dm: Refactor for new bio cloning/splitting

We need to convert the dm code to the new bvec_iter primitives which
respect bi_bvec_done; they also allow us to drastically simplify dm's
bio splitting code.

Also, it's no longer necessary to save/restore the bvec array anymore -
driver conversions for immutable bvecs are done, so drivers should never
be modifying it.

Also kill bio_sector_offset(), dm was the only user and it doesn't make
much sense anymore.

Signed-off-by: Kent Overstreet <kmo@daterainc.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Alasdair Kergon <agk@redhat.com>
Cc: dm-devel@redhat.com
Reviewed-by: Mike Snitzer <snitzer@redhat.com>

1 files changed, 20 insertions, 154 deletions

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index ccd064ea4fe6..44a2fa6814ce 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1155,7 +1155,6 @@ struct clone_info {
         struct dm_io *io;
         sector_t sector;
         sector_t sector_count;
-        unsigned short idx;
 };
 
 static void bio_setup_sector(struct bio *bio, sector_t sector, sector_t len)
@@ -1164,68 +1163,24 @@ static void bio_setup_sector(struct bio *bio, sector_t sector, sector_t len)
         bio->bi_iter.bi_size = to_bytes(len);
 }
 
-static void bio_setup_bv(struct bio *bio, unsigned short idx, unsigned short bv_count)
-{
-        bio->bi_iter.bi_idx = idx;
-        bio->bi_vcnt = idx + bv_count;
-        bio->bi_flags &= ~(1 << BIO_SEG_VALID);
-}
-
-static void clone_bio_integrity(struct bio *bio, struct bio *clone,
-                                unsigned short idx, unsigned len, unsigned offset,
-                                unsigned trim)
-{
-        if (!bio_integrity(bio))
-                return;
-
-        bio_integrity_clone(clone, bio, GFP_NOIO);
-
-        if (trim)
-                bio_integrity_trim(clone, bio_sector_offset(bio, idx, offset), len);
-}
-
-/*
- * Creates a little bio that just does part of a bvec.
- */
-static void clone_split_bio(struct dm_target_io *tio, struct bio *bio,
-                            sector_t sector, unsigned short idx,
-                            unsigned offset, unsigned len)
-{
-        struct bio *clone = &tio->clone;
-        struct bio_vec *bv = bio->bi_io_vec + idx;
-
-        *clone->bi_io_vec = *bv;
-
-        bio_setup_sector(clone, sector, len);
-
-        clone->bi_bdev = bio->bi_bdev;
-        clone->bi_rw = bio->bi_rw;
-        clone->bi_vcnt = 1;
-        clone->bi_io_vec->bv_offset = offset;
-        clone->bi_io_vec->bv_len = clone->bi_iter.bi_size;
-        clone->bi_flags |= 1 << BIO_CLONED;
-
-        clone_bio_integrity(bio, clone, idx, len, offset, 1);
-}
-
 /*
  * Creates a bio that consists of range of complete bvecs.
  */
 static void clone_bio(struct dm_target_io *tio, struct bio *bio,
-                      sector_t sector, unsigned short idx,
-                      unsigned short bv_count, unsigned len)
+                      sector_t sector, unsigned len)
 {
         struct bio *clone = &tio->clone;
-        unsigned trim = 0;
 
-        __bio_clone(clone, bio);
-        bio_setup_sector(clone, sector, len);
-        bio_setup_bv(clone, idx, bv_count);
+        __bio_clone_fast(clone, bio);
+
+        if (bio_integrity(bio))
+                bio_integrity_clone(clone, bio, GFP_NOIO);
+
+        bio_advance(clone, to_bytes(sector - clone->bi_iter.bi_sector));
+        clone->bi_iter.bi_size = to_bytes(len);
 
-        if (idx != bio->bi_iter.bi_idx ||
-            clone->bi_iter.bi_size < bio->bi_iter.bi_size)
-                trim = 1;
-        clone_bio_integrity(bio, clone, idx, len, 0, trim);
+        if (bio_integrity(bio))
+                bio_integrity_trim(clone, 0, len);
 }
 
 static struct dm_target_io *alloc_tio(struct clone_info *ci,
@@ -1258,7 +1213,7 @@ static void __clone_and_map_simple_bio(struct clone_info *ci,
          * ci->bio->bi_max_vecs is BIO_INLINE_VECS anyway, for both flush
          * and discard, so no need for concern about wasted bvec allocations.
          */
-         __bio_clone(clone, ci->bio);
+         __bio_clone_fast(clone, ci->bio);
         if (len)
                 bio_setup_sector(clone, ci->sector, len);
 
@@ -1287,10 +1242,7 @@ static int __send_empty_flush(struct clone_info *ci)
 }
 
 static void __clone_and_map_data_bio(struct clone_info *ci, struct dm_target *ti,
-                                     sector_t sector, int nr_iovecs,
-                                     unsigned short idx, unsigned short bv_count,
-                                     unsigned offset, unsigned len,
-                                     unsigned split_bvec)
+                                     sector_t sector, unsigned len)
 {
         struct bio *bio = ci->bio;
         struct dm_target_io *tio;
@@ -1304,11 +1256,8 @@ static void __clone_and_map_data_bio(struct clone_info *ci, struct dm_target *ti
                 num_target_bios = ti->num_write_bios(ti, bio);
 
         for (target_bio_nr = 0; target_bio_nr < num_target_bios; target_bio_nr++) {
-                tio = alloc_tio(ci, ti, nr_iovecs, target_bio_nr);
-                if (split_bvec)
-                        clone_split_bio(tio, bio, sector, idx, offset, len);
-                else
-                        clone_bio(tio, bio, sector, idx, bv_count, len);
+                tio = alloc_tio(ci, ti, 0, target_bio_nr);
+                clone_bio(tio, bio, sector, len);
                 __map_bio(tio);
         }
 }
@@ -1380,68 +1329,13 @@ static int __send_write_same(struct clone_info *ci)
 }
 
 /*
- * Find maximum number of sectors / bvecs we can process with a single bio.
- */
-static sector_t __len_within_target(struct clone_info *ci, sector_t max, int *idx)
-{
-        struct bio *bio = ci->bio;
-        sector_t bv_len, total_len = 0;
-
-        for (*idx = ci->idx; max && (*idx < bio->bi_vcnt); (*idx)++) {
-                bv_len = to_sector(bio->bi_io_vec[*idx].bv_len);
-
-                if (bv_len > max)
-                        break;
-
-                max -= bv_len;
-                total_len += bv_len;
-        }
-
-        return total_len;
-}
-
-static int __split_bvec_across_targets(struct clone_info *ci,
-                                       struct dm_target *ti, sector_t max)
-{
-        struct bio *bio = ci->bio;
-        struct bio_vec *bv = bio->bi_io_vec + ci->idx;
-        sector_t remaining = to_sector(bv->bv_len);
-        unsigned offset = 0;
-        sector_t len;
-
-        do {
-                if (offset) {
-                        ti = dm_table_find_target(ci->map, ci->sector);
-                        if (!dm_target_is_valid(ti))
-                                return -EIO;
-
-                        max = max_io_len(ci->sector, ti);
-                }
-
-                len = min(remaining, max);
-
-                __clone_and_map_data_bio(ci, ti, ci->sector, 1, ci->idx, 0,
-                                         bv->bv_offset + offset, len, 1);
-
-                ci->sector += len;
-                ci->sector_count -= len;
-                offset += to_bytes(len);
-        } while (remaining -= len);
-
-        ci->idx++;
-
-        return 0;
-}
-
-/*
  * Select the correct strategy for processing a non-flush bio.
  */
 static int __split_and_process_non_flush(struct clone_info *ci)
 {
         struct bio *bio = ci->bio;
         struct dm_target *ti;
-        sector_t len, max;
-        int idx;
+        unsigned len;
 
         if (unlikely(bio->bi_rw & REQ_DISCARD))
                 return __send_discard(ci);
@@ -1452,41 +1346,14 @@ static int __split_and_process_non_flush(struct clone_info *ci)
         if (!dm_target_is_valid(ti))
                 return -EIO;
 
-        max = max_io_len(ci->sector, ti);
-
-        /*
-         * Optimise for the simple case where we can do all of
-         * the remaining io with a single clone.
-         */
-        if (ci->sector_count <= max) {
-                __clone_and_map_data_bio(ci, ti, ci->sector, bio->bi_max_vecs,
-                                         ci->idx, bio->bi_vcnt - ci->idx, 0,
-                                         ci->sector_count, 0);
-                ci->sector_count = 0;
-                return 0;
-        }
-
-        /*
-         * There are some bvecs that don't span targets.
-         * Do as many of these as possible.
-         */
-        if (to_sector(bio->bi_io_vec[ci->idx].bv_len) <= max) {
-                len = __len_within_target(ci, max, &idx);
-
-                __clone_and_map_data_bio(ci, ti, ci->sector, bio->bi_max_vecs,
-                                         ci->idx, idx - ci->idx, 0, len, 0);
+        len = min_t(sector_t, max_io_len(ci->sector, ti), ci->sector_count);
 
-                ci->sector += len;
-                ci->sector_count -= len;
-                ci->idx = idx;
+        __clone_and_map_data_bio(ci, ti, ci->sector, len);
 
-                return 0;
-        }
+        ci->sector += len;
+        ci->sector_count -= len;
 
-        /*
-         * Handle a bvec that must be split between two or more targets.
-         */
-        return __split_bvec_across_targets(ci, ti, max);
+        return 0;
 }
 
 /*
@@ -1512,7 +1379,6 @@ static void __split_and_process_bio(struct mapped_device *md,
         ci.io->md = md;
         spin_lock_init(&ci.io->endio_lock);
         ci.sector = bio->bi_iter.bi_sector;
-        ci.idx = bio->bi_iter.bi_idx;
 
         start_io_acct(ci.io);