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 08188f1615d..fadf69a2764 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];