[PATCH 04/12] f2fs: remove wrong f2fs_bug_on when merging extents

[Jaegeuk Kim <jaegeuk@kernel.org>]

In f2fs_update_extent_tree, if there is existing extent, f2fs tries to split
it with two parts.
In each trial, __insert_extent_tree checks __is_front/back_mergeable, and then
if it hits to go, there is f2fs_bug_on(!den), which triggers a kernel panic.

Actually, we don't need to check this. Instead, we can do __try_back_merge only
when there exists a den pointer.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
---
 fs/f2fs/data.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 9bedfa8..7817167 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -519,19 +519,19 @@ static struct extent_node *__insert_extent_tree(struct f2fs_sb_info *sbi,
 
 		if (ei->fofs < en->ei.fofs) {
 			if (__is_front_mergeable(ei, &en->ei)) {
-				f2fs_bug_on(sbi, !den);
 				en->ei.fofs = ei->fofs;
 				en->ei.blk = ei->blk;
 				en->ei.len += ei->len;
-				*den = __try_back_merge(sbi, et, en);
+				if (den)
+					*den = __try_back_merge(sbi, et, en);
 				return en;
 			}
 			p = &(*p)->rb_left;
 		} else if (ei->fofs >= en->ei.fofs + en->ei.len) {
 			if (__is_back_mergeable(ei, &en->ei)) {
-				f2fs_bug_on(sbi, !den);
 				en->ei.len += ei->len;
-				*den = __try_front_merge(sbi, et, en);
+				if (den)
+					*den = __try_front_merge(sbi, et, en);
 				return en;
 			}
 			p = &(*p)->rb_right;
-- 
2.1.1