Skip to content

Commit

Permalink
super: use locking helpers
Browse files Browse the repository at this point in the history 
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 <jack@suse.cz>
Message-Id: <20230818-vfs-super-fixes-v3-v3-1-9f0b1876e46b@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
  • Loading branch information
Christian Brauner committed Aug 21, 2023
1 parent e127b9b commit 0ed3359
Showing 1 changed file with 78 additions and 48 deletions.
126 changes: 78 additions & 48 deletions fs/super.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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.
Expand Down Expand Up @@ -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;
}

Expand Down Expand Up @@ -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);
Expand Down Expand Up @@ -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);
}
}

Expand All @@ -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);
}
}
Expand All @@ -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;
}
Expand Down Expand Up @@ -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;
Expand All @@ -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);

Expand Down Expand Up @@ -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);
Expand Down Expand Up @@ -685,15 +721,15 @@ EXPORT_SYMBOL(sget);

void drop_super(struct super_block *sb)
{
up_read(&sb->s_umount);
super_unlock_shared(sb);
put_super(sb);
}

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);
Expand Down Expand Up @@ -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)
Expand Down Expand Up @@ -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)
Expand Down Expand Up @@ -813,7 +849,7 @@ struct super_block *get_active_super(struct block_device *bdev)
if (sb->s_bdev == bdev) {
if (!grab_super(sb))
goto restart;
up_write(&sb->s_umount);
super_unlock_excl(sb);
return sb;
}
}
Expand All @@ -833,17 +869,11 @@ struct super_block *user_get_super(dev_t dev, bool excl)
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);
Expand Down Expand Up @@ -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)
Expand Down Expand Up @@ -954,7 +984,7 @@ int reconfigure_super(struct fs_context *fc)

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;
Expand All @@ -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)
Expand All @@ -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);
}
}

Expand Down Expand Up @@ -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;
Expand All @@ -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)
Expand All @@ -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 = {
Expand Down Expand Up @@ -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) {
Expand Down Expand Up @@ -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) {
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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);
Expand All @@ -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;
}

Expand All @@ -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;
}
}
Expand All @@ -1790,7 +1820,7 @@ static int thaw_super_locked(struct super_block *sb)
*/
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);
Expand Down

0 comments on commit 0ed3359

Please sign in to comment.