Re: [PATCH v2 3/5] xfs: fix off-by-one error in rtbitmap cross-reference

[Brian Foster <bfoster@redhat.com>]

On Mon, Jan 14, 2019 at 12:32:01PM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> Fix an off-by-one error in the realtime bitmap "is used" cross-reference
> helper function if the realtime extent size is a single block.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---

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

>  fs/xfs/scrub/rtbitmap.c |    5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/xfs/scrub/rtbitmap.c b/fs/xfs/scrub/rtbitmap.c
> index 665d4bbb17cc..dbe115b075f7 100644
> --- a/fs/xfs/scrub/rtbitmap.c
> +++ b/fs/xfs/scrub/rtbitmap.c
> @@ -141,9 +141,8 @@ xchk_xref_is_used_rt_space(
>  	startext = fsbno;
>  	endext = fsbno + len - 1;
>  	do_div(startext, sc->mp->m_sb.sb_rextsize);
> -	if (do_div(endext, sc->mp->m_sb.sb_rextsize))
> -		endext++;
> -	extcount = endext - startext;
> +	do_div(endext, sc->mp->m_sb.sb_rextsize);
> +	extcount = endext - startext + 1;
>  	xfs_ilock(sc->mp->m_rbmip, XFS_ILOCK_SHARED | XFS_ILOCK_RTBITMAP);
>  	error = xfs_rtalloc_extent_is_free(sc->mp, sc->tp, startext, extcount,
>  			&is_free);