md: add proper merge_bvec handling to RAID0 and Linear.
These personalities currently set a max request size of one page when any member device has a merge_bvec_fn because they don't bother to call that function. This causes extra works in splitting and combining requests. So make the extra effort to call the merge_bvec_fn when it exists so that we end up with larger requests out the bottom. Signed-off-by: NeilBrown <neilb@suse.de>
This commit is contained in:
NeilBrown
parent
dafb20fa34
commit
ba13da47ff
3 changed files with 107 additions and 88 deletions
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@ -68,10 +68,19 @@ static int linear_mergeable_bvec(struct request_queue *q,
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struct dev_info *dev0;
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unsigned long maxsectors, bio_sectors = bvm->bi_size >> 9;
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sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);
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int maxbytes = biovec->bv_len;
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struct request_queue *subq;
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rcu_read_lock();
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dev0 = which_dev(mddev, sector);
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maxsectors = dev0->end_sector - sector;
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subq = bdev_get_queue(dev0->rdev->bdev);
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if (subq->merge_bvec_fn) {
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bvm->bi_bdev = dev0->rdev->bdev;
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bvm->bi_sector -= dev0->end_sector - dev0->rdev->sectors;
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maxbytes = min(maxbytes, subq->merge_bvec_fn(subq, bvm,
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biovec));
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}
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rcu_read_unlock();
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if (maxsectors < bio_sectors)
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@ -80,12 +89,12 @@ static int linear_mergeable_bvec(struct request_queue *q,
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maxsectors -= bio_sectors;
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if (maxsectors <= (PAGE_SIZE >> 9 ) && bio_sectors == 0)
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return biovec->bv_len;
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/* The bytes available at this offset could be really big,
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* so we cap at 2^31 to avoid overflow */
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if (maxsectors > (1 << (31-9)))
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return 1<<31;
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return maxsectors << 9;
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return maxbytes;
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if (maxsectors > (maxbytes >> 9))
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return maxbytes;
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else
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return maxsectors << 9;
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}
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static int linear_congested(void *data, int bits)
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@ -158,15 +167,6 @@ static struct linear_conf *linear_conf(struct mddev *mddev, int raid_disks)
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disk_stack_limits(mddev->gendisk, rdev->bdev,
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rdev->data_offset << 9);
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/* as we don't honour merge_bvec_fn, we must never risk
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* violating it, so limit max_segments to 1 lying within
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* a single page.
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*/
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if (rdev->bdev->bd_disk->queue->merge_bvec_fn) {
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blk_queue_max_segments(mddev->queue, 1);
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blk_queue_segment_boundary(mddev->queue,
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PAGE_CACHE_SIZE - 1);
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}
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conf->array_sectors += rdev->sectors;
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cnt++;
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@ -188,16 +188,10 @@ static int create_strip_zones(struct mddev *mddev, struct r0conf **private_conf)
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disk_stack_limits(mddev->gendisk, rdev1->bdev,
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rdev1->data_offset << 9);
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/* as we don't honour merge_bvec_fn, we must never risk
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* violating it, so limit ->max_segments to 1, lying within
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* a single page.
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*/
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if (rdev1->bdev->bd_disk->queue->merge_bvec_fn) {
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blk_queue_max_segments(mddev->queue, 1);
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blk_queue_segment_boundary(mddev->queue,
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PAGE_CACHE_SIZE - 1);
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}
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if (rdev1->bdev->bd_disk->queue->merge_bvec_fn)
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conf->has_merge_bvec = 1;
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if (!smallest || (rdev1->sectors < smallest->sectors))
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smallest = rdev1;
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cnt++;
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@ -290,8 +284,64 @@ static int create_strip_zones(struct mddev *mddev, struct r0conf **private_conf)
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return err;
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}
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/* Find the zone which holds a particular offset
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* Update *sectorp to be an offset in that zone
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*/
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static struct strip_zone *find_zone(struct r0conf *conf,
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sector_t *sectorp)
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{
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int i;
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struct strip_zone *z = conf->strip_zone;
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sector_t sector = *sectorp;
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for (i = 0; i < conf->nr_strip_zones; i++)
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if (sector < z[i].zone_end) {
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if (i)
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*sectorp = sector - z[i-1].zone_end;
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return z + i;
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}
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BUG();
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}
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/*
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* remaps the bio to the target device. we separate two flows.
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* power 2 flow and a general flow for the sake of perfromance
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*/
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static struct md_rdev *map_sector(struct mddev *mddev, struct strip_zone *zone,
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sector_t sector, sector_t *sector_offset)
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{
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unsigned int sect_in_chunk;
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sector_t chunk;
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struct r0conf *conf = mddev->private;
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int raid_disks = conf->strip_zone[0].nb_dev;
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unsigned int chunk_sects = mddev->chunk_sectors;
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if (is_power_of_2(chunk_sects)) {
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int chunksect_bits = ffz(~chunk_sects);
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/* find the sector offset inside the chunk */
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sect_in_chunk = sector & (chunk_sects - 1);
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sector >>= chunksect_bits;
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/* chunk in zone */
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chunk = *sector_offset;
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/* quotient is the chunk in real device*/
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sector_div(chunk, zone->nb_dev << chunksect_bits);
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} else{
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sect_in_chunk = sector_div(sector, chunk_sects);
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chunk = *sector_offset;
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sector_div(chunk, chunk_sects * zone->nb_dev);
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}
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/*
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* position the bio over the real device
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* real sector = chunk in device + starting of zone
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* + the position in the chunk
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*/
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*sector_offset = (chunk * chunk_sects) + sect_in_chunk;
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return conf->devlist[(zone - conf->strip_zone)*raid_disks
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+ sector_div(sector, zone->nb_dev)];
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}
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/**
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* raid0_mergeable_bvec -- tell bio layer if a two requests can be merged
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* raid0_mergeable_bvec -- tell bio layer if two requests can be merged
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* @q: request queue
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* @bvm: properties of new bio
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* @biovec: the request that could be merged to it.
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@ -303,10 +353,15 @@ static int raid0_mergeable_bvec(struct request_queue *q,
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struct bio_vec *biovec)
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{
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struct mddev *mddev = q->queuedata;
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struct r0conf *conf = mddev->private;
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sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);
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sector_t sector_offset = sector;
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int max;
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unsigned int chunk_sectors = mddev->chunk_sectors;
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unsigned int bio_sectors = bvm->bi_size >> 9;
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struct strip_zone *zone;
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struct md_rdev *rdev;
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struct request_queue *subq;
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if (is_power_of_2(chunk_sectors))
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max = (chunk_sectors - ((sector & (chunk_sectors-1))
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@ -314,10 +369,27 @@ static int raid0_mergeable_bvec(struct request_queue *q,
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else
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max = (chunk_sectors - (sector_div(sector, chunk_sectors)
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+ bio_sectors)) << 9;
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if (max < 0) max = 0; /* bio_add cannot handle a negative return */
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if (max < 0)
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max = 0; /* bio_add cannot handle a negative return */
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if (max <= biovec->bv_len && bio_sectors == 0)
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return biovec->bv_len;
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else
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if (max < biovec->bv_len)
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/* too small already, no need to check further */
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return max;
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if (!conf->has_merge_bvec)
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return max;
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/* May need to check subordinate device */
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sector = sector_offset;
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zone = find_zone(mddev->private, §or_offset);
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rdev = map_sector(mddev, zone, sector, §or_offset);
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subq = bdev_get_queue(rdev->bdev);
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if (subq->merge_bvec_fn) {
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bvm->bi_bdev = rdev->bdev;
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bvm->bi_sector = sector_offset + zone->dev_start +
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rdev->data_offset;
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return min(max, subq->merge_bvec_fn(subq, bvm, biovec));
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} else
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return max;
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}
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@ -397,62 +469,6 @@ static int raid0_stop(struct mddev *mddev)
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return 0;
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}
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/* Find the zone which holds a particular offset
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* Update *sectorp to be an offset in that zone
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*/
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static struct strip_zone *find_zone(struct r0conf *conf,
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sector_t *sectorp)
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{
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int i;
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struct strip_zone *z = conf->strip_zone;
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sector_t sector = *sectorp;
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for (i = 0; i < conf->nr_strip_zones; i++)
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if (sector < z[i].zone_end) {
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if (i)
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*sectorp = sector - z[i-1].zone_end;
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return z + i;
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}
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BUG();
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}
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/*
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* remaps the bio to the target device. we separate two flows.
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* power 2 flow and a general flow for the sake of perfromance
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*/
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static struct md_rdev *map_sector(struct mddev *mddev, struct strip_zone *zone,
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sector_t sector, sector_t *sector_offset)
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{
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unsigned int sect_in_chunk;
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sector_t chunk;
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struct r0conf *conf = mddev->private;
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int raid_disks = conf->strip_zone[0].nb_dev;
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unsigned int chunk_sects = mddev->chunk_sectors;
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if (is_power_of_2(chunk_sects)) {
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int chunksect_bits = ffz(~chunk_sects);
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/* find the sector offset inside the chunk */
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sect_in_chunk = sector & (chunk_sects - 1);
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sector >>= chunksect_bits;
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/* chunk in zone */
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chunk = *sector_offset;
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/* quotient is the chunk in real device*/
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sector_div(chunk, zone->nb_dev << chunksect_bits);
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} else{
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sect_in_chunk = sector_div(sector, chunk_sects);
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chunk = *sector_offset;
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sector_div(chunk, chunk_sects * zone->nb_dev);
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}
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/*
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* position the bio over the real device
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* real sector = chunk in device + starting of zone
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* + the position in the chunk
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*/
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*sector_offset = (chunk * chunk_sects) + sect_in_chunk;
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return conf->devlist[(zone - conf->strip_zone)*raid_disks
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+ sector_div(sector, zone->nb_dev)];
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}
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/*
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* Is io distribute over 1 or more chunks ?
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*/
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@ -505,7 +521,7 @@ static void raid0_make_request(struct mddev *mddev, struct bio *bio)
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}
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sector_offset = bio->bi_sector;
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zone = find_zone(mddev->private, §or_offset);
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zone = find_zone(mddev->private, §or_offset);
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tmp_dev = map_sector(mddev, zone, bio->bi_sector,
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§or_offset);
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bio->bi_bdev = tmp_dev->bdev;
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@ -4,13 +4,16 @@
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struct strip_zone {
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sector_t zone_end; /* Start of the next zone (in sectors) */
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sector_t dev_start; /* Zone offset in real dev (in sectors) */
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int nb_dev; /* # of devices attached to the zone */
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int nb_dev; /* # of devices attached to the zone */
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};
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struct r0conf {
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struct strip_zone *strip_zone;
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struct md_rdev **devlist; /* lists of rdevs, pointed to by strip_zone->dev */
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int nr_strip_zones;
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struct strip_zone *strip_zone;
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struct md_rdev **devlist; /* lists of rdevs, pointed to
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* by strip_zone->dev */
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int nr_strip_zones;
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int has_merge_bvec; /* at least one member has
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* a merge_bvec_fn */
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};
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#endif
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