[PATCH] Btrfs: fix crash due to not cleaning up tree log block's dirty bits

[Liu Bo <bo.li.liu@oracle.com>]

In cases that the whole fs flips into readonly status due to failures in
critical sections, then log tree's blocks are still dirty, and this leads
to a crash during umount time, the crash is about use-after-free,

umount
 -> close_ctree
    -> stop workers
    -> iput(btree_inode)
       -> iput_final
          -> write_inode_now
	     -> ...
	       -> queue job on stop'd workers

cc: <stable@vger.kernel.org> v3.12+
Fixes: 681ae50917df ("Btrfs: cleanup reserved space when freeing tree log on error")
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
---
 fs/btrfs/tree-log.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index 7bf9b31..22046ed 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -2494,6 +2494,9 @@ static noinline int walk_down_log_tree(struct btrfs_trans_handle *trans,
 					clean_tree_block(fs_info, next);
 					btrfs_wait_tree_block_writeback(next);
 					btrfs_tree_unlock(next);
+				} else {
+					if (test_and_clear_bit(EXTENT_BUFFER_DIRTY, &next->bflags))
+						clear_extent_buffer_dirty(next);
 				}
 
 				WARN_ON(root_owner !=
@@ -2574,6 +2577,9 @@ static noinline int walk_up_log_tree(struct btrfs_trans_handle *trans,
 					clean_tree_block(fs_info, next);
 					btrfs_wait_tree_block_writeback(next);
 					btrfs_tree_unlock(next);
+				} else {
+					if (test_and_clear_bit(EXTENT_BUFFER_DIRTY, &next->bflags))
+						clear_extent_buffer_dirty(next);
 				}
 
 				WARN_ON(root_owner != BTRFS_TREE_LOG_OBJECTID);
@@ -2652,6 +2658,9 @@ static int walk_log_tree(struct btrfs_trans_handle *trans,
 				clean_tree_block(fs_info, next);
 				btrfs_wait_tree_block_writeback(next);
 				btrfs_tree_unlock(next);
+			} else {
+				if (test_and_clear_bit(EXTENT_BUFFER_DIRTY, &next->bflags))
+					clear_extent_buffer_dirty(next);
 			}
 
 			WARN_ON(log->root_key.objectid !=
-- 
2.9.4