Btrfs: fix possible empty list access when flushing the delalloc inodes

We didn't have a lock to protect the access to the delalloc inodes list, that is
we might access a empty delalloc inodes list if someone start flushing delalloc
inodes because the delalloc inodes were moved into a other list temporarily.
Fix it by wrapping the access with a lock.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fb.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 5f4921554f0a..2a9d32e193a5 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1490,6 +1490,7 @@ struct btrfs_fs_info {
          */
         struct list_head ordered_roots;
 
+        struct mutex delalloc_root_mutex;
         spinlock_t delalloc_root_lock;
         /* all fs/file tree roots that have delalloc inodes. */
         struct list_head delalloc_roots;
@@ -1805,6 +1806,7 @@ struct btrfs_root {
         spinlock_t root_item_lock;
         atomic_t refs;
 
+        struct mutex delalloc_mutex;
         spinlock_t delalloc_lock;
         /*
          * all of the inodes that have delalloc bytes.  It is possible for