Commit 0ed33598 authored by Christian Brauner's avatar Christian Brauner
Browse files

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: default avatarJan Kara <jack@suse.cz>
Message-Id: <20230818-vfs-super-fixes-v3-v3-1-9f0b1876e46b@kernel.org>
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent e127b9bc

fs/super.c

+78 −48
Original line number Diff line number Diff line
@@ -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 @@ 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;

		}

	}
@@ -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);
@@ -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 @@ 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;
@@ -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 @@ 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);