ocfs2: lock the metaecc process for xattr bucket

For other metadata in ocfs2, metaecc is checked in ocfs2_read_blocks
with io_mutex held. While for xattr bucket, it is calculated by
the whole buckets. So we have to add a spin_lock to prevent multiple
processes calculating metaecc.

Signed-off-by: Tao Ma <tao.ma@oracle.com>
Tested-by: Tristan Ye <tristan.ye@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>
diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c
index b1cb38f..1c3acc4 100644
--- a/fs/ocfs2/super.c
+++ b/fs/ocfs2/super.c
@@ -1747,6 +1747,7 @@
 	INIT_LIST_HEAD(&osb->blocked_lock_list);
 	osb->blocked_lock_count = 0;
 	spin_lock_init(&osb->osb_lock);
+	spin_lock_init(&osb->osb_xattr_lock);
 	ocfs2_init_inode_steal_slot(osb);
 
 	atomic_set(&osb->alloc_stats.moves, 0);