From 099768b0c605f55167c0c211afbfeeeea79b56eb Mon Sep 17 00:00:00 2001 From: Xue jiufei Date: Wed, 24 Jun 2015 16:55:09 -0700 Subject: [PATCH] ocfs2: remove BUG_ON(!empty_extent) in __ocfs2_rotate_tree_left() ocfs2_rotate_tree_left() calls __ocfs2_rotate_tree_left() for left rotation while non-rightmost path containing an empty extent in the leaf block. __ocfs2_rotate_tree_left() returns -EAGAIN if right subtree having an empty extent and pass the empty_extent_path to caller. The caller ocfs2_rotate_tree_left() will restart rotation from the returned path. It will trigger the BUG_ON(!ocfs2_is_empty_extent) when the et on disk is as follows: eb0 is the leaf block of path(say path_a) passed to ocfs2_rotate_tree_left, which has an empty rec[0]. eb1 is the leaf block of path(say path_b) that just right to path_a, which has no empty record. eb2 is the leaf block of path(say path_c) that just right to path_b, which has an empty rec[0]. And path_c is also the rightmost path. Now we want to remove the empty rec[0] in eb0: ocfs2_rotate_tree_left: -> call __ocfs2_rotate_tree_left with path_a as its input *path* -> call ocfs2_rotate_subtree_left with path_a as its input *left_path* and path_b as its input *right_path*. it will move rec[0] in eb1 to eb0, and rec[0] in eb0 is not empty now. -> continue to call ocfs2_rotate_subtree_left with path_b as its input *left_path* and path_c as its input *right_path*, and return -EAGAIN because eb2 has an empty rec[0] -> call __ocfs2_rotate_tree_left with path_c as it input, rotate all records in eb2 to left and return 0. -> call __ocfs2_rotate_tree_left with path_a as its input, and triggers the BUG_ON(!ocfs2_is_empty_extent) as the rec[0] in eb0 is not empty. So the BUG_ON() should be removed and return 0 if rec[0] is no longer an empty extent. Signed-off-by: joyce.xue Cc: Mark Fasheh Cc: Joel Becker Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/ocfs2/alloc.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/ocfs2/alloc.c b/fs/ocfs2/alloc.c index ea4c822531cc..5997c00a1515 100644 --- a/fs/ocfs2/alloc.c +++ b/fs/ocfs2/alloc.c @@ -2925,7 +2925,8 @@ static int __ocfs2_rotate_tree_left(handle_t *handle, struct ocfs2_path *right_path = NULL; struct super_block *sb = ocfs2_metadata_cache_get_super(et->et_ci); - BUG_ON(!ocfs2_is_empty_extent(&(path_leaf_el(path)->l_recs[0]))); + if (!ocfs2_is_empty_extent(&(path_leaf_el(path)->l_recs[0]))) + return 0; *empty_extent_path = NULL; -- 2.20.1