linux/fs/super.c
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   1/*
   2 *  linux/fs/super.c
   3 *
   4 *  Copyright (C) 1991, 1992  Linus Torvalds
   5 *
   6 *  super.c contains code to handle: - mount structures
   7 *                                   - super-block tables
   8 *                                   - filesystem drivers list
   9 *                                   - mount system call
  10 *                                   - umount system call
  11 *                                   - ustat system call
  12 *
  13 * GK 2/5/95  -  Changed to support mounting the root fs via NFS
  14 *
  15 *  Added kerneld support: Jacques Gelinas and Bjorn Ekwall
  16 *  Added change_root: Werner Almesberger & Hans Lermen, Feb '96
  17 *  Added options to /proc/mounts:
  18 *    Torbjörn Lindh (torbjorn.lindh@gopta.se), April 14, 1996.
  19 *  Added devfs support: Richard Gooch <rgooch@atnf.csiro.au>, 13-JAN-1998
  20 *  Heavily rewritten for 'one fs - one tree' dcache architecture. AV, Mar 2000
  21 */
  22
  23#include <linux/export.h>
  24#include <linux/slab.h>
  25#include <linux/acct.h>
  26#include <linux/blkdev.h>
  27#include <linux/mount.h>
  28#include <linux/security.h>
  29#include <linux/writeback.h>            /* for the emergency remount stuff */
  30#include <linux/idr.h>
  31#include <linux/mutex.h>
  32#include <linux/backing-dev.h>
  33#include <linux/rculist_bl.h>
  34#include <linux/cleancache.h>
  35#include <linux/fsnotify.h>
  36#include <linux/lockdep.h>
  37#include "internal.h"
  38
  39
  40LIST_HEAD(super_blocks);
  41DEFINE_SPINLOCK(sb_lock);
  42
  43static char *sb_writers_name[SB_FREEZE_LEVELS] = {
  44        "sb_writers",
  45        "sb_pagefaults",
  46        "sb_internal",
  47};
  48
  49/*
  50 * One thing we have to be careful of with a per-sb shrinker is that we don't
  51 * drop the last active reference to the superblock from within the shrinker.
  52 * If that happens we could trigger unregistering the shrinker from within the
  53 * shrinker path and that leads to deadlock on the shrinker_rwsem. Hence we
  54 * take a passive reference to the superblock to avoid this from occurring.
  55 */
  56static int prune_super(struct shrinker *shrink, struct shrink_control *sc)
  57{
  58        struct super_block *sb;
  59        int     fs_objects = 0;
  60        int     total_objects;
  61
  62        sb = container_of(shrink, struct super_block, s_shrink);
  63
  64        /*
  65         * Deadlock avoidance.  We may hold various FS locks, and we don't want
  66         * to recurse into the FS that called us in clear_inode() and friends..
  67         */
  68        if (sc->nr_to_scan && !(sc->gfp_mask & __GFP_FS))
  69                return -1;
  70
  71        if (!grab_super_passive(sb))
  72                return -1;
  73
  74        if (sb->s_op && sb->s_op->nr_cached_objects)
  75                fs_objects = sb->s_op->nr_cached_objects(sb);
  76
  77        total_objects = sb->s_nr_dentry_unused +
  78                        sb->s_nr_inodes_unused + fs_objects + 1;
  79
  80        if (sc->nr_to_scan) {
  81                int     dentries;
  82                int     inodes;
  83
  84                /* proportion the scan between the caches */
  85                dentries = (sc->nr_to_scan * sb->s_nr_dentry_unused) /
  86                                                        total_objects;
  87                inodes = (sc->nr_to_scan * sb->s_nr_inodes_unused) /
  88                                                        total_objects;
  89                if (fs_objects)
  90                        fs_objects = (sc->nr_to_scan * fs_objects) /
  91                                                        total_objects;
  92                /*
  93                 * prune the dcache first as the icache is pinned by it, then
  94                 * prune the icache, followed by the filesystem specific caches
  95                 */
  96                prune_dcache_sb(sb, dentries);
  97                prune_icache_sb(sb, inodes);
  98
  99                if (fs_objects && sb->s_op->free_cached_objects) {
 100                        sb->s_op->free_cached_objects(sb, fs_objects);
 101                        fs_objects = sb->s_op->nr_cached_objects(sb);
 102                }
 103                total_objects = sb->s_nr_dentry_unused +
 104                                sb->s_nr_inodes_unused + fs_objects;
 105        }
 106
 107        total_objects = (total_objects / 100) * sysctl_vfs_cache_pressure;
 108        drop_super(sb);
 109        return total_objects;
 110}
 111
 112static int init_sb_writers(struct super_block *s, struct file_system_type *type)
 113{
 114        int err;
 115        int i;
 116
 117        for (i = 0; i < SB_FREEZE_LEVELS; i++) {
 118                err = percpu_counter_init(&s->s_writers.counter[i], 0);
 119                if (err < 0)
 120                        goto err_out;
 121                lockdep_init_map(&s->s_writers.lock_map[i], sb_writers_name[i],
 122                                 &type->s_writers_key[i], 0);
 123        }
 124        init_waitqueue_head(&s->s_writers.wait);
 125        init_waitqueue_head(&s->s_writers.wait_unfrozen);
 126        return 0;
 127err_out:
 128        while (--i >= 0)
 129                percpu_counter_destroy(&s->s_writers.counter[i]);
 130        return err;
 131}
 132
 133static void destroy_sb_writers(struct super_block *s)
 134{
 135        int i;
 136
 137        for (i = 0; i < SB_FREEZE_LEVELS; i++)
 138                percpu_counter_destroy(&s->s_writers.counter[i]);
 139}
 140
 141/**
 142 *      alloc_super     -       create new superblock
 143 *      @type:  filesystem type superblock should belong to
 144 *      @flags: the mount flags
 145 *
 146 *      Allocates and initializes a new &struct super_block.  alloc_super()
 147 *      returns a pointer new superblock or %NULL if allocation had failed.
 148 */
 149static struct super_block *alloc_super(struct file_system_type *type, int flags)
 150{
 151        struct super_block *s = kzalloc(sizeof(struct super_block),  GFP_USER);
 152        static const struct super_operations default_op;
 153
 154        if (s) {
 155                if (security_sb_alloc(s)) {
 156                        /*
 157                         * We cannot call security_sb_free() without
 158                         * security_sb_alloc() succeeding. So bail out manually
 159                         */
 160                        kfree(s);
 161                        s = NULL;
 162                        goto out;
 163                }
 164#ifdef CONFIG_SMP
 165                s->s_files = alloc_percpu(struct list_head);
 166                if (!s->s_files)
 167                        goto err_out;
 168                else {
 169                        int i;
 170
 171                        for_each_possible_cpu(i)
 172                                INIT_LIST_HEAD(per_cpu_ptr(s->s_files, i));
 173                }
 174#else
 175                INIT_LIST_HEAD(&s->s_files);
 176#endif
 177                if (init_sb_writers(s, type))
 178                        goto err_out;
 179                s->s_flags = flags;
 180                s->s_bdi = &default_backing_dev_info;
 181                INIT_HLIST_NODE(&s->s_instances);
 182                INIT_HLIST_BL_HEAD(&s->s_anon);
 183                INIT_LIST_HEAD(&s->s_inodes);
 184                INIT_LIST_HEAD(&s->s_dentry_lru);
 185                INIT_LIST_HEAD(&s->s_inode_lru);
 186                spin_lock_init(&s->s_inode_lru_lock);
 187                INIT_LIST_HEAD(&s->s_mounts);
 188                init_rwsem(&s->s_umount);
 189                lockdep_set_class(&s->s_umount, &type->s_umount_key);
 190                /*
 191                 * sget() can have s_umount recursion.
 192                 *
 193                 * When it cannot find a suitable sb, it allocates a new
 194                 * one (this one), and tries again to find a suitable old
 195                 * one.
 196                 *
 197                 * In case that succeeds, it will acquire the s_umount
 198                 * lock of the old one. Since these are clearly distrinct
 199                 * locks, and this object isn't exposed yet, there's no
 200                 * risk of deadlocks.
 201                 *
 202                 * Annotate this by putting this lock in a different
 203                 * subclass.
 204                 */
 205                down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING);
 206                s->s_count = 1;
 207                atomic_set(&s->s_active, 1);
 208                mutex_init(&s->s_vfs_rename_mutex);
 209                lockdep_set_class(&s->s_vfs_rename_mutex, &type->s_vfs_rename_key);
 210                mutex_init(&s->s_dquot.dqio_mutex);
 211                mutex_init(&s->s_dquot.dqonoff_mutex);
 212                init_rwsem(&s->s_dquot.dqptr_sem);
 213                s->s_maxbytes = MAX_NON_LFS;
 214                s->s_op = &default_op;
 215                s->s_time_gran = 1000000000;
 216                s->cleancache_poolid = -1;
 217
 218                s->s_shrink.seeks = DEFAULT_SEEKS;
 219                s->s_shrink.shrink = prune_super;
 220                s->s_shrink.batch = 1024;
 221        }
 222out:
 223        return s;
 224err_out:
 225        security_sb_free(s);
 226#ifdef CONFIG_SMP
 227        if (s->s_files)
 228                free_percpu(s->s_files);
 229#endif
 230        destroy_sb_writers(s);
 231        kfree(s);
 232        s = NULL;
 233        goto out;
 234}
 235
 236/**
 237 *      destroy_super   -       frees a superblock
 238 *      @s: superblock to free
 239 *
 240 *      Frees a superblock.
 241 */
 242static inline void destroy_super(struct super_block *s)
 243{
 244#ifdef CONFIG_SMP
 245        free_percpu(s->s_files);
 246#endif
 247        destroy_sb_writers(s);
 248        security_sb_free(s);
 249        WARN_ON(!list_empty(&s->s_mounts));
 250        kfree(s->s_subtype);
 251        kfree(s->s_options);
 252        kfree(s);
 253}
 254
 255/* Superblock refcounting  */
 256
 257/*
 258 * Drop a superblock's refcount.  The caller must hold sb_lock.
 259 */
 260static void __put_super(struct super_block *sb)
 261{
 262        if (!--sb->s_count) {
 263                list_del_init(&sb->s_list);
 264                destroy_super(sb);
 265        }
 266}
 267
 268/**
 269 *      put_super       -       drop a temporary reference to superblock
 270 *      @sb: superblock in question
 271 *
 272 *      Drops a temporary reference, frees superblock if there's no
 273 *      references left.
 274 */
 275static void put_super(struct super_block *sb)
 276{
 277        spin_lock(&sb_lock);
 278        __put_super(sb);
 279        spin_unlock(&sb_lock);
 280}
 281
 282
 283/**
 284 *      deactivate_locked_super -       drop an active reference to superblock
 285 *      @s: superblock to deactivate
 286 *
 287 *      Drops an active reference to superblock, converting it into a temprory
 288 *      one if there is no other active references left.  In that case we
 289 *      tell fs driver to shut it down and drop the temporary reference we
 290 *      had just acquired.
 291 *
 292 *      Caller holds exclusive lock on superblock; that lock is released.
 293 */
 294void deactivate_locked_super(struct super_block *s)
 295{
 296        struct file_system_type *fs = s->s_type;
 297        if (atomic_dec_and_test(&s->s_active)) {
 298                cleancache_invalidate_fs(s);
 299                fs->kill_sb(s);
 300
 301                /* caches are now gone, we can safely kill the shrinker now */
 302                unregister_shrinker(&s->s_shrink);
 303                put_filesystem(fs);
 304                put_super(s);
 305        } else {
 306                up_write(&s->s_umount);
 307        }
 308}
 309
 310EXPORT_SYMBOL(deactivate_locked_super);
 311
 312/**
 313 *      deactivate_super        -       drop an active reference to superblock
 314 *      @s: superblock to deactivate
 315 *
 316 *      Variant of deactivate_locked_super(), except that superblock is *not*
 317 *      locked by caller.  If we are going to drop the final active reference,
 318 *      lock will be acquired prior to that.
 319 */
 320void deactivate_super(struct super_block *s)
 321{
 322        if (!atomic_add_unless(&s->s_active, -1, 1)) {
 323                down_write(&s->s_umount);
 324                deactivate_locked_super(s);
 325        }
 326}
 327
 328EXPORT_SYMBOL(deactivate_super);
 329
 330/**
 331 *      grab_super - acquire an active reference
 332 *      @s: reference we are trying to make active
 333 *
 334 *      Tries to acquire an active reference.  grab_super() is used when we
 335 *      had just found a superblock in super_blocks or fs_type->fs_supers
 336 *      and want to turn it into a full-blown active reference.  grab_super()
 337 *      is called with sb_lock held and drops it.  Returns 1 in case of
 338 *      success, 0 if we had failed (superblock contents was already dead or
 339 *      dying when grab_super() had been called).
 340 */
 341static int grab_super(struct super_block *s) __releases(sb_lock)
 342{
 343        if (atomic_inc_not_zero(&s->s_active)) {
 344                spin_unlock(&sb_lock);
 345                return 1;
 346        }
 347        /* it's going away */
 348        s->s_count++;
 349        spin_unlock(&sb_lock);
 350        /* wait for it to die */
 351        down_write(&s->s_umount);
 352        up_write(&s->s_umount);
 353        put_super(s);
 354        return 0;
 355}
 356
 357/*
 358 *      grab_super_passive - acquire a passive reference
 359 *      @sb: reference we are trying to grab
 360 *
 361 *      Tries to acquire a passive reference. This is used in places where we
 362 *      cannot take an active reference but we need to ensure that the
 363 *      superblock does not go away while we are working on it. It returns
 364 *      false if a reference was not gained, and returns true with the s_umount
 365 *      lock held in read mode if a reference is gained. On successful return,
 366 *      the caller must drop the s_umount lock and the passive reference when
 367 *      done.
 368 */
 369bool grab_super_passive(struct super_block *sb)
 370{
 371        spin_lock(&sb_lock);
 372        if (hlist_unhashed(&sb->s_instances)) {
 373                spin_unlock(&sb_lock);
 374                return false;
 375        }
 376
 377        sb->s_count++;
 378        spin_unlock(&sb_lock);
 379
 380        if (down_read_trylock(&sb->s_umount)) {
 381                if (sb->s_root && (sb->s_flags & MS_BORN))
 382                        return true;
 383                up_read(&sb->s_umount);
 384        }
 385
 386        put_super(sb);
 387        return false;
 388}
 389
 390/**
 391 *      generic_shutdown_super  -       common helper for ->kill_sb()
 392 *      @sb: superblock to kill
 393 *
 394 *      generic_shutdown_super() does all fs-independent work on superblock
 395 *      shutdown.  Typical ->kill_sb() should pick all fs-specific objects
 396 *      that need destruction out of superblock, call generic_shutdown_super()
 397 *      and release aforementioned objects.  Note: dentries and inodes _are_
 398 *      taken care of and do not need specific handling.
 399 *
 400 *      Upon calling this function, the filesystem may no longer alter or
 401 *      rearrange the set of dentries belonging to this super_block, nor may it
 402 *      change the attachments of dentries to inodes.
 403 */
 404void generic_shutdown_super(struct super_block *sb)
 405{
 406        const struct super_operations *sop = sb->s_op;
 407
 408        if (sb->s_root) {
 409                shrink_dcache_for_umount(sb);
 410                sync_filesystem(sb);
 411                sb->s_flags &= ~MS_ACTIVE;
 412
 413                fsnotify_unmount_inodes(&sb->s_inodes);
 414
 415                evict_inodes(sb);
 416
 417                if (sop->put_super)
 418                        sop->put_super(sb);
 419
 420                if (!list_empty(&sb->s_inodes)) {
 421                        printk("VFS: Busy inodes after unmount of %s. "
 422                           "Self-destruct in 5 seconds.  Have a nice day...\n",
 423                           sb->s_id);
 424                }
 425        }
 426        spin_lock(&sb_lock);
 427        /* should be initialized for __put_super_and_need_restart() */
 428        hlist_del_init(&sb->s_instances);
 429        spin_unlock(&sb_lock);
 430        up_write(&sb->s_umount);
 431}
 432
 433EXPORT_SYMBOL(generic_shutdown_super);
 434
 435/**
 436 *      sget    -       find or create a superblock
 437 *      @type:  filesystem type superblock should belong to
 438 *      @test:  comparison callback
 439 *      @set:   setup callback
 440 *      @flags: mount flags
 441 *      @data:  argument to each of them
 442 */
 443struct super_block *sget(struct file_system_type *type,
 444                        int (*test)(struct super_block *,void *),
 445                        int (*set)(struct super_block *,void *),
 446                        int flags,
 447                        void *data)
 448{
 449        struct super_block *s = NULL;
 450        struct super_block *old;
 451        int err;
 452
 453retry:
 454        spin_lock(&sb_lock);
 455        if (test) {
 456                hlist_for_each_entry(old, &type->fs_supers, s_instances) {
 457                        if (!test(old, data))
 458                                continue;
 459                        if (!grab_super(old))
 460                                goto retry;
 461                        if (s) {
 462                                up_write(&s->s_umount);
 463                                destroy_super(s);
 464                                s = NULL;
 465                        }
 466                        down_write(&old->s_umount);
 467                        if (unlikely(!(old->s_flags & MS_BORN))) {
 468                                deactivate_locked_super(old);
 469                                goto retry;
 470                        }
 471                        return old;
 472                }
 473        }
 474        if (!s) {
 475                spin_unlock(&sb_lock);
 476                s = alloc_super(type, flags);
 477                if (!s)
 478                        return ERR_PTR(-ENOMEM);
 479                goto retry;
 480        }
 481                
 482        err = set(s, data);
 483        if (err) {
 484                spin_unlock(&sb_lock);
 485                up_write(&s->s_umount);
 486                destroy_super(s);
 487                return ERR_PTR(err);
 488        }
 489        s->s_type = type;
 490        strlcpy(s->s_id, type->name, sizeof(s->s_id));
 491        list_add_tail(&s->s_list, &super_blocks);
 492        hlist_add_head(&s->s_instances, &type->fs_supers);
 493        spin_unlock(&sb_lock);
 494        get_filesystem(type);
 495        register_shrinker(&s->s_shrink);
 496        return s;
 497}
 498
 499EXPORT_SYMBOL(sget);
 500
 501void drop_super(struct super_block *sb)
 502{
 503        up_read(&sb->s_umount);
 504        put_super(sb);
 505}
 506
 507EXPORT_SYMBOL(drop_super);
 508
 509/**
 510 *      iterate_supers - call function for all active superblocks
 511 *      @f: function to call
 512 *      @arg: argument to pass to it
 513 *
 514 *      Scans the superblock list and calls given function, passing it
 515 *      locked superblock and given argument.
 516 */
 517void iterate_supers(void (*f)(struct super_block *, void *), void *arg)
 518{
 519        struct super_block *sb, *p = NULL;
 520
 521        spin_lock(&sb_lock);
 522        list_for_each_entry(sb, &super_blocks, s_list) {
 523                if (hlist_unhashed(&sb->s_instances))
 524                        continue;
 525                sb->s_count++;
 526                spin_unlock(&sb_lock);
 527
 528                down_read(&sb->s_umount);
 529                if (sb->s_root && (sb->s_flags & MS_BORN))
 530                        f(sb, arg);
 531                up_read(&sb->s_umount);
 532
 533                spin_lock(&sb_lock);
 534                if (p)
 535                        __put_super(p);
 536                p = sb;
 537        }
 538        if (p)
 539                __put_super(p);
 540        spin_unlock(&sb_lock);
 541}
 542
 543/**
 544 *      iterate_supers_type - call function for superblocks of given type
 545 *      @type: fs type
 546 *      @f: function to call
 547 *      @arg: argument to pass to it
 548 *
 549 *      Scans the superblock list and calls given function, passing it
 550 *      locked superblock and given argument.
 551 */
 552void iterate_supers_type(struct file_system_type *type,
 553        void (*f)(struct super_block *, void *), void *arg)
 554{
 555        struct super_block *sb, *p = NULL;
 556
 557        spin_lock(&sb_lock);
 558        hlist_for_each_entry(sb, &type->fs_supers, s_instances) {
 559                sb->s_count++;
 560                spin_unlock(&sb_lock);
 561
 562                down_read(&sb->s_umount);
 563                if (sb->s_root && (sb->s_flags & MS_BORN))
 564                        f(sb, arg);
 565                up_read(&sb->s_umount);
 566
 567                spin_lock(&sb_lock);
 568                if (p)
 569                        __put_super(p);
 570                p = sb;
 571        }
 572        if (p)
 573                __put_super(p);
 574        spin_unlock(&sb_lock);
 575}
 576
 577EXPORT_SYMBOL(iterate_supers_type);
 578
 579/**
 580 *      get_super - get the superblock of a device
 581 *      @bdev: device to get the superblock for
 582 *      
 583 *      Scans the superblock list and finds the superblock of the file system
 584 *      mounted on the device given. %NULL is returned if no match is found.
 585 */
 586
 587struct super_block *get_super(struct block_device *bdev)
 588{
 589        struct super_block *sb;
 590
 591        if (!bdev)
 592                return NULL;
 593
 594        spin_lock(&sb_lock);
 595rescan:
 596        list_for_each_entry(sb, &super_blocks, s_list) {
 597                if (hlist_unhashed(&sb->s_instances))
 598                        continue;
 599                if (sb->s_bdev == bdev) {
 600                        sb->s_count++;
 601                        spin_unlock(&sb_lock);
 602                        down_read(&sb->s_umount);
 603                        /* still alive? */
 604                        if (sb->s_root && (sb->s_flags & MS_BORN))
 605                                return sb;
 606                        up_read(&sb->s_umount);
 607                        /* nope, got unmounted */
 608                        spin_lock(&sb_lock);
 609                        __put_super(sb);
 610                        goto rescan;
 611                }
 612        }
 613        spin_unlock(&sb_lock);
 614        return NULL;
 615}
 616
 617EXPORT_SYMBOL(get_super);
 618
 619/**
 620 *      get_super_thawed - get thawed superblock of a device
 621 *      @bdev: device to get the superblock for
 622 *
 623 *      Scans the superblock list and finds the superblock of the file system
 624 *      mounted on the device. The superblock is returned once it is thawed
 625 *      (or immediately if it was not frozen). %NULL is returned if no match
 626 *      is found.
 627 */
 628struct super_block *get_super_thawed(struct block_device *bdev)
 629{
 630        while (1) {
 631                struct super_block *s = get_super(bdev);
 632                if (!s || s->s_writers.frozen == SB_UNFROZEN)
 633                        return s;
 634                up_read(&s->s_umount);
 635                wait_event(s->s_writers.wait_unfrozen,
 636                           s->s_writers.frozen == SB_UNFROZEN);
 637                put_super(s);
 638        }
 639}
 640EXPORT_SYMBOL(get_super_thawed);
 641
 642/**
 643 * get_active_super - get an active reference to the superblock of a device
 644 * @bdev: device to get the superblock for
 645 *
 646 * Scans the superblock list and finds the superblock of the file system
 647 * mounted on the device given.  Returns the superblock with an active
 648 * reference or %NULL if none was found.
 649 */
 650struct super_block *get_active_super(struct block_device *bdev)
 651{
 652        struct super_block *sb;
 653
 654        if (!bdev)
 655                return NULL;
 656
 657restart:
 658        spin_lock(&sb_lock);
 659        list_for_each_entry(sb, &super_blocks, s_list) {
 660                if (hlist_unhashed(&sb->s_instances))
 661                        continue;
 662                if (sb->s_bdev == bdev) {
 663                        if (grab_super(sb)) /* drops sb_lock */
 664                                return sb;
 665                        else
 666                                goto restart;
 667                }
 668        }
 669        spin_unlock(&sb_lock);
 670        return NULL;
 671}
 672 
 673struct super_block *user_get_super(dev_t dev)
 674{
 675        struct super_block *sb;
 676
 677        spin_lock(&sb_lock);
 678rescan:
 679        list_for_each_entry(sb, &super_blocks, s_list) {
 680                if (hlist_unhashed(&sb->s_instances))
 681                        continue;
 682                if (sb->s_dev ==  dev) {
 683                        sb->s_count++;
 684                        spin_unlock(&sb_lock);
 685                        down_read(&sb->s_umount);
 686                        /* still alive? */
 687                        if (sb->s_root && (sb->s_flags & MS_BORN))
 688                                return sb;
 689                        up_read(&sb->s_umount);
 690                        /* nope, got unmounted */
 691                        spin_lock(&sb_lock);
 692                        __put_super(sb);
 693                        goto rescan;
 694                }
 695        }
 696        spin_unlock(&sb_lock);
 697        return NULL;
 698}
 699
 700/**
 701 *      do_remount_sb - asks filesystem to change mount options.
 702 *      @sb:    superblock in question
 703 *      @flags: numeric part of options
 704 *      @data:  the rest of options
 705 *      @force: whether or not to force the change
 706 *
 707 *      Alters the mount options of a mounted file system.
 708 */
 709int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
 710{
 711        int retval;
 712        int remount_ro;
 713
 714        if (sb->s_writers.frozen != SB_UNFROZEN)
 715                return -EBUSY;
 716
 717#ifdef CONFIG_BLOCK
 718        if (!(flags & MS_RDONLY) && bdev_read_only(sb->s_bdev))
 719                return -EACCES;
 720#endif
 721
 722        if (flags & MS_RDONLY)
 723                acct_auto_close(sb);
 724        shrink_dcache_sb(sb);
 725        sync_filesystem(sb);
 726
 727        remount_ro = (flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY);
 728
 729        /* If we are remounting RDONLY and current sb is read/write,
 730           make sure there are no rw files opened */
 731        if (remount_ro) {
 732                if (force) {
 733                        mark_files_ro(sb);
 734                } else {
 735                        retval = sb_prepare_remount_readonly(sb);
 736                        if (retval)
 737                                return retval;
 738                }
 739        }
 740
 741        if (sb->s_op->remount_fs) {
 742                retval = sb->s_op->remount_fs(sb, &flags, data);
 743                if (retval) {
 744                        if (!force)
 745                                goto cancel_readonly;
 746                        /* If forced remount, go ahead despite any errors */
 747                        WARN(1, "forced remount of a %s fs returned %i\n",
 748                             sb->s_type->name, retval);
 749                }
 750        }
 751        sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK);
 752        /* Needs to be ordered wrt mnt_is_readonly() */
 753        smp_wmb();
 754        sb->s_readonly_remount = 0;
 755
 756        /*
 757         * Some filesystems modify their metadata via some other path than the
 758         * bdev buffer cache (eg. use a private mapping, or directories in
 759         * pagecache, etc). Also file data modifications go via their own
 760         * mappings. So If we try to mount readonly then copy the filesystem
 761         * from bdev, we could get stale data, so invalidate it to give a best
 762         * effort at coherency.
 763         */
 764        if (remount_ro && sb->s_bdev)
 765                invalidate_bdev(sb->s_bdev);
 766        return 0;
 767
 768cancel_readonly:
 769        sb->s_readonly_remount = 0;
 770        return retval;
 771}
 772
 773static void do_emergency_remount(struct work_struct *work)
 774{
 775        struct super_block *sb, *p = NULL;
 776
 777        spin_lock(&sb_lock);
 778        list_for_each_entry(sb, &super_blocks, s_list) {
 779                if (hlist_unhashed(&sb->s_instances))
 780                        continue;
 781                sb->s_count++;
 782                spin_unlock(&sb_lock);
 783                down_write(&sb->s_umount);
 784                if (sb->s_root && sb->s_bdev && (sb->s_flags & MS_BORN) &&
 785                    !(sb->s_flags & MS_RDONLY)) {
 786                        /*
 787                         * What lock protects sb->s_flags??
 788                         */
 789                        do_remount_sb(sb, MS_RDONLY, NULL, 1);
 790                }
 791                up_write(&sb->s_umount);
 792                spin_lock(&sb_lock);
 793                if (p)
 794                        __put_super(p);
 795                p = sb;
 796        }
 797        if (p)
 798                __put_super(p);
 799        spin_unlock(&sb_lock);
 800        kfree(work);
 801        printk("Emergency Remount complete\n");
 802}
 803
 804void emergency_remount(void)
 805{
 806        struct work_struct *work;
 807
 808        work = kmalloc(sizeof(*work), GFP_ATOMIC);
 809        if (work) {
 810                INIT_WORK(work, do_emergency_remount);
 811                schedule_work(work);
 812        }
 813}
 814
 815/*
 816 * Unnamed block devices are dummy devices used by virtual
 817 * filesystems which don't use real block-devices.  -- jrs
 818 */
 819
 820static DEFINE_IDA(unnamed_dev_ida);
 821static DEFINE_SPINLOCK(unnamed_dev_lock);/* protects the above */
 822static int unnamed_dev_start = 0; /* don't bother trying below it */
 823
 824int get_anon_bdev(dev_t *p)
 825{
 826        int dev;
 827        int error;
 828
 829 retry:
 830        if (ida_pre_get(&unnamed_dev_ida, GFP_ATOMIC) == 0)
 831                return -ENOMEM;
 832        spin_lock(&unnamed_dev_lock);
 833        error = ida_get_new_above(&unnamed_dev_ida, unnamed_dev_start, &dev);
 834        if (!error)
 835                unnamed_dev_start = dev + 1;
 836        spin_unlock(&unnamed_dev_lock);
 837        if (error == -EAGAIN)
 838                /* We raced and lost with another CPU. */
 839                goto retry;
 840        else if (error)
 841                return -EAGAIN;
 842
 843        if (dev == (1 << MINORBITS)) {
 844                spin_lock(&unnamed_dev_lock);
 845                ida_remove(&unnamed_dev_ida, dev);
 846                if (unnamed_dev_start > dev)
 847                        unnamed_dev_start = dev;
 848                spin_unlock(&unnamed_dev_lock);
 849                return -EMFILE;
 850        }
 851        *p = MKDEV(0, dev & MINORMASK);
 852        return 0;
 853}
 854EXPORT_SYMBOL(get_anon_bdev);
 855
 856void free_anon_bdev(dev_t dev)
 857{
 858        int slot = MINOR(dev);
 859        spin_lock(&unnamed_dev_lock);
 860        ida_remove(&unnamed_dev_ida, slot);
 861        if (slot < unnamed_dev_start)
 862                unnamed_dev_start = slot;
 863        spin_unlock(&unnamed_dev_lock);
 864}
 865EXPORT_SYMBOL(free_anon_bdev);
 866
 867int set_anon_super(struct super_block *s, void *data)
 868{
 869        int error = get_anon_bdev(&s->s_dev);
 870        if (!error)
 871                s->s_bdi = &noop_backing_dev_info;
 872        return error;
 873}
 874
 875EXPORT_SYMBOL(set_anon_super);
 876
 877void kill_anon_super(struct super_block *sb)
 878{
 879        dev_t dev = sb->s_dev;
 880        generic_shutdown_super(sb);
 881        free_anon_bdev(dev);
 882}
 883
 884EXPORT_SYMBOL(kill_anon_super);
 885
 886void kill_litter_super(struct super_block *sb)
 887{
 888        if (sb->s_root)
 889                d_genocide(sb->s_root);
 890        kill_anon_super(sb);
 891}
 892
 893EXPORT_SYMBOL(kill_litter_super);
 894
 895static int ns_test_super(struct super_block *sb, void *data)
 896{
 897        return sb->s_fs_info == data;
 898}
 899
 900static int ns_set_super(struct super_block *sb, void *data)
 901{
 902        sb->s_fs_info = data;
 903        return set_anon_super(sb, NULL);
 904}
 905
 906struct dentry *mount_ns(struct file_system_type *fs_type, int flags,
 907        void *data, int (*fill_super)(struct super_block *, void *, int))
 908{
 909        struct super_block *sb;
 910
 911        sb = sget(fs_type, ns_test_super, ns_set_super, flags, data);
 912        if (IS_ERR(sb))
 913                return ERR_CAST(sb);
 914
 915        if (!sb->s_root) {
 916                int err;
 917                err = fill_super(sb, data, flags & MS_SILENT ? 1 : 0);
 918                if (err) {
 919                        deactivate_locked_super(sb);
 920                        return ERR_PTR(err);
 921                }
 922
 923                sb->s_flags |= MS_ACTIVE;
 924        }
 925
 926        return dget(sb->s_root);
 927}
 928
 929EXPORT_SYMBOL(mount_ns);
 930
 931#ifdef CONFIG_BLOCK
 932static int set_bdev_super(struct super_block *s, void *data)
 933{
 934        s->s_bdev = data;
 935        s->s_dev = s->s_bdev->bd_dev;
 936
 937        /*
 938         * We set the bdi here to the queue backing, file systems can
 939         * overwrite this in ->fill_super()
 940         */
 941        s->s_bdi = &bdev_get_queue(s->s_bdev)->backing_dev_info;
 942        return 0;
 943}
 944
 945static int test_bdev_super(struct super_block *s, void *data)
 946{
 947        return (void *)s->s_bdev == data;
 948}
 949
 950struct dentry *mount_bdev(struct file_system_type *fs_type,
 951        int flags, const char *dev_name, void *data,
 952        int (*fill_super)(struct super_block *, void *, int))
 953{
 954        struct block_device *bdev;
 955        struct super_block *s;
 956        fmode_t mode = FMODE_READ | FMODE_EXCL;
 957        int error = 0;
 958
 959        if (!(flags & MS_RDONLY))
 960                mode |= FMODE_WRITE;
 961
 962        bdev = blkdev_get_by_path(dev_name, mode, fs_type);
 963        if (IS_ERR(bdev))
 964                return ERR_CAST(bdev);
 965
 966        /*
 967         * once the super is inserted into the list by sget, s_umount
 968         * will protect the lockfs code from trying to start a snapshot
 969         * while we are mounting
 970         */
 971        mutex_lock(&bdev->bd_fsfreeze_mutex);
 972        if (bdev->bd_fsfreeze_count > 0) {
 973                mutex_unlock(&bdev->bd_fsfreeze_mutex);
 974                error = -EBUSY;
 975                goto error_bdev;
 976        }
 977        s = sget(fs_type, test_bdev_super, set_bdev_super, flags | MS_NOSEC,
 978                 bdev);
 979        mutex_unlock(&bdev->bd_fsfreeze_mutex);
 980        if (IS_ERR(s))
 981                goto error_s;
 982
 983        if (s->s_root) {
 984                if ((flags ^ s->s_flags) & MS_RDONLY) {
 985                        deactivate_locked_super(s);
 986                        error = -EBUSY;
 987                        goto error_bdev;
 988                }
 989
 990                /*
 991                 * s_umount nests inside bd_mutex during
 992                 * __invalidate_device().  blkdev_put() acquires
 993                 * bd_mutex and can't be called under s_umount.  Drop
 994                 * s_umount temporarily.  This is safe as we're
 995                 * holding an active reference.
 996                 */
 997                up_write(&s->s_umount);
 998                blkdev_put(bdev, mode);
 999                down_write(&s->s_umount);
1000        } else {
1001                char b[BDEVNAME_SIZE];
1002
1003                s->s_mode = mode;
1004                strlcpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id));
1005                sb_set_blocksize(s, block_size(bdev));
1006                error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
1007                if (error) {
1008                        deactivate_locked_super(s);
1009                        goto error;
1010                }
1011
1012                s->s_flags |= MS_ACTIVE;
1013                bdev->bd_super = s;
1014        }
1015
1016        return dget(s->s_root);
1017
1018error_s:
1019        error = PTR_ERR(s);
1020error_bdev:
1021        blkdev_put(bdev, mode);
1022error:
1023        return ERR_PTR(error);
1024}
1025EXPORT_SYMBOL(mount_bdev);
1026
1027void kill_block_super(struct super_block *sb)
1028{
1029        struct block_device *bdev = sb->s_bdev;
1030        fmode_t mode = sb->s_mode;
1031
1032        bdev->bd_super = NULL;
1033        generic_shutdown_super(sb);
1034        sync_blockdev(bdev);
1035        WARN_ON_ONCE(!(mode & FMODE_EXCL));
1036        blkdev_put(bdev, mode | FMODE_EXCL);
1037}
1038
1039EXPORT_SYMBOL(kill_block_super);
1040#endif
1041
1042struct dentry *mount_nodev(struct file_system_type *fs_type,
1043        int flags, void *data,
1044        int (*fill_super)(struct super_block *, void *, int))
1045{
1046        int error;
1047        struct super_block *s = sget(fs_type, NULL, set_anon_super, flags, NULL);
1048
1049        if (IS_ERR(s))
1050                return ERR_CAST(s);
1051
1052        error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
1053        if (error) {
1054                deactivate_locked_super(s);
1055                return ERR_PTR(error);
1056        }
1057        s->s_flags |= MS_ACTIVE;
1058        return dget(s->s_root);
1059}
1060EXPORT_SYMBOL(mount_nodev);
1061
1062static int compare_single(struct super_block *s, void *p)
1063{
1064        return 1;
1065}
1066
1067struct dentry *mount_single(struct file_system_type *fs_type,
1068        int flags, void *data,
1069        int (*fill_super)(struct super_block *, void *, int))
1070{
1071        struct super_block *s;
1072        int error;
1073
1074        s = sget(fs_type, compare_single, set_anon_super, flags, NULL);
1075        if (IS_ERR(s))
1076                return ERR_CAST(s);
1077        if (!s->s_root) {
1078                error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
1079                if (error) {
1080                        deactivate_locked_super(s);
1081                        return ERR_PTR(error);
1082                }
1083                s->s_flags |= MS_ACTIVE;
1084        } else {
1085                do_remount_sb(s, flags, data, 0);
1086        }
1087        return dget(s->s_root);
1088}
1089EXPORT_SYMBOL(mount_single);
1090
1091struct dentry *
1092mount_fs(struct file_system_type *type, int flags, const char *name, void *data)
1093{
1094        struct dentry *root;
1095        struct super_block *sb;
1096        char *secdata = NULL;
1097        int error = -ENOMEM;
1098
1099        if (data && !(type->fs_flags & FS_BINARY_MOUNTDATA)) {
1100                secdata = alloc_secdata();
1101                if (!secdata)
1102                        goto out;
1103
1104                error = security_sb_copy_data(data, secdata);
1105                if (error)
1106                        goto out_free_secdata;
1107        }
1108
1109        root = type->mount(type, flags, name, data);
1110        if (IS_ERR(root)) {
1111                error = PTR_ERR(root);
1112                goto out_free_secdata;
1113        }
1114        sb = root->d_sb;
1115        BUG_ON(!sb);
1116        WARN_ON(!sb->s_bdi);
1117        WARN_ON(sb->s_bdi == &default_backing_dev_info);
1118        sb->s_flags |= MS_BORN;
1119
1120        error = security_sb_kern_mount(sb, flags, secdata);
1121        if (error)
1122                goto out_sb;
1123
1124        /*
1125         * filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE
1126         * but s_maxbytes was an unsigned long long for many releases. Throw
1127         * this warning for a little while to try and catch filesystems that
1128         * violate this rule.
1129         */
1130        WARN((sb->s_maxbytes < 0), "%s set sb->s_maxbytes to "
1131                "negative value (%lld)\n", type->name, sb->s_maxbytes);
1132
1133        up_write(&sb->s_umount);
1134        free_secdata(secdata);
1135        return root;
1136out_sb:
1137        dput(root);
1138        deactivate_locked_super(sb);
1139out_free_secdata:
1140        free_secdata(secdata);
1141out:
1142        return ERR_PTR(error);
1143}
1144
1145/*
1146 * This is an internal function, please use sb_end_{write,pagefault,intwrite}
1147 * instead.
1148 */
1149void __sb_end_write(struct super_block *sb, int level)
1150{
1151        percpu_counter_dec(&sb->s_writers.counter[level-1]);
1152        /*
1153         * Make sure s_writers are updated before we wake up waiters in
1154         * freeze_super().
1155         */
1156        smp_mb();
1157        if (waitqueue_active(&sb->s_writers.wait))
1158                wake_up(&sb->s_writers.wait);
1159        rwsem_release(&sb->s_writers.lock_map[level-1], 1, _RET_IP_);
1160}
1161EXPORT_SYMBOL(__sb_end_write);
1162
1163#ifdef CONFIG_LOCKDEP
1164/*
1165 * We want lockdep to tell us about possible deadlocks with freezing but
1166 * it's it bit tricky to properly instrument it. Getting a freeze protection
1167 * works as getting a read lock but there are subtle problems. XFS for example
1168 * gets freeze protection on internal level twice in some cases, which is OK
1169 * only because we already hold a freeze protection also on higher level. Due
1170 * to these cases we have to tell lockdep we are doing trylock when we
1171 * already hold a freeze protection for a higher freeze level.
1172 */
1173static void acquire_freeze_lock(struct super_block *sb, int level, bool trylock,
1174                                unsigned long ip)
1175{
1176        int i;
1177
1178        if (!trylock) {
1179                for (i = 0; i < level - 1; i++)
1180                        if (lock_is_held(&sb->s_writers.lock_map[i])) {
1181                                trylock = true;
1182                                break;
1183                        }
1184        }
1185        rwsem_acquire_read(&sb->s_writers.lock_map[level-1], 0, trylock, ip);
1186}
1187#endif
1188
1189/*
1190 * This is an internal function, please use sb_start_{write,pagefault,intwrite}
1191 * instead.
1192 */
1193int __sb_start_write(struct super_block *sb, int level, bool wait)
1194{
1195retry:
1196        if (unlikely(sb->s_writers.frozen >= level)) {
1197                if (!wait)
1198                        return 0;
1199                wait_event(sb->s_writers.wait_unfrozen,
1200                           sb->s_writers.frozen < level);
1201        }
1202
1203#ifdef CONFIG_LOCKDEP
1204        acquire_freeze_lock(sb, level, !wait, _RET_IP_);
1205#endif
1206        percpu_counter_inc(&sb->s_writers.counter[level-1]);
1207        /*
1208         * Make sure counter is updated before we check for frozen.
1209         * freeze_super() first sets frozen and then checks the counter.
1210         */
1211        smp_mb();
1212        if (unlikely(sb->s_writers.frozen >= level)) {
1213                __sb_end_write(sb, level);
1214                goto retry;
1215        }
1216        return 1;
1217}
1218EXPORT_SYMBOL(__sb_start_write);
1219
1220/**
1221 * sb_wait_write - wait until all writers to given file system finish
1222 * @sb: the super for which we wait
1223 * @level: type of writers we wait for (normal vs page fault)
1224 *
1225 * This function waits until there are no writers of given type to given file
1226 * system. Caller of this function should make sure there can be no new writers
1227 * of type @level before calling this function. Otherwise this function can
1228 * livelock.
1229 */
1230static void sb_wait_write(struct super_block *sb, int level)
1231{
1232        s64 writers;
1233
1234        /*
1235         * We just cycle-through lockdep here so that it does not complain
1236         * about returning with lock to userspace
1237         */
1238        rwsem_acquire(&sb->s_writers.lock_map[level-1], 0, 0, _THIS_IP_);
1239        rwsem_release(&sb->s_writers.lock_map[level-1], 1, _THIS_IP_);
1240
1241        do {
1242                DEFINE_WAIT(wait);
1243
1244                /*
1245                 * We use a barrier in prepare_to_wait() to separate setting
1246                 * of frozen and checking of the counter
1247                 */
1248                prepare_to_wait(&sb->s_writers.wait, &wait,
1249                                TASK_UNINTERRUPTIBLE);
1250
1251                writers = percpu_counter_sum(&sb->s_writers.counter[level-1]);
1252                if (writers)
1253                        schedule();
1254
1255                finish_wait(&sb->s_writers.wait, &wait);
1256        } while (writers);
1257}
1258
1259/**
1260 * freeze_super - lock the filesystem and force it into a consistent state
1261 * @sb: the super to lock
1262 *
1263 * Syncs the super to make sure the filesystem is consistent and calls the fs's
1264 * freeze_fs.  Subsequent calls to this without first thawing the fs will return
1265 * -EBUSY.
1266 *
1267 * During this function, sb->s_writers.frozen goes through these values:
1268 *
1269 * SB_UNFROZEN: File system is normal, all writes progress as usual.
1270 *
1271 * SB_FREEZE_WRITE: The file system is in the process of being frozen.  New
1272 * writes should be blocked, though page faults are still allowed. We wait for
1273 * all writes to complete and then proceed to the next stage.
1274 *
1275 * SB_FREEZE_PAGEFAULT: Freezing continues. Now also page faults are blocked
1276 * but internal fs threads can still modify the filesystem (although they
1277 * should not dirty new pages or inodes), writeback can run etc. After waiting
1278 * for all running page faults we sync the filesystem which will clean all
1279 * dirty pages and inodes (no new dirty pages or inodes can be created when
1280 * sync is running).
1281 *
1282 * SB_FREEZE_FS: The file system is frozen. Now all internal sources of fs
1283 * modification are blocked (e.g. XFS preallocation truncation on inode
1284 * reclaim). This is usually implemented by blocking new transactions for
1285 * filesystems that have them and need this additional guard. After all
1286 * internal writers are finished we call ->freeze_fs() to finish filesystem
1287 * freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is
1288 * mostly auxiliary for filesystems to verify they do not modify frozen fs.
1289 *
1290 * sb->s_writers.frozen is protected by sb->s_umount.
1291 */
1292int freeze_super(struct super_block *sb)
1293{
1294        int ret;
1295
1296        atomic_inc(&sb->s_active);
1297        down_write(&sb->s_umount);
1298        if (sb->s_writers.frozen != SB_UNFROZEN) {
1299                deactivate_locked_super(sb);
1300                return -EBUSY;
1301        }
1302
1303        if (!(sb->s_flags & MS_BORN)) {
1304                up_write(&sb->s_umount);
1305                return 0;       /* sic - it's "nothing to do" */
1306        }
1307
1308        if (sb->s_flags & MS_RDONLY) {
1309                /* Nothing to do really... */
1310                sb->s_writers.frozen = SB_FREEZE_COMPLETE;
1311                up_write(&sb->s_umount);
1312                return 0;
1313        }
1314
1315        /* From now on, no new normal writers can start */
1316        sb->s_writers.frozen = SB_FREEZE_WRITE;
1317        smp_wmb();
1318
1319        /* Release s_umount to preserve sb_start_write -> s_umount ordering */
1320        up_write(&sb->s_umount);
1321
1322        sb_wait_write(sb, SB_FREEZE_WRITE);
1323
1324        /* Now we go and block page faults... */
1325        down_write(&sb->s_umount);
1326        sb->s_writers.frozen = SB_FREEZE_PAGEFAULT;
1327        smp_wmb();
1328
1329        sb_wait_write(sb, SB_FREEZE_PAGEFAULT);
1330
1331        /* All writers are done so after syncing there won't be dirty data */
1332        sync_filesystem(sb);
1333
1334        /* Now wait for internal filesystem counter */
1335        sb->s_writers.frozen = SB_FREEZE_FS;
1336        smp_wmb();
1337        sb_wait_write(sb, SB_FREEZE_FS);
1338
1339        if (sb->s_op->freeze_fs) {
1340                ret = sb->s_op->freeze_fs(sb);
1341                if (ret) {
1342                        printk(KERN_ERR
1343                                "VFS:Filesystem freeze failed\n");
1344                        sb->s_writers.frozen = SB_UNFROZEN;
1345                        smp_wmb();
1346                        wake_up(&sb->s_writers.wait_unfrozen);
1347                        deactivate_locked_super(sb);
1348                        return ret;
1349                }
1350        }
1351        /*
1352         * This is just for debugging purposes so that fs can warn if it
1353         * sees write activity when frozen is set to SB_FREEZE_COMPLETE.
1354         */
1355        sb->s_writers.frozen = SB_FREEZE_COMPLETE;
1356        up_write(&sb->s_umount);
1357        return 0;
1358}
1359EXPORT_SYMBOL(freeze_super);
1360
1361/**
1362 * thaw_super -- unlock filesystem
1363 * @sb: the super to thaw
1364 *
1365 * Unlocks the filesystem and marks it writeable again after freeze_super().
1366 */
1367int thaw_super(struct super_block *sb)
1368{
1369        int error;
1370
1371        down_write(&sb->s_umount);
1372        if (sb->s_writers.frozen == SB_UNFROZEN) {
1373                up_write(&sb->s_umount);
1374                return -EINVAL;
1375        }
1376
1377        if (sb->s_flags & MS_RDONLY)
1378                goto out;
1379
1380        if (sb->s_op->unfreeze_fs) {
1381                error = sb->s_op->unfreeze_fs(sb);
1382                if (error) {
1383                        printk(KERN_ERR
1384                                "VFS:Filesystem thaw failed\n");
1385                        up_write(&sb->s_umount);
1386                        return error;
1387                }
1388        }
1389
1390out:
1391        sb->s_writers.frozen = SB_UNFROZEN;
1392        smp_wmb();
1393        wake_up(&sb->s_writers.wait_unfrozen);
1394        deactivate_locked_super(sb);
1395
1396        return 0;
1397}
1398EXPORT_SYMBOL(thaw_super);
1399
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