Btrfs: Fix async caching interaction with unmount

- don't stop the caching thread until btrfs_commit_super return.

- if caching is interrupted by umount, set last to (u64)-1.
  otherwise the un-scanned range of block group will be considered
  as free extent.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 08188f1615d9..fadf69a2764b 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -288,8 +288,10 @@ again:
 
         while (1) {
                 smp_mb();
-                if (block_group->fs_info->closing)
+                if (block_group->fs_info->closing > 1) {
+                        last = (u64)-1;
                         break;
+                }
 
                 leaf = path->nodes[0];
                 slot = path->slots[0];