From 9a7e10e7ba66ce23c8fdc1cac18cade7a0f6840d Mon Sep 17 00:00:00 2001 From: Liu Bo Date: Fri, 5 Jan 2018 12:51:15 -0700 Subject: [PATCH] Btrfs: add WARN_ONCE to detect unexpected error from merge_extent_mapping This is a subtle case, so in order to understand the problem, it'd be good to know the content of existing and em when any error occurs. Signed-off-by: Liu Bo Reviewed-by: Josef Bacik Signed-off-by: David Sterba --- fs/btrfs/extent_map.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c index 6fe8b14e11cf..914662428dbd 100644 --- a/fs/btrfs/extent_map.c +++ b/fs/btrfs/extent_map.c @@ -562,17 +562,24 @@ int btrfs_add_extent_mapping(struct extent_map_tree *em_tree, *em_in = existing; ret = 0; } else { + u64 orig_start = em->start; + u64 orig_len = em->len; + /* * The existing extent map is the one nearest to * the [start, start + len) range which overlaps */ ret = merge_extent_mapping(em_tree, existing, em, start); - free_extent_map(existing); if (ret) { free_extent_map(em); *em_in = NULL; + WARN_ONCE(ret, +"unexpected error %d: merge existing(start %llu len %llu) with em(start %llu len %llu)\n", + ret, existing->start, existing->len, + orig_start, orig_len); } + free_extent_map(existing); } } -- 2.30.2