Re: [PATCH v2] xfs_scrub: don't use statvfs to collect filesystem summary counts

[Brian Foster <bfoster@redhat.com>]

On Mon, Oct 05, 2020 at 09:37:37AM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> The function scrub_scan_estimate_blocks naïvely uses the statvfs counts
> to estimate the size and free blocks on the data volume.  Unfortunately,
> it fails to account for the fact that statvfs can return the size and
> free counts for the realtime volume if the root directory has the
> rtinherit flag set, which leads to phase 7 reporting totally absurd
> quantities.
> 
> Eric pointed out a further problem with statvfs, which is that the file
> counts are clamped to the current user's project quota inode limits.
> Therefore, we must not use statvfs for querying the filesystem summary
> counts.
> 
> The XFS_IOC_FSCOUNTS ioctl returns all the data we need, so use that
> instead.
> 
> Fixes: 604dd3345f35 ("xfs_scrub: filesystem counter collection functions")
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
> v2: drop statvfs entirely
> ---

This doesn't seem to apply to for-next..?

Brian

>  scrub/fscounters.c |   27 ++++-----------------------
>  1 file changed, 4 insertions(+), 23 deletions(-)
> 
> diff --git a/scrub/fscounters.c b/scrub/fscounters.c
> index f9d64f8c008f..e9901fcdf6df 100644
> --- a/scrub/fscounters.c
> +++ b/scrub/fscounters.c
> @@ -130,38 +130,19 @@ scrub_scan_estimate_blocks(
>  	unsigned long long		*f_free)
>  {
>  	struct xfs_fsop_counts		fc;
> -	struct xfs_fsop_resblks		rb;
> -	struct statvfs			sfs;
>  	int				error;
>  
> -	/* Grab the fstatvfs counters, since it has to report accurately. */
> -	error = fstatvfs(ctx->mnt.fd, &sfs);
> -	if (error)
> -		return errno;
> -
>  	/* Fetch the filesystem counters. */
>  	error = ioctl(ctx->mnt.fd, XFS_IOC_FSCOUNTS, &fc);
>  	if (error)
>  		return errno;
>  
> -	/*
> -	 * XFS reserves some blocks to prevent hard ENOSPC, so add those
> -	 * blocks back to the free data counts.
> -	 */
> -	error = ioctl(ctx->mnt.fd, XFS_IOC_GET_RESBLKS, &rb);
> -	if (error)
> -		return errno;
> -
> -	sfs.f_bfree += rb.resblks_avail;
> -
> -	*d_blocks = sfs.f_blocks;
> -	if (ctx->mnt.fsgeom.logstart > 0)
> -		*d_blocks += ctx->mnt.fsgeom.logblocks;
> -	*d_bfree = sfs.f_bfree;
> +	*d_blocks = ctx->mnt.fsgeom.datablocks;
> +	*d_bfree = fc.freedata;
>  	*r_blocks = ctx->mnt.fsgeom.rtblocks;
>  	*r_bfree = fc.freertx;
> -	*f_files = sfs.f_files;
> -	*f_free = sfs.f_ffree;
> +	*f_files = fc.allocino;
> +	*f_free = fc.freeino;
>  
>  	return 0;
>  }
>