[PATCH] block: Fix bad range check in bio_sector_offset

[PATCH] block: Fix bad range check in bio_sector_offset

[Martin K. Petersen]

DM would occasionally end up splitting data integrity-enabled requests
incorrectly. The culprit was a bad range check in bio_sector_offset.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Cc: <stable@vger.kernel.org>

diff --git a/fs/bio.c b/fs/bio.c
index 9bfade8..b9a6744 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -1552,8 +1552,8 @@ sector_t bio_sector_offset(struct bio *bio, unsigned short index,
 	sector_sz = queue_logical_block_size(bio->bi_bdev->bd_disk->queue);
 	sectors = 0;
 
-	if (index >= bio->bi_idx)
-		index = bio->bi_vcnt - 1;
+	if (index > bio->bi_vcnt)
+		return 0;
 
 	__bio_for_each_segment(bv, bio, i, 0) {
 		if (i == index) {

Re: [PATCH] block: Fix bad range check in bio_sector_offset

[Jeff Moyer]

"Martin K. Petersen" <martin.petersen@oracle.com> writes:

> DM would occasionally end up splitting data integrity-enabled requests
> incorrectly. The culprit was a bad range check in bio_sector_offset.

The patch looks ok to me, but what is the user visible behavior when
this happens?

Cheers,
Jeff

Re: [PATCH] block: Fix bad range check in bio_sector_offset

[Martin K. Petersen]

>>>>> "Jeff" == Jeff Moyer <jmoyer@redhat.com> writes:

>> DM would occasionally end up splitting data integrity-enabled
>> requests incorrectly. The culprit was a bad range check in
>> bio_sector_offset.

Jeff> The patch looks ok to me, but what is the user visible behavior
Jeff> when this happens?

We'd occasionally end up mapping a bad integrity scatterlist and the HBA
would abort the I/O with a protection information error.

-- 
Martin K. Petersen	Oracle Linux Engineering

Re: [PATCH] block: Fix bad range check in bio_sector_offset

[Jens Axboe]

On 2012-08-28 11:03, Martin K. Petersen wrote:
> 
> DM would occasionally end up splitting data integrity-enabled requests
> incorrectly. The culprit was a bad range check in bio_sector_offset.
> 
> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
> Cc: <stable@vger.kernel.org>
> 
> diff --git a/fs/bio.c b/fs/bio.c
> index 9bfade8..b9a6744 100644
> --- a/fs/bio.c
> +++ b/fs/bio.c
> @@ -1552,8 +1552,8 @@ sector_t bio_sector_offset(struct bio *bio, unsigned short index,
>  	sector_sz = queue_logical_block_size(bio->bi_bdev->bd_disk->queue);
>  	sectors = 0;
>  
> -	if (index >= bio->bi_idx)
> -		index = bio->bi_vcnt - 1;
> +	if (index > bio->bi_vcnt)
> +		return 0;
>  
>  	__bio_for_each_segment(bv, bio, i, 0) {
>  		if (i == index) {

Good catch, merged.

-- 
Jens Axboe

Re: [PATCH] block: Fix bad range check in bio_sector_offset

[Jeff Moyer]

"Martin K. Petersen" <martin.petersen@oracle.com> writes:

>>>>>> "Jeff" == Jeff Moyer <jmoyer@redhat.com> writes:
>
>>> DM would occasionally end up splitting data integrity-enabled
>>> requests incorrectly. The culprit was a bad range check in
>>> bio_sector_offset.
>
> Jeff> The patch looks ok to me, but what is the user visible behavior
> Jeff> when this happens?
>
> We'd occasionally end up mapping a bad integrity scatterlist and the HBA
> would abort the I/O with a protection information error.

Thanks for the explanation, Martin!

Acked-by: Jeff Moyer <jmoyer@redhat.com>