[PATCH] mutex subsystem, semaphore to mutex: VFS, sb->s_lock

This patch converts the superblock-lock semaphore to a mutex, affecting
lock_super()/unlock_super(). Tested on ext3 and XFS.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

fs/ext3/super.c

@@ -2150,7 +2150,7 @@ int ext3_force_commit(struct super_block *sb)
 
 static void ext3_write_super (struct super_block * sb)
 {
-	if (down_trylock(&sb->s_lock) == 0)
+	if (mutex_trylock(&sb->s_lock) != 0)
 		BUG();
 	sb->s_dirt = 0;
 }

fs/ocfs2/super.c

@@ -169,7 +169,7 @@ static match_table_t tokens = {
  */
 static void ocfs2_write_super(struct super_block *sb)
 {
-	if (down_trylock(&sb->s_lock) == 0)
+	if (mutex_trylock(&sb->s_lock) != 0)
 		BUG();
 	sb->s_dirt = 0;
 }

fs/super.c

@@ -72,7 +72,7 @@ static struct super_block *alloc_super(void)
 		INIT_HLIST_HEAD(&s->s_anon);
 		INIT_LIST_HEAD(&s->s_inodes);
 		init_rwsem(&s->s_umount);
-		sema_init(&s->s_lock, 1);
+		mutex_init(&s->s_lock);
 		down_write(&s->s_umount);
 		s->s_count = S_BIAS;
 		atomic_set(&s->s_active, 1);

include/linux/fs.h

@@ -821,7 +821,7 @@ struct super_block {
 	unsigned long		s_magic;
 	struct dentry		*s_root;
 	struct rw_semaphore	s_umount;
-	struct semaphore	s_lock;
+	struct mutex		s_lock;
 	int			s_count;
 	int			s_syncing;
 	int			s_need_sync_fs;
@@ -893,13 +893,13 @@ static inline int has_fs_excl(void)
 static inline void lock_super(struct super_block * sb)
 {
 	get_fs_excl();
-	down(&sb->s_lock);
+	mutex_lock(&sb->s_lock);
 }
 
 static inline void unlock_super(struct super_block * sb)
 {
 	put_fs_excl();
-	up(&sb->s_lock);
+	mutex_unlock(&sb->s_lock);
 }
 
 /*