From e86807862e6880809f191c4cea7f88a489f0ed34 Mon Sep 17 00:00:00 2001

From: Theodore Ts'o <tytso@mit.edu>

Date: Sun, 30 Dec 2018 23:20:39 -0500

Subject: [PATCH] ext4: avoid kernel warning when writing the superblock to a

 dead device

Git-commit: e86807862e6880809f191c4cea7f88a489f0ed34

Patch-mainline: v5.0-rc1

References: bsc#1124981

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

Acked-by: Jan Kara <jack@suse.cz>

---

 fs/ext4/super.c | 2 +-

 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c

index d6c142d73d99..fb12d3c17c1b 100644

--- a/fs/ext4/super.c

+++ b/fs/ext4/super.c

@@ -4902,7 +4902,7 @@ static int ext4_commit_super(struct super_block *sb, int sync)

 	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

-- 

2.16.4