[Acked] [Vivid][PATCH] sd: Fix max transfer length for 4k disks

[Andy Whitcroft]

On Fri, Feb 06, 2015 at 02:17:11PM -0600, Chris J Arges wrote:
> From: Brian King <brking at linux.vnet.ibm.com>
> 
> BugLink: http://bugs.launchpad.net/bugs/1418339
> 
> The following patch fixes an issue observed with 4k sector disks
> where the max_hw_sectors attribute was getting set too large in
> sd_revalidate_disk. Since sdkp->max_xfer_blocks is in units
> of SCSI logical blocks and queue_max_hw_sectors is in units of
> 512 byte blocks, on a 4k sector disk, every time we went through
> sd_revalidate_disk, we were taking the current value of
> queue_max_hw_sectors and increasing it by a factor of 8. Fix
> this by only shifting sdkp->max_xfer_blocks.
> 
> Cc: stable at vger.kernel.org
> Signed-off-by: Brian King <brking at linux.vnet.ibm.com>
> Reviewed-by: Paolo Bonzini <pbonzini at redhat.com>
> Reviewed-by: Martin K. Petersen <martin.petersen at oracle.com>
> Signed-off-by: Christoph Hellwig <hch at lst.de>
> (cherry picked from commit 3a9794d32984b67a6d8992226918618f0e51e5d5)
> Signed-off-by: Chris J Arges <chris.j.arges at canonical.com>
> ---
>  drivers/scsi/sd.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
> index cfba74c..dd8c8d6 100644
> --- a/drivers/scsi/sd.c
> +++ b/drivers/scsi/sd.c
> @@ -2818,9 +2818,11 @@ static int sd_revalidate_disk(struct gendisk *disk)
>  	 */
>  	sd_set_flush_flag(sdkp);
>  
> -	max_xfer = min_not_zero(queue_max_hw_sectors(sdkp->disk->queue),
> -				sdkp->max_xfer_blocks);
> +	max_xfer = sdkp->max_xfer_blocks;
>  	max_xfer <<= ilog2(sdp->sector_size) - 9;
> +
> +	max_xfer = min_not_zero(queue_max_hw_sectors(sdkp->disk->queue),
> +				max_xfer);
>  	blk_queue_max_hw_sectors(sdkp->disk->queue, max_xfer);
>  	set_capacity(disk, sdkp->capacity);
>  	sd_config_write_same(sdkp);

Looks to do something sane, and be upstream and stable.  

Acked-by: Andy Whitcroft <apw at canonical.com>

-apw