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[PATCH] md: define raid5_mergeable_bvec

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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: Neil Brown <neilb@suse.de>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Raz Ben-Jehuda(caro) 2006-12-10 02:20:45 -08:00 committed by Linus Torvalds
parent 0d4ca600fc
commit 23032a0eb9
1 changed files with 24 additions and 0 deletions
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24
drivers/md/raid5.c
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@ -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) {