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authorRaz Ben-Jehuda(caro) <raziebe@gmail.com>2006-12-10 02:20:45 -0800
committerLinus Torvalds <torvalds@woody.osdl.org>2006-12-10 09:57:20 -0800
commit23032a0eb97c8eaae8ac9d17373b53b19d0f5413 (patch)
tree7021309ed7a591c6ae93f7347fb23482cea85163 /drivers/md
parent0d4ca600fcf5c5f3a0c195ccf37e989b83451dd4 (diff)
downloadblackbird-op-linux-23032a0eb97c8eaae8ac9d17373b53b19d0f5413.tar.gz
blackbird-op-linux-23032a0eb97c8eaae8ac9d17373b53b19d0f5413.zip
[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: 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>
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/raid5.c24
1 files changed, 24 insertions, 0 deletions
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 52914d5cec76..b86ceba04f6f 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -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) {
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