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: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
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@ -176,6 +176,7 @@ static int stripe_ctr(struct dm_target *ti, unsigned int argc, char **argv)
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ti->split_io = chunk_size;
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ti->num_flush_requests = stripes;
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ti->num_discard_requests = stripes;
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sc->chunk_shift = ffs(chunk_size) - 1;
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sc->chunk_mask = ((sector_t) chunk_size) - 1;
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@ -230,6 +231,39 @@ static void stripe_map_sector(struct stripe_c *sc, sector_t sector,
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*result = (chunk << sc->chunk_shift) | (offset & sc->chunk_mask);
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}
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static void stripe_map_range_sector(struct stripe_c *sc, sector_t sector,
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uint32_t target_stripe, sector_t *result)
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{
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uint32_t stripe;
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stripe_map_sector(sc, sector, &stripe, result);
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if (stripe == target_stripe)
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return;
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*result &= ~sc->chunk_mask; /* round down */
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if (target_stripe < stripe)
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*result += sc->chunk_mask + 1; /* next chunk */
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}
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static int stripe_map_discard(struct stripe_c *sc, struct bio *bio,
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uint32_t target_stripe)
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{
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sector_t begin, end;
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stripe_map_range_sector(sc, bio->bi_sector, target_stripe, &begin);
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stripe_map_range_sector(sc, bio->bi_sector + bio_sectors(bio),
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target_stripe, &end);
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if (begin < end) {
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bio->bi_bdev = sc->stripe[target_stripe].dev->bdev;
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bio->bi_sector = begin + sc->stripe[target_stripe].physical_start;
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bio->bi_size = to_bytes(end - begin);
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return DM_MAPIO_REMAPPED;
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} else {
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/* The range doesn't map to the target stripe */
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bio_endio(bio, 0);
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return DM_MAPIO_SUBMITTED;
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}
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}
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static int stripe_map(struct dm_target *ti, struct bio *bio,
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union map_info *map_context)
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{
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@ -243,6 +277,11 @@ static int stripe_map(struct dm_target *ti, struct bio *bio,
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bio->bi_bdev = sc->stripe[target_request_nr].dev->bdev;
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return DM_MAPIO_REMAPPED;
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}
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if (unlikely(bio->bi_rw & REQ_DISCARD)) {
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target_request_nr = map_context->target_request_nr;
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BUG_ON(target_request_nr >= sc->stripes);
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return stripe_map_discard(sc, bio, target_request_nr);
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}
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stripe_map_sector(sc, bio->bi_sector, &stripe, &bio->bi_sector);
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