[PATCH v2] ext4: Fix bug on in ext4_es_cache_extent as ext4_split_extent_at failed

[Ye Bin]

We got follow bug_on when run fsstress with injecting IO fault:
[130747.323114] kernel BUG at fs/ext4/extents_status.c:762!
[130747.323117] Internal error: Oops - BUG: 0 [#1] SMP
......
[130747.334329] Call trace:
[130747.334553]  ext4_es_cache_extent+0x150/0x168 [ext4]
[130747.334975]  ext4_cache_extents+0x64/0xe8 [ext4]
[130747.335368]  ext4_find_extent+0x300/0x330 [ext4]
[130747.335759]  ext4_ext_map_blocks+0x74/0x1178 [ext4]
[130747.336179]  ext4_map_blocks+0x2f4/0x5f0 [ext4]
[130747.336567]  ext4_mpage_readpages+0x4a8/0x7a8 [ext4]
[130747.336995]  ext4_readpage+0x54/0x100 [ext4]
[130747.337359]  generic_file_buffered_read+0x410/0xae8
[130747.337767]  generic_file_read_iter+0x114/0x190
[130747.338152]  ext4_file_read_iter+0x5c/0x140 [ext4]
[130747.338556]  __vfs_read+0x11c/0x188
[130747.338851]  vfs_read+0x94/0x150
[130747.339110]  ksys_read+0x74/0xf0

If call ext4_ext_insert_extent failed but new extent already inserted, we just
update "ex->ee_len = orig_ex.ee_len", this will lead to extent overlap, then
cause bug on when cache extent.
If call ext4_ext_insert_extent failed don't update ex->ee_len with old value.
Maybe there will lead to block leak, but it can be fixed by fsck later.

Signed-off-by: Ye Bin <yebin10@xxxxxxxxxx>
---
 fs/ext4/extents.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 77c84d6f1af6..6161db9c17c9 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -3245,8 +3245,11 @@ static int ext4_split_extent_at(handle_t *handle,
 		err = ext4_zeroout_es(inode, &zero_ex);
 
 		goto out;
-	} else if (err)
+	} else if (err == -EROFS) {
+		return err;
+	} else {
 		goto fix_extent_len;
+	}
 
 out:
 	ext4_ext_show_leaf(inode, path);
-- 
2.25.4