ext4: fix ext4_error_err save negative errno into superblock

Fix As write_mmp_block() so that it returns -EIO instead of 1, so that
the correct error gets saved into the superblock.

Cc: stable@kernel.org
Fixes: 54d3adbc29 ("ext4: save all error info in save_error_info() and drop ext4_set_errno()")
Reported-by: Liu Zhi Qiang <liuzhiqiang26@huawei.com>
Signed-off-by: Ye Bin <yebin10@huawei.com>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Link: https://lore.kernel.org/r/20210406025331.148343-1-yebin10@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/mmp.c

@@ -56,7 +56,7 @@ static int write_mmp_block(struct super_block *sb, struct buffer_head *bh)
 	wait_on_buffer(bh);
 	sb_end_write(sb);
 	if (unlikely(!buffer_uptodate(bh)))
-		return 1;
+		return -EIO;
 
 	return 0;
 }