X-Git-Url: https://nv-tegra.nvidia.com/r/gitweb?p=linux-3.10.git;a=blobdiff_plain;f=fs%2Fsuper.c;h=eb03b484fbd34ad211fd84e4fc8ffa0e6f2a50f0;hp=60b1e50cbf536c25aa6c667567448cf0b4705514;hb=rel-24-uda-r1;hpb=ee9b6d61a2a43c5952eb43283f8db284a4e70b8a diff --git a/fs/super.c b/fs/super.c index 60b1e50cbf5..eb03b484fbd 100644 --- a/fs/super.c +++ b/fs/super.c @@ -15,87 +15,202 @@ * Added kerneld support: Jacques Gelinas and Bjorn Ekwall * Added change_root: Werner Almesberger & Hans Lermen, Feb '96 * Added options to /proc/mounts: - * Torbjörn Lindh (torbjorn.lindh@gopta.se), April 14, 1996. + * Torbjörn Lindh (torbjorn.lindh@gopta.se), April 14, 1996. * Added devfs support: Richard Gooch , 13-JAN-1998 * Heavily rewritten for 'one fs - one tree' dcache architecture. AV, Mar 2000 */ -#include +#include #include -#include -#include #include #include -#include -#include -#include /* for fsync_super() */ #include #include -#include -#include #include /* for the emergency remount stuff */ #include -#include #include -#include +#include +#include +#include +#include +#include +#include "internal.h" -void get_filesystem(struct file_system_type *fs); -void put_filesystem(struct file_system_type *fs); -struct file_system_type *get_fs_type(const char *name); - LIST_HEAD(super_blocks); DEFINE_SPINLOCK(sb_lock); +static char *sb_writers_name[SB_FREEZE_LEVELS] = { + "sb_writers", + "sb_pagefaults", + "sb_internal", +}; + +/* + * One thing we have to be careful of with a per-sb shrinker is that we don't + * drop the last active reference to the superblock from within the shrinker. + * If that happens we could trigger unregistering the shrinker from within the + * shrinker path and that leads to deadlock on the shrinker_rwsem. Hence we + * take a passive reference to the superblock to avoid this from occurring. + */ +static int prune_super(struct shrinker *shrink, struct shrink_control *sc) +{ + struct super_block *sb; + int fs_objects = 0; + int total_objects; + + sb = container_of(shrink, struct super_block, s_shrink); + + /* + * Deadlock avoidance. We may hold various FS locks, and we don't want + * to recurse into the FS that called us in clear_inode() and friends.. + */ + if (sc->nr_to_scan && !(sc->gfp_mask & __GFP_FS)) + return -1; + + if (!grab_super_passive(sb)) + return -1; + + if (sb->s_op && sb->s_op->nr_cached_objects) + fs_objects = sb->s_op->nr_cached_objects(sb); + + total_objects = sb->s_nr_dentry_unused + + sb->s_nr_inodes_unused + fs_objects + 1; + if (!total_objects) + total_objects = 1; + + if (sc->nr_to_scan) { + int dentries; + int inodes; + + /* proportion the scan between the caches */ + dentries = (sc->nr_to_scan * sb->s_nr_dentry_unused) / + total_objects; + inodes = (sc->nr_to_scan * sb->s_nr_inodes_unused) / + total_objects; + if (fs_objects) + fs_objects = (sc->nr_to_scan * fs_objects) / + total_objects; + /* + * prune the dcache first as the icache is pinned by it, then + * prune the icache, followed by the filesystem specific caches + */ + prune_dcache_sb(sb, dentries); + prune_icache_sb(sb, inodes); + + if (fs_objects && sb->s_op->free_cached_objects) { + sb->s_op->free_cached_objects(sb, fs_objects); + fs_objects = sb->s_op->nr_cached_objects(sb); + } + total_objects = sb->s_nr_dentry_unused + + sb->s_nr_inodes_unused + fs_objects; + } + + total_objects = (total_objects / 100) * sysctl_vfs_cache_pressure; + drop_super(sb); + return total_objects; +} + +static int init_sb_writers(struct super_block *s, struct file_system_type *type) +{ + int err; + int i; + + for (i = 0; i < SB_FREEZE_LEVELS; i++) { + err = percpu_counter_init(&s->s_writers.counter[i], 0); + if (err < 0) + goto err_out; + lockdep_init_map(&s->s_writers.lock_map[i], sb_writers_name[i], + &type->s_writers_key[i], 0); + } + init_waitqueue_head(&s->s_writers.wait); + init_waitqueue_head(&s->s_writers.wait_unfrozen); + return 0; +err_out: + while (--i >= 0) + percpu_counter_destroy(&s->s_writers.counter[i]); + return err; +} + +static void destroy_sb_writers(struct super_block *s) +{ + int i; + + for (i = 0; i < SB_FREEZE_LEVELS; i++) + percpu_counter_destroy(&s->s_writers.counter[i]); +} + /** * alloc_super - create new superblock * @type: filesystem type superblock should belong to + * @flags: the mount flags * * Allocates and initializes a new &struct super_block. alloc_super() * returns a pointer new superblock or %NULL if allocation had failed. */ -static struct super_block *alloc_super(struct file_system_type *type) +static struct super_block *alloc_super(struct file_system_type *type, int flags) { struct super_block *s = kzalloc(sizeof(struct super_block), GFP_USER); - static struct super_operations default_op; + static const struct super_operations default_op; if (s) { - if (security_sb_alloc(s)) { - kfree(s); - s = NULL; - goto out; - } - INIT_LIST_HEAD(&s->s_dirty); - INIT_LIST_HEAD(&s->s_io); - INIT_LIST_HEAD(&s->s_files); - INIT_LIST_HEAD(&s->s_instances); - INIT_HLIST_HEAD(&s->s_anon); + if (security_sb_alloc(s)) + goto out_free_sb; + + if (init_sb_writers(s, type)) + goto err_out; + s->s_flags = flags; + s->s_bdi = &default_backing_dev_info; + INIT_HLIST_NODE(&s->s_instances); + INIT_HLIST_BL_HEAD(&s->s_anon); INIT_LIST_HEAD(&s->s_inodes); + INIT_LIST_HEAD(&s->s_dentry_lru); + INIT_LIST_HEAD(&s->s_inode_lru); + spin_lock_init(&s->s_inode_lru_lock); + INIT_LIST_HEAD(&s->s_mounts); init_rwsem(&s->s_umount); - mutex_init(&s->s_lock); lockdep_set_class(&s->s_umount, &type->s_umount_key); /* - * The locking rules for s_lock are up to the - * filesystem. For example ext3fs has different - * lock ordering than usbfs: + * sget() can have s_umount recursion. + * + * When it cannot find a suitable sb, it allocates a new + * one (this one), and tries again to find a suitable old + * one. + * + * In case that succeeds, it will acquire the s_umount + * lock of the old one. Since these are clearly distrinct + * locks, and this object isn't exposed yet, there's no + * risk of deadlocks. + * + * Annotate this by putting this lock in a different + * subclass. */ - lockdep_set_class(&s->s_lock, &type->s_lock_key); - down_write(&s->s_umount); - s->s_count = S_BIAS; + down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING); + s->s_count = 1; atomic_set(&s->s_active, 1); mutex_init(&s->s_vfs_rename_mutex); + lockdep_set_class(&s->s_vfs_rename_mutex, &type->s_vfs_rename_key); mutex_init(&s->s_dquot.dqio_mutex); mutex_init(&s->s_dquot.dqonoff_mutex); init_rwsem(&s->s_dquot.dqptr_sem); - init_waitqueue_head(&s->s_wait_unfrozen); s->s_maxbytes = MAX_NON_LFS; - s->dq_op = sb_dquot_ops; - s->s_qcop = sb_quotactl_ops; s->s_op = &default_op; s->s_time_gran = 1000000000; + s->cleancache_poolid = -1; + + s->s_shrink.seeks = DEFAULT_SEEKS; + s->s_shrink.shrink = prune_super; + s->s_shrink.batch = 1024; } out: return s; +err_out: + security_sb_free(s); + destroy_sb_writers(s); +out_free_sb: + kfree(s); + s = NULL; + goto out; } /** @@ -106,46 +221,25 @@ out: */ static inline void destroy_super(struct super_block *s) { + destroy_sb_writers(s); security_sb_free(s); + WARN_ON(!list_empty(&s->s_mounts)); + kfree(s->s_subtype); + kfree(s->s_options); kfree(s); } /* Superblock refcounting */ /* - * Drop a superblock's refcount. Returns non-zero if the superblock was - * destroyed. The caller must hold sb_lock. + * Drop a superblock's refcount. The caller must hold sb_lock. */ -int __put_super(struct super_block *sb) +static void __put_super(struct super_block *sb) { - int ret = 0; - if (!--sb->s_count) { + list_del_init(&sb->s_list); destroy_super(sb); - ret = 1; - } - return ret; -} - -/* - * Drop a superblock's refcount. - * Returns non-zero if the superblock is about to be destroyed and - * at least is already removed from super_blocks list, so if we are - * making a loop through super blocks then we need to restart. - * The caller must hold sb_lock. - */ -int __put_super_and_need_restart(struct super_block *sb) -{ - /* check for race with generic_shutdown_super() */ - if (list_empty(&sb->s_list)) { - /* super block is removed, need to restart... */ - __put_super(sb); - return 1; } - /* can't be the last, since s_list is still in use */ - sb->s_count--; - BUG_ON(sb->s_count == 0); - return 0; } /** @@ -164,25 +258,47 @@ static void put_super(struct super_block *sb) /** - * deactivate_super - drop an active reference to superblock + * deactivate_locked_super - drop an active reference to superblock * @s: superblock to deactivate * - * Drops an active reference to superblock, acquiring a temprory one if - * there is no active references left. In that case we lock superblock, + * Drops an active reference to superblock, converting it into a temprory + * one if there is no other active references left. In that case we * tell fs driver to shut it down and drop the temporary reference we * had just acquired. + * + * Caller holds exclusive lock on superblock; that lock is released. */ -void deactivate_super(struct super_block *s) +void deactivate_locked_super(struct super_block *s) { struct file_system_type *fs = s->s_type; - if (atomic_dec_and_lock(&s->s_active, &sb_lock)) { - s->s_count -= S_BIAS-1; - spin_unlock(&sb_lock); - DQUOT_OFF(s); - down_write(&s->s_umount); + if (atomic_dec_and_test(&s->s_active)) { + cleancache_invalidate_fs(s); fs->kill_sb(s); + + /* caches are now gone, we can safely kill the shrinker now */ + unregister_shrinker(&s->s_shrink); put_filesystem(fs); put_super(s); + } else { + up_write(&s->s_umount); + } +} + +EXPORT_SYMBOL(deactivate_locked_super); + +/** + * deactivate_super - drop an active reference to superblock + * @s: superblock to deactivate + * + * Variant of deactivate_locked_super(), except that superblock is *not* + * locked by caller. If we are going to drop the final active reference, + * lock will be acquired prior to that. + */ +void deactivate_super(struct super_block *s) +{ + if (!atomic_add_unless(&s->s_active, -1, 1)) { + down_write(&s->s_umount); + deactivate_locked_super(s); } } @@ -197,76 +313,55 @@ EXPORT_SYMBOL(deactivate_super); * and want to turn it into a full-blown active reference. grab_super() * is called with sb_lock held and drops it. Returns 1 in case of * success, 0 if we had failed (superblock contents was already dead or - * dying when grab_super() had been called). + * dying when grab_super() had been called). Note that this is only + * called for superblocks not in rundown mode (== ones still on ->fs_supers + * of their type), so increment of ->s_count is OK here. */ static int grab_super(struct super_block *s) __releases(sb_lock) { s->s_count++; spin_unlock(&sb_lock); down_write(&s->s_umount); - if (s->s_root) { - spin_lock(&sb_lock); - if (s->s_count > S_BIAS) { - atomic_inc(&s->s_active); - s->s_count--; - spin_unlock(&sb_lock); - return 1; - } - spin_unlock(&sb_lock); + if ((s->s_flags & MS_BORN) && atomic_inc_not_zero(&s->s_active)) { + put_super(s); + return 1; } up_write(&s->s_umount); put_super(s); - yield(); return 0; } /* - * Superblock locking. We really ought to get rid of these two. + * grab_super_passive - acquire a passive reference + * @sb: reference we are trying to grab + * + * Tries to acquire a passive reference. This is used in places where we + * cannot take an active reference but we need to ensure that the + * superblock does not go away while we are working on it. It returns + * false if a reference was not gained, and returns true with the s_umount + * lock held in read mode if a reference is gained. On successful return, + * the caller must drop the s_umount lock and the passive reference when + * done. */ -void lock_super(struct super_block * sb) +bool grab_super_passive(struct super_block *sb) { - get_fs_excl(); - mutex_lock(&sb->s_lock); -} - -void unlock_super(struct super_block * sb) -{ - put_fs_excl(); - mutex_unlock(&sb->s_lock); -} + spin_lock(&sb_lock); + if (hlist_unhashed(&sb->s_instances)) { + spin_unlock(&sb_lock); + return false; + } -EXPORT_SYMBOL(lock_super); -EXPORT_SYMBOL(unlock_super); + sb->s_count++; + spin_unlock(&sb_lock); -/* - * Write out and wait upon all dirty data associated with this - * superblock. Filesystem data as well as the underlying block - * device. Takes the superblock lock. Requires a second blkdev - * flush by the caller to complete the operation. - */ -void __fsync_super(struct super_block *sb) -{ - sync_inodes_sb(sb, 0); - DQUOT_SYNC(sb); - lock_super(sb); - if (sb->s_dirt && sb->s_op->write_super) - sb->s_op->write_super(sb); - unlock_super(sb); - if (sb->s_op->sync_fs) - sb->s_op->sync_fs(sb, 1); - sync_blockdev(sb->s_bdev); - sync_inodes_sb(sb, 1); -} + if (down_read_trylock(&sb->s_umount)) { + if (sb->s_root && (sb->s_flags & MS_BORN)) + return true; + up_read(&sb->s_umount); + } -/* - * Write out and wait upon all dirty data associated with this - * superblock. Filesystem data as well as the underlying block - * device. Takes the superblock lock. - */ -int fsync_super(struct super_block *sb) -{ - __fsync_super(sb); - return sync_blockdev(sb->s_bdev); + put_super(sb); + return false; } /** @@ -289,32 +384,30 @@ void generic_shutdown_super(struct super_block *sb) if (sb->s_root) { shrink_dcache_for_umount(sb); - fsync_super(sb); - lock_super(sb); + sync_filesystem(sb); sb->s_flags &= ~MS_ACTIVE; - /* bad name - it should be evict_inodes() */ - invalidate_inodes(sb); - lock_kernel(); - if (sop->write_super && sb->s_dirt) - sop->write_super(sb); + fsnotify_unmount_inodes(&sb->s_inodes); + + evict_inodes(sb); + + if (sb->s_dio_done_wq) { + destroy_workqueue(sb->s_dio_done_wq); + sb->s_dio_done_wq = NULL; + } + if (sop->put_super) sop->put_super(sb); - /* Forget any remaining inodes */ - if (invalidate_inodes(sb)) { + if (!list_empty(&sb->s_inodes)) { printk("VFS: Busy inodes after unmount of %s. " "Self-destruct in 5 seconds. Have a nice day...\n", sb->s_id); } - - unlock_kernel(); - unlock_super(sb); } spin_lock(&sb_lock); /* should be initialized for __put_super_and_need_restart() */ - list_del_init(&sb->s_list); - list_del(&sb->s_instances); + hlist_del_init(&sb->s_instances); spin_unlock(&sb_lock); up_write(&sb->s_umount); } @@ -326,33 +419,38 @@ EXPORT_SYMBOL(generic_shutdown_super); * @type: filesystem type superblock should belong to * @test: comparison callback * @set: setup callback + * @flags: mount flags * @data: argument to each of them */ struct super_block *sget(struct file_system_type *type, int (*test)(struct super_block *,void *), int (*set)(struct super_block *,void *), + int flags, void *data) { struct super_block *s = NULL; - struct list_head *p; + struct super_block *old; int err; retry: spin_lock(&sb_lock); - if (test) list_for_each(p, &type->fs_supers) { - struct super_block *old; - old = list_entry(p, struct super_block, s_instances); - if (!test(old, data)) - continue; - if (!grab_super(old)) - goto retry; - if (s) - destroy_super(s); - return old; + if (test) { + hlist_for_each_entry(old, &type->fs_supers, s_instances) { + if (!test(old, data)) + continue; + if (!grab_super(old)) + goto retry; + if (s) { + up_write(&s->s_umount); + destroy_super(s); + s = NULL; + } + return old; + } } if (!s) { spin_unlock(&sb_lock); - s = alloc_super(type); + s = alloc_super(type, flags); if (!s) return ERR_PTR(-ENOMEM); goto retry; @@ -361,15 +459,17 @@ retry: err = set(s, data); if (err) { spin_unlock(&sb_lock); + up_write(&s->s_umount); destroy_super(s); return ERR_PTR(err); } s->s_type = type; strlcpy(s->s_id, type->name, sizeof(s->s_id)); list_add_tail(&s->s_list, &super_blocks); - list_add(&s->s_instances, &type->fs_supers); + hlist_add_head(&s->s_instances, &type->fs_supers); spin_unlock(&sb_lock); get_filesystem(type); + register_shrinker(&s->s_shrink); return s; } @@ -383,94 +483,76 @@ void drop_super(struct super_block *sb) EXPORT_SYMBOL(drop_super); -static inline void write_super(struct super_block *sb) -{ - lock_super(sb); - if (sb->s_root && sb->s_dirt) - if (sb->s_op->write_super) - sb->s_op->write_super(sb); - unlock_super(sb); -} - -/* - * Note: check the dirty flag before waiting, so we don't - * hold up the sync while mounting a device. (The newly - * mounted device won't need syncing.) +/** + * iterate_supers - call function for all active superblocks + * @f: function to call + * @arg: argument to pass to it + * + * Scans the superblock list and calls given function, passing it + * locked superblock and given argument. */ -void sync_supers(void) +void iterate_supers(void (*f)(struct super_block *, void *), void *arg) { - struct super_block *sb; + struct super_block *sb, *p = NULL; spin_lock(&sb_lock); -restart: list_for_each_entry(sb, &super_blocks, s_list) { - if (sb->s_dirt) { - sb->s_count++; - spin_unlock(&sb_lock); - down_read(&sb->s_umount); - write_super(sb); - up_read(&sb->s_umount); - spin_lock(&sb_lock); - if (__put_super_and_need_restart(sb)) - goto restart; - } + if (hlist_unhashed(&sb->s_instances)) + continue; + sb->s_count++; + spin_unlock(&sb_lock); + + down_read(&sb->s_umount); + if (sb->s_root && (sb->s_flags & MS_BORN)) + f(sb, arg); + up_read(&sb->s_umount); + + spin_lock(&sb_lock); + if (p) + __put_super(p); + p = sb; } + if (p) + __put_super(p); spin_unlock(&sb_lock); } -/* - * Call the ->sync_fs super_op against all filesytems which are r/w and - * which implement it. - * - * This operation is careful to avoid the livelock which could easily happen - * if two or more filesystems are being continuously dirtied. s_need_sync_fs - * is used only here. We set it against all filesystems and then clear it as - * we sync them. So redirtied filesystems are skipped. - * - * But if process A is currently running sync_filesytems and then process B - * calls sync_filesystems as well, process B will set all the s_need_sync_fs - * flags again, which will cause process A to resync everything. Fix that with - * a local mutex. +/** + * iterate_supers_type - call function for superblocks of given type + * @type: fs type + * @f: function to call + * @arg: argument to pass to it * - * (Fabian) Avoid sync_fs with clean fs & wait mode 0 + * Scans the superblock list and calls given function, passing it + * locked superblock and given argument. */ -void sync_filesystems(int wait) +void iterate_supers_type(struct file_system_type *type, + void (*f)(struct super_block *, void *), void *arg) { - struct super_block *sb; - static DEFINE_MUTEX(mutex); + struct super_block *sb, *p = NULL; - mutex_lock(&mutex); /* Could be down_interruptible */ spin_lock(&sb_lock); - list_for_each_entry(sb, &super_blocks, s_list) { - if (!sb->s_op->sync_fs) - continue; - if (sb->s_flags & MS_RDONLY) - continue; - sb->s_need_sync_fs = 1; - } - -restart: - list_for_each_entry(sb, &super_blocks, s_list) { - if (!sb->s_need_sync_fs) - continue; - sb->s_need_sync_fs = 0; - if (sb->s_flags & MS_RDONLY) - continue; /* hm. Was remounted r/o meanwhile */ + hlist_for_each_entry(sb, &type->fs_supers, s_instances) { sb->s_count++; spin_unlock(&sb_lock); + down_read(&sb->s_umount); - if (sb->s_root && (wait || sb->s_dirt)) - sb->s_op->sync_fs(sb, wait); + if (sb->s_root && (sb->s_flags & MS_BORN)) + f(sb, arg); up_read(&sb->s_umount); - /* restart only when sb is no longer on the list */ + spin_lock(&sb_lock); - if (__put_super_and_need_restart(sb)) - goto restart; + if (p) + __put_super(p); + p = sb; } + if (p) + __put_super(p); spin_unlock(&sb_lock); - mutex_unlock(&mutex); } +EXPORT_SYMBOL(iterate_supers_type); + /** * get_super - get the superblock of a device * @bdev: device to get the superblock for @@ -479,7 +561,7 @@ restart: * mounted on the device given. %NULL is returned if no match is found. */ -struct super_block * get_super(struct block_device *bdev) +struct super_block *get_super(struct block_device *bdev) { struct super_block *sb; @@ -489,17 +571,20 @@ struct super_block * get_super(struct block_device *bdev) spin_lock(&sb_lock); rescan: list_for_each_entry(sb, &super_blocks, s_list) { + if (hlist_unhashed(&sb->s_instances)) + continue; if (sb->s_bdev == bdev) { sb->s_count++; spin_unlock(&sb_lock); down_read(&sb->s_umount); - if (sb->s_root) + /* still alive? */ + if (sb->s_root && (sb->s_flags & MS_BORN)) return sb; up_read(&sb->s_umount); - /* restart only when sb is no longer on the list */ + /* nope, got unmounted */ spin_lock(&sb_lock); - if (__put_super_and_need_restart(sb)) - goto rescan; + __put_super(sb); + goto rescan; } } spin_unlock(&sb_lock); @@ -507,75 +592,88 @@ rescan: } EXPORT_SYMBOL(get_super); + +/** + * get_super_thawed - get thawed superblock of a device + * @bdev: device to get the superblock for + * + * Scans the superblock list and finds the superblock of the file system + * mounted on the device. The superblock is returned once it is thawed + * (or immediately if it was not frozen). %NULL is returned if no match + * is found. + */ +struct super_block *get_super_thawed(struct block_device *bdev) +{ + while (1) { + struct super_block *s = get_super(bdev); + if (!s || s->s_writers.frozen == SB_UNFROZEN) + return s; + up_read(&s->s_umount); + wait_event(s->s_writers.wait_unfrozen, + s->s_writers.frozen == SB_UNFROZEN); + put_super(s); + } +} +EXPORT_SYMBOL(get_super_thawed); + +/** + * get_active_super - get an active reference to the superblock of a device + * @bdev: device to get the superblock for + * + * Scans the superblock list and finds the superblock of the file system + * mounted on the device given. Returns the superblock with an active + * reference or %NULL if none was found. + */ +struct super_block *get_active_super(struct block_device *bdev) +{ + struct super_block *sb; + + if (!bdev) + return NULL; + +restart: + spin_lock(&sb_lock); + list_for_each_entry(sb, &super_blocks, s_list) { + if (hlist_unhashed(&sb->s_instances)) + continue; + if (sb->s_bdev == bdev) { + if (!grab_super(sb)) + goto restart; + up_write(&sb->s_umount); + return sb; + } + } + spin_unlock(&sb_lock); + return NULL; +} -struct super_block * user_get_super(dev_t dev) +struct super_block *user_get_super(dev_t dev) { struct super_block *sb; spin_lock(&sb_lock); rescan: list_for_each_entry(sb, &super_blocks, s_list) { + if (hlist_unhashed(&sb->s_instances)) + continue; if (sb->s_dev == dev) { sb->s_count++; spin_unlock(&sb_lock); down_read(&sb->s_umount); - if (sb->s_root) + /* still alive? */ + if (sb->s_root && (sb->s_flags & MS_BORN)) return sb; up_read(&sb->s_umount); - /* restart only when sb is no longer on the list */ + /* nope, got unmounted */ spin_lock(&sb_lock); - if (__put_super_and_need_restart(sb)) - goto rescan; + __put_super(sb); + goto rescan; } } spin_unlock(&sb_lock); return NULL; } -asmlinkage long sys_ustat(unsigned dev, struct ustat __user * ubuf) -{ - struct super_block *s; - struct ustat tmp; - struct kstatfs sbuf; - int err = -EINVAL; - - s = user_get_super(new_decode_dev(dev)); - if (s == NULL) - goto out; - err = vfs_statfs(s->s_root, &sbuf); - drop_super(s); - if (err) - goto out; - - memset(&tmp,0,sizeof(struct ustat)); - tmp.f_tfree = sbuf.f_bfree; - tmp.f_tinode = sbuf.f_ffree; - - err = copy_to_user(ubuf,&tmp,sizeof(struct ustat)) ? -EFAULT : 0; -out: - return err; -} - -/** - * mark_files_ro - * @sb: superblock in question - * - * All files are marked read/only. We don't care about pending - * delete files so this should be used in 'force' mode only - */ - -static void mark_files_ro(struct super_block *sb) -{ - struct file *f; - - file_list_lock(); - list_for_each_entry(f, &sb->s_files, f_u.fu_list) { - if (S_ISREG(f->f_path.dentry->d_inode->i_mode) && file_count(f)) - f->f_mode &= ~FMODE_WRITE; - } - file_list_unlock(); -} - /** * do_remount_sb - asks filesystem to change mount options. * @sb: superblock in question @@ -588,65 +686,108 @@ static void mark_files_ro(struct super_block *sb) int do_remount_sb(struct super_block *sb, int flags, void *data, int force) { int retval; - + int remount_ro; + + if (sb->s_writers.frozen != SB_UNFROZEN) + return -EBUSY; + #ifdef CONFIG_BLOCK if (!(flags & MS_RDONLY) && bdev_read_only(sb->s_bdev)) return -EACCES; #endif + if (flags & MS_RDONLY) acct_auto_close(sb); shrink_dcache_sb(sb); - fsync_super(sb); + sync_filesystem(sb); + + remount_ro = (flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY); /* If we are remounting RDONLY and current sb is read/write, make sure there are no rw files opened */ - if ((flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY)) { - if (force) - mark_files_ro(sb); - else if (!fs_may_remount_ro(sb)) - return -EBUSY; + if (remount_ro) { + if (force) { + sb->s_readonly_remount = 1; + smp_wmb(); + } else { + retval = sb_prepare_remount_readonly(sb); + if (retval) + return retval; + } } if (sb->s_op->remount_fs) { - lock_super(sb); retval = sb->s_op->remount_fs(sb, &flags, data); - unlock_super(sb); - if (retval) - return retval; + if (retval) { + if (!force) + goto cancel_readonly; + /* If forced remount, go ahead despite any errors */ + WARN(1, "forced remount of a %s fs returned %i\n", + sb->s_type->name, retval); + } } sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK); + /* Needs to be ordered wrt mnt_is_readonly() */ + smp_wmb(); + sb->s_readonly_remount = 0; + + /* + * Some filesystems modify their metadata via some other path than the + * bdev buffer cache (eg. use a private mapping, or directories in + * pagecache, etc). Also file data modifications go via their own + * mappings. So If we try to mount readonly then copy the filesystem + * from bdev, we could get stale data, so invalidate it to give a best + * effort at coherency. + */ + if (remount_ro && sb->s_bdev) + invalidate_bdev(sb->s_bdev); return 0; + +cancel_readonly: + sb->s_readonly_remount = 0; + return retval; } -static void do_emergency_remount(unsigned long foo) +static void do_emergency_remount(struct work_struct *work) { - struct super_block *sb; + struct super_block *sb, *p = NULL; spin_lock(&sb_lock); list_for_each_entry(sb, &super_blocks, s_list) { + if (hlist_unhashed(&sb->s_instances)) + continue; sb->s_count++; spin_unlock(&sb_lock); - down_read(&sb->s_umount); - if (sb->s_root && sb->s_bdev && !(sb->s_flags & MS_RDONLY)) { + down_write(&sb->s_umount); + if (sb->s_root && sb->s_bdev && (sb->s_flags & MS_BORN) && + !(sb->s_flags & MS_RDONLY)) { /* - * ->remount_fs needs lock_kernel(). - * * What lock protects sb->s_flags?? */ - lock_kernel(); do_remount_sb(sb, MS_RDONLY, NULL, 1); - unlock_kernel(); } - drop_super(sb); + up_write(&sb->s_umount); spin_lock(&sb_lock); + if (p) + __put_super(p); + p = sb; } + if (p) + __put_super(p); spin_unlock(&sb_lock); + kfree(work); printk("Emergency Remount complete\n"); } void emergency_remount(void) { - pdflush_operation(do_emergency_remount, 0); + struct work_struct *work; + + work = kmalloc(sizeof(*work), GFP_ATOMIC); + if (work) { + INIT_WORK(work, do_emergency_remount); + schedule_work(work); + } } /* @@ -654,19 +795,22 @@ void emergency_remount(void) * filesystems which don't use real block-devices. -- jrs */ -static struct idr unnamed_dev_idr; +static DEFINE_IDA(unnamed_dev_ida); static DEFINE_SPINLOCK(unnamed_dev_lock);/* protects the above */ +static int unnamed_dev_start = 0; /* don't bother trying below it */ -int set_anon_super(struct super_block *s, void *data) +int get_anon_bdev(dev_t *p) { int dev; int error; retry: - if (idr_pre_get(&unnamed_dev_idr, GFP_ATOMIC) == 0) + if (ida_pre_get(&unnamed_dev_ida, GFP_ATOMIC) == 0) return -ENOMEM; spin_lock(&unnamed_dev_lock); - error = idr_get_new(&unnamed_dev_idr, NULL, &dev); + error = ida_get_new_above(&unnamed_dev_ida, unnamed_dev_start, &dev); + if (!error) + unnamed_dev_start = dev + 1; spin_unlock(&unnamed_dev_lock); if (error == -EAGAIN) /* We raced and lost with another CPU. */ @@ -674,35 +818,49 @@ int set_anon_super(struct super_block *s, void *data) else if (error) return -EAGAIN; - if ((dev & MAX_ID_MASK) == (1 << MINORBITS)) { + if (dev == (1 << MINORBITS)) { spin_lock(&unnamed_dev_lock); - idr_remove(&unnamed_dev_idr, dev); + ida_remove(&unnamed_dev_ida, dev); + if (unnamed_dev_start > dev) + unnamed_dev_start = dev; spin_unlock(&unnamed_dev_lock); return -EMFILE; } - s->s_dev = MKDEV(0, dev & MINORMASK); + *p = MKDEV(0, dev & MINORMASK); return 0; } +EXPORT_SYMBOL(get_anon_bdev); -EXPORT_SYMBOL(set_anon_super); - -void kill_anon_super(struct super_block *sb) +void free_anon_bdev(dev_t dev) { - int slot = MINOR(sb->s_dev); - - generic_shutdown_super(sb); + int slot = MINOR(dev); spin_lock(&unnamed_dev_lock); - idr_remove(&unnamed_dev_idr, slot); + ida_remove(&unnamed_dev_ida, slot); + if (slot < unnamed_dev_start) + unnamed_dev_start = slot; spin_unlock(&unnamed_dev_lock); } +EXPORT_SYMBOL(free_anon_bdev); -EXPORT_SYMBOL(kill_anon_super); +int set_anon_super(struct super_block *s, void *data) +{ + int error = get_anon_bdev(&s->s_dev); + if (!error) + s->s_bdi = &noop_backing_dev_info; + return error; +} + +EXPORT_SYMBOL(set_anon_super); -void __init unnamed_dev_init(void) +void kill_anon_super(struct super_block *sb) { - idr_init(&unnamed_dev_idr); + dev_t dev = sb->s_dev; + generic_shutdown_super(sb); + free_anon_bdev(dev); } +EXPORT_SYMBOL(kill_anon_super); + void kill_litter_super(struct super_block *sb) { if (sb->s_root) @@ -712,11 +870,53 @@ void kill_litter_super(struct super_block *sb) EXPORT_SYMBOL(kill_litter_super); +static int ns_test_super(struct super_block *sb, void *data) +{ + return sb->s_fs_info == data; +} + +static int ns_set_super(struct super_block *sb, void *data) +{ + sb->s_fs_info = data; + return set_anon_super(sb, NULL); +} + +struct dentry *mount_ns(struct file_system_type *fs_type, int flags, + void *data, int (*fill_super)(struct super_block *, void *, int)) +{ + struct super_block *sb; + + sb = sget(fs_type, ns_test_super, ns_set_super, flags, data); + if (IS_ERR(sb)) + return ERR_CAST(sb); + + if (!sb->s_root) { + int err; + err = fill_super(sb, data, flags & MS_SILENT ? 1 : 0); + if (err) { + deactivate_locked_super(sb); + return ERR_PTR(err); + } + + sb->s_flags |= MS_ACTIVE; + } + + return dget(sb->s_root); +} + +EXPORT_SYMBOL(mount_ns); + #ifdef CONFIG_BLOCK static int set_bdev_super(struct super_block *s, void *data) { s->s_bdev = data; s->s_dev = s->s_bdev->bd_dev; + + /* + * We set the bdi here to the queue backing, file systems can + * overwrite this in ->fill_super() + */ + s->s_bdi = &bdev_get_queue(s->s_bdev)->backing_dev_info; return 0; } @@ -725,215 +925,452 @@ static int test_bdev_super(struct super_block *s, void *data) return (void *)s->s_bdev == data; } -static void bdev_uevent(struct block_device *bdev, enum kobject_action action) -{ - if (bdev->bd_disk) { - if (bdev->bd_part) - kobject_uevent(&bdev->bd_part->kobj, action); - else - kobject_uevent(&bdev->bd_disk->kobj, action); - } -} - -int get_sb_bdev(struct file_system_type *fs_type, +struct dentry *mount_bdev(struct file_system_type *fs_type, int flags, const char *dev_name, void *data, - int (*fill_super)(struct super_block *, void *, int), - struct vfsmount *mnt) + int (*fill_super)(struct super_block *, void *, int)) { struct block_device *bdev; struct super_block *s; + fmode_t mode = FMODE_READ | FMODE_EXCL; int error = 0; - bdev = open_bdev_excl(dev_name, flags, fs_type); + if (!(flags & MS_RDONLY)) + mode |= FMODE_WRITE; + + bdev = blkdev_get_by_path(dev_name, mode, fs_type); if (IS_ERR(bdev)) - return PTR_ERR(bdev); + return ERR_CAST(bdev); /* * once the super is inserted into the list by sget, s_umount * will protect the lockfs code from trying to start a snapshot * while we are mounting */ - down(&bdev->bd_mount_sem); - s = sget(fs_type, test_bdev_super, set_bdev_super, bdev); - up(&bdev->bd_mount_sem); + mutex_lock(&bdev->bd_fsfreeze_mutex); + if (bdev->bd_fsfreeze_count > 0) { + mutex_unlock(&bdev->bd_fsfreeze_mutex); + error = -EBUSY; + goto error_bdev; + } + s = sget(fs_type, test_bdev_super, set_bdev_super, flags | MS_NOSEC, + bdev); + mutex_unlock(&bdev->bd_fsfreeze_mutex); if (IS_ERR(s)) goto error_s; if (s->s_root) { if ((flags ^ s->s_flags) & MS_RDONLY) { - up_write(&s->s_umount); - deactivate_super(s); + deactivate_locked_super(s); error = -EBUSY; goto error_bdev; } - close_bdev_excl(bdev); + /* + * s_umount nests inside bd_mutex during + * __invalidate_device(). blkdev_put() acquires + * bd_mutex and can't be called under s_umount. Drop + * s_umount temporarily. This is safe as we're + * holding an active reference. + */ + up_write(&s->s_umount); + blkdev_put(bdev, mode); + down_write(&s->s_umount); } else { char b[BDEVNAME_SIZE]; - s->s_flags = flags; + s->s_mode = mode; strlcpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id)); sb_set_blocksize(s, block_size(bdev)); error = fill_super(s, data, flags & MS_SILENT ? 1 : 0); if (error) { - up_write(&s->s_umount); - deactivate_super(s); + deactivate_locked_super(s); goto error; } s->s_flags |= MS_ACTIVE; - bdev_uevent(bdev, KOBJ_MOUNT); + bdev->bd_super = s; } - return simple_set_mnt(mnt, s); + return dget(s->s_root); error_s: error = PTR_ERR(s); error_bdev: - close_bdev_excl(bdev); + blkdev_put(bdev, mode); error: - return error; + return ERR_PTR(error); } - -EXPORT_SYMBOL(get_sb_bdev); +EXPORT_SYMBOL(mount_bdev); void kill_block_super(struct super_block *sb) { struct block_device *bdev = sb->s_bdev; + fmode_t mode = sb->s_mode; - bdev_uevent(bdev, KOBJ_UMOUNT); + bdev->bd_super = NULL; generic_shutdown_super(sb); sync_blockdev(bdev); - close_bdev_excl(bdev); + WARN_ON_ONCE(!(mode & FMODE_EXCL)); + blkdev_put(bdev, mode | FMODE_EXCL); } EXPORT_SYMBOL(kill_block_super); #endif -int get_sb_nodev(struct file_system_type *fs_type, +struct dentry *mount_nodev(struct file_system_type *fs_type, int flags, void *data, - int (*fill_super)(struct super_block *, void *, int), - struct vfsmount *mnt) + int (*fill_super)(struct super_block *, void *, int)) { int error; - struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL); + struct super_block *s = sget(fs_type, NULL, set_anon_super, flags, NULL); if (IS_ERR(s)) - return PTR_ERR(s); - - s->s_flags = flags; + return ERR_CAST(s); error = fill_super(s, data, flags & MS_SILENT ? 1 : 0); if (error) { - up_write(&s->s_umount); - deactivate_super(s); - return error; + deactivate_locked_super(s); + return ERR_PTR(error); } s->s_flags |= MS_ACTIVE; - return simple_set_mnt(mnt, s); + return dget(s->s_root); } - -EXPORT_SYMBOL(get_sb_nodev); +EXPORT_SYMBOL(mount_nodev); static int compare_single(struct super_block *s, void *p) { return 1; } -int get_sb_single(struct file_system_type *fs_type, +struct dentry *mount_single(struct file_system_type *fs_type, int flags, void *data, - int (*fill_super)(struct super_block *, void *, int), - struct vfsmount *mnt) + int (*fill_super)(struct super_block *, void *, int)) { struct super_block *s; int error; - s = sget(fs_type, compare_single, set_anon_super, NULL); + s = sget(fs_type, compare_single, set_anon_super, flags, NULL); if (IS_ERR(s)) - return PTR_ERR(s); + return ERR_CAST(s); if (!s->s_root) { - s->s_flags = flags; error = fill_super(s, data, flags & MS_SILENT ? 1 : 0); if (error) { - up_write(&s->s_umount); - deactivate_super(s); - return error; + deactivate_locked_super(s); + return ERR_PTR(error); } s->s_flags |= MS_ACTIVE; + } else { + do_remount_sb(s, flags, data, 0); } - do_remount_sb(s, flags, data, 0); - return simple_set_mnt(mnt, s); + return dget(s->s_root); } +EXPORT_SYMBOL(mount_single); -EXPORT_SYMBOL(get_sb_single); - -struct vfsmount * -vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data) +struct dentry * +mount_fs(struct file_system_type *type, int flags, const char *name, void *data) { - struct vfsmount *mnt; + struct dentry *root; + struct super_block *sb; char *secdata = NULL; - int error; - - if (!type) - return ERR_PTR(-ENODEV); - - error = -ENOMEM; - mnt = alloc_vfsmnt(name); - if (!mnt) - goto out; + int error = -ENOMEM; - if (data) { + if (data && !(type->fs_flags & FS_BINARY_MOUNTDATA)) { secdata = alloc_secdata(); if (!secdata) - goto out_mnt; + goto out; - error = security_sb_copy_data(type, data, secdata); + error = security_sb_copy_data(data, secdata); if (error) goto out_free_secdata; } - error = type->get_sb(type, flags, name, data, mnt); - if (error < 0) + root = type->mount(type, flags, name, data); + if (IS_ERR(root)) { + error = PTR_ERR(root); goto out_free_secdata; + } + sb = root->d_sb; + BUG_ON(!sb); + WARN_ON(!sb->s_bdi); + WARN_ON(sb->s_bdi == &default_backing_dev_info); + sb->s_flags |= MS_BORN; + + error = security_sb_kern_mount(sb, flags, secdata); + if (error) + goto out_sb; - error = security_sb_kern_mount(mnt->mnt_sb, secdata); - if (error) - goto out_sb; + /* + * filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE + * but s_maxbytes was an unsigned long long for many releases. Throw + * this warning for a little while to try and catch filesystems that + * violate this rule. + */ + WARN((sb->s_maxbytes < 0), "%s set sb->s_maxbytes to " + "negative value (%lld)\n", type->name, sb->s_maxbytes); - mnt->mnt_mountpoint = mnt->mnt_root; - mnt->mnt_parent = mnt; - up_write(&mnt->mnt_sb->s_umount); + up_write(&sb->s_umount); free_secdata(secdata); - return mnt; + return root; out_sb: - dput(mnt->mnt_root); - up_write(&mnt->mnt_sb->s_umount); - deactivate_super(mnt->mnt_sb); + dput(root); + deactivate_locked_super(sb); out_free_secdata: free_secdata(secdata); -out_mnt: - free_vfsmnt(mnt); out: return ERR_PTR(error); } -EXPORT_SYMBOL_GPL(vfs_kern_mount); +/* + * This is an internal function, please use sb_end_{write,pagefault,intwrite} + * instead. + */ +void __sb_end_write(struct super_block *sb, int level) +{ + percpu_counter_dec(&sb->s_writers.counter[level-1]); + /* + * Make sure s_writers are updated before we wake up waiters in + * freeze_super(). + */ + smp_mb(); + if (waitqueue_active(&sb->s_writers.wait)) + wake_up(&sb->s_writers.wait); + rwsem_release(&sb->s_writers.lock_map[level-1], 1, _RET_IP_); +} +EXPORT_SYMBOL(__sb_end_write); -struct vfsmount * -do_kern_mount(const char *fstype, int flags, const char *name, void *data) +#ifdef CONFIG_LOCKDEP +/* + * We want lockdep to tell us about possible deadlocks with freezing but + * it's it bit tricky to properly instrument it. Getting a freeze protection + * works as getting a read lock but there are subtle problems. XFS for example + * gets freeze protection on internal level twice in some cases, which is OK + * only because we already hold a freeze protection also on higher level. Due + * to these cases we have to tell lockdep we are doing trylock when we + * already hold a freeze protection for a higher freeze level. + */ +static void acquire_freeze_lock(struct super_block *sb, int level, bool trylock, + unsigned long ip) { - struct file_system_type *type = get_fs_type(fstype); - struct vfsmount *mnt; - if (!type) - return ERR_PTR(-ENODEV); - mnt = vfs_kern_mount(type, flags, name, data); - put_filesystem(type); - return mnt; + int i; + + if (!trylock) { + for (i = 0; i < level - 1; i++) + if (lock_is_held(&sb->s_writers.lock_map[i])) { + trylock = true; + break; + } + } + rwsem_acquire_read(&sb->s_writers.lock_map[level-1], 0, trylock, ip); } +#endif -struct vfsmount *kern_mount(struct file_system_type *type) +/* + * This is an internal function, please use sb_start_{write,pagefault,intwrite} + * instead. + */ +int __sb_start_write(struct super_block *sb, int level, bool wait) { - return vfs_kern_mount(type, 0, type->name, NULL); +retry: + if (unlikely(sb->s_writers.frozen >= level)) { + if (!wait) + return 0; + wait_event(sb->s_writers.wait_unfrozen, + sb->s_writers.frozen < level); + } + +#ifdef CONFIG_LOCKDEP + acquire_freeze_lock(sb, level, !wait, _RET_IP_); +#endif + percpu_counter_inc(&sb->s_writers.counter[level-1]); + /* + * Make sure counter is updated before we check for frozen. + * freeze_super() first sets frozen and then checks the counter. + */ + smp_mb(); + if (unlikely(sb->s_writers.frozen >= level)) { + __sb_end_write(sb, level); + goto retry; + } + return 1; +} +EXPORT_SYMBOL(__sb_start_write); + +/** + * sb_wait_write - wait until all writers to given file system finish + * @sb: the super for which we wait + * @level: type of writers we wait for (normal vs page fault) + * + * This function waits until there are no writers of given type to given file + * system. Caller of this function should make sure there can be no new writers + * of type @level before calling this function. Otherwise this function can + * livelock. + */ +static void sb_wait_write(struct super_block *sb, int level) +{ + s64 writers; + + /* + * We just cycle-through lockdep here so that it does not complain + * about returning with lock to userspace + */ + rwsem_acquire(&sb->s_writers.lock_map[level-1], 0, 0, _THIS_IP_); + rwsem_release(&sb->s_writers.lock_map[level-1], 1, _THIS_IP_); + + do { + DEFINE_WAIT(wait); + + /* + * We use a barrier in prepare_to_wait() to separate setting + * of frozen and checking of the counter + */ + prepare_to_wait(&sb->s_writers.wait, &wait, + TASK_UNINTERRUPTIBLE); + + writers = percpu_counter_sum(&sb->s_writers.counter[level-1]); + if (writers) + schedule(); + + finish_wait(&sb->s_writers.wait, &wait); + } while (writers); } -EXPORT_SYMBOL(kern_mount); +/** + * freeze_super - lock the filesystem and force it into a consistent state + * @sb: the super to lock + * + * Syncs the super to make sure the filesystem is consistent and calls the fs's + * freeze_fs. Subsequent calls to this without first thawing the fs will return + * -EBUSY. + * + * During this function, sb->s_writers.frozen goes through these values: + * + * SB_UNFROZEN: File system is normal, all writes progress as usual. + * + * SB_FREEZE_WRITE: The file system is in the process of being frozen. New + * writes should be blocked, though page faults are still allowed. We wait for + * all writes to complete and then proceed to the next stage. + * + * SB_FREEZE_PAGEFAULT: Freezing continues. Now also page faults are blocked + * but internal fs threads can still modify the filesystem (although they + * should not dirty new pages or inodes), writeback can run etc. After waiting + * for all running page faults we sync the filesystem which will clean all + * dirty pages and inodes (no new dirty pages or inodes can be created when + * sync is running). + * + * SB_FREEZE_FS: The file system is frozen. Now all internal sources of fs + * modification are blocked (e.g. XFS preallocation truncation on inode + * reclaim). This is usually implemented by blocking new transactions for + * filesystems that have them and need this additional guard. After all + * internal writers are finished we call ->freeze_fs() to finish filesystem + * freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is + * mostly auxiliary for filesystems to verify they do not modify frozen fs. + * + * sb->s_writers.frozen is protected by sb->s_umount. + */ +int freeze_super(struct super_block *sb) +{ + int ret; + + atomic_inc(&sb->s_active); + down_write(&sb->s_umount); + if (sb->s_writers.frozen != SB_UNFROZEN) { + deactivate_locked_super(sb); + return -EBUSY; + } + + if (!(sb->s_flags & MS_BORN)) { + up_write(&sb->s_umount); + return 0; /* sic - it's "nothing to do" */ + } + + if (sb->s_flags & MS_RDONLY) { + /* Nothing to do really... */ + sb->s_writers.frozen = SB_FREEZE_COMPLETE; + up_write(&sb->s_umount); + return 0; + } + + /* From now on, no new normal writers can start */ + sb->s_writers.frozen = SB_FREEZE_WRITE; + smp_wmb(); + + /* Release s_umount to preserve sb_start_write -> s_umount ordering */ + up_write(&sb->s_umount); + + sb_wait_write(sb, SB_FREEZE_WRITE); + + /* Now we go and block page faults... */ + down_write(&sb->s_umount); + sb->s_writers.frozen = SB_FREEZE_PAGEFAULT; + smp_wmb(); + + sb_wait_write(sb, SB_FREEZE_PAGEFAULT); + + /* All writers are done so after syncing there won't be dirty data */ + sync_filesystem(sb); + + /* Now wait for internal filesystem counter */ + sb->s_writers.frozen = SB_FREEZE_FS; + smp_wmb(); + sb_wait_write(sb, SB_FREEZE_FS); + + if (sb->s_op->freeze_fs) { + ret = sb->s_op->freeze_fs(sb); + if (ret) { + printk(KERN_ERR + "VFS:Filesystem freeze failed\n"); + sb->s_writers.frozen = SB_UNFROZEN; + smp_wmb(); + wake_up(&sb->s_writers.wait_unfrozen); + deactivate_locked_super(sb); + return ret; + } + } + /* + * This is just for debugging purposes so that fs can warn if it + * sees write activity when frozen is set to SB_FREEZE_COMPLETE. + */ + sb->s_writers.frozen = SB_FREEZE_COMPLETE; + up_write(&sb->s_umount); + return 0; +} +EXPORT_SYMBOL(freeze_super); + +/** + * thaw_super -- unlock filesystem + * @sb: the super to thaw + * + * Unlocks the filesystem and marks it writeable again after freeze_super(). + */ +int thaw_super(struct super_block *sb) +{ + int error; + + down_write(&sb->s_umount); + if (sb->s_writers.frozen == SB_UNFROZEN) { + up_write(&sb->s_umount); + return -EINVAL; + } + + if (sb->s_flags & MS_RDONLY) + goto out; + + if (sb->s_op->unfreeze_fs) { + error = sb->s_op->unfreeze_fs(sb); + if (error) { + printk(KERN_ERR + "VFS:Filesystem thaw failed\n"); + up_write(&sb->s_umount); + return error; + } + } + +out: + sb->s_writers.frozen = SB_UNFROZEN; + smp_wmb(); + wake_up(&sb->s_writers.wait_unfrozen); + deactivate_locked_super(sb); + + return 0; +} +EXPORT_SYMBOL(thaw_super);