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Commit fbb704ef authored by raz ben yehuda's avatar raz ben yehuda Committed by NeilBrown
Browse files

md: raid0 :Enables chunk size other than powers of 2. 



Maintain two flows, one for pow2 chunk sizes (which uses masks and
shift), and a flow for the general case (which uses sector_div).
This is for the sake of performance.

 - introduce map_sector and is_io_in_chunk_boundary to encapsulate
   those two flows better for raid0_make_request
 - fix blk_mergeable to support the two flows.

Signed-off-by: default avatar <raziebe@gmail.com>
Signed-off-by: default avatarNeilBrown <neilb@suse.de>
parent 2ac06c33

drivers/md/raid0.c

+77 −30
Original line number Diff line number Diff line
@@ -273,7 +273,12 @@ static int raid0_mergeable_bvec(struct request_queue *q, 
	unsigned int chunk_sectors = mddev->chunk_size >> 9;

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



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

	if (is_power_of_2(mddev->chunk_size))

		max =  (chunk_sectors - ((sector & (chunk_sectors-1))

						+ bio_sectors)) << 9;

	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 <= biovec->bv_len && bio_sectors == 0)

		return biovec->bv_len;
@@ -299,9 +304,8 @@ static int raid0_run(mddev_t *mddev) 
{

	int ret;



	if (mddev->chunk_size == 0 ||

	    !is_power_of_2(mddev->chunk_size)) {

		printk(KERN_ERR "md/raid0: chunk size must be a power of 2.\n");

	if (mddev->chunk_size == 0) {

		printk(KERN_ERR "md/raid0: chunk size must be set.\n");

		return -EINVAL;

	}

	blk_queue_max_sectors(mddev->queue, mddev->chunk_size >> 9);
@@ -367,15 +371,65 @@ static struct strip_zone *find_zone(struct raid0_private_data *conf, 
	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 mdk_rdev_t *map_sector(mddev_t *mddev, struct strip_zone *zone,

				sector_t sector, sector_t *sector_offset)

{

	unsigned int sect_in_chunk;

	sector_t chunk;

	raid0_conf_t *conf = mddev->private;

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



	if (is_power_of_2(mddev->chunk_size)) {

		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)*mddev->raid_disks

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

}



/*

 * Is io distribute over 1 or more chunks ?

*/

static inline int is_io_in_chunk_boundary(mddev_t *mddev,

			unsigned int chunk_sects, struct bio *bio)

{

	if (likely(is_power_of_2(mddev->chunk_size))) {

		return chunk_sects >= ((bio->bi_sector & (chunk_sects-1))

					+ (bio->bi_size >> 9));

	} else{

		sector_t sector = bio->bi_sector;

		return chunk_sects >= (sector_div(sector, chunk_sects)

						+ (bio->bi_size >> 9));

	}

}



static int raid0_make_request(struct request_queue *q, struct bio *bio)

{

	mddev_t *mddev = q->queuedata;

	unsigned int sect_in_chunk, chunksect_bits, chunk_sects;

	raid0_conf_t *conf = mddev->private;

	unsigned int chunk_sects;

	sector_t sector_offset;

	struct strip_zone *zone;

	mdk_rdev_t *tmp_dev;

	sector_t chunk;

	sector_t sector, rsect, sector_offset;

	const int rw = bio_data_dir(bio);

	int cpu;
@@ -391,10 +445,8 @@ static int raid0_make_request (struct request_queue *q, struct bio *bio) 
	part_stat_unlock();



	chunk_sects = mddev->chunk_size >> 9;

	chunksect_bits = ffz(~chunk_sects);

	sector = bio->bi_sector;



	if (unlikely(chunk_sects < (bio->bi_sector & (chunk_sects - 1)) + (bio->bi_size >> 9))) {

	if (unlikely(!is_io_in_chunk_boundary(mddev, chunk_sects, bio))) {

		sector_t sector = bio->bi_sector;

		struct bio_pair *bp;

		/* Sanity check -- queue functions should prevent this happening */

		if (bio->bi_vcnt != 1 ||
@@ -403,7 +455,12 @@ static int raid0_make_request (struct request_queue *q, struct bio *bio) 
		/* This is a one page bio that upper layers

		 * refuse to split for us, so we need to split it.

		 */

		bp = bio_split(bio, chunk_sects - (bio->bi_sector & (chunk_sects - 1)));

		if (likely(is_power_of_2(mddev->chunk_size)))

			bp = bio_split(bio, chunk_sects - (sector &

							   (chunk_sects-1)));

		else

			bp = bio_split(bio, chunk_sects -

				       sector_div(sector, chunk_sects));

		if (raid0_make_request(q, &bp->bio1))

			generic_make_request(&bp->bio1);

		if (raid0_make_request(q, &bp->bio2))
@@ -412,24 +469,14 @@ static int raid0_make_request (struct request_queue *q, struct bio *bio) 
		bio_pair_release(bp);

		return 0;

	}

	sector_offset = sector;

	zone = find_zone(conf, &sector_offset);

	sect_in_chunk = bio->bi_sector & (chunk_sects - 1);

	{

		sector_t x = sector_offset >> chunksect_bits;



		sector_div(x, zone->nb_dev);

		chunk = x;



		x = sector >> chunksect_bits;

		tmp_dev = conf->devlist[(zone - conf->strip_zone)*mddev->raid_disks

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

	}

	rsect = (chunk << chunksect_bits) + zone->dev_start + sect_in_chunk;



	sector_offset = bio->bi_sector;

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

	tmp_dev = map_sector(mddev, zone, bio->bi_sector,

			     &sector_offset);

	bio->bi_bdev = tmp_dev->bdev;

	bio->bi_sector = rsect + tmp_dev->data_offset;



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

		tmp_dev->data_offset;

	/*

	 * Let the main block layer submit the IO and resolve recursion:

	 */