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Subject[PATCH 035 of 35] Simplify bio splitting in dm.

Use the new bio_multi_split to simplify dm bio splitting.

Signed-off-by: Neil Brown <neilb@suse.de>

### Diffstat output
./drivers/md/dm.c | 166 ++++++------------------------------------------------
1 file changed, 20 insertions(+), 146 deletions(-)
diff .prev/drivers/md/dm.c ./drivers/md/dm.c
--- .prev/drivers/md/dm.c 2007-07-31 11:21:22.000000000 +1000
+++ ./drivers/md/dm.c 2007-07-31 11:21:30.000000000 +1000
@@ -526,11 +526,6 @@ static void clone_endio(struct bio *bio,

dec_pending(tio->io, error);

- /*
- * Store md for cleanup instead of tio which is about to get freed.
- */
- bio->bi_private = md->bs;
-
bio_put(bio);
free_tio(md, tio);
}
@@ -590,10 +585,6 @@ static void __map_bio(struct dm_target *
/* error the io and bail out, or requeue it if needed */
md = tio->io->md;
dec_pending(tio->io, r);
- /*
- * Store bio_set for cleanup.
- */
- clone->bi_private = md->bs;
bio_put(clone);
free_tio(md, tio);
} else if (r) {
@@ -607,149 +598,35 @@ struct clone_info {
struct dm_table *map;
struct bio *bio;
struct dm_io *io;
- sector_t sector;
- sector_t sector_count;
- unsigned short idx;
};

-static void dm_bio_destructor(struct bio *bio)
-{
- struct bio_set *bs = bio->bi_private;
-
- bio_free(bio, bs);
-}
-
-/*
- * Creates a little bio that is just does part of a bvec.
- */
-static struct bio *split_bvec(struct bio *bio, sector_t sector,
- unsigned short idx, unsigned int offset,
- unsigned int len, struct bio_set *bs)
-{
- struct bio *clone;
- struct bio_vec *bv = bio->bi_io_vec + idx;
-
- clone = bio_alloc_bioset(GFP_NOIO, 1, bs);
- clone->bi_destructor = dm_bio_destructor;
- *clone->bi_io_vec = *bv;
-
- clone->bi_sector = sector;
- clone->bi_bdev = bio->bi_bdev;
- clone->bi_rw = bio->bi_rw;
- clone->bi_vcnt = 1;
- clone->bi_size = to_bytes(len);
- clone->bi_io_vec->bv_offset = offset;
- clone->bi_io_vec->bv_len = clone->bi_size;
-
- return clone;
-}
-
-/*
- * Creates a bio that consists of range of complete bvecs.
- */
-static struct bio *clone_bio(struct bio *bio, sector_t sector,
- unsigned short idx, unsigned short bv_count,
- unsigned int len, struct bio_set *bs)
-{
- struct bio *clone;
-
- clone = bio_alloc_bioset(GFP_NOIO, bio->bi_max_vecs, bs);
- __bio_clone(clone, bio);
- clone->bi_destructor = dm_bio_destructor;
- clone->bi_sector = sector;
- clone->bi_io_vec += idx;
- clone->bi_vcnt = bv_count;
- clone->bi_size = to_bytes(len);
-
- return clone;
-}
-
static void __clone_and_map(struct clone_info *ci)
{
- struct bio *clone, *bio = ci->bio;
- struct dm_target *ti = dm_table_find_target(ci->map, ci->sector);
- sector_t len = 0, max = max_io_len(ci->md, ci->sector, ti);
- struct dm_target_io *tio;
+ struct bio *bio = ci->bio;
+ struct bio *remainder = bio;

- /*
- * Allocate a target io object.
- */
- tio = alloc_tio(ci->md);
- tio->io = ci->io;
- tio->ti = ti;
- memset(&tio->info, 0, sizeof(tio->info));
+ while (remainder) {
+ struct bio *clone;
+ struct dm_target *ti =
+ dm_table_find_target(ci->map,
+ remainder->bi_sector);
+ sector_t len = 0;
+ sector_t max = max_io_len(ci->md, remainder->bi_sector, ti);
+ struct dm_target_io *tio;

- if (ci->sector_count <= max) {
/*
- * Optimise for the simple case where we can do all of
- * the remaining io with a single clone.
+ * Allocate a target io object.
*/
- clone = clone_bio(bio, ci->sector, ci->idx,
- bio->bi_vcnt - ci->idx, ci->sector_count,
- ci->md->bs);
- __map_bio(ti, clone, tio);
- ci->sector_count = 0;
-
- } else if (to_sector(bio->bi_io_vec[ci->idx].bv_len) <= max) {
- /*
- * There are some bvecs that don't span targets.
- * Do as many of these as possible.
- */
- int i;
- sector_t remaining = max;
- sector_t bv_len;
-
- for (i = ci->idx; remaining && (i < bio->bi_vcnt); i++) {
- bv_len = to_sector(bio->bi_io_vec[i].bv_len);
+ tio = alloc_tio(ci->md);
+ tio->io = ci->io;
+ tio->ti = ti;
+ memset(&tio->info, 0, sizeof(tio->info));

- if (bv_len > remaining)
- break;
+ len = min_t(unsigned int, remainder->bi_size>>9, max);

- remaining -= bv_len;
- len += bv_len;
- }
-
- clone = clone_bio(bio, ci->sector, ci->idx, i - ci->idx, len,
- ci->md->bs);
+ clone = bio_multi_split(bio, len, &remainder);
__map_bio(ti, clone, tio);
-
- ci->sector += len;
- ci->sector_count -= len;
- ci->idx = i;
-
- } else {
- /*
- * Handle a bvec that must be split between two or more targets.
- */
- struct bio_vec *bv = bio->bi_io_vec + ci->idx;
- sector_t remaining = to_sector(bv->bv_len);
- unsigned int offset = 0;
-
- do {
- if (offset) {
- ti = dm_table_find_target(ci->map, ci->sector);
- max = max_io_len(ci->md, ci->sector, ti);
-
- tio = alloc_tio(ci->md);
- tio->io = ci->io;
- tio->ti = ti;
- memset(&tio->info, 0, sizeof(tio->info));
- }
-
- len = min(remaining, max);
-
- clone = split_bvec(bio, ci->sector, ci->idx,
- bv->bv_offset + offset, len,
- ci->md->bs);
-
- __map_bio(ti, clone, tio);
-
- ci->sector += len;
- ci->sector_count -= len;
- offset += to_bytes(len);
- } while (remaining -= len);
-
- ci->idx++;
+ atomic_dec(&bio->bi_iocnt);
}
}

@@ -773,13 +650,10 @@ static void __split_bio(struct mapped_de
atomic_set(&ci.io->io_count, 1);
ci.io->bio = bio;
ci.io->md = md;
- ci.sector = bio->bi_sector;
- ci.sector_count = bio_sectors(bio);
- ci.idx = 0;

start_io_acct(ci.io);
- while (ci.sector_count)
- __clone_and_map(&ci);
+
+ __clone_and_map(&ci);

/* drop the extra reference count */
dec_pending(ci.io, 0);
-
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