[PATCH 5.9 346/391] ext4: fix bdev write error check failed when mount fs with ro

[Greg Kroah-Hartman]

From: Zhang Xiaoxu <zhangxiaoxu5@xxxxxxxxxx>

commit 9704a322ea67fdb05fc66cf431fdd01c2424bbd9 upstream.

Consider a situation when a filesystem was uncleanly shutdown and the
orphan list is not empty and a read-only mount is attempted. The orphan
list cleanup during mount will fail with:

ext4_check_bdev_write_error:193: comm mount: Error while async write back metadata

This happens because sbi->s_bdev_wb_err is not initialized when mounting
the filesystem in read only mode and so ext4_check_bdev_write_error()
falsely triggers.

Initialize sbi->s_bdev_wb_err unconditionally to avoid this problem.

Fixes: bc71726c7257 ("ext4: abort the filesystem if failed to async write metadata buffer")
Cc: stable@xxxxxxxxxx
Signed-off-by: Zhang Xiaoxu <zhangxiaoxu5@xxxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Link: https://lore.kernel.org/r/20200928020556.710971-1-zhangxiaoxu5@xxxxxxxxxx
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/ext4/super.c |   13 ++-----------
 1 file changed, 2 insertions(+), 11 deletions(-)

--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -4826,9 +4826,8 @@ no_journal:
 	 * used to detect the metadata async write error.
 	 */
 	spin_lock_init(&sbi->s_bdev_wb_lock);
-	if (!sb_rdonly(sb))
-		errseq_check_and_advance(&sb->s_bdev->bd_inode->i_mapping->wb_err,
-					 &sbi->s_bdev_wb_err);
+	errseq_check_and_advance(&sb->s_bdev->bd_inode->i_mapping->wb_err,
+				 &sbi->s_bdev_wb_err);
 	sb->s_bdev->bd_super = sb;
 	EXT4_SB(sb)->s_mount_state |= EXT4_ORPHAN_FS;
 	ext4_orphan_cleanup(sb, es);
@@ -5721,14 +5720,6 @@ static int ext4_remount(struct super_blo
 			}
 
 			/*
-			 * Update the original bdev mapping's wb_err value
-			 * which could be used to detect the metadata async
-			 * write error.
-			 */
-			errseq_check_and_advance(&sb->s_bdev->bd_inode->i_mapping->wb_err,
-						 &sbi->s_bdev_wb_err);
-
-			/*
 			 * Mounting a RDONLY partition read-write, so reread
 			 * and store the current valid flag.  (It may have
 			 * been changed by e2fsck since we originally mounted