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authorChristoph Hellwig <hch@lst.de>2009-08-03 23:28:06 +0200
committerAl Viro <viro@zeniv.linux.org.uk>2009-09-24 07:47:39 -0400
commit4fadd7bb20a1e7c774ed88dc703d8fbcd00ff917 (patch)
treea6f3df6f19d27e81f35a93f8858b73bd4273f420
parent1ba50bbe93ebb98e83b174a85eff76af430c4e5b (diff)
freeze_bdev: kill bd_mount_sem
Now that we have the freeze count there is not much reason for bd_mount_sem anymore. The actual freeze/thaw operations are serialized using the bd_fsfreeze_mutex, and the only other place we take bd_mount_sem is get_sb_bdev which tries to prevent mounting a filesystem while the block device is frozen. Instead of add a check for bd_fsfreeze_count and return -EBUSY if a filesystem is frozen. While that is a change in user visible behaviour a failing mount is much better for this case rather than having the mount process stuck uninterruptible for a long time. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
-rw-r--r--fs/block_dev.c8
-rw-r--r--fs/super.c9
-rw-r--r--include/linux/fs.h1
3 files changed, 8 insertions, 10 deletions
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 5d1ed50bd46c..22506eb4a58e 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -216,8 +216,6 @@ EXPORT_SYMBOL(fsync_bdev);
* freeze_bdev -- lock a filesystem and force it into a consistent state
* @bdev: blockdevice to lock
*
- * 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.
* The reference counter (bd_fsfreeze_count) guarantees that only the last
@@ -240,7 +238,6 @@ struct super_block *freeze_bdev(struct block_device *bdev)
}
bdev->bd_fsfreeze_count++;
- down(&bdev->bd_mount_sem);
sb = get_super(bdev);
if (sb && !(sb->s_flags & MS_RDONLY)) {
sb->s_frozen = SB_FREEZE_WRITE;
@@ -260,7 +257,6 @@ struct super_block *freeze_bdev(struct block_device *bdev)
"VFS:Filesystem freeze failed\n");
sb->s_frozen = SB_UNFROZEN;
drop_super(sb);
- up(&bdev->bd_mount_sem);
bdev->bd_fsfreeze_count--;
mutex_unlock(&bdev->bd_fsfreeze_mutex);
return ERR_PTR(error);
@@ -271,7 +267,7 @@ struct super_block *freeze_bdev(struct block_device *bdev)
sync_blockdev(bdev);
mutex_unlock(&bdev->bd_fsfreeze_mutex);
- return sb; /* thaw_bdev releases s->s_umount and bd_mount_sem */
+ return sb; /* thaw_bdev releases s->s_umount */
}
EXPORT_SYMBOL(freeze_bdev);
@@ -321,7 +317,6 @@ int thaw_bdev(struct block_device *bdev, struct super_block *sb)
drop_super(sb);
}
- up(&bdev->bd_mount_sem);
mutex_unlock(&bdev->bd_fsfreeze_mutex);
return 0;
}
@@ -430,7 +425,6 @@ static void init_once(void *foo)
memset(bdev, 0, sizeof(*bdev));
mutex_init(&bdev->bd_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/super.c b/fs/super.c
index 4906e2d8f400..1cb26a3e3df0 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -743,9 +743,14 @@ 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
*/
- down(&bdev->bd_mount_sem);
+ mutex_lock(&bdev->bd_fsfreeze_mutex);
+ if (bdev->bd_fsfreeze_count > 0) {
+ mutex_unlock(&bdev->bd_fsfreeze_mutex);
+ error = -EBUSY;
+ goto error_bdev;
+ }
s = sget(fs_type, test_bdev_super, set_bdev_super, bdev);
- up(&bdev->bd_mount_sem);
+ mutex_unlock(&bdev->bd_fsfreeze_mutex);
if (IS_ERR(s))
goto error_s;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index cbb7724c11d3..72dfbd423974 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -640,7 +640,6 @@ struct block_device {
struct super_block * bd_super;
int bd_openers;
struct mutex bd_mutex; /* open/close mutex */
- struct semaphore bd_mount_sem;
struct list_head bd_inodes;
void * bd_holder;
int bd_holders;