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Commit 12d319b9 authored by Stefan Haberland's avatar Stefan Haberland Committed by Martin Schwidefsky
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s390/dasd: fix performance drop 



Commit ca369d51 ("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: default avatarStefan Haberland <sth@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org # 4.4+
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 52499d93

drivers/s390/block/dasd.c

+1 −0
Original line number Diff line number Diff line
@@ -3035,6 +3035,7 @@ static void dasd_setup_queue(struct dasd_block *block) 
		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);