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- // SPDX-License-Identifier: GPL-2.0
- /*
- * 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/fscrypt.h>
- #include <linux/fsnotify.h>
- #include <linux/lockdep.h>
- #include <linux/user_namespace.h>
- #include <linux/fs_context.h>
- #include <uapi/linux/mount.h>
- #include "internal.h"
- static int thaw_super_locked(struct super_block *sb);
- 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);
- /*
- * We don't call trylock_super() here as it is a scalability bottleneck,
- * so we're exposed to partial setup state. The shrinker rwsem does not
- * protect filesystem operations backing list_lru_shrink_count() or
- * s_op->nr_cached_objects(). Counts can change between
- * super_cache_count and super_cache_scan, so we really don't need locks
- * here.
- *
- * However, if we are currently mounting the superblock, the underlying
- * filesystem might be in a state of partial construction and hence it
- * is dangerous to access it. trylock_super() uses a SB_BORN check to
- * avoid this situation, so do the same here. The memory barrier is
- * matched with the one in mount_fs() as we don't hold locks here.
- */
- if (!(sb->s_flags & SB_BORN))
- return 0;
- smp_rmb();
- 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);
- if (!total_objects)
- return SHRINK_EMPTY;
- 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);
- }
- /* Free a superblock that has never been seen by anyone */
- static void destroy_unused_super(struct super_block *s)
- {
- if (!s)
- return;
- up_write(&s->s_umount);
- list_lru_destroy(&s->s_dentry_lru);
- list_lru_destroy(&s->s_inode_lru);
- security_sb_free(s);
- put_user_ns(s->s_user_ns);
- kfree(s->s_subtype);
- free_prealloced_shrinker(&s->s_shrink);
- /* no delays needed */
- destroy_super_work(&s->destroy_work);
- }
- /**
- * alloc_super - create new superblock
- * @type: filesystem type superblock should belong to
- * @flags: the mount flags
- * @user_ns: User namespace for the super_block
- *
- * 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 user_namespace *user_ns)
- {
- 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);
- s->s_user_ns = get_user_ns(user_ns);
- 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);
- 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;
- if (s->s_user_ns != &init_user_ns)
- s->s_iflags |= SB_I_NODEV;
- INIT_HLIST_NODE(&s->s_instances);
- INIT_HLIST_BL_HEAD(&s->s_roots);
- mutex_init(&s->s_sync_lock);
- INIT_LIST_HEAD(&s->s_inodes);
- spin_lock_init(&s->s_inode_list_lock);
- INIT_LIST_HEAD(&s->s_inodes_wb);
- spin_lock_init(&s->s_inode_wblist_lock);
- 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);
- init_rwsem(&s->s_dquot.dqio_sem);
- s->s_maxbytes = MAX_NON_LFS;
- s->s_op = &default_op;
- s->s_time_gran = 1000000000;
- s->s_time_min = TIME64_MIN;
- s->s_time_max = TIME64_MAX;
- 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;
- if (prealloc_shrinker(&s->s_shrink))
- goto fail;
- if (list_lru_init_memcg(&s->s_dentry_lru, &s->s_shrink))
- goto fail;
- if (list_lru_init_memcg(&s->s_inode_lru, &s->s_shrink))
- goto fail;
- return s;
- fail:
- destroy_unused_super(s);
- return NULL;
- }
- /* Superblock refcounting */
- /*
- * Drop a superblock's refcount. The caller must hold sb_lock.
- */
- static void __put_super(struct super_block *s)
- {
- if (!--s->s_count) {
- list_del_init(&s->s_list);
- WARN_ON(s->s_dentry_lru.node);
- WARN_ON(s->s_inode_lru.node);
- WARN_ON(!list_empty(&s->s_mounts));
- security_sb_free(s);
- fscrypt_sb_free(s);
- put_user_ns(s->s_user_ns);
- kfree(s->s_subtype);
- call_rcu(&s->rcu, destroy_super_rcu);
- }
- }
- /**
- * 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 & SB_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 & SB_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 &= ~SB_ACTIVE;
- cgroup_writeback_umount();
- /* evict all inodes with zero refcount */
- evict_inodes(sb);
- /* only nonzero refcount inodes can have marks */
- fsnotify_sb_delete(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);
- if (sb->s_bdi != &noop_backing_dev_info) {
- bdi_put(sb->s_bdi);
- sb->s_bdi = &noop_backing_dev_info;
- }
- }
- EXPORT_SYMBOL(generic_shutdown_super);
- bool mount_capable(struct fs_context *fc)
- {
- if (!(fc->fs_type->fs_flags & FS_USERNS_MOUNT))
- return capable(CAP_SYS_ADMIN);
- else
- return ns_capable(fc->user_ns, CAP_SYS_ADMIN);
- }
- /**
- * sget_fc - Find or create a superblock
- * @fc: Filesystem context.
- * @test: Comparison callback
- * @set: Setup callback
- *
- * Find or create a superblock using the parameters stored in the filesystem
- * context and the two callback functions.
- *
- * If an extant superblock is matched, then that will be returned with an
- * elevated reference count that the caller must transfer or discard.
- *
- * If no match is made, a new superblock will be allocated and basic
- * initialisation will be performed (s_type, s_fs_info and s_id will be set and
- * the set() callback will be invoked), the superblock will be published and it
- * will be returned in a partially constructed state with SB_BORN and SB_ACTIVE
- * as yet unset.
- */
- struct super_block *sget_fc(struct fs_context *fc,
- int (*test)(struct super_block *, struct fs_context *),
- int (*set)(struct super_block *, struct fs_context *))
- {
- struct super_block *s = NULL;
- struct super_block *old;
- struct user_namespace *user_ns = fc->global ? &init_user_ns : fc->user_ns;
- int err;
- retry:
- spin_lock(&sb_lock);
- if (test) {
- hlist_for_each_entry(old, &fc->fs_type->fs_supers, s_instances) {
- if (test(old, fc))
- goto share_extant_sb;
- }
- }
- if (!s) {
- spin_unlock(&sb_lock);
- s = alloc_super(fc->fs_type, fc->sb_flags, user_ns);
- if (!s)
- return ERR_PTR(-ENOMEM);
- goto retry;
- }
- s->s_fs_info = fc->s_fs_info;
- err = set(s, fc);
- if (err) {
- s->s_fs_info = NULL;
- spin_unlock(&sb_lock);
- destroy_unused_super(s);
- return ERR_PTR(err);
- }
- fc->s_fs_info = NULL;
- s->s_type = fc->fs_type;
- s->s_iflags |= fc->s_iflags;
- strlcpy(s->s_id, s->s_type->name, sizeof(s->s_id));
- list_add_tail(&s->s_list, &super_blocks);
- hlist_add_head(&s->s_instances, &s->s_type->fs_supers);
- spin_unlock(&sb_lock);
- get_filesystem(s->s_type);
- register_shrinker_prepared(&s->s_shrink);
- return s;
- share_extant_sb:
- if (user_ns != old->s_user_ns) {
- spin_unlock(&sb_lock);
- destroy_unused_super(s);
- return ERR_PTR(-EBUSY);
- }
- if (!grab_super(old))
- goto retry;
- destroy_unused_super(s);
- return old;
- }
- EXPORT_SYMBOL(sget_fc);
- /**
- * 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 user_namespace *user_ns = current_user_ns();
- struct super_block *s = NULL;
- struct super_block *old;
- int err;
- /* We don't yet pass the user namespace of the parent
- * mount through to here so always use &init_user_ns
- * until that changes.
- */
- if (flags & SB_SUBMOUNT)
- user_ns = &init_user_ns;
- retry:
- spin_lock(&sb_lock);
- if (test) {
- hlist_for_each_entry(old, &type->fs_supers, s_instances) {
- if (!test(old, data))
- continue;
- if (user_ns != old->s_user_ns) {
- spin_unlock(&sb_lock);
- destroy_unused_super(s);
- return ERR_PTR(-EBUSY);
- }
- if (!grab_super(old))
- goto retry;
- destroy_unused_super(s);
- return old;
- }
- }
- if (!s) {
- spin_unlock(&sb_lock);
- s = alloc_super(type, (flags & ~SB_SUBMOUNT), user_ns);
- if (!s)
- return ERR_PTR(-ENOMEM);
- goto retry;
- }
- err = set(s, data);
- if (err) {
- spin_unlock(&sb_lock);
- destroy_unused_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_prepared(&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);
- void drop_super_exclusive(struct super_block *sb)
- {
- up_write(&sb->s_umount);
- put_super(sb);
- }
- EXPORT_SYMBOL(drop_super_exclusive);
- static void __iterate_supers(void (*f)(struct super_block *))
- {
- 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);
- f(sb);
- spin_lock(&sb_lock);
- if (p)
- __put_super(p);
- p = sb;
- }
- if (p)
- __put_super(p);
- spin_unlock(&sb_lock);
- }
- /**
- * 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 & SB_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 & SB_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);
- static struct super_block *__get_super(struct block_device *bdev, bool excl)
- {
- 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);
- if (!excl)
- down_read(&sb->s_umount);
- else
- down_write(&sb->s_umount);
- /* still alive? */
- if (sb->s_root && (sb->s_flags & SB_BORN))
- return sb;
- if (!excl)
- up_read(&sb->s_umount);
- else
- up_write(&sb->s_umount);
- /* nope, got unmounted */
- spin_lock(&sb_lock);
- __put_super(sb);
- goto rescan;
- }
- }
- spin_unlock(&sb_lock);
- return NULL;
- }
- /**
- * 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)
- {
- return __get_super(bdev, false);
- }
- EXPORT_SYMBOL(get_super);
- static struct super_block *__get_super_thawed(struct block_device *bdev,
- bool excl)
- {
- while (1) {
- struct super_block *s = __get_super(bdev, excl);
- if (!s || s->s_writers.frozen == SB_UNFROZEN)
- return s;
- if (!excl)
- up_read(&s->s_umount);
- else
- up_write(&s->s_umount);
- wait_event(s->s_writers.wait_unfrozen,
- s->s_writers.frozen == SB_UNFROZEN);
- put_super(s);
- }
- }
- /**
- * 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)
- {
- return __get_super_thawed(bdev, false);
- }
- EXPORT_SYMBOL(get_super_thawed);
- /**
- * get_super_exclusive_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) and s_umount semaphore is held
- * in exclusive mode. %NULL is returned if no match is found.
- */
- struct super_block *get_super_exclusive_thawed(struct block_device *bdev)
- {
- return __get_super_thawed(bdev, true);
- }
- EXPORT_SYMBOL(get_super_exclusive_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 & SB_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;
- }
- /**
- * reconfigure_super - asks filesystem to change superblock parameters
- * @fc: The superblock and configuration
- *
- * Alters the configuration parameters of a live superblock.
- */
- int reconfigure_super(struct fs_context *fc)
- {
- struct super_block *sb = fc->root->d_sb;
- int retval;
- bool remount_ro = false;
- bool force = fc->sb_flags & SB_FORCE;
- if (fc->sb_flags_mask & ~MS_RMT_MASK)
- return -EINVAL;
- if (sb->s_writers.frozen != SB_UNFROZEN)
- return -EBUSY;
- retval = security_sb_remount(sb, fc->security);
- if (retval)
- return retval;
- if (fc->sb_flags_mask & SB_RDONLY) {
- #ifdef CONFIG_BLOCK
- if (!(fc->sb_flags & SB_RDONLY) && bdev_read_only(sb->s_bdev))
- return -EACCES;
- #endif
- remount_ro = (fc->sb_flags & SB_RDONLY) && !sb_rdonly(sb);
- }
- 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 = !sb_rdonly(sb);
- }
- }
- shrink_dcache_sb(sb);
- /* If we are reconfiguring to RDONLY and current sb is read/write,
- * make sure there are no files open for writing.
- */
- if (remount_ro) {
- if (force) {
- sb->s_readonly_remount = 1;
- smp_wmb();
- } else {
- retval = sb_prepare_remount_readonly(sb);
- if (retval)
- return retval;
- }
- }
- if (fc->ops->reconfigure) {
- retval = fc->ops->reconfigure(fc);
- 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);
- }
- }
- WRITE_ONCE(sb->s_flags, ((sb->s_flags & ~fc->sb_flags_mask) |
- (fc->sb_flags & fc->sb_flags_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_callback(struct super_block *sb)
- {
- down_write(&sb->s_umount);
- if (sb->s_root && sb->s_bdev && (sb->s_flags & SB_BORN) &&
- !sb_rdonly(sb)) {
- struct fs_context *fc;
- fc = fs_context_for_reconfigure(sb->s_root,
- SB_RDONLY | SB_FORCE, SB_RDONLY);
- if (!IS_ERR(fc)) {
- if (parse_monolithic_mount_data(fc, NULL) == 0)
- (void)reconfigure_super(fc);
- put_fs_context(fc);
- }
- }
- up_write(&sb->s_umount);
- }
- static void do_emergency_remount(struct work_struct *work)
- {
- __iterate_supers(do_emergency_remount_callback);
- 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);
- }
- }
- static void do_thaw_all_callback(struct super_block *sb)
- {
- down_write(&sb->s_umount);
- if (sb->s_root && sb->s_flags & SB_BORN) {
- emergency_thaw_bdev(sb);
- thaw_super_locked(sb);
- } else {
- up_write(&sb->s_umount);
- }
- }
- static void do_thaw_all(struct work_struct *work)
- {
- __iterate_supers(do_thaw_all_callback);
- kfree(work);
- printk(KERN_WARNING "Emergency Thaw complete\n");
- }
- /**
- * emergency_thaw_all -- forcibly thaw every frozen filesystem
- *
- * Used for emergency unfreeze of all filesystems via SysRq
- */
- void emergency_thaw_all(void)
- {
- struct work_struct *work;
- work = kmalloc(sizeof(*work), GFP_ATOMIC);
- if (work) {
- INIT_WORK(work, do_thaw_all);
- schedule_work(work);
- }
- }
- static DEFINE_IDA(unnamed_dev_ida);
- /**
- * get_anon_bdev - Allocate a block device for filesystems which don't have one.
- * @p: Pointer to a dev_t.
- *
- * Filesystems which don't use real block devices can call this function
- * to allocate a virtual block device.
- *
- * Context: Any context. Frequently called while holding sb_lock.
- * Return: 0 on success, -EMFILE if there are no anonymous bdevs left
- * or -ENOMEM if memory allocation failed.
- */
- int get_anon_bdev(dev_t *p)
- {
- int dev;
- /*
- * Many userspace utilities consider an FSID of 0 invalid.
- * Always return at least 1 from get_anon_bdev.
- */
- dev = ida_alloc_range(&unnamed_dev_ida, 1, (1 << MINORBITS) - 1,
- GFP_ATOMIC);
- if (dev == -ENOSPC)
- dev = -EMFILE;
- if (dev < 0)
- return dev;
- *p = MKDEV(0, dev);
- return 0;
- }
- EXPORT_SYMBOL(get_anon_bdev);
- void free_anon_bdev(dev_t dev)
- {
- ida_free(&unnamed_dev_ida, MINOR(dev));
- }
- 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);
- int set_anon_super_fc(struct super_block *sb, struct fs_context *fc)
- {
- return set_anon_super(sb, NULL);
- }
- EXPORT_SYMBOL(set_anon_super_fc);
- static int test_keyed_super(struct super_block *sb, struct fs_context *fc)
- {
- return sb->s_fs_info == fc->s_fs_info;
- }
- static int test_single_super(struct super_block *s, struct fs_context *fc)
- {
- return 1;
- }
- /**
- * vfs_get_super - Get a superblock with a search key set in s_fs_info.
- * @fc: The filesystem context holding the parameters
- * @keying: How to distinguish superblocks
- * @fill_super: Helper to initialise a new superblock
- *
- * Search for a superblock and create a new one if not found. The search
- * criterion is controlled by @keying. If the search fails, a new superblock
- * is created and @fill_super() is called to initialise it.
- *
- * @keying can take one of a number of values:
- *
- * (1) vfs_get_single_super - Only one superblock of this type may exist on the
- * system. This is typically used for special system filesystems.
- *
- * (2) vfs_get_keyed_super - Multiple superblocks may exist, but they must have
- * distinct keys (where the key is in s_fs_info). Searching for the same
- * key again will turn up the superblock for that key.
- *
- * (3) vfs_get_independent_super - Multiple superblocks may exist and are
- * unkeyed. Each call will get a new superblock.
- *
- * A permissions check is made by sget_fc() unless we're getting a superblock
- * for a kernel-internal mount or a submount.
- */
- int vfs_get_super(struct fs_context *fc,
- enum vfs_get_super_keying keying,
- int (*fill_super)(struct super_block *sb,
- struct fs_context *fc))
- {
- int (*test)(struct super_block *, struct fs_context *);
- struct super_block *sb;
- int err;
- switch (keying) {
- case vfs_get_single_super:
- case vfs_get_single_reconf_super:
- test = test_single_super;
- break;
- case vfs_get_keyed_super:
- test = test_keyed_super;
- break;
- case vfs_get_independent_super:
- test = NULL;
- break;
- default:
- BUG();
- }
- sb = sget_fc(fc, test, set_anon_super_fc);
- if (IS_ERR(sb))
- return PTR_ERR(sb);
- if (!sb->s_root) {
- err = fill_super(sb, fc);
- if (err)
- goto error;
- sb->s_flags |= SB_ACTIVE;
- fc->root = dget(sb->s_root);
- } else {
- fc->root = dget(sb->s_root);
- if (keying == vfs_get_single_reconf_super) {
- err = reconfigure_super(fc);
- if (err < 0) {
- dput(fc->root);
- fc->root = NULL;
- goto error;
- }
- }
- }
- return 0;
- error:
- deactivate_locked_super(sb);
- return err;
- }
- EXPORT_SYMBOL(vfs_get_super);
- int get_tree_nodev(struct fs_context *fc,
- int (*fill_super)(struct super_block *sb,
- struct fs_context *fc))
- {
- return vfs_get_super(fc, vfs_get_independent_super, fill_super);
- }
- EXPORT_SYMBOL(get_tree_nodev);
- int get_tree_single(struct fs_context *fc,
- int (*fill_super)(struct super_block *sb,
- struct fs_context *fc))
- {
- return vfs_get_super(fc, vfs_get_single_super, fill_super);
- }
- EXPORT_SYMBOL(get_tree_single);
- int get_tree_single_reconf(struct fs_context *fc,
- int (*fill_super)(struct super_block *sb,
- struct fs_context *fc))
- {
- return vfs_get_super(fc, vfs_get_single_reconf_super, fill_super);
- }
- EXPORT_SYMBOL(get_tree_single_reconf);
- int get_tree_keyed(struct fs_context *fc,
- int (*fill_super)(struct super_block *sb,
- struct fs_context *fc),
- void *key)
- {
- fc->s_fs_info = key;
- return vfs_get_super(fc, vfs_get_keyed_super, fill_super);
- }
- EXPORT_SYMBOL(get_tree_keyed);
- #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;
- s->s_bdi = bdi_get(s->s_bdev->bd_bdi);
- if (blk_queue_stable_writes(s->s_bdev->bd_disk->queue))
- s->s_iflags |= SB_I_STABLE_WRITES;
- return 0;
- }
- static int set_bdev_super_fc(struct super_block *s, struct fs_context *fc)
- {
- return set_bdev_super(s, fc->sget_key);
- }
- static int test_bdev_super_fc(struct super_block *s, struct fs_context *fc)
- {
- return s->s_bdev == fc->sget_key;
- }
- /**
- * get_tree_bdev - Get a superblock based on a single block device
- * @fc: The filesystem context holding the parameters
- * @fill_super: Helper to initialise a new superblock
- */
- int get_tree_bdev(struct fs_context *fc,
- int (*fill_super)(struct super_block *,
- struct fs_context *))
- {
- struct block_device *bdev;
- struct super_block *s;
- fmode_t mode = FMODE_READ | FMODE_EXCL;
- int error = 0;
- if (!(fc->sb_flags & SB_RDONLY))
- mode |= FMODE_WRITE;
- if (!fc->source)
- return invalf(fc, "No source specified");
- bdev = blkdev_get_by_path(fc->source, mode, fc->fs_type);
- if (IS_ERR(bdev)) {
- errorf(fc, "%s: Can't open blockdev", fc->source);
- return PTR_ERR(bdev);
- }
- /* Once the superblock is inserted into the list by sget_fc(), 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);
- warnf(fc, "%pg: Can't mount, blockdev is frozen", bdev);
- blkdev_put(bdev, mode);
- return -EBUSY;
- }
- fc->sb_flags |= SB_NOSEC;
- fc->sget_key = bdev;
- s = sget_fc(fc, test_bdev_super_fc, set_bdev_super_fc);
- mutex_unlock(&bdev->bd_fsfreeze_mutex);
- if (IS_ERR(s)) {
- blkdev_put(bdev, mode);
- return PTR_ERR(s);
- }
- if (s->s_root) {
- /* Don't summarily change the RO/RW state. */
- if ((fc->sb_flags ^ s->s_flags) & SB_RDONLY) {
- warnf(fc, "%pg: Can't mount, would change RO state", bdev);
- deactivate_locked_super(s);
- blkdev_put(bdev, mode);
- return -EBUSY;
- }
- /*
- * 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, fc);
- if (error) {
- deactivate_locked_super(s);
- return error;
- }
- s->s_flags |= SB_ACTIVE;
- bdev->bd_super = s;
- }
- BUG_ON(fc->root);
- fc->root = dget(s->s_root);
- return 0;
- }
- EXPORT_SYMBOL(get_tree_bdev);
- 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 & SB_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 | SB_NOSEC,
- bdev);
- mutex_unlock(&bdev->bd_fsfreeze_mutex);
- if (IS_ERR(s))
- goto error_s;
- if (s->s_root) {
- if ((flags ^ s->s_flags) & SB_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 & SB_SILENT ? 1 : 0);
- if (error) {
- deactivate_locked_super(s);
- goto error;
- }
- s->s_flags |= SB_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_NS(mount_bdev, ANDROID_GKI_VFS_EXPORT_ONLY);
- 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_NS(kill_block_super, ANDROID_GKI_VFS_EXPORT_ONLY);
- #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 & SB_SILENT ? 1 : 0);
- if (error) {
- deactivate_locked_super(s);
- return ERR_PTR(error);
- }
- s->s_flags |= SB_ACTIVE;
- return dget(s->s_root);
- }
- EXPORT_SYMBOL(mount_nodev);
- int reconfigure_single(struct super_block *s,
- int flags, void *data)
- {
- struct fs_context *fc;
- int ret;
- /* The caller really need to be passing fc down into mount_single(),
- * then a chunk of this can be removed. [Bollocks -- AV]
- * Better yet, reconfiguration shouldn't happen, but rather the second
- * mount should be rejected if the parameters are not compatible.
- */
- fc = fs_context_for_reconfigure(s->s_root, flags, MS_RMT_MASK);
- if (IS_ERR(fc))
- return PTR_ERR(fc);
- ret = parse_monolithic_mount_data(fc, data);
- if (ret < 0)
- goto out;
- ret = reconfigure_super(fc);
- out:
- put_fs_context(fc);
- return ret;
- }
- 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 & SB_SILENT ? 1 : 0);
- if (!error)
- s->s_flags |= SB_ACTIVE;
- } else {
- error = reconfigure_single(s, flags, data);
- }
- if (unlikely(error)) {
- deactivate_locked_super(s);
- return ERR_PTR(error);
- }
- return dget(s->s_root);
- }
- EXPORT_SYMBOL(mount_single);
- /**
- * vfs_get_tree - Get the mountable root
- * @fc: The superblock configuration context.
- *
- * The filesystem is invoked to get or create a superblock which can then later
- * be used for mounting. The filesystem places a pointer to the root to be
- * used for mounting in @fc->root.
- */
- int vfs_get_tree(struct fs_context *fc)
- {
- struct super_block *sb;
- int error;
- if (fc->root)
- return -EBUSY;
- /* Get the mountable root in fc->root, with a ref on the root and a ref
- * on the superblock.
- */
- error = fc->ops->get_tree(fc);
- if (error < 0)
- return error;
- if (!fc->root) {
- pr_err("Filesystem %s get_tree() didn't set fc->root\n",
- fc->fs_type->name);
- /* We don't know what the locking state of the superblock is -
- * if there is a superblock.
- */
- BUG();
- }
- sb = fc->root->d_sb;
- WARN_ON(!sb->s_bdi);
- /*
- * Write barrier is for super_cache_count(). We place it before setting
- * SB_BORN as the data dependency between the two functions is the
- * superblock structure contents that we just set up, not the SB_BORN
- * flag.
- */
- smp_wmb();
- sb->s_flags |= SB_BORN;
- error = security_sb_set_mnt_opts(sb, fc->security, 0, NULL);
- if (unlikely(error)) {
- fc_drop_locked(fc);
- return error;
- }
- /*
- * 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", fc->fs_type->name, sb->s_maxbytes);
- return 0;
- }
- EXPORT_SYMBOL(vfs_get_tree);
- /*
- * Setup private BDI for given superblock. It gets automatically cleaned up
- * in generic_shutdown_super().
- */
- int super_setup_bdi_name(struct super_block *sb, char *fmt, ...)
- {
- struct backing_dev_info *bdi;
- int err;
- va_list args;
- bdi = bdi_alloc(NUMA_NO_NODE);
- if (!bdi)
- return -ENOMEM;
- va_start(args, fmt);
- err = bdi_register_va(bdi, fmt, args);
- va_end(args);
- if (err) {
- bdi_put(bdi);
- return err;
- }
- WARN_ON(sb->s_bdi != &noop_backing_dev_info);
- sb->s_bdi = bdi;
- return 0;
- }
- EXPORT_SYMBOL(super_setup_bdi_name);
- /*
- * Setup private BDI for given superblock. I gets automatically cleaned up
- * in generic_shutdown_super().
- */
- int super_setup_bdi(struct super_block *sb)
- {
- static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0);
- return super_setup_bdi_name(sb, "%.28s-%ld", sb->s_type->name,
- atomic_long_inc_return(&bdi_seq));
- }
- EXPORT_SYMBOL(super_setup_bdi);
- /**
- * 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 these locks, the
- * ownership goes to the caller of thaw_super() which does unlock().
- */
- static void lockdep_sb_freeze_release(struct super_block *sb)
- {
- int level;
- for (level = SB_FREEZE_LEVELS - 1; level >= 0; level--)
- percpu_rwsem_release(sb->s_writers.rw_sem + level, 0, _THIS_IP_);
- }
- /*
- * Tell lockdep we are holding these locks before we call ->unfreeze_fs(sb).
- */
- static void lockdep_sb_freeze_acquire(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_);
- }
- static void sb_freeze_unlock(struct super_block *sb, int level)
- {
- for (level--; 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 & SB_BORN)) {
- up_write(&sb->s_umount);
- return 0; /* sic - it's "nothing to do" */
- }
- if (sb_rdonly(sb)) {
- /* 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 */
- ret = sync_filesystem(sb);
- if (ret) {
- sb->s_writers.frozen = SB_UNFROZEN;
- sb_freeze_unlock(sb, SB_FREEZE_PAGEFAULT);
- wake_up(&sb->s_writers.wait_unfrozen);
- deactivate_locked_super(sb);
- return ret;
- }
- /* 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, SB_FREEZE_FS);
- wake_up(&sb->s_writers.wait_unfrozen);
- deactivate_locked_super(sb);
- return ret;
- }
- }
- /*
- * For debugging purposes so that fs can warn if it sees write activity
- * when frozen is set to SB_FREEZE_COMPLETE, and for thaw_super().
- */
- sb->s_writers.frozen = SB_FREEZE_COMPLETE;
- lockdep_sb_freeze_release(sb);
- 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().
- */
- static int thaw_super_locked(struct super_block *sb)
- {
- int error;
- if (sb->s_writers.frozen != SB_FREEZE_COMPLETE) {
- up_write(&sb->s_umount);
- return -EINVAL;
- }
- if (sb_rdonly(sb)) {
- sb->s_writers.frozen = SB_UNFROZEN;
- goto out;
- }
- lockdep_sb_freeze_acquire(sb);
- if (sb->s_op->unfreeze_fs) {
- error = sb->s_op->unfreeze_fs(sb);
- if (error) {
- printk(KERN_ERR
- "VFS:Filesystem thaw failed\n");
- lockdep_sb_freeze_release(sb);
- up_write(&sb->s_umount);
- return error;
- }
- }
- sb->s_writers.frozen = SB_UNFROZEN;
- sb_freeze_unlock(sb, SB_FREEZE_FS);
- out:
- wake_up(&sb->s_writers.wait_unfrozen);
- deactivate_locked_super(sb);
- return 0;
- }
- int thaw_super(struct super_block *sb)
- {
- down_write(&sb->s_umount);
- return thaw_super_locked(sb);
- }
- EXPORT_SYMBOL(thaw_super);
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