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 <jack@suse.cz>
Message-Id: <20230818-vfs-super-fixes-v3-v3-1-9f0b1876e46b@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: brauner

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);
@@ -685,15 +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);
@@ -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);