sd: Fix maximum I/O size for BLOCK_PC requests

Commit bcdb247c6b6a ("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: Martin K. Petersen <martin.petersen@oracle.com>
Reported-by: Brian King <brking@linux.vnet.ibm.com>
Tested-by: Brian King <brking@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org # 3.17+
Signed-off-by: James Bottomley <JBottomley@Odin.com>

diff --git a/block/blk-settings.c b/block/blk-settings.c
index 12600bf..e0057d0 100644 (file)
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -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

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 3b2fcb4..a20da8c 100644 (file)
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -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);