From 0ed33598ddf308782ca621755df5d23dcff34b64 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Fri, 18 Aug 2023 16:00:48 +0200 Subject: [PATCH] super: use locking helpers Replace the open-coded {down,up}_{read,write}() calls with simple wrappers. Follow-up patches will benefit from this as well. Reviewed-by: Jan Kara Message-Id: <20230818-vfs-super-fixes-v3-v3-1-9f0b1876e46b@kernel.org> Signed-off-by: Christian Brauner --- fs/super.c | 126 ++++++++++++++++++++++++++++++++++++++----------------------- 1 file changed, 78 insertions(+), 48 deletions(-) diff --git a/fs/super.c b/fs/super.c index c878e73..b12e2f2 100644 --- a/fs/super.c +++ b/fs/super.c @@ -50,6 +50,42 @@ static char *sb_writers_name[SB_FREEZE_LEVELS] = { "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_lock_shared(struct super_block *sb) +{ + super_lock(sb, false); +} + +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); +} + /* * 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. @@ -110,7 +146,7 @@ static unsigned long super_cache_scan(struct shrinker *shrink, freed += sb->s_op->free_cached_objects(sb, sc); } - up_read(&sb->s_umount); + super_unlock_shared(sb); return freed; } @@ -176,7 +212,7 @@ static void destroy_unused_super(struct super_block *s) { if (!s) return; - up_write(&s->s_umount); + super_unlock_excl(s); list_lru_destroy(&s->s_dentry_lru); list_lru_destroy(&s->s_inode_lru); security_sb_free(s); @@ -340,7 +376,7 @@ void deactivate_locked_super(struct super_block *s) put_filesystem(fs); put_super(s); } else { - up_write(&s->s_umount); + super_unlock_excl(s); } } @@ -357,7 +393,7 @@ EXPORT_SYMBOL(deactivate_locked_super); void deactivate_super(struct super_block *s) { if (!atomic_add_unless(&s->s_active, -1, 1)) { - down_write(&s->s_umount); + super_lock_excl(s); deactivate_locked_super(s); } } @@ -381,12 +417,12 @@ static int grab_super(struct super_block *s) __releases(sb_lock) { s->s_count++; spin_unlock(&sb_lock); - down_write(&s->s_umount); + super_lock_excl(s); if ((s->s_flags & SB_BORN) && atomic_inc_not_zero(&s->s_active)) { put_super(s); return 1; } - up_write(&s->s_umount); + super_unlock_excl(s); put_super(s); return 0; } @@ -414,7 +450,7 @@ bool trylock_super(struct super_block *sb) if (!hlist_unhashed(&sb->s_instances) && sb->s_root && (sb->s_flags & SB_BORN)) return true; - up_read(&sb->s_umount); + super_unlock_shared(sb); } return false; @@ -439,13 +475,13 @@ bool trylock_super(struct super_block *sb) void retire_super(struct super_block *sb) { WARN_ON(!sb->s_bdev); - down_write(&sb->s_umount); + 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; - up_write(&sb->s_umount); + super_unlock_excl(sb); } EXPORT_SYMBOL(retire_super); @@ -521,7 +557,7 @@ void generic_shutdown_super(struct super_block *sb) /* should be initialized for __put_super_and_need_restart() */ hlist_del_init(&sb->s_instances); spin_unlock(&sb_lock); - up_write(&sb->s_umount); + 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); @@ -685,7 +721,7 @@ EXPORT_SYMBOL(sget); void drop_super(struct super_block *sb) { - up_read(&sb->s_umount); + super_unlock_shared(sb); put_super(sb); } @@ -693,7 +729,7 @@ EXPORT_SYMBOL(drop_super); void drop_super_exclusive(struct super_block *sb) { - up_write(&sb->s_umount); + super_unlock_excl(sb); put_super(sb); } EXPORT_SYMBOL(drop_super_exclusive); @@ -739,10 +775,10 @@ void iterate_supers(void (*f)(struct super_block *, void *), void *arg) sb->s_count++; spin_unlock(&sb_lock); - down_read(&sb->s_umount); + super_lock_shared(sb); if (sb->s_root && (sb->s_flags & SB_BORN)) f(sb, arg); - up_read(&sb->s_umount); + super_unlock_shared(sb); spin_lock(&sb_lock); if (p) @@ -773,10 +809,10 @@ void iterate_supers_type(struct file_system_type *type, sb->s_count++; spin_unlock(&sb_lock); - down_read(&sb->s_umount); + super_lock_shared(sb); if (sb->s_root && (sb->s_flags & SB_BORN)) f(sb, arg); - up_read(&sb->s_umount); + super_unlock_shared(sb); spin_lock(&sb_lock); if (p) @@ -813,7 +849,7 @@ restart: if (sb->s_bdev == bdev) { if (!grab_super(sb)) goto restart; - up_write(&sb->s_umount); + super_unlock_excl(sb); return sb; } } @@ -833,17 +869,11 @@ rescan: if (sb->s_dev == dev) { sb->s_count++; spin_unlock(&sb_lock); - if (excl) - down_write(&sb->s_umount); - else - down_read(&sb->s_umount); + super_lock(sb, excl); /* still alive? */ if (sb->s_root && (sb->s_flags & SB_BORN)) return sb; - if (excl) - up_write(&sb->s_umount); - else - up_read(&sb->s_umount); + super_unlock(sb, excl); /* nope, got unmounted */ spin_lock(&sb_lock); __put_super(sb); @@ -889,9 +919,9 @@ int reconfigure_super(struct fs_context *fc) if (remount_ro) { if (!hlist_empty(&sb->s_pins)) { - up_write(&sb->s_umount); + super_unlock_excl(sb); group_pin_kill(&sb->s_pins); - down_write(&sb->s_umount); + super_lock_excl(sb); if (!sb->s_root) return 0; if (sb->s_writers.frozen != SB_UNFROZEN) @@ -954,7 +984,7 @@ cancel_readonly: static void do_emergency_remount_callback(struct super_block *sb) { - down_write(&sb->s_umount); + super_lock_excl(sb); if (sb->s_root && sb->s_bdev && (sb->s_flags & SB_BORN) && !sb_rdonly(sb)) { struct fs_context *fc; @@ -967,7 +997,7 @@ static void do_emergency_remount_callback(struct super_block *sb) put_fs_context(fc); } } - up_write(&sb->s_umount); + super_unlock_excl(sb); } static void do_emergency_remount(struct work_struct *work) @@ -990,12 +1020,12 @@ void emergency_remount(void) static void do_thaw_all_callback(struct super_block *sb) { - down_write(&sb->s_umount); + super_lock_excl(sb); if (sb->s_root && sb->s_flags & SB_BORN) { emergency_thaw_bdev(sb); thaw_super_locked(sb); } else { - up_write(&sb->s_umount); + super_unlock_excl(sb); } } @@ -1182,10 +1212,10 @@ EXPORT_SYMBOL(get_tree_keyed); */ static bool lock_active_super(struct super_block *sb) { - down_read(&sb->s_umount); + super_lock_shared(sb); if (!sb->s_root || (sb->s_flags & (SB_ACTIVE | SB_BORN)) != (SB_ACTIVE | SB_BORN)) { - up_read(&sb->s_umount); + super_unlock_shared(sb); return false; } return true; @@ -1208,7 +1238,7 @@ static void fs_bdev_mark_dead(struct block_device *bdev, bool surprise) if (sb->s_op->shutdown) sb->s_op->shutdown(sb); - up_read(&sb->s_umount); + super_unlock_shared(sb); } static void fs_bdev_sync(struct block_device *bdev) @@ -1220,7 +1250,7 @@ static void fs_bdev_sync(struct block_device *bdev) if (!lock_active_super(sb)) return; sync_filesystem(sb); - up_read(&sb->s_umount); + super_unlock_shared(sb); } const struct blk_holder_ops fs_holder_ops = { @@ -1342,9 +1372,9 @@ int get_tree_bdev(struct fs_context *fc, * bdev_mark_dead()). It is safe because we have active sb * reference and SB_BORN is not set yet. */ - up_write(&s->s_umount); + super_unlock_excl(s); error = setup_bdev_super(s, fc->sb_flags, fc); - down_write(&s->s_umount); + super_lock_excl(s); if (!error) error = fill_super(s, fc); if (error) { @@ -1394,9 +1424,9 @@ struct dentry *mount_bdev(struct file_system_type *fs_type, * bdev_mark_dead()). It is safe because we have active sb * reference and SB_BORN is not set yet. */ - up_write(&s->s_umount); + super_unlock_excl(s); error = setup_bdev_super(s, flags, NULL); - down_write(&s->s_umount); + super_lock_excl(s); if (!error) error = fill_super(s, data, flags & SB_SILENT ? 1 : 0); if (error) { @@ -1685,29 +1715,29 @@ int freeze_super(struct super_block *sb) int ret; atomic_inc(&sb->s_active); - down_write(&sb->s_umount); + super_lock_excl(sb); if (sb->s_writers.frozen != SB_UNFROZEN) { deactivate_locked_super(sb); return -EBUSY; } if (!(sb->s_flags & SB_BORN)) { - up_write(&sb->s_umount); + super_unlock_excl(sb); 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); + super_unlock_excl(sb); 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); + super_unlock_excl(sb); sb_wait_write(sb, SB_FREEZE_WRITE); - down_write(&sb->s_umount); + super_lock_excl(sb); /* Now we go and block page faults... */ sb->s_writers.frozen = SB_FREEZE_PAGEFAULT; @@ -1743,7 +1773,7 @@ int freeze_super(struct super_block *sb) */ sb->s_writers.frozen = SB_FREEZE_COMPLETE; lockdep_sb_freeze_release(sb); - up_write(&sb->s_umount); + super_unlock_excl(sb); return 0; } EXPORT_SYMBOL(freeze_super); @@ -1753,7 +1783,7 @@ static int thaw_super_locked(struct super_block *sb) int error; if (sb->s_writers.frozen != SB_FREEZE_COMPLETE) { - up_write(&sb->s_umount); + super_unlock_excl(sb); return -EINVAL; } @@ -1770,7 +1800,7 @@ static int thaw_super_locked(struct super_block *sb) printk(KERN_ERR "VFS:Filesystem thaw failed\n"); lockdep_sb_freeze_release(sb); - up_write(&sb->s_umount); + super_unlock_excl(sb); return error; } } @@ -1790,7 +1820,7 @@ out: */ int thaw_super(struct super_block *sb) { - down_write(&sb->s_umount); + super_lock_excl(sb); return thaw_super_locked(sb); } EXPORT_SYMBOL(thaw_super); -- 2.7.4