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Commit ba13da47 authored by NeilBrown's avatar NeilBrown
Browse files

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: default avatarNeilBrown <neilb@suse.de>
parent dafb20fa

drivers/md/linear.c

+15 −15
Original line number Diff line number Diff line
@@ -68,10 +68,19 @@ static int linear_mergeable_bvec(struct request_queue *q, 
	struct dev_info *dev0;

	unsigned long maxsectors, bio_sectors = bvm->bi_size >> 9;

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

	int maxbytes = biovec->bv_len;

	struct request_queue *subq;



	rcu_read_lock();

	dev0 = which_dev(mddev, sector);

	maxsectors = dev0->end_sector - sector;

	subq = bdev_get_queue(dev0->rdev->bdev);

	if (subq->merge_bvec_fn) {

		bvm->bi_bdev = dev0->rdev->bdev;

		bvm->bi_sector -= dev0->end_sector - dev0->rdev->sectors;

		maxbytes = min(maxbytes, subq->merge_bvec_fn(subq, bvm,

							     biovec));

	}

	rcu_read_unlock();



	if (maxsectors < bio_sectors)
@@ -80,11 +89,11 @@ static int linear_mergeable_bvec(struct request_queue *q, 
		maxsectors -= bio_sectors;



	if (maxsectors <= (PAGE_SIZE >> 9 ) && bio_sectors == 0)

		return biovec->bv_len;

	/* The bytes available at this offset could be really big,

	 * so we cap at 2^31 to avoid overflow */

	if (maxsectors > (1 << (31-9)))

		return 1<<31;

		return maxbytes;



	if (maxsectors > (maxbytes >> 9))

		return maxbytes;

	else

		return maxsectors << 9;

}
@@ -158,15 +167,6 @@ static struct linear_conf *linear_conf(struct mddev *mddev, int raid_disks) 


		disk_stack_limits(mddev->gendisk, rdev->bdev,

				  rdev->data_offset << 9);

		/* as we don't honour merge_bvec_fn, we must never risk

		 * violating it, so limit max_segments to 1 lying within

		 * a single page.

		 */

		if (rdev->bdev->bd_disk->queue->merge_bvec_fn) {

			blk_queue_max_segments(mddev->queue, 1);

			blk_queue_segment_boundary(mddev->queue,

						   PAGE_CACHE_SIZE - 1);

		}



		conf->array_sectors += rdev->sectors;

		cnt++;

drivers/md/raid0.c

+85 −69
Original line number Diff line number Diff line
@@ -188,16 +188,10 @@ static int create_strip_zones(struct mddev *mddev, struct r0conf **private_conf) 


		disk_stack_limits(mddev->gendisk, rdev1->bdev,

				  rdev1->data_offset << 9);

		/* as we don't honour merge_bvec_fn, we must never risk

		 * violating it, so limit ->max_segments to 1, lying within

		 * a single page.

		 */



		if (rdev1->bdev->bd_disk->queue->merge_bvec_fn) {

			blk_queue_max_segments(mddev->queue, 1);

			blk_queue_segment_boundary(mddev->queue,

						   PAGE_CACHE_SIZE - 1);

		}

		if (rdev1->bdev->bd_disk->queue->merge_bvec_fn)

			conf->has_merge_bvec = 1;



		if (!smallest || (rdev1->sectors < smallest->sectors))

			smallest = rdev1;

		cnt++;
@@ -290,8 +284,64 @@ static int create_strip_zones(struct mddev *mddev, struct r0conf **private_conf) 
	return err;

}



/* Find the zone which holds a particular offset

 * Update *sectorp to be an offset in that zone

 */

static struct strip_zone *find_zone(struct r0conf *conf,

				    sector_t *sectorp)

{

	int i;

	struct strip_zone *z = conf->strip_zone;

	sector_t sector = *sectorp;



	for (i = 0; i < conf->nr_strip_zones; i++)

		if (sector < z[i].zone_end) {

			if (i)

				*sectorp = sector - z[i-1].zone_end;

			return z + i;

		}

	BUG();

}



/*

 * remaps the bio to the target device. we separate two flows.

 * power 2 flow and a general flow for the sake of perfromance

*/

static struct md_rdev *map_sector(struct mddev *mddev, struct strip_zone *zone,

				sector_t sector, sector_t *sector_offset)

{

	unsigned int sect_in_chunk;

	sector_t chunk;

	struct r0conf *conf = mddev->private;

	int raid_disks = conf->strip_zone[0].nb_dev;

	unsigned int chunk_sects = mddev->chunk_sectors;



	if (is_power_of_2(chunk_sects)) {

		int chunksect_bits = ffz(~chunk_sects);

		/* find the sector offset inside the chunk */

		sect_in_chunk  = sector & (chunk_sects - 1);

		sector >>= chunksect_bits;

		/* chunk in zone */

		chunk = *sector_offset;

		/* quotient is the chunk in real device*/

		sector_div(chunk, zone->nb_dev << chunksect_bits);

	} else{

		sect_in_chunk = sector_div(sector, chunk_sects);

		chunk = *sector_offset;

		sector_div(chunk, chunk_sects * zone->nb_dev);

	}

	/*

	*  position the bio over the real device

	*  real sector = chunk in device + starting of zone

	*	+ the position in the chunk

	*/

	*sector_offset = (chunk * chunk_sects) + sect_in_chunk;

	return conf->devlist[(zone - conf->strip_zone)*raid_disks

			     + sector_div(sector, zone->nb_dev)];

}



/**

 *	raid0_mergeable_bvec -- tell bio layer if a two requests can be merged

 *	raid0_mergeable_bvec -- tell bio layer if two requests can be merged

 *	@q: request queue

 *	@bvm: properties of new bio

 *	@biovec: the request that could be merged to it.
@@ -303,10 +353,15 @@ static int raid0_mergeable_bvec(struct request_queue *q, 
				struct bio_vec *biovec)

{

	struct mddev *mddev = q->queuedata;

	struct r0conf *conf = mddev->private;

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

	sector_t sector_offset = sector;

	int max;

	unsigned int chunk_sectors = mddev->chunk_sectors;

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

	struct strip_zone *zone;

	struct md_rdev *rdev;

	struct request_queue *subq;



	if (is_power_of_2(chunk_sectors))

		max =  (chunk_sectors - ((sector & (chunk_sectors-1))
@@ -314,10 +369,27 @@ static int raid0_mergeable_bvec(struct request_queue *q, 
	else

		max =  (chunk_sectors - (sector_div(sector, chunk_sectors)

						+ bio_sectors)) << 9;

	if (max < 0) max = 0; /* bio_add cannot handle a negative return */

	if (max < 0)

		max = 0; /* bio_add cannot handle a negative return */

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

		return biovec->bv_len;

	else 

	if (max < biovec->bv_len)

		/* too small already, no need to check further */

		return max;

	if (!conf->has_merge_bvec)

		return max;



	/* May need to check subordinate device */

	sector = sector_offset;

	zone = find_zone(mddev->private, &sector_offset);

	rdev = map_sector(mddev, zone, sector, &sector_offset);

	subq = bdev_get_queue(rdev->bdev);

	if (subq->merge_bvec_fn) {

		bvm->bi_bdev = rdev->bdev;

		bvm->bi_sector = sector_offset + zone->dev_start +

			rdev->data_offset;

		return min(max, subq->merge_bvec_fn(subq, bvm, biovec));

	} else

		return max;

}
@@ -397,62 +469,6 @@ static int raid0_stop(struct mddev *mddev) 
	return 0;

}



/* Find the zone which holds a particular offset

 * Update *sectorp to be an offset in that zone

 */

static struct strip_zone *find_zone(struct r0conf *conf,

				    sector_t *sectorp)

{

	int i;

	struct strip_zone *z = conf->strip_zone;

	sector_t sector = *sectorp;



	for (i = 0; i < conf->nr_strip_zones; i++)

		if (sector < z[i].zone_end) {

			if (i)

				*sectorp = sector - z[i-1].zone_end;

			return z + i;

		}

	BUG();

}



/*

 * remaps the bio to the target device. we separate two flows.

 * power 2 flow and a general flow for the sake of perfromance

*/

static struct md_rdev *map_sector(struct mddev *mddev, struct strip_zone *zone,

				sector_t sector, sector_t *sector_offset)

{

	unsigned int sect_in_chunk;

	sector_t chunk;

	struct r0conf *conf = mddev->private;

	int raid_disks = conf->strip_zone[0].nb_dev;

	unsigned int chunk_sects = mddev->chunk_sectors;



	if (is_power_of_2(chunk_sects)) {

		int chunksect_bits = ffz(~chunk_sects);

		/* find the sector offset inside the chunk */

		sect_in_chunk  = sector & (chunk_sects - 1);

		sector >>= chunksect_bits;

		/* chunk in zone */

		chunk = *sector_offset;

		/* quotient is the chunk in real device*/

		sector_div(chunk, zone->nb_dev << chunksect_bits);

	} else{

		sect_in_chunk = sector_div(sector, chunk_sects);

		chunk = *sector_offset;

		sector_div(chunk, chunk_sects * zone->nb_dev);

	}

	/*

	*  position the bio over the real device

	*  real sector = chunk in device + starting of zone

	*	+ the position in the chunk

	*/

	*sector_offset = (chunk * chunk_sects) + sect_in_chunk;

	return conf->devlist[(zone - conf->strip_zone)*raid_disks

			     + sector_div(sector, zone->nb_dev)];

}



/*

 * Is io distribute over 1 or more chunks ?

*/

drivers/md/raid0.h

+7 −4
Original line number Diff line number Diff line
@@ -9,8 +9,11 @@ struct strip_zone { 


struct r0conf {

	struct strip_zone	*strip_zone;

	struct md_rdev **devlist; /* lists of rdevs, pointed to by strip_zone->dev */

	struct md_rdev		**devlist; /* lists of rdevs, pointed to

					    * by strip_zone->dev */

	int			nr_strip_zones;

	int			has_merge_bvec;	/* at least one member has

						 * a merge_bvec_fn */

};



#endif