linux-kernel - [PATCH 3.19.y-ckt 061/102] sd: Fix maximum I/O size for BLOCK

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Date:	Tue, 22 Sep 2015 10:51:57 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	"Martin K. Petersen" <martin.petersen@...cle.com>,
	James Bottomley <JBottomley@...n.com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.19.y-ckt 061/102] sd: Fix maximum I/O size for BLOCK_PC requests

3.19.8-ckt7 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: "Martin K. Petersen" <martin.petersen@...cle.com>

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.

Signed-off-by: Martin K. Petersen <martin.petersen@...cle.com>
Reported-by: Brian King <brking@...ux.vnet.ibm.com>
Tested-by: Brian King <brking@...ux.vnet.ibm.com>
Signed-off-by: James Bottomley <JBottomley@...n.com>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 block/blk-settings.c | 4 ++--
 drivers/scsi/sd.c    | 6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/block/blk-settings.c b/block/blk-settings.c
index 12600bf..e0057d0 100644
--- 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 7f71d7d..c80e1fe 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -2794,9 +2794,9 @@ 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);
-- 
1.9.1

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