Btrfs: remove scrub_super_lock holding in btrfs_sync_log()
Originally, we introduced scrub_super_lock to synchronize
tree log code with scrubbing super.
However we can replace scrub_super_lock with device_list_mutex,
because writing super will hold this mutex, this will reduce an extra
lock holding when writing supers in sync log code.
Signed-off-by: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index b72f540..49e0ff0 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -132,7 +132,9 @@
/* all of the devices in the FS, protected by a mutex
* so we can safely walk it to write out the supers without
- * worrying about add/remove by the multi-device code
+ * worrying about add/remove by the multi-device code.
+ * Scrubbing super can kick off supers writing by holding
+ * this mutex lock.
*/
struct mutex device_list_mutex;
struct list_head devices;