Re: [PATCH] xfs: don't write a corrupt unmount record to force summary counter recalc

[Brian Foster <bfoster@redhat.com>]

On Thu, Mar 26, 2020 at 06:14:17PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> In commit f467cad95f5e3, I added the ability to force a recalculation of
> the filesystem summary counters if they seemed incorrect.  This was done
> (not entirely correctly) by tweaking the log code to write an unmount
> record without the UMOUNT_TRANS flag set.  At next mount, the log
> recovery code will fail to find the unmount record and go into recovery,
> which triggers the recalculation.
> 
> What actually gets written to the log is what ought to be an unmount
> record, but without any flags set to indicate what kind of record it
> actually is.  This worked to trigger the recalculation, but we shouldn't
> write bogus log records when we could simply write nothing.
> 
> Fixes: f467cad95f5e3 ("xfs: force summary counter recalc at next mount")
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---

Reviewed-by: Brian Foster <bfoster@redhat.com>

>  fs/xfs/xfs_log.c |   27 ++++++++++++++-------------
>  1 file changed, 14 insertions(+), 13 deletions(-)
> 
> diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
> index 46108ca20d85..00fda2e8e738 100644
> --- a/fs/xfs/xfs_log.c
> +++ b/fs/xfs/xfs_log.c
> @@ -835,19 +835,6 @@ xlog_unmount_write(
>  	if (error)
>  		goto out_err;
>  
> -	/*
> -	 * If we think the summary counters are bad, clear the unmount header
> -	 * flag in the unmount record so that the summary counters will be
> -	 * recalculated during log recovery at next mount.  Refer to
> -	 * xlog_check_unmount_rec for more details.
> -	 */
> -	if (XFS_TEST_ERROR(xfs_fs_has_sickness(mp, XFS_SICK_FS_COUNTERS), mp,
> -			XFS_ERRTAG_FORCE_SUMMARY_RECALC)) {
> -		xfs_alert(mp, "%s: will fix summary counters at next mount",
> -				__func__);
> -		flags &= ~XLOG_UNMOUNT_TRANS;
> -	}
> -
>  	error = xlog_write_unmount_record(log, tic, &lsn, flags);
>  	/*
>  	 * At this point, we're umounting anyway, so there's no point in
> @@ -913,6 +900,20 @@ xfs_log_unmount_write(
>  
>  	if (XLOG_FORCED_SHUTDOWN(log))
>  		return;
> +
> +	/*
> +	 * If we think the summary counters are bad, avoid writing the unmount
> +	 * record to force log recovery at next mount, after which the summary
> +	 * counters will be recalculated.  Refer to xlog_check_unmount_rec for
> +	 * more details.
> +	 */
> +	if (XFS_TEST_ERROR(xfs_fs_has_sickness(mp, XFS_SICK_FS_COUNTERS), mp,
> +			XFS_ERRTAG_FORCE_SUMMARY_RECALC)) {
> +		xfs_alert(mp, "%s: will fix summary counters at next mount",
> +				__func__);
> +		return;
> +	}
> +
>  	xfs_log_unmount_verify_iclog(log);
>  	xlog_unmount_write(log);
>  }
>