| /* |
| * linux/fs/super.c |
| * |
| * Copyright (C) 1991, 1992 Linus Torvalds |
| * |
| * super.c contains code to handle: - mount structures |
| * - super-block tables |
| * - filesystem drivers list |
| * - mount system call |
| * - umount system call |
| * - ustat system call |
| * |
| * GK 2/5/95 - Changed to support mounting the root fs via NFS |
| * |
| * 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. |
| * Added devfs support: Richard Gooch <rgooch@atnf.csiro.au>, 13-JAN-1998 |
| * Heavily rewritten for 'one fs - one tree' dcache architecture. AV, Mar 2000 |
| */ |
| |
| #include <linux/export.h> |
| #include <linux/slab.h> |
| #include <linux/blkdev.h> |
| #include <linux/mount.h> |
| #include <linux/security.h> |
| #include <linux/writeback.h> /* for the emergency remount stuff */ |
| #include <linux/idr.h> |
| #include <linux/mutex.h> |
| #include <linux/backing-dev.h> |
| #include <linux/rculist_bl.h> |
| #include <linux/cleancache.h> |
| #include <linux/fsnotify.h> |
| #include <linux/lockdep.h> |
| #include "internal.h" |
| |
| |
| static LIST_HEAD(super_blocks); |
| static 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 unsigned long super_cache_scan(struct shrinker *shrink, |
| struct shrink_control *sc) |
| { |
| struct super_block *sb; |
| long fs_objects = 0; |
| long total_objects; |
| long freed = 0; |
| long dentries; |
| long inodes; |
| |
| 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->gfp_mask & __GFP_FS)) |
| return SHRINK_STOP; |
| |
| if (!trylock_super(sb)) |
| return SHRINK_STOP; |
| |
| if (sb->s_op->nr_cached_objects) |
| fs_objects = sb->s_op->nr_cached_objects(sb, sc); |
| |
| inodes = list_lru_shrink_count(&sb->s_inode_lru, sc); |
| dentries = list_lru_shrink_count(&sb->s_dentry_lru, sc); |
| total_objects = dentries + inodes + fs_objects + 1; |
| if (!total_objects) |
| total_objects = 1; |
| |
| /* proportion the scan between the caches */ |
| dentries = mult_frac(sc->nr_to_scan, dentries, total_objects); |
| inodes = mult_frac(sc->nr_to_scan, inodes, total_objects); |
| fs_objects = mult_frac(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 |
| * |
| * Ensure that we always scan at least one object - memcg kmem |
| * accounting uses this to fully empty the caches. |
| */ |
| sc->nr_to_scan = dentries + 1; |
| freed = prune_dcache_sb(sb, sc); |
| sc->nr_to_scan = inodes + 1; |
| freed += prune_icache_sb(sb, sc); |
| |
| if (fs_objects) { |
| sc->nr_to_scan = fs_objects + 1; |
| freed += sb->s_op->free_cached_objects(sb, sc); |
| } |
| |
| up_read(&sb->s_umount); |
| return freed; |
| } |
| |
| static unsigned long super_cache_count(struct shrinker *shrink, |
| struct shrink_control *sc) |
| { |
| struct super_block *sb; |
| long total_objects = 0; |
| |
| sb = container_of(shrink, struct super_block, s_shrink); |
| |
| /* |
| * Don't call trylock_super as it is a potential |
| * scalability bottleneck. The counts could get updated |
| * between super_cache_count and super_cache_scan anyway. |
| * Call to super_cache_count with shrinker_rwsem held |
| * ensures the safety of call to list_lru_shrink_count() and |
| * s_op->nr_cached_objects(). |
| */ |
| if (sb->s_op && sb->s_op->nr_cached_objects) |
| total_objects = sb->s_op->nr_cached_objects(sb, sc); |
| |
| total_objects += list_lru_shrink_count(&sb->s_dentry_lru, sc); |
| total_objects += list_lru_shrink_count(&sb->s_inode_lru, sc); |
| |
| total_objects = vfs_pressure_ratio(total_objects); |
| return total_objects; |
| } |
| |
| static void destroy_super_work(struct work_struct *work) |
| { |
| struct super_block *s = container_of(work, struct super_block, |
| destroy_work); |
| int i; |
| |
| for (i = 0; i < SB_FREEZE_LEVELS; i++) |
| percpu_free_rwsem(&s->s_writers.rw_sem[i]); |
| kfree(s); |
| } |
| |
| static void destroy_super_rcu(struct rcu_head *head) |
| { |
| struct super_block *s = container_of(head, struct super_block, rcu); |
| INIT_WORK(&s->destroy_work, destroy_super_work); |
| schedule_work(&s->destroy_work); |
| } |
| |
| /** |
| * destroy_super - frees a superblock |
| * @s: superblock to free |
| * |
| * Frees a superblock. |
| */ |
| static void destroy_super(struct super_block *s) |
| { |
| list_lru_destroy(&s->s_dentry_lru); |
| list_lru_destroy(&s->s_inode_lru); |
| security_sb_free(s); |
| WARN_ON(!list_empty(&s->s_mounts)); |
| kfree(s->s_subtype); |
| kfree(s->s_options); |
| call_rcu(&s->rcu, destroy_super_rcu); |
| } |
| |
| /** |
| * 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, int flags) |
| { |
| struct super_block *s = kzalloc(sizeof(struct super_block), GFP_USER); |
| static const struct super_operations default_op; |
| int i; |
| |
| if (!s) |
| return NULL; |
| |
| INIT_LIST_HEAD(&s->s_mounts); |
| |
| if (security_sb_alloc(s)) |
| goto fail; |
| |
| for (i = 0; i < SB_FREEZE_LEVELS; i++) { |
| if (__percpu_init_rwsem(&s->s_writers.rw_sem[i], |
| sb_writers_name[i], |
| &type->s_writers_key[i])) |
| goto fail; |
| } |
| init_waitqueue_head(&s->s_writers.wait_unfrozen); |
| s->s_bdi = &noop_backing_dev_info; |
| s->s_flags = flags; |
| INIT_HLIST_NODE(&s->s_instances); |
| INIT_HLIST_BL_HEAD(&s->s_anon); |
| mutex_init(&s->s_sync_lock); |
| INIT_LIST_HEAD(&s->s_inodes); |
| spin_lock_init(&s->s_inode_list_lock); |
| |
| if (list_lru_init_memcg(&s->s_dentry_lru)) |
| goto fail; |
| if (list_lru_init_memcg(&s->s_inode_lru)) |
| goto fail; |
| |
| init_rwsem(&s->s_umount); |
| lockdep_set_class(&s->s_umount, &type->s_umount_key); |
| /* |
| * 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. |
| */ |
| 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); |
| s->s_maxbytes = MAX_NON_LFS; |
| s->s_op = &default_op; |
| s->s_time_gran = 1000000000; |
| s->cleancache_poolid = CLEANCACHE_NO_POOL; |
| |
| s->s_shrink.seeks = DEFAULT_SEEKS; |
| s->s_shrink.scan_objects = super_cache_scan; |
| s->s_shrink.count_objects = super_cache_count; |
| s->s_shrink.batch = 1024; |
| s->s_shrink.flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE; |
| return s; |
| |
| fail: |
| destroy_super(s); |
| return NULL; |
| } |
| |
| /* Superblock refcounting */ |
| |
| /* |
| * Drop a superblock's refcount. The caller must hold sb_lock. |
| */ |
| static void __put_super(struct super_block *sb) |
| { |
| if (!--sb->s_count) { |
| list_del_init(&sb->s_list); |
| destroy_super(sb); |
| } |
| } |
| |
| /** |
| * put_super - drop a temporary reference to superblock |
| * @sb: superblock in question |
| * |
| * Drops a temporary reference, frees superblock if there's no |
| * references left. |
| */ |
| static void put_super(struct super_block *sb) |
| { |
| spin_lock(&sb_lock); |
| __put_super(sb); |
| spin_unlock(&sb_lock); |
| } |
| |
| |
| /** |
| * deactivate_locked_super - drop an active reference to superblock |
| * @s: superblock to deactivate |
| * |
| * Drops an active reference to superblock, converting it into a temporary |
| * 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_locked_super(struct super_block *s) |
| { |
| struct file_system_type *fs = s->s_type; |
| if (atomic_dec_and_test(&s->s_active)) { |
| cleancache_invalidate_fs(s); |
| unregister_shrinker(&s->s_shrink); |
| fs->kill_sb(s); |
| |
| /* |
| * Since list_lru_destroy() may sleep, we cannot call it from |
| * put_super(), where we hold the sb_lock. Therefore we destroy |
| * the lru lists right now. |
| */ |
| list_lru_destroy(&s->s_dentry_lru); |
| list_lru_destroy(&s->s_inode_lru); |
| |
| 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); |
| } |
| } |
| |
| EXPORT_SYMBOL(deactivate_super); |
| |
| /** |
| * grab_super - acquire an active reference |
| * @s: reference we are trying to make active |
| * |
| * Tries to acquire an active reference. grab_super() is used when we |
| * had just found a superblock in super_blocks or fs_type->fs_supers |
| * 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). 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_flags & MS_BORN) && atomic_inc_not_zero(&s->s_active)) { |
| put_super(s); |
| return 1; |
| } |
| up_write(&s->s_umount); |
| put_super(s); |
| return 0; |
| } |
| |
| /* |
| * trylock_super - try to grab ->s_umount shared |
| * @sb: reference we are trying to grab |
| * |
| * Try to prevent fs shutdown. This is used in places where we |
| * cannot take an active reference but we need to ensure that the |
| * filesystem is not shut down while we are working on it. It returns |
| * false if we cannot acquire s_umount or if we lose the race and |
| * filesystem already got into shutdown, and returns true with the s_umount |
| * lock held in read mode in case of success. On successful return, |
| * the caller must drop the s_umount lock when done. |
| * |
| * Note that unlike get_super() et.al. this one does *not* bump ->s_count. |
| * The reason why it's safe is that we are OK with doing trylock instead |
| * of down_read(). There's a couple of places that are OK with that, but |
| * it's very much not a general-purpose interface. |
| */ |
| bool trylock_super(struct super_block *sb) |
| { |
| if (down_read_trylock(&sb->s_umount)) { |
| if (!hlist_unhashed(&sb->s_instances) && |
| sb->s_root && (sb->s_flags & MS_BORN)) |
| return true; |
| up_read(&sb->s_umount); |
| } |
| |
| return false; |
| } |
| |
| /** |
| * generic_shutdown_super - common helper for ->kill_sb() |
| * @sb: superblock to kill |
| * |
| * generic_shutdown_super() does all fs-independent work on superblock |
| * shutdown. Typical ->kill_sb() should pick all fs-specific objects |
| * that need destruction out of superblock, call generic_shutdown_super() |
| * and release aforementioned objects. Note: dentries and inodes _are_ |
| * taken care of and do not need specific handling. |
| * |
| * Upon calling this function, the filesystem may no longer alter or |
| * rearrange the set of dentries belonging to this super_block, nor may it |
| * change the attachments of dentries to inodes. |
| */ |
| void generic_shutdown_super(struct super_block *sb) |
| { |
| const struct super_operations *sop = sb->s_op; |
| |
| if (sb->s_root) { |
| shrink_dcache_for_umount(sb); |
| sync_filesystem(sb); |
| sb->s_flags &= ~MS_ACTIVE; |
| |
| fsnotify_unmount_inodes(sb); |
| cgroup_writeback_umount(); |
| |
| 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); |
| |
| 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); |
| } |
| } |
| spin_lock(&sb_lock); |
| /* should be initialized for __put_super_and_need_restart() */ |
| hlist_del_init(&sb->s_instances); |
| spin_unlock(&sb_lock); |
| up_write(&sb->s_umount); |
| } |
| |
| EXPORT_SYMBOL(generic_shutdown_super); |
| |
| /** |
| * sget - find or create a superblock |
| * @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 super_block *old; |
| int err; |
| |
| retry: |
| spin_lock(&sb_lock); |
| 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, flags); |
| if (!s) |
| return ERR_PTR(-ENOMEM); |
| goto 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); |
| hlist_add_head(&s->s_instances, &type->fs_supers); |
| spin_unlock(&sb_lock); |
| get_filesystem(type); |
| register_shrinker(&s->s_shrink); |
| return s; |
| } |
| |
| EXPORT_SYMBOL(sget); |
| |
| void drop_super(struct super_block *sb) |
| { |
| up_read(&sb->s_umount); |
| put_super(sb); |
| } |
| |
| EXPORT_SYMBOL(drop_super); |
| |
| /** |
| * 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 iterate_supers(void (*f)(struct super_block *, void *), void *arg) |
| { |
| 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_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); |
| } |
| |
| /** |
| * iterate_supers_type - call function for superblocks of given type |
| * @type: fs type |
| * @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 iterate_supers_type(struct file_system_type *type, |
| void (*f)(struct super_block *, void *), void *arg) |
| { |
| struct super_block *sb, *p = NULL; |
| |
| spin_lock(&sb_lock); |
| 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 && (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); |
| } |
| |
| EXPORT_SYMBOL(iterate_supers_type); |
| |
| /** |
| * get_super - get 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. %NULL is returned if no match is found. |
| */ |
| |
| struct super_block *get_super(struct block_device *bdev) |
| { |
| struct super_block *sb; |
| |
| if (!bdev) |
| return NULL; |
| |
| 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); |
| /* still alive? */ |
| if (sb->s_root && (sb->s_flags & MS_BORN)) |
| return sb; |
| up_read(&sb->s_umount); |
| /* nope, got unmounted */ |
| spin_lock(&sb_lock); |
| __put_super(sb); |
| goto rescan; |
| } |
| } |
| spin_unlock(&sb_lock); |
| return NULL; |
| } |
| |
| 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 *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); |
| /* still alive? */ |
| if (sb->s_root && (sb->s_flags & MS_BORN)) |
| return sb; |
| up_read(&sb->s_umount); |
| /* nope, got unmounted */ |
| spin_lock(&sb_lock); |
| __put_super(sb); |
| goto rescan; |
| } |
| } |
| spin_unlock(&sb_lock); |
| return NULL; |
| } |
| |
| /** |
| * do_remount_sb - asks filesystem to change mount options. |
| * @sb: superblock in question |
| * @flags: numeric part of options |
| * @data: the rest of options |
| * @force: whether or not to force the change |
| * |
| * Alters the mount options of a mounted file system. |
| */ |
| 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 |
| |
| remount_ro = (flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY); |
| |
| if (remount_ro) { |
| if (!hlist_empty(&sb->s_pins)) { |
| up_write(&sb->s_umount); |
| group_pin_kill(&sb->s_pins); |
| down_write(&sb->s_umount); |
| if (!sb->s_root) |
| return 0; |
| if (sb->s_writers.frozen != SB_UNFROZEN) |
| return -EBUSY; |
| remount_ro = (flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY); |
| } |
| } |
| shrink_dcache_sb(sb); |
| |
| /* If we are remounting RDONLY and current sb is read/write, |
| make sure there are no rw files opened */ |
| 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) { |
| retval = sb->s_op->remount_fs(sb, &flags, data); |
| 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(struct work_struct *work) |
| { |
| 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_write(&sb->s_umount); |
| if (sb->s_root && sb->s_bdev && (sb->s_flags & MS_BORN) && |
| !(sb->s_flags & MS_RDONLY)) { |
| /* |
| * What lock protects sb->s_flags?? |
| */ |
| do_remount_sb(sb, MS_RDONLY, NULL, 1); |
| } |
| 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) |
| { |
| struct work_struct *work; |
| |
| work = kmalloc(sizeof(*work), GFP_ATOMIC); |
| if (work) { |
| INIT_WORK(work, do_emergency_remount); |
| schedule_work(work); |
| } |
| } |
| |
| /* |
| * Unnamed block devices are dummy devices used by virtual |
| * filesystems which don't use real block-devices. -- jrs |
| */ |
| |
| static DEFINE_IDA(unnamed_dev_ida); |
| static DEFINE_SPINLOCK(unnamed_dev_lock);/* protects the above */ |
| /* Many userspace utilities consider an FSID of 0 invalid. |
| * Always return at least 1 from get_anon_bdev. |
| */ |
| static int unnamed_dev_start = 1; |
| |
| int get_anon_bdev(dev_t *p) |
| { |
| int dev; |
| int error; |
| |
| retry: |
| if (ida_pre_get(&unnamed_dev_ida, GFP_ATOMIC) == 0) |
| return -ENOMEM; |
| spin_lock(&unnamed_dev_lock); |
| 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. */ |
| goto retry; |
| else if (error) |
| return -EAGAIN; |
| |
| if (dev >= (1 << MINORBITS)) { |
| spin_lock(&unnamed_dev_lock); |
| ida_remove(&unnamed_dev_ida, dev); |
| if (unnamed_dev_start > dev) |
| unnamed_dev_start = dev; |
| spin_unlock(&unnamed_dev_lock); |
| return -EMFILE; |
| } |
| *p = MKDEV(0, dev & MINORMASK); |
| return 0; |
| } |
| EXPORT_SYMBOL(get_anon_bdev); |
| |
| void free_anon_bdev(dev_t dev) |
| { |
| int slot = MINOR(dev); |
| spin_lock(&unnamed_dev_lock); |
| 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); |
| |
| int set_anon_super(struct super_block *s, void *data) |
| { |
| return get_anon_bdev(&s->s_dev); |
| } |
| |
| EXPORT_SYMBOL(set_anon_super); |
| |
| void kill_anon_super(struct super_block *sb) |
| { |
| 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) |
| d_genocide(sb->s_root); |
| kill_anon_super(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; |
| } |
| |
| static int test_bdev_super(struct super_block *s, void *data) |
| { |
| return (void *)s->s_bdev == data; |
| } |
| |
| 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 block_device *bdev; |
| struct super_block *s; |
| fmode_t mode = FMODE_READ | FMODE_EXCL; |
| int error = 0; |
| |
| if (!(flags & MS_RDONLY)) |
| mode |= FMODE_WRITE; |
| |
| bdev = blkdev_get_by_path(dev_name, mode, fs_type); |
| if (IS_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 |
| */ |
| 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) { |
| deactivate_locked_super(s); |
| error = -EBUSY; |
| goto error_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 { |
| s->s_mode = mode; |
| snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev); |
| sb_set_blocksize(s, block_size(bdev)); |
| error = fill_super(s, data, flags & MS_SILENT ? 1 : 0); |
| if (error) { |
| deactivate_locked_super(s); |
| goto error; |
| } |
| |
| s->s_flags |= MS_ACTIVE; |
| bdev->bd_super = s; |
| } |
| |
| return dget(s->s_root); |
| |
| error_s: |
| error = PTR_ERR(s); |
| error_bdev: |
| blkdev_put(bdev, mode); |
| error: |
| return ERR_PTR(error); |
| } |
| 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->bd_super = NULL; |
| generic_shutdown_super(sb); |
| sync_blockdev(bdev); |
| WARN_ON_ONCE(!(mode & FMODE_EXCL)); |
| blkdev_put(bdev, mode | FMODE_EXCL); |
| } |
| |
| EXPORT_SYMBOL(kill_block_super); |
| #endif |
| |
| struct dentry *mount_nodev(struct file_system_type *fs_type, |
| int flags, void *data, |
| int (*fill_super)(struct super_block *, void *, int)) |
| { |
| int error; |
| struct super_block *s = sget(fs_type, NULL, set_anon_super, flags, NULL); |
| |
| if (IS_ERR(s)) |
| return ERR_CAST(s); |
| |
| error = fill_super(s, data, flags & MS_SILENT ? 1 : 0); |
| if (error) { |
| deactivate_locked_super(s); |
| return ERR_PTR(error); |
| } |
| s->s_flags |= MS_ACTIVE; |
| return dget(s->s_root); |
| } |
| EXPORT_SYMBOL(mount_nodev); |
| |
| static int compare_single(struct super_block *s, void *p) |
| { |
| return 1; |
| } |
| |
| struct dentry *mount_single(struct file_system_type *fs_type, |
| int flags, void *data, |
| int (*fill_super)(struct super_block *, void *, int)) |
| { |
| struct super_block *s; |
| int error; |
| |
| s = sget(fs_type, compare_single, set_anon_super, flags, NULL); |
| if (IS_ERR(s)) |
| return ERR_CAST(s); |
| if (!s->s_root) { |
| error = fill_super(s, data, flags & MS_SILENT ? 1 : 0); |
| if (error) { |
| deactivate_locked_super(s); |
| return ERR_PTR(error); |
| } |
| s->s_flags |= MS_ACTIVE; |
| } else { |
| do_remount_sb(s, flags, data, 0); |
| } |
| return dget(s->s_root); |
| } |
| EXPORT_SYMBOL(mount_single); |
| |
| struct dentry * |
| mount_fs(struct file_system_type *type, int flags, const char *name, void *data) |
| { |
| struct dentry *root; |
| struct super_block *sb; |
| char *secdata = NULL; |
| int error = -ENOMEM; |
| |
| if (data && !(type->fs_flags & FS_BINARY_MOUNTDATA)) { |
| secdata = alloc_secdata(); |
| if (!secdata) |
| goto out; |
| |
| error = security_sb_copy_data(data, secdata); |
| if (error) |
| goto out_free_secdata; |
| } |
| |
| 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); |
| sb->s_flags |= MS_BORN; |
| |
| error = security_sb_kern_mount(sb, flags, 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); |
| |
| up_write(&sb->s_umount); |
| free_secdata(secdata); |
| return root; |
| out_sb: |
| dput(root); |
| deactivate_locked_super(sb); |
| out_free_secdata: |
| free_secdata(secdata); |
| out: |
| return ERR_PTR(error); |
| } |
| |
| /* |
| * This is an internal function, please use sb_end_{write,pagefault,intwrite} |
| * instead. |
| */ |
| void __sb_end_write(struct super_block *sb, int level) |
| { |
| percpu_up_read(sb->s_writers.rw_sem + level-1); |
| } |
| EXPORT_SYMBOL(__sb_end_write); |
| |
| /* |
| * 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) |
| { |
| bool force_trylock = false; |
| int ret = 1; |
| |
| #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 use wait == F (trylock mode) which must not fail. |
| */ |
| if (wait) { |
| int i; |
| |
| for (i = 0; i < level - 1; i++) |
| if (percpu_rwsem_is_held(sb->s_writers.rw_sem + i)) { |
| force_trylock = true; |
| break; |
| } |
| } |
| #endif |
| if (wait && !force_trylock) |
| percpu_down_read(sb->s_writers.rw_sem + level-1); |
| else |
| ret = percpu_down_read_trylock(sb->s_writers.rw_sem + level-1); |
| |
| WARN_ON(force_trylock && !ret); |
| return ret; |
| } |
| 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. |
| */ |
| static void sb_wait_write(struct super_block *sb, int level) |
| { |
| percpu_down_write(sb->s_writers.rw_sem + level-1); |
| /* |
| * We are going to return to userspace and forget about this lock, the |
| * ownership goes to the caller of thaw_super() which does unlock. |
| * |
| * FIXME: we should do this before return from freeze_super() after we |
| * called sync_filesystem(sb) and s_op->freeze_fs(sb), and thaw_super() |
| * should re-acquire these locks before s_op->unfreeze_fs(sb). However |
| * this leads to lockdep false-positives, so currently we do the early |
| * release right after acquire. |
| */ |
| percpu_rwsem_release(sb->s_writers.rw_sem + level-1, 0, _THIS_IP_); |
| } |
| |
| static void sb_freeze_unlock(struct super_block *sb) |
| { |
| int level; |
| |
| for (level = 0; level < SB_FREEZE_LEVELS; ++level) |
| percpu_rwsem_acquire(sb->s_writers.rw_sem + level, 0, _THIS_IP_); |
| |
| for (level = SB_FREEZE_LEVELS - 1; level >= 0; level--) |
| percpu_up_write(sb->s_writers.rw_sem + level); |
| } |
| |
| /** |
| * 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; |
| } |
| |
| sb->s_writers.frozen = SB_FREEZE_WRITE; |
| /* Release s_umount to preserve sb_start_write -> s_umount ordering */ |
| up_write(&sb->s_umount); |
| sb_wait_write(sb, SB_FREEZE_WRITE); |
| down_write(&sb->s_umount); |
| |
| /* Now we go and block page faults... */ |
| sb->s_writers.frozen = SB_FREEZE_PAGEFAULT; |
| 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; |
| 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; |
| sb_freeze_unlock(sb); |
| 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) { |
| sb->s_writers.frozen = SB_UNFROZEN; |
| 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; |
| } |
| } |
| |
| sb->s_writers.frozen = SB_UNFROZEN; |
| sb_freeze_unlock(sb); |
| out: |
| wake_up(&sb->s_writers.wait_unfrozen); |
| deactivate_locked_super(sb); |
| return 0; |
| } |
| EXPORT_SYMBOL(thaw_super); |