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Diffstat (limited to 'fs/super.c')
| -rw-r--r-- | fs/super.c | 2141 |
1 files changed, 2141 insertions, 0 deletions
diff --git a/fs/super.c b/fs/super.c new file mode 100644 index 0000000000..2d762ce67f --- /dev/null +++ b/fs/super.c @@ -0,0 +1,2141 @@ +// 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/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, enum freeze_holder who); + +static LIST_HEAD(super_blocks); +static DEFINE_SPINLOCK(sb_lock); + +static char *sb_writers_name[SB_FREEZE_LEVELS] = { + "sb_writers", + "sb_pagefaults", + "sb_internal", +}; + +static inline void __super_lock(struct super_block *sb, bool excl) +{ + if (excl) + down_write(&sb->s_umount); + else + down_read(&sb->s_umount); +} + +static inline void super_unlock(struct super_block *sb, bool excl) +{ + if (excl) + up_write(&sb->s_umount); + else + up_read(&sb->s_umount); +} + +static inline void __super_lock_excl(struct super_block *sb) +{ + __super_lock(sb, true); +} + +static inline void super_unlock_excl(struct super_block *sb) +{ + super_unlock(sb, true); +} + +static inline void super_unlock_shared(struct super_block *sb) +{ + super_unlock(sb, false); +} + +static inline bool wait_born(struct super_block *sb) +{ + unsigned int flags; + + /* + * Pairs with smp_store_release() in super_wake() and ensures + * that we see SB_BORN or SB_DYING after we're woken. + */ + flags = smp_load_acquire(&sb->s_flags); + return flags & (SB_BORN | SB_DYING); +} + +/** + * super_lock - wait for superblock to become ready and lock it + * @sb: superblock to wait for + * @excl: whether exclusive access is required + * + * If the superblock has neither passed through vfs_get_tree() or + * generic_shutdown_super() yet wait for it to happen. Either superblock + * creation will succeed and SB_BORN is set by vfs_get_tree() or we're + * woken and we'll see SB_DYING. + * + * The caller must have acquired a temporary reference on @sb->s_count. + * + * Return: This returns true if SB_BORN was set, false if SB_DYING was + * set. The function acquires s_umount and returns with it held. + */ +static __must_check bool super_lock(struct super_block *sb, bool excl) +{ + + lockdep_assert_not_held(&sb->s_umount); + +relock: + __super_lock(sb, excl); + + /* + * Has gone through generic_shutdown_super() in the meantime. + * @sb->s_root is NULL and @sb->s_active is 0. No one needs to + * grab a reference to this. Tell them so. + */ + if (sb->s_flags & SB_DYING) + return false; + + /* Has called ->get_tree() successfully. */ + if (sb->s_flags & SB_BORN) + return true; + + super_unlock(sb, excl); + + /* wait until the superblock is ready or dying */ + wait_var_event(&sb->s_flags, wait_born(sb)); + + /* + * Neither SB_BORN nor SB_DYING are ever unset so we never loop. + * Just reacquire @sb->s_umount for the caller. + */ + goto relock; +} + +/* wait and acquire read-side of @sb->s_umount */ +static inline bool super_lock_shared(struct super_block *sb) +{ + return super_lock(sb, false); +} + +/* wait and acquire write-side of @sb->s_umount */ +static inline bool super_lock_excl(struct super_block *sb) +{ + return super_lock(sb, true); +} + +/* wake waiters */ +#define SUPER_WAKE_FLAGS (SB_BORN | SB_DYING | SB_DEAD) +static void super_wake(struct super_block *sb, unsigned int flag) +{ + WARN_ON_ONCE((flag & ~SUPER_WAKE_FLAGS)); + WARN_ON_ONCE(hweight32(flag & SUPER_WAKE_FLAGS) > 1); + + /* + * Pairs with smp_load_acquire() in super_lock() to make sure + * all initializations in the superblock are seen by the user + * seeing SB_BORN sent. + */ + smp_store_release(&sb->s_flags, sb->s_flags | flag); + /* + * Pairs with the barrier in prepare_to_wait_event() to make sure + * ___wait_var_event() either sees SB_BORN set or + * waitqueue_active() check in wake_up_var() sees the waiter. + */ + smp_mb(); + wake_up_var(&sb->s_flags); +} + +/* + * 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 (!super_trylock_shared(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); + } + + super_unlock_shared(sb); + 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 super_trylock_shared() 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. super_trylock_shared() 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; + super_unlock_excl(s); + 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; + } + 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->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, "sb-%s", type->name)) + 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); + 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. + */ +void put_super(struct super_block *sb) +{ + spin_lock(&sb_lock); + __put_super(sb); + spin_unlock(&sb_lock); +} + +static void kill_super_notify(struct super_block *sb) +{ + lockdep_assert_not_held(&sb->s_umount); + + /* already notified earlier */ + if (sb->s_flags & SB_DEAD) + return; + + /* + * Remove it from @fs_supers so it isn't found by new + * sget{_fc}() walkers anymore. Any concurrent mounter still + * managing to grab a temporary reference is guaranteed to + * already see SB_DYING and will wait until we notify them about + * SB_DEAD. + */ + spin_lock(&sb_lock); + hlist_del_init(&sb->s_instances); + spin_unlock(&sb_lock); + + /* + * Let concurrent mounts know that this thing is really dead. + * We don't need @sb->s_umount here as every concurrent caller + * will see SB_DYING and either discard the superblock or wait + * for SB_DEAD. + */ + super_wake(sb, SB_DEAD); +} + +/** + * 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)) { + unregister_shrinker(&s->s_shrink); + fs->kill_sb(s); + + kill_super_notify(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 { + super_unlock_excl(s); + } +} + +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)) { + __super_lock_excl(s); + 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) +{ + bool born; + + s->s_count++; + spin_unlock(&sb_lock); + born = super_lock_excl(s); + if (born && atomic_inc_not_zero(&s->s_active)) { + put_super(s); + return 1; + } + super_unlock_excl(s); + put_super(s); + return 0; +} + +static inline bool wait_dead(struct super_block *sb) +{ + unsigned int flags; + + /* + * Pairs with memory barrier in super_wake() and ensures + * that we see SB_DEAD after we're woken. + */ + flags = smp_load_acquire(&sb->s_flags); + return flags & SB_DEAD; +} + +/** + * grab_super_dead - acquire an active reference to a superblock + * @sb: superblock to acquire + * + * Acquire a temporary reference on a superblock and try to trade it for + * an active reference. This is used in sget{_fc}() to wait for a + * superblock to either become SB_BORN or for it to pass through + * sb->kill() and be marked as SB_DEAD. + * + * Return: This returns true if an active reference could be acquired, + * false if not. + */ +static bool grab_super_dead(struct super_block *sb) +{ + + sb->s_count++; + if (grab_super(sb)) { + put_super(sb); + lockdep_assert_held(&sb->s_umount); + return true; + } + wait_var_event(&sb->s_flags, wait_dead(sb)); + lockdep_assert_not_held(&sb->s_umount); + put_super(sb); + return false; +} + +/* + * super_trylock_shared - 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 super_trylock_shared(struct super_block *sb) +{ + if (down_read_trylock(&sb->s_umount)) { + if (!(sb->s_flags & SB_DYING) && sb->s_root && + (sb->s_flags & SB_BORN)) + return true; + super_unlock_shared(sb); + } + + return false; +} + +/** + * retire_super - prevents superblock from being reused + * @sb: superblock to retire + * + * The function marks superblock to be ignored in superblock test, which + * prevents it from being reused for any new mounts. If the superblock has + * a private bdi, it also unregisters it, but doesn't reduce the refcount + * of the superblock to prevent potential races. The refcount is reduced + * by generic_shutdown_super(). The function can not be called + * concurrently with generic_shutdown_super(). It is safe to call the + * function multiple times, subsequent calls have no effect. + * + * The marker will affect the re-use only for block-device-based + * superblocks. Other superblocks will still get marked if this function + * is used, but that will not affect their reusability. + */ +void retire_super(struct super_block *sb) +{ + WARN_ON(!sb->s_bdev); + __super_lock_excl(sb); + if (sb->s_iflags & SB_I_PERSB_BDI) { + bdi_unregister(sb->s_bdi); + sb->s_iflags &= ~SB_I_PERSB_BDI; + } + sb->s_iflags |= SB_I_RETIRED; + super_unlock_excl(sb); +} +EXPORT_SYMBOL(retire_super); + +/** + * 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); + + /* + * Clean up and evict any inodes that still have references due + * to fsnotify or the security policy. + */ + fsnotify_sb_delete(sb); + security_sb_delete(sb); + + /* + * Now that all potentially-encrypted inodes have been evicted, + * the fscrypt keyring can be destroyed. + */ + fscrypt_destroy_keyring(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 (CHECK_DATA_CORRUPTION(!list_empty(&sb->s_inodes), + "VFS: Busy inodes after unmount of %s (%s)", + sb->s_id, sb->s_type->name)) { + /* + * Adding a proper bailout path here would be hard, but + * we can at least make it more likely that a later + * iput_final() or such crashes cleanly. + */ + struct inode *inode; + + spin_lock(&sb->s_inode_list_lock); + list_for_each_entry(inode, &sb->s_inodes, i_sb_list) { + inode->i_op = VFS_PTR_POISON; + inode->i_sb = VFS_PTR_POISON; + inode->i_mapping = VFS_PTR_POISON; + } + spin_unlock(&sb->s_inode_list_lock); + } + } + /* + * Broadcast to everyone that grabbed a temporary reference to this + * superblock before we removed it from @fs_supers that the superblock + * is dying. Every walker of @fs_supers outside of sget{_fc}() will now + * discard this superblock and treat it as dead. + * + * We leave the superblock on @fs_supers so it can be found by + * sget{_fc}() until we passed sb->kill_sb(). + */ + super_wake(sb, SB_DYING); + super_unlock_excl(sb); + if (sb->s_bdi != &noop_backing_dev_info) { + if (sb->s_iflags & SB_I_PERSB_BDI) + bdi_unregister(sb->s_bdi); + 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 + * + * Create a new superblock or find an existing one. + * + * The @test callback is used to find a matching existing superblock. + * Whether or not the requested parameters in @fc are taken into account + * is specific to the @test callback that is used. They may even be + * completely ignored. + * + * If an extant superblock is matched, it will be returned unless: + * + * (1) the namespace the filesystem context @fc and the extant + * superblock's namespace differ + * + * (2) the filesystem context @fc has requested that reusing an extant + * superblock is not allowed + * + * In both cases EBUSY will be returned. + * + * 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. + * + * Return: On success, an extant or newly created superblock is + * returned. On failure an error pointer is returned. + */ +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; + strscpy(s->s_id, s->s_type->name, sizeof(s->s_id)); + /* + * Make the superblock visible on @super_blocks and @fs_supers. + * It's in a nascent state and users should wait on SB_BORN or + * SB_DYING to be set. + */ + 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 || fc->exclusive) { + spin_unlock(&sb_lock); + destroy_unused_super(s); + if (fc->exclusive) + warnfc(fc, "reusing existing filesystem not allowed"); + else + warnfc(fc, "reusing existing filesystem in another namespace not allowed"); + return ERR_PTR(-EBUSY); + } + if (!grab_super_dead(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_dead(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; + strscpy(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) +{ + super_unlock_shared(sb); + put_super(sb); +} + +EXPORT_SYMBOL(drop_super); + +void drop_super_exclusive(struct super_block *sb) +{ + super_unlock_excl(sb); + 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) { + /* Pairs with memory marrier in super_wake(). */ + if (smp_load_acquire(&sb->s_flags) & SB_DYING) + 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) { + bool born; + + sb->s_count++; + spin_unlock(&sb_lock); + + born = super_lock_shared(sb); + if (born && sb->s_root) + f(sb, arg); + super_unlock_shared(sb); + + 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) { + bool born; + + sb->s_count++; + spin_unlock(&sb_lock); + + born = super_lock_shared(sb); + if (born && sb->s_root) + f(sb, arg); + super_unlock_shared(sb); + + 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_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; + + spin_lock(&sb_lock); + list_for_each_entry(sb, &super_blocks, s_list) { + if (sb->s_bdev == bdev) { + if (!grab_super(sb)) + return NULL; + super_unlock_excl(sb); + return sb; + } + } + spin_unlock(&sb_lock); + return NULL; +} + +struct super_block *user_get_super(dev_t dev, bool excl) +{ + struct super_block *sb; + + spin_lock(&sb_lock); + list_for_each_entry(sb, &super_blocks, s_list) { + if (sb->s_dev == dev) { + bool born; + + sb->s_count++; + spin_unlock(&sb_lock); + /* still alive? */ + born = super_lock(sb, excl); + if (born && sb->s_root) + return sb; + super_unlock(sb, excl); + /* nope, got unmounted */ + spin_lock(&sb_lock); + __put_super(sb); + break; + } + } + 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 remount_rw = 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) && sb->s_bdev && + bdev_read_only(sb->s_bdev)) + return -EACCES; +#endif + remount_rw = !(fc->sb_flags & SB_RDONLY) && sb_rdonly(sb); + remount_ro = (fc->sb_flags & SB_RDONLY) && !sb_rdonly(sb); + } + + if (remount_ro) { + if (!hlist_empty(&sb->s_pins)) { + super_unlock_excl(sb); + group_pin_kill(&sb->s_pins); + __super_lock_excl(sb); + 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_start_ro_state_change(sb); + } else { + retval = sb_prepare_remount_readonly(sb); + if (retval) + return retval; + } + } else if (remount_rw) { + /* + * Protect filesystem's reconfigure code from writes from + * userspace until reconfigure finishes. + */ + sb_start_ro_state_change(sb); + } + + 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))); + sb_end_ro_state_change(sb); + + /* + * 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_end_ro_state_change(sb); + return retval; +} + +static void do_emergency_remount_callback(struct super_block *sb) +{ + bool born = super_lock_excl(sb); + + if (born && sb->s_root && sb->s_bdev && !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); + } + } + super_unlock_excl(sb); +} + +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) +{ + bool born = super_lock_excl(sb); + + if (born && sb->s_root) { + if (IS_ENABLED(CONFIG_BLOCK)) + while (sb->s_bdev && !thaw_bdev(sb->s_bdev)) + pr_warn("Emergency Thaw on %pg\n", sb->s_bdev); + thaw_super_locked(sb, FREEZE_HOLDER_USERSPACE); + } else { + super_unlock_excl(sb); + } +} + +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); + kill_super_notify(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; +} + +static int vfs_get_super(struct fs_context *fc, + int (*test)(struct super_block *, struct fs_context *), + int (*fill_super)(struct super_block *sb, + struct fs_context *fc)) +{ + struct super_block *sb; + int err; + + 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); + return 0; + +error: + deactivate_locked_super(sb); + return err; +} + +int get_tree_nodev(struct fs_context *fc, + int (*fill_super)(struct super_block *sb, + struct fs_context *fc)) +{ + return vfs_get_super(fc, NULL, 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, test_single_super, fill_super); +} +EXPORT_SYMBOL(get_tree_single); + +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, test_keyed_super, fill_super); +} +EXPORT_SYMBOL(get_tree_keyed); + +static int set_bdev_super(struct super_block *s, void *data) +{ + s->s_dev = *(dev_t *)data; + return 0; +} + +static int super_s_dev_set(struct super_block *s, struct fs_context *fc) +{ + return set_bdev_super(s, fc->sget_key); +} + +static int super_s_dev_test(struct super_block *s, struct fs_context *fc) +{ + return !(s->s_iflags & SB_I_RETIRED) && + s->s_dev == *(dev_t *)fc->sget_key; +} + +/** + * sget_dev - Find or create a superblock by device number + * @fc: Filesystem context. + * @dev: device number + * + * Find or create a superblock using the provided device number that + * will be stored in fc->sget_key. + * + * 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, s_id, s_dev will + * be set). The superblock will be published and it will be returned in + * a partially constructed state with SB_BORN and SB_ACTIVE as yet + * unset. + * + * Return: an existing or newly created superblock on success, an error + * pointer on failure. + */ +struct super_block *sget_dev(struct fs_context *fc, dev_t dev) +{ + fc->sget_key = &dev; + return sget_fc(fc, super_s_dev_test, super_s_dev_set); +} +EXPORT_SYMBOL(sget_dev); + +#ifdef CONFIG_BLOCK +/* + * Lock a super block that the callers holds a reference to. + * + * The caller needs to ensure that the super_block isn't being freed while + * calling this function, e.g. by holding a lock over the call to this function + * and the place that clears the pointer to the superblock used by this function + * before freeing the superblock. + */ +static bool super_lock_shared_active(struct super_block *sb) +{ + bool born = super_lock_shared(sb); + + if (!born || !sb->s_root || !(sb->s_flags & SB_ACTIVE)) { + super_unlock_shared(sb); + return false; + } + return true; +} + +static void fs_bdev_mark_dead(struct block_device *bdev, bool surprise) +{ + struct super_block *sb = bdev->bd_holder; + + /* bd_holder_lock ensures that the sb isn't freed */ + lockdep_assert_held(&bdev->bd_holder_lock); + + if (!super_lock_shared_active(sb)) + return; + + if (!surprise) + sync_filesystem(sb); + shrink_dcache_sb(sb); + invalidate_inodes(sb); + if (sb->s_op->shutdown) + sb->s_op->shutdown(sb); + + super_unlock_shared(sb); +} + +static void fs_bdev_sync(struct block_device *bdev) +{ + struct super_block *sb = bdev->bd_holder; + + lockdep_assert_held(&bdev->bd_holder_lock); + + if (!super_lock_shared_active(sb)) + return; + sync_filesystem(sb); + super_unlock_shared(sb); +} + +const struct blk_holder_ops fs_holder_ops = { + .mark_dead = fs_bdev_mark_dead, + .sync = fs_bdev_sync, +}; +EXPORT_SYMBOL_GPL(fs_holder_ops); + +int setup_bdev_super(struct super_block *sb, int sb_flags, + struct fs_context *fc) +{ + blk_mode_t mode = sb_open_mode(sb_flags); + struct block_device *bdev; + + bdev = blkdev_get_by_dev(sb->s_dev, mode, sb, &fs_holder_ops); + if (IS_ERR(bdev)) { + if (fc) + errorf(fc, "%s: Can't open blockdev", fc->source); + return PTR_ERR(bdev); + } + + /* + * This really should be in blkdev_get_by_dev, but right now can't due + * to legacy issues that require us to allow opening a block device node + * writable from userspace even for a read-only block device. + */ + if ((mode & BLK_OPEN_WRITE) && bdev_read_only(bdev)) { + blkdev_put(bdev, sb); + return -EACCES; + } + + /* + * Until SB_BORN flag is set, there can be no active superblock + * references and thus no filesystem freezing. get_active_super() will + * just loop waiting for SB_BORN so even freeze_bdev() cannot proceed. + * + * It is enough to check bdev was not frozen before we set s_bdev. + */ + mutex_lock(&bdev->bd_fsfreeze_mutex); + if (bdev->bd_fsfreeze_count > 0) { + mutex_unlock(&bdev->bd_fsfreeze_mutex); + if (fc) + warnf(fc, "%pg: Can't mount, blockdev is frozen", bdev); + blkdev_put(bdev, sb); + return -EBUSY; + } + spin_lock(&sb_lock); + sb->s_bdev = bdev; + sb->s_bdi = bdi_get(bdev->bd_disk->bdi); + if (bdev_stable_writes(bdev)) + sb->s_iflags |= SB_I_STABLE_WRITES; + spin_unlock(&sb_lock); + mutex_unlock(&bdev->bd_fsfreeze_mutex); + + snprintf(sb->s_id, sizeof(sb->s_id), "%pg", bdev); + shrinker_debugfs_rename(&sb->s_shrink, "sb-%s:%s", sb->s_type->name, + sb->s_id); + sb_set_blocksize(sb, block_size(bdev)); + return 0; +} +EXPORT_SYMBOL_GPL(setup_bdev_super); + +/** + * 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 super_block *s; + int error = 0; + dev_t dev; + + if (!fc->source) + return invalf(fc, "No source specified"); + + error = lookup_bdev(fc->source, &dev); + if (error) { + errorf(fc, "%s: Can't lookup blockdev", fc->source); + return error; + } + + fc->sb_flags |= SB_NOSEC; + s = sget_dev(fc, dev); + if (IS_ERR(s)) + 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", s->s_bdev); + deactivate_locked_super(s); + return -EBUSY; + } + } else { + /* + * We drop s_umount here because we need to open the bdev and + * bdev->open_mutex ranks above s_umount (blkdev_put() -> + * bdev_mark_dead()). It is safe because we have active sb + * reference and SB_BORN is not set yet. + */ + super_unlock_excl(s); + error = setup_bdev_super(s, fc->sb_flags, fc); + __super_lock_excl(s); + if (!error) + error = fill_super(s, fc); + if (error) { + deactivate_locked_super(s); + return error; + } + s->s_flags |= SB_ACTIVE; + } + + 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 !(s->s_iflags & SB_I_RETIRED) && s->s_dev == *(dev_t *)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 super_block *s; + int error; + dev_t dev; + + error = lookup_bdev(dev_name, &dev); + if (error) + return ERR_PTR(error); + + flags |= SB_NOSEC; + s = sget(fs_type, test_bdev_super, set_bdev_super, flags, &dev); + if (IS_ERR(s)) + return ERR_CAST(s); + + if (s->s_root) { + if ((flags ^ s->s_flags) & SB_RDONLY) { + deactivate_locked_super(s); + return ERR_PTR(-EBUSY); + } + } else { + /* + * We drop s_umount here because we need to open the bdev and + * bdev->open_mutex ranks above s_umount (blkdev_put() -> + * bdev_mark_dead()). It is safe because we have active sb + * reference and SB_BORN is not set yet. + */ + super_unlock_excl(s); + error = setup_bdev_super(s, flags, NULL); + __super_lock_excl(s); + if (!error) + 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_bdev); + +void kill_block_super(struct super_block *sb) +{ + struct block_device *bdev = sb->s_bdev; + + generic_shutdown_super(sb); + if (bdev) { + sync_blockdev(bdev); + blkdev_put(bdev, sb); + } +} + +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 & 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); + + /* + * super_wake() contains a memory barrier which also care of + * ordering 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. + */ + super_wake(sb, 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; + sb->s_iflags |= SB_I_PERSB_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); +} + +static int wait_for_partially_frozen(struct super_block *sb) +{ + int ret = 0; + + do { + unsigned short old = sb->s_writers.frozen; + + up_write(&sb->s_umount); + ret = wait_var_event_killable(&sb->s_writers.frozen, + sb->s_writers.frozen != old); + down_write(&sb->s_umount); + } while (ret == 0 && + sb->s_writers.frozen != SB_UNFROZEN && + sb->s_writers.frozen != SB_FREEZE_COMPLETE); + + return ret; +} + +/** + * freeze_super - lock the filesystem and force it into a consistent state + * @sb: the super to lock + * @who: context that wants to freeze + * + * 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 may return + * -EBUSY. + * + * @who should be: + * * %FREEZE_HOLDER_USERSPACE if userspace wants to freeze the fs; + * * %FREEZE_HOLDER_KERNEL if the kernel wants to freeze the fs. + * + * The @who argument distinguishes between the kernel and userspace trying to + * freeze the filesystem. Although there cannot be multiple kernel freezes or + * multiple userspace freezes in effect at any given time, the kernel and + * userspace can both hold a filesystem frozen. The filesystem remains frozen + * until there are no kernel or userspace freezes in effect. + * + * 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, enum freeze_holder who) +{ + int ret; + + atomic_inc(&sb->s_active); + if (!super_lock_excl(sb)) + WARN(1, "Dying superblock while freezing!"); + +retry: + if (sb->s_writers.frozen == SB_FREEZE_COMPLETE) { + if (sb->s_writers.freeze_holders & who) { + deactivate_locked_super(sb); + return -EBUSY; + } + + WARN_ON(sb->s_writers.freeze_holders == 0); + + /* + * Someone else already holds this type of freeze; share the + * freeze and assign the active ref to the freeze. + */ + sb->s_writers.freeze_holders |= who; + super_unlock_excl(sb); + return 0; + } + + if (sb->s_writers.frozen != SB_UNFROZEN) { + ret = wait_for_partially_frozen(sb); + if (ret) { + deactivate_locked_super(sb); + return ret; + } + + goto retry; + } + + if (!(sb->s_flags & SB_BORN)) { + super_unlock_excl(sb); + return 0; /* sic - it's "nothing to do" */ + } + + if (sb_rdonly(sb)) { + /* Nothing to do really... */ + sb->s_writers.freeze_holders |= who; + sb->s_writers.frozen = SB_FREEZE_COMPLETE; + wake_up_var(&sb->s_writers.frozen); + super_unlock_excl(sb); + return 0; + } + + sb->s_writers.frozen = SB_FREEZE_WRITE; + /* Release s_umount to preserve sb_start_write -> s_umount ordering */ + super_unlock_excl(sb); + sb_wait_write(sb, SB_FREEZE_WRITE); + if (!super_lock_excl(sb)) + WARN(1, "Dying superblock while freezing!"); + + /* 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_var(&sb->s_writers.frozen); + 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_var(&sb->s_writers.frozen); + 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.freeze_holders |= who; + sb->s_writers.frozen = SB_FREEZE_COMPLETE; + wake_up_var(&sb->s_writers.frozen); + lockdep_sb_freeze_release(sb); + super_unlock_excl(sb); + return 0; +} +EXPORT_SYMBOL(freeze_super); + +/* + * Undoes the effect of a freeze_super_locked call. If the filesystem is + * frozen both by userspace and the kernel, a thaw call from either source + * removes that state without releasing the other state or unlocking the + * filesystem. + */ +static int thaw_super_locked(struct super_block *sb, enum freeze_holder who) +{ + int error; + + if (sb->s_writers.frozen == SB_FREEZE_COMPLETE) { + if (!(sb->s_writers.freeze_holders & who)) { + super_unlock_excl(sb); + return -EINVAL; + } + + /* + * Freeze is shared with someone else. Release our hold and + * drop the active ref that freeze_super assigned to the + * freezer. + */ + if (sb->s_writers.freeze_holders & ~who) { + sb->s_writers.freeze_holders &= ~who; + deactivate_locked_super(sb); + return 0; + } + } else { + super_unlock_excl(sb); + return -EINVAL; + } + + if (sb_rdonly(sb)) { + sb->s_writers.freeze_holders &= ~who; + sb->s_writers.frozen = SB_UNFROZEN; + wake_up_var(&sb->s_writers.frozen); + 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); + super_unlock_excl(sb); + return error; + } + } + + sb->s_writers.freeze_holders &= ~who; + sb->s_writers.frozen = SB_UNFROZEN; + wake_up_var(&sb->s_writers.frozen); + sb_freeze_unlock(sb, SB_FREEZE_FS); +out: + deactivate_locked_super(sb); + return 0; +} + +/** + * thaw_super -- unlock filesystem + * @sb: the super to thaw + * @who: context that wants to freeze + * + * Unlocks the filesystem and marks it writeable again after freeze_super() + * if there are no remaining freezes on the filesystem. + * + * @who should be: + * * %FREEZE_HOLDER_USERSPACE if userspace wants to thaw the fs; + * * %FREEZE_HOLDER_KERNEL if the kernel wants to thaw the fs. + */ +int thaw_super(struct super_block *sb, enum freeze_holder who) +{ + if (!super_lock_excl(sb)) + WARN(1, "Dying superblock while thawing!"); + return thaw_super_locked(sb, who); +} +EXPORT_SYMBOL(thaw_super); + +/* + * Create workqueue for deferred direct IO completions. We allocate the + * workqueue when it's first needed. This avoids creating workqueue for + * filesystems that don't need it and also allows us to create the workqueue + * late enough so the we can include s_id in the name of the workqueue. + */ +int sb_init_dio_done_wq(struct super_block *sb) +{ + struct workqueue_struct *old; + struct workqueue_struct *wq = alloc_workqueue("dio/%s", + WQ_MEM_RECLAIM, 0, + sb->s_id); + if (!wq) + return -ENOMEM; + /* + * This has to be atomic as more DIOs can race to create the workqueue + */ + old = cmpxchg(&sb->s_dio_done_wq, NULL, wq); + /* Someone created workqueue before us? Free ours... */ + if (old) + destroy_workqueue(wq); + return 0; +} |