4.20-stable review patch. If anyone has any objections, please let me know.
------------------
From: Theodore Ts'o <tytso@xxxxxxx>
commit e86807862e6880809f191c4cea7f88a489f0ed34 upstream.
The xfstests generic/475 test switches the underlying device with
dm-error while running a stress test. This results in a large number
of file system errors, and since we can't lock the buffer head when
marking the superblock dirty in the ext4_grp_locked_error() case, it's
possible the superblock to be !buffer_uptodate() without
buffer_write_io_error() being true.
We need to set buffer_uptodate() before we call mark_buffer_dirty() or
this will trigger a WARN_ON. It's safe to do this since the
superblock must have been properly read into memory or the mount would
have been successful. So if buffer_uptodate() is not set, we can
safely assume that this happened due to a failed attempt to write the
superblock.
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/ext4/super.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -4905,7 +4905,7 @@ static int ext4_commit_super(struct supe
ext4_superblock_csum_set(sb);
if (sync)
lock_buffer(sbh);
- if (buffer_write_io_error(sbh)) {
+ if (buffer_write_io_error(sbh) || !buffer_uptodate(sbh)) {
/*
* Oh, dear. A previous attempt to write the
* superblock failed. This could happen because the
