Commit 7b76ec11 authored by Mikulas Patocka's avatar Mikulas Patocka Committed by Alasdair G Kergon
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dm stripe: support discards 



The DM core will submit a discard bio to the stripe target for each
stripe in a striped DM device.  The stripe target will determine
stripe-specific portions of the supplied bio to be remapped into
individual (at most 'num_discard_requests' extents).  If a given
stripe-specific discard bio doesn't touch a particular stripe the bio
will be dropped.

Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
parent a79245b3

drivers/md/dm-stripe.c

+39 −0
Original line number Diff line number Diff line
@@ -176,6 +176,7 @@ static int stripe_ctr(struct dm_target *ti, unsigned int argc, char **argv) 


	ti->split_io = chunk_size;

	ti->num_flush_requests = stripes;

	ti->num_discard_requests = stripes;



	sc->chunk_shift = ffs(chunk_size) - 1;

	sc->chunk_mask = ((sector_t) chunk_size) - 1;
@@ -230,6 +231,39 @@ static void stripe_map_sector(struct stripe_c *sc, sector_t sector, 
	*result = (chunk << sc->chunk_shift) | (offset & sc->chunk_mask);

}



static void stripe_map_range_sector(struct stripe_c *sc, sector_t sector,

				    uint32_t target_stripe, sector_t *result)

{

	uint32_t stripe;



	stripe_map_sector(sc, sector, &stripe, result);

	if (stripe == target_stripe)

		return;

	*result &= ~sc->chunk_mask;			/* round down */

	if (target_stripe < stripe)

		*result += sc->chunk_mask + 1;		/* next chunk */

}



static int stripe_map_discard(struct stripe_c *sc, struct bio *bio,

			      uint32_t target_stripe)

{

	sector_t begin, end;



	stripe_map_range_sector(sc, bio->bi_sector, target_stripe, &begin);

	stripe_map_range_sector(sc, bio->bi_sector + bio_sectors(bio),

				target_stripe, &end);

	if (begin < end) {

		bio->bi_bdev = sc->stripe[target_stripe].dev->bdev;

		bio->bi_sector = begin + sc->stripe[target_stripe].physical_start;

		bio->bi_size = to_bytes(end - begin);

		return DM_MAPIO_REMAPPED;

	} else {

		/* The range doesn't map to the target stripe */

		bio_endio(bio, 0);

		return DM_MAPIO_SUBMITTED;

	}

}



static int stripe_map(struct dm_target *ti, struct bio *bio,

		      union map_info *map_context)

{
@@ -243,6 +277,11 @@ static int stripe_map(struct dm_target *ti, struct bio *bio, 
		bio->bi_bdev = sc->stripe[target_request_nr].dev->bdev;

		return DM_MAPIO_REMAPPED;

	}

	if (unlikely(bio->bi_rw & REQ_DISCARD)) {

		target_request_nr = map_context->target_request_nr;

		BUG_ON(target_request_nr >= sc->stripes);

		return stripe_map_discard(sc, bio, target_request_nr);

	}



	stripe_map_sector(sc, bio->bi_sector, &stripe, &bio->bi_sector);

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