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dm stripe: support discards

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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: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This commit is contained in:
Mikulas Patocka 2010-08-12 04:14:26 +01:00 committed by Alasdair G Kergon
parent a79245b3e5
commit 7b76ec11fe
1 changed files with 39 additions and 0 deletions
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39
drivers/md/dm-stripe.c
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@ -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);