Re: [PATCH 1/1] scsi: Fix max transfer length for 4k disks

[Paolo Bonzini <pbonzini@redhat.com>]

On 29/01/2015 22:54, Brian King wrote:
> 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<stable@vger.kernel.org>
> Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
> ---
> 
>  drivers/scsi/sd.c |    6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff -puN drivers/scsi/sd.c~sd_revalidate_4k drivers/scsi/sd.c
> --- linux/drivers/scsi/sd.c~sd_revalidate_4k	2015-01-29 14:44:23.316171187 -0600
> +++ linux-bjking1/drivers/scsi/sd.c	2015-01-29 14:51:05.846126392 -0600
> @@ -2800,9 +2800,11 @@ static int sd_revalidate_disk(struct gen
>  	 */
>  	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);
> _
> 
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Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>