Patch "s390/dasd: fix performance drop" has been added to the 4.4-stable tree

Patch "s390/dasd: fix performance drop" has been added to the 4.4-stable tree

[gregkh]

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

    s390/dasd: fix performance drop

to the 4.4-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:
     s390-dasd-fix-performance-drop.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 12d319b920fa673a4d5e7c1785c5dc82dcd15257 Mon Sep 17 00:00:00 2001
From: Stefan Haberland <sth@linux.vnet.ibm.com>
Date: Fri, 12 Feb 2016 14:50:52 +0100
Subject: s390/dasd: fix performance drop

From: Stefan Haberland <sth@linux.vnet.ibm.com>

commit 12d319b920fa673a4d5e7c1785c5dc82dcd15257 upstream.

Commit ca369d51b ("sd: Fix device-imposed transfer length limits")
introduced a new queue limit max_dev_sectors which limits the maximum
sectors for requests. The default value leads to small dasd requests
and therefor to a performance drop.
Set the max_dev_sectors value to the same value as the max_hw_sectors
to use the maximum available request size for DASD devices.

Signed-off-by: Stefan Haberland <sth@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/s390/block/dasd.c |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/s390/block/dasd.c
+++ b/drivers/s390/block/dasd.c
@@ -3031,6 +3031,7 @@ static void dasd_setup_queue(struct dasd
 		max = block->base->discipline->max_blocks << block->s2b_shift;
 	}
 	queue_flag_set_unlocked(QUEUE_FLAG_NONROT, block->request_queue);
+	block->request_queue->limits.max_dev_sectors = max;
 	blk_queue_logical_block_size(block->request_queue,
 				     block->bp_block);
 	blk_queue_max_hw_sectors(block->request_queue, max);


Patches currently in stable-queue which might be from sth@linux.vnet.ibm.com are

queue-4.4/s390-dasd-fix-performance-drop.patch