From 9a7e10e7ba66ce23c8fdc1cac18cade7a0f6840d Mon Sep 17 00:00:00 2001
From: Liu Bo <bo.li.liu@oracle.com>
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 <bo.li.liu@oracle.com>
Reviewed-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
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 6fe8b14e11cf0..914662428dbd4 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