Re: [PATCH -next] ext4: fix super block checksum incorrect after mount

[yebin]

On 2022/5/25 15:51, Ritesh Harjani wrote:
> On 22/05/25 09:29AM, Ye Bin wrote:
> > We got issue as follows:
> > [home]# mount  /dev/sda  test
> > EXT4-fs (sda): warning: mounting fs with errors, running e2fsck is recommended
> > [home]# dmesg
> > EXT4-fs (sda): warning: mounting fs with errors, running e2fsck is recommended
> > EXT4-fs (sda): Errors on filesystem, clearing orphan list.
> > EXT4-fs (sda): recovery complete
> > EXT4-fs (sda): mounted filesystem with ordered data mode. Quota mode: none.
> > [home]# debugfs /dev/sda
> > debugfs 1.46.5 (30-Dec-2021)
> > Checksum errors in superblock!  Retrying...
> >
> > Reason is ext4_orphan_cleanup will reset ‘s_last_orphan’ but not update
> > super block checksum.
> > To solve above issue, defer update super block checksum after ext4_orphan_cleanup.
> I agree with the analysis. However after [1], I think all updates to superblock
> (including checksum computation) should be done within buffer lock.
> (lock_buffer(), unlock_buffer()).
>
> [1]: https://lore.kernel.org/all/20201216101844.22917-4-jack@xxxxxxx/
>
> With lock changes added, feel free to add -
>
> Reviewed-by: Ritesh Harjani <ritesh.list@xxxxxxxxx>
Thanks for your reply.
I think there should be no concurrent  modification at this time.
So there's no need to hold buffer lock.
Am I missing something?
> > Signed-off-by: Ye Bin <yebin10@xxxxxxxxxx>
> > ---
> >   fs/ext4/super.c | 16 ++++++++--------
> >   1 file changed, 8 insertions(+), 8 deletions(-)
> >
> > diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> > index f9a3ad683b4a..c47204029429 100644
> > --- a/fs/ext4/super.c
> > +++ b/fs/ext4/super.c
> > @@ -5300,14 +5300,6 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
> >   		err = percpu_counter_init(&sbi->s_freeinodes_counter, freei,
> >   					  GFP_KERNEL);
> >   	}
> > -	/*
> > -	 * Update the checksum after updating free space/inode
> > -	 * counters.  Otherwise the superblock can have an incorrect
> > -	 * checksum in the buffer cache until it is written out and
> > -	 * e2fsprogs programs trying to open a file system immediately
> > -	 * after it is mounted can fail.
> > -	 */
> > -	ext4_superblock_csum_set(sb);
> >   	if (!err)
> >   		err = percpu_counter_init(&sbi->s_dirs_counter,
> >   					  ext4_count_dirs(sb), GFP_KERNEL);
> > @@ -5365,6 +5357,14 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
> >   	EXT4_SB(sb)->s_mount_state |= EXT4_ORPHAN_FS;
> >   	ext4_orphan_cleanup(sb, es);
> >   	EXT4_SB(sb)->s_mount_state &= ~EXT4_ORPHAN_FS;
> > +	/*
> > +	 * Update the checksum after updating free space/inode counters and
> > +	 * ext4_orphan_cleanup. Otherwise the superblock can have an incorrect
> > +	 * checksum in the buffer cache until it is written out and
> > +	 * e2fsprogs programs trying to open a file system immediately
> > +	 * after it is mounted can fail.
> > +	 */
> > +	ext4_superblock_csum_set(sb);
> >   	if (needs_recovery) {
> >   		ext4_msg(sb, KERN_INFO, "recovery complete");
> >   		err = ext4_mark_recovery_complete(sb, es);
> > --
> > 2.31.1
> .