Re: [PATCH v3] ext4: handle errors on ext4_commit_super

["Theodore Y. Ts'o" <tytso@mit.edu>]

On Mon, Apr 23, 2018 at 08:46:26AM -0600, Jaegeuk Kim wrote:
> When remounting ext4 from ro to rw, currently it allows its transition,
> even if ext4_commit_super() returns EIO. Even worse thing is, after that,
> fs/buffer complains buffer dirty bits like:
> 
>  Call trace:
>  [<ffffff9750c259dc>] mark_buffer_dirty+0x184/0x1a4
>  [<ffffff9750cb398c>] __ext4_handle_dirty_super+0x4c/0xfc
>  [<ffffff9750c7a9fc>] ext4_file_open+0x154/0x1c0
>  [<ffffff9750bea51c>] do_dentry_open+0x114/0x2d0
>  [<ffffff9750bea75c>] vfs_open+0x5c/0x94
>  [<ffffff9750bf879c>] path_openat+0x668/0xfe8
>  [<ffffff9750bf8088>] do_filp_open+0x74/0x120
>  [<ffffff9750beac98>] do_sys_open+0x148/0x254
>  [<ffffff9750beade0>] SyS_openat+0x10/0x18
>  [<ffffff9750a83ab0>] el0_svc_naked+0x24/0x28
>  EXT4-fs (dm-1): previous I/O error to superblock detected
>  Buffer I/O error on dev dm-1, logical block 0, lost sync page write
>  EXT4-fs (dm-1): re-mounted. Opts: (null)
>  Buffer I/O error on dev dm-1, logical block 80, lost async page write
> 
> Cc: "Theodore Ts'o" <tytso@mit.edu>
> Cc: Andreas Dilger <adilger.kernel@dilger.ca>
> Cc: linux-ext4@vger.kernel.org
> Cc: Jaegeuk Kim <jaegeuk@kernel.org>
> Signed-off-by: Jaegeuk Kim <jaegeuk@google.com>

Applied with a fix up to ext4_fill_super() when it calls
ext4_setup_super() with the changed error return semantics.

		   	    - Ted

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index aac33c155363..1388e56bb3f5 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -4254,8 +4254,12 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 		goto failed_mount4;
 	}
 
-	if (ext4_setup_super(sb, es, sb_rdonly(sb)))
+	ret = ext4_setup_super(sb, es, sb_rdonly(sb));
+	if (ret == -EROFS) {
 		sb->s_flags |= SB_RDONLY;
+		ret = 0;
+	} else if (ret)
+		goto failed_mount4a;
 
 	/* determine the minimum size of new large inodes, if present */
 	if (sbi->s_inode_size > EXT4_GOOD_OLD_INODE_SIZE &&