * - called only by cache manager daemon
 911 */
 912int cachefiles_cull(struct cachefiles_cache *cache, struct dentry *dir,
 913                    char *filename)
 914{
 915        struct dentry *victim;
 916        int ret;
 917
 918        _enter(",%*.*s/,%s",
 919               dir->d_name.len, dir->d_name.len, dir->d_name.name, filename);
 920
 921        victim = cachefiles_check_active(cache, dir, filename);
 922        if (IS_ERR(victim))
 923                return PTR_ERR(victim);
 924
 925        _debug("victim -> %p %s",
 926               victim, victim->d_inode ? "positive" : "negative");
 927
 928        /* okay... the victim is not being used so we can cull it
 929         * - start by marking it as stale
 930         */
 931        _debug("victim is cullable");
 932
 933        ret = cachefiles_remove_object_xattr(cache, victim);
 934        if (ret < 0)
 935                goto error_unlock;
 936
 937        /*  actually remove the victim (drops the dir mutex) */
 938        _debug("bury");
 939
 940        ret = cachefiles_bury_object(cache, dir, victim, false);
 941        if (ret < 0)
 942                goto error;
 943
 944        dput(victim);
 945        _leave(" = 0");
 946        return 0;
 947
 948error_unlock:
 949        mutex_unlock(&dir->d_inode->i_mutex);
 950error:
 951        dput(victim);
 952        if (ret == -ENOENT) {
 953                /* file or dir now absent - probably retired by netfs */
 954                _leave(" = -ESTALE [absent]");
 955                return -ESTALE;
 956        }
 957
 958        if (ret != -ENOMEM) {
 959                kerror("Internal error: %d", ret);
 960                ret = -EIO;
 961        }
 962
 963        _leave(" = %d", ret);
 964        return ret;
 965}
 966
 967/*
 968 * find out if an object is in use or not
 969 * - called only by cache manager daemon
 970 * - returns -EBUSY or 0 to indicate whether an object is in use or not
 971 */
 972int cachefiles_check_in_use(struct cachefiles_cache *cache, struct dentry *dir,
 973                            char *filename)
 974{
 975        struct dentry *victim;
 976
 977        //_enter(",%*.*s/,%s",
 978        //       dir->d_name.len, dir->d_name.len, dir->d_name.name, filename);
 979
 980        victim = cachefiles_check_active(cache, dir, filename);
 981        if (IS_ERR(victim))
 982                return PTR_ERR(victim);
 983
 984        mutex_unlock(&dir->d_inode->i_mutex);
 985        dput(victim);
 986        //_leave(" = 0");
 987        return 0;
 988}
 989
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