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Commit 23032a0e authored by Raz Ben-Jehuda(caro)'s avatar Raz Ben-Jehuda(caro) Committed by Linus Torvalds
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[PATCH] md: define raid5_mergeable_bvec 



This will encourage read request to be on only one device, so we will often be
able to bypass the cache for read requests.

Signed-off-by: default avatarNeil Brown <neilb@suse.de>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 0d4ca600

drivers/md/raid5.c

+24 −0
Original line number Diff line number Diff line
@@ -2611,6 +2611,28 @@ static int raid5_congested(void *data, int bits) 
	return 0;

}



/* We want read requests to align with chunks where possible,

 * but write requests don't need to.

 */

static int raid5_mergeable_bvec(request_queue_t *q, struct bio *bio, struct bio_vec *biovec)

{

	mddev_t *mddev = q->queuedata;

	sector_t sector = bio->bi_sector + get_start_sect(bio->bi_bdev);

	int max;

	unsigned int chunk_sectors = mddev->chunk_size >> 9;

	unsigned int bio_sectors = bio->bi_size >> 9;



	if (bio_data_dir(bio))

		return biovec->bv_len; /* always allow writes to be mergeable */



	max =  (chunk_sectors - ((sector & (chunk_sectors - 1)) + bio_sectors)) << 9;

	if (max < 0) max = 0;

	if (max <= biovec->bv_len && bio_sectors == 0)

		return biovec->bv_len;

	else

		return max;

}



static int make_request(request_queue_t *q, struct bio * bi)

{

	mddev_t *mddev = q->queuedata;
@@ -3320,6 +3342,8 @@ static int run(mddev_t *mddev) 
	mddev->array_size =  mddev->size * (conf->previous_raid_disks -

					    conf->max_degraded);



	blk_queue_merge_bvec(mddev->queue, raid5_mergeable_bvec);



	return 0;

abort:

	if (conf) {