2017-03-27 14:19:12

by Fam Zheng

Subject: [PATCH] sd: Consider max_xfer_blocks if opt_xfer_blocks is unusable

If device reports a small max_xfer_blocks and a zero opt_xfer_blocks, we
end up using BLK_DEF_MAX_SECTORS, which is wrong and r/w of that size
may get error.

Fixes: ca369d51b3e ("block/sd: Fix device-imposed transfer length limits")
Signed-off-by: Fam Zheng <[email protected]>
---
drivers/scsi/sd.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index fcfeddc..e2e21ab 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -2957,6 +2957,7 @@ static int sd_revalidate_disk(struct gendisk *disk)
rw_max = logical_to_sectors(sdp, sdkp->opt_xfer_blocks);
} else
rw_max = BLK_DEF_MAX_SECTORS;
+ rw_max = min_not_zero(rw_max, dev_max);

/* Combine with controller limits */
q->limits.max_sectors = min(rw_max, queue_max_hw_sectors(q));
--
2.9.3

2017-03-27 16:07:34

by Laurence Oberman

Subject: Re: [PATCH] sd: Consider max_xfer_blocks if opt_xfer_blocks is unusable

----- Original Message -----
> From: "Fam Zheng" <[email protected]>
> To: [email protected]
> Cc: "Martin K. Petersen" <[email protected]>, [email protected], [email protected], "James E.J.
> Bottomley" <[email protected]>
> Sent: Monday, March 27, 2017 10:18:31 AM
> Subject: [PATCH] sd: Consider max_xfer_blocks if opt_xfer_blocks is unusable
>
> If device reports a small max_xfer_blocks and a zero opt_xfer_blocks, we
> end up using BLK_DEF_MAX_SECTORS, which is wrong and r/w of that size
> may get error.
>
> Fixes: ca369d51b3e ("block/sd: Fix device-imposed transfer length limits")
> Signed-off-by: Fam Zheng <[email protected]>
> ---
> drivers/scsi/sd.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
> index fcfeddc..e2e21ab 100644
> --- a/drivers/scsi/sd.c
> +++ b/drivers/scsi/sd.c
> @@ -2957,6 +2957,7 @@ static int sd_revalidate_disk(struct gendisk *disk)
> rw_max = logical_to_sectors(sdp, sdkp->opt_xfer_blocks);
> } else
> rw_max = BLK_DEF_MAX_SECTORS;
> + rw_max = min_not_zero(rw_max, dev_max);
>
> /* Combine with controller limits */
> q->limits.max_sectors = min(rw_max, queue_max_hw_sectors(q));
> --
> 2.9.3
>
>
Looks good to me and addresses the issue we faced.
FInal confirmation this change is OK to come from Martin or James.

Reviewed-by: Laurence Oberman <[email protected]>

2017-03-28 02:12:12

by Martin K. Petersen

Subject: Re: [PATCH] sd: Consider max_xfer_blocks if opt_xfer_blocks is unusable

Fam Zheng <[email protected]> writes:

Hi Fam,

> --- a/drivers/scsi/sd.c
> +++ b/drivers/scsi/sd.c
> @@ -2957,6 +2957,7 @@ static int sd_revalidate_disk(struct gendisk *disk)
> rw_max = logical_to_sectors(sdp, sdkp->opt_xfer_blocks);
> } else
> rw_max = BLK_DEF_MAX_SECTORS;
> + rw_max = min_not_zero(rw_max, dev_max);

rw_max is in sectors, dev_max is in logical blocks.

>
> /* Combine with controller limits */
> q->limits.max_sectors = min(rw_max, queue_max_hw_sectors(q));

--
Martin K. Petersen Oracle Linux Engineering