[PATCH] Revert bd_mount_mutex back to a semaphore

Revert bd_mount_mutex back to a semaphore so that xfs_freeze -f /mnt/newtest;
xfs_freeze -u /mnt/newtest works safely and doesn't produce lockdep warnings.

(XFS unlocks the semaphore from a different task, by design.  The mutex
code warns about this)

Signed-off-by: Dave Chinner <dgc@sgi.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

5 files changed, 9 insertions, 9 deletions

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 1715d6b5f411..8b18e43b82fe 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -411,7 +411,7 @@ static void init_once(void * foo, struct kmem_cache * cachep, unsigned long flag
         {
                 memset(bdev, 0, sizeof(*bdev));
                 mutex_init(&bdev->bd_mutex);
-                mutex_init(&bdev->bd_mount_mutex);
+                sema_init(&bdev->bd_mount_sem, 1);
                 INIT_LIST_HEAD(&bdev->bd_inodes);
                 INIT_LIST_HEAD(&bdev->bd_list);
 #ifdef CONFIG_SYSFS
diff --git a/fs/buffer.c b/fs/buffer.c
index 263f88e4dffb..3b116078b4c3 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -180,7 +180,7 @@ int fsync_bdev(struct block_device *bdev)
  * freeze_bdev  --  lock a filesystem and force it into a consistent state
  * @bdev:       blockdevice to lock
  *
- * This takes the block device bd_mount_mutex to make sure no new mounts
+ * This takes the block device bd_mount_sem to make sure no new mounts
  * happen on bdev until thaw_bdev() is called.
  * If a superblock is found on this device, we take the s_umount semaphore
  * on it to make sure nobody unmounts until the snapshot creation is done.
@@ -189,7 +189,7 @@ struct super_block *freeze_bdev(struct block_device *bdev)
 {
         struct super_block *sb;
 
-        mutex_lock(&bdev->bd_mount_mutex);
+        down(&bdev->bd_mount_sem);
         sb = get_super(bdev);
         if (sb && !(sb->s_flags & MS_RDONLY)) {
                 sb->s_frozen = SB_FREEZE_WRITE;
@@ -231,7 +231,7 @@ void thaw_bdev(struct block_device *bdev, struct super_block *sb)
                 drop_super(sb);
         }
 
-        mutex_unlock(&bdev->bd_mount_mutex);
+        up(&bdev->bd_mount_sem);
 }
 EXPORT_SYMBOL(thaw_bdev);
 
diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c
index d14e139d2674..ee80b8a5e7bc 100644
--- a/fs/gfs2/ops_fstype.c
+++ b/fs/gfs2/ops_fstype.c
@@ -867,9 +867,9 @@ static int gfs2_get_sb_meta(struct file_system_type *fs_type, int flags,
                 error = -EBUSY;
                 goto error;
         }
-        mutex_lock(&sb->s_bdev->bd_mount_mutex);
+        down(&sb->s_bdev->bd_mount_sem);
         new = sget(fs_type, test_bdev_super, set_bdev_super, sb->s_bdev);
-        mutex_unlock(&sb->s_bdev->bd_mount_mutex);
+        up(&sb->s_bdev->bd_mount_sem);
         if (IS_ERR(new)) {
                 error = PTR_ERR(new);
                 goto error;
diff --git a/fs/super.c b/fs/super.c
index f961e0307997..3e7458c2bb76 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -753,9 +753,9 @@ int get_sb_bdev(struct file_system_type *fs_type,
          * will protect the lockfs code from trying to start a snapshot
          * while we are mounting
          */
-        mutex_lock(&bdev->bd_mount_mutex);
+        down(&bdev->bd_mount_sem);
         s = sget(fs_type, test_bdev_super, set_bdev_super, bdev);
-        mutex_unlock(&bdev->bd_mount_mutex);
+        up(&bdev->bd_mount_sem);
         if (IS_ERR(s))
                 goto error_s;
 
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 14a337cc3464..1410e5330c8d 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -459,7 +459,7 @@ struct block_device {
         struct inode *          bd_inode;       /* will die */
         int                     bd_openers;
         struct mutex            bd_mutex;       /* open/close mutex */
-        struct mutex            bd_mount_mutex; /* mount mutex */
+        struct semaphore        bd_mount_sem;
         struct list_head        bd_inodes;
         void *                  bd_holder;
         int                     bd_holders;