4.20-stable review patch. If anyone has any objections, please let me know.
------------------
From: Theodore Ts'o tytso@mit.edu
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@mit.edu Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- 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