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Commit 2800aac1 authored by Martin K. Petersen's avatar Martin K. Petersen Committed by Jens Axboe
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block: Update blk_queue_max_sectors and documentation 



Clarify blk_queue_max_sectors and update documentation.

Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 024f9066

block/blk-settings.c

+17 −13
Original line number Diff line number Diff line
@@ -212,26 +212,30 @@ EXPORT_SYMBOL(blk_queue_bounce_limit); 
/**

 * blk_queue_max_sectors - set max sectors for a request for this queue

 * @q:  the request queue for the device

 * @max_sectors:  max sectors in the usual 512b unit

 * @max_hw_sectors:  max hardware sectors in the usual 512b unit

 *

 * Description:

 *    Enables a low level driver to set an upper limit on the size of

 *    received requests.

 *    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.

 *

 *    max_sectors is a soft limit imposed by the block layer for

 *    filesystem type requests.  This value can be overridden on a

 *    per-device basis in /sys/block/<device>/queue/max_sectors_kb.

 *    The soft limit can not exceed max_hw_sectors.

 **/

void blk_queue_max_sectors(struct request_queue *q, unsigned int max_sectors)

void blk_queue_max_sectors(struct request_queue *q, unsigned int max_hw_sectors)

{

	if ((max_sectors << 9) < PAGE_CACHE_SIZE) {

		max_sectors = 1 << (PAGE_CACHE_SHIFT - 9);

	if ((max_hw_sectors << 9) < PAGE_CACHE_SIZE) {

		max_hw_sectors = 1 << (PAGE_CACHE_SHIFT - 9);

		printk(KERN_INFO "%s: set to minimum %d\n",

		       __func__, max_sectors);

		       __func__, max_hw_sectors);

	}



	if (BLK_DEF_MAX_SECTORS > max_sectors)

		q->limits.max_hw_sectors = q->limits.max_sectors = max_sectors;

	else {

		q->limits.max_sectors = BLK_DEF_MAX_SECTORS;

		q->limits.max_hw_sectors = max_sectors;

	}

	q->limits.max_hw_sectors = max_hw_sectors;

	q->limits.max_sectors = min_t(unsigned int, max_hw_sectors,

				      BLK_DEF_MAX_SECTORS);

}

EXPORT_SYMBOL(blk_queue_max_sectors);