diff options
Diffstat (limited to 'kernel/fs/super.c')
| -rw-r--r-- | kernel/fs/super.c | 1396 |
1 files changed, 1396 insertions, 0 deletions
diff --git a/kernel/fs/super.c b/kernel/fs/super.c new file mode 100644 index 000000000..928c20f47 --- /dev/null +++ b/kernel/fs/super.c @@ -0,0 +1,1396 @@ +/* + * 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; +} + +/** + * destroy_super - frees a superblock + * @s: superblock to free + * + * Frees a superblock. + */ +static void destroy_super(struct super_block *s) +{ + int i; + list_lru_destroy(&s->s_dentry_lru); + list_lru_destroy(&s->s_inode_lru); + for (i = 0; i < SB_FREEZE_LEVELS; i++) + percpu_counter_destroy(&s->s_writers.counter[i]); + security_sb_free(s); + WARN_ON(!list_empty(&s->s_mounts)); + kfree(s->s_subtype); + kfree(s->s_options); + kfree_rcu(s, 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_counter_init(&s->s_writers.counter[i], 0, + GFP_KERNEL) < 0) + goto fail; + 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); + s->s_bdi = &noop_backing_dev_info; + s->s_flags = flags; + INIT_HLIST_NODE(&s->s_instances); + INIT_HLIST_BL_HEAD(&s->s_anon); + INIT_LIST_HEAD(&s->s_inodes); + + 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 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_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->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); + + 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 { + char b[BDEVNAME_SIZE]; + + 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) { + 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_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); + +#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) +{ + 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 + +/* + * 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) +{ +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); +} + +/** + * 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); |