[PATCH] xfs: calculate correct offset in xfs_scrub_quota_item

[PATCH] xfs: calculate correct offset in xfs_scrub_quota_item

[Eric Sandeen]

It's only used for tracepoints so it's relatively harmless,
but the offset is calculated incorrectly in xfs_scrub_quota_item.

qi_dqperchunk is the nr. of dquots per "chunk" which we have
conveniently *cough* defined to always be 1 FSB.  Therefore 
block_offset * qi_dqperchunk == first id in that chunk,
and so offset = id / qi_dqperchunk

id * dqperchunk is ... meaningless.

Fixes-coverity-id: 1423965
Fixes: c2fc338c ("xfs: scrub quota information")
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
---

compile-tested only

diff --git a/fs/xfs/scrub/quota.c b/fs/xfs/scrub/quota.c
index 8e58ba8..2eac160 100644
--- a/fs/xfs/scrub/quota.c
+++ b/fs/xfs/scrub/quota.c
@@ -107,7 +107,7 @@
 	unsigned long long		rcount;
 	xfs_ino_t			fs_icount;
 
-	offset = id * qi->qi_dqperchunk;
+	offset = id / qi->qi_dqperchunk;
 
 	/*
 	 * We fed $id and DQNEXT into the xfs_qm_dqget call, which means

Re: [PATCH] xfs: calculate correct offset in xfs_scrub_quota_item

[Darrick J. Wong]

On Mon, Nov 27, 2017 at 06:04:55PM -0600, Eric Sandeen wrote:
> It's only used for tracepoints so it's relatively harmless,
> but the offset is calculated incorrectly in xfs_scrub_quota_item.
> 
> qi_dqperchunk is the nr. of dquots per "chunk" which we have
> conveniently *cough* defined to always be 1 FSB.  Therefore 
> block_offset * qi_dqperchunk == first id in that chunk,
> and so offset = id / qi_dqperchunk
> 
> id * dqperchunk is ... meaningless.
> 
> Fixes-coverity-id: 1423965
> Fixes: c2fc338c ("xfs: scrub quota information")
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>

Looks ok, will test
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

> ---
> 
> compile-tested only
> 
> diff --git a/fs/xfs/scrub/quota.c b/fs/xfs/scrub/quota.c
> index 8e58ba8..2eac160 100644
> --- a/fs/xfs/scrub/quota.c
> +++ b/fs/xfs/scrub/quota.c
> @@ -107,7 +107,7 @@
>  	unsigned long long		rcount;
>  	xfs_ino_t			fs_icount;
>  
> -	offset = id * qi->qi_dqperchunk;
> +	offset = id / qi->qi_dqperchunk;
>  
>  	/*
>  	 * We fed $id and DQNEXT into the xfs_qm_dqget call, which means
> --
> To unsubscribe from this list: send the line "unsubscribe linux-xfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html