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Commit 4f258a46 authored by Martin K. Petersen's avatar Martin K. Petersen Committed by James Bottomley
Browse files

sd: Fix maximum I/O size for BLOCK_PC requests 



Commit bcdb247c ("sd: Limit transfer length") clamped the maximum
size of an I/O request to the MAXIMUM TRANSFER LENGTH field in the BLOCK
LIMITS VPD. This had the unfortunate effect of also limiting the maximum
size of non-filesystem requests sent to the device through sg/bsg.

Avoid using blk_queue_max_hw_sectors() and set the max_sectors queue
limit directly.

Also update the comment in blk_limits_max_hw_sectors() to clarify that
max_hw_sectors defines the limit for the I/O controller only.

Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
Reported-by: default avatarBrian King <brking@linux.vnet.ibm.com>
Tested-by: default avatarBrian King <brking@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org # 3.17+
Signed-off-by: default avatarJames Bottomley <JBottomley@Odin.com>
parent 8f2777f5

block/blk-settings.c

+2 −2
Original line number Diff line number Diff line
@@ -241,8 +241,8 @@ EXPORT_SYMBOL(blk_queue_bounce_limit); 
 * Description:

 *    Enables a low level driver to set a hard upper limit,

 *    max_hw_sectors, on the size of requests.  max_hw_sectors is set by

 *    the device driver based upon the combined capabilities of I/O

 *    controller and storage device.

 *    the device driver based upon the capabilities of the I/O

 *    controller.

 *

 *    max_sectors is a soft limit imposed by the block layer for

 *    filesystem type requests.  This value can be overridden on a

drivers/scsi/sd.c

+3 −3
Original line number Diff line number Diff line
@@ -2770,9 +2770,9 @@ static int sd_revalidate_disk(struct gendisk *disk) 
	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);

	sdkp->disk->queue->limits.max_sectors =

		min_not_zero(queue_max_hw_sectors(sdkp->disk->queue), max_xfer);



	set_capacity(disk, sdkp->capacity);

	sd_config_write_same(sdkp);

	kfree(buffer);