Patch "sd: Fix maximum I/O size for BLOCK_PC requests" has been added to the 4.1-stable tree

This is a note to let you know that I've just added the patch titled

sd: Fix maximum I/O size for BLOCK_PC requests

to the 4.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
sd-fix-maximum-i-o-size-for-block_pc-requests.patch
and it can be found in the queue-4.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: "Martin K. Petersen" <[email protected]>
Date: Tue, 23 Jun 2015 12:13:59 -0400
Subject: sd: Fix maximum I/O size for BLOCK_PC requests

From: "Martin K. Petersen" <[email protected]>

commit 4f258a46346c03fa0bbb6199ffaf4e1f9f599660 upstream.

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.

---
 block/blk-settings.c |    4 ++--
 drivers/scsi/sd.c    |    6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

@@ -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

@@ -2770,9 +2770,9 @@ static int sd_revalidate_disk(struct gen
 	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);

Patches currently in stable-queue which might be from [email protected] are

queue-4.1/sd-fix-maximum-i-o-size-for-block_pc-requests.patch