block: Introduce new bio_split()

The new bio_split() can split arbitrary bios - it's not restricted to
single page bios, like the old bio_split() (previously renamed to
bio_pair_split()). It also has different semantics - it doesn't allocate
a struct bio_pair, leaving it up to the caller to handle completions.

Then convert the existing bio_pair_split() users to the new bio_split()
- and also nvme, which was open coding bio splitting.

(We have to take that BUG_ON() out of bio_integrity_trim() because this
bio_split() needs to use it, and there's no reason it has to be used on
bios marked as cloned; BIO_CLONED doesn't seem to have clearly
documented semantics anyways.)

Signed-off-by: Kent Overstreet <kmo@daterainc.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Matthew Wilcox <matthew.r.wilcox@intel.com>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Neil Brown <neilb@suse.de>

3 files changed, 8 insertions, 87 deletions

diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
index 6b6fe935be73..964353c5329d 100644
--- a/drivers/md/bcache/bcache.h
+++ b/drivers/md/bcache/bcache.h
@@ -901,7 +901,6 @@ void bch_bbio_endio(struct cache_set *, struct bio *, int, const char *);
 void bch_bbio_free(struct bio *, struct cache_set *);
 struct bio *bch_bbio_alloc(struct cache_set *);
 
-struct bio *bch_bio_split(struct bio *, int, gfp_t, struct bio_set *);
 void bch_generic_make_request(struct bio *, struct bio_split_pool *);
 void __bch_submit_bbio(struct bio *, struct cache_set *);
 void bch_submit_bbio(struct bio *, struct cache_set *, struct bkey *, unsigned);
diff --git a/drivers/md/bcache/io.c b/drivers/md/bcache/io.c
index 522f95778443..fa028fa82df4 100644
--- a/drivers/md/bcache/io.c
+++ b/drivers/md/bcache/io.c
@@ -11,84 +11,6 @@
 
 #include <linux/blkdev.h>
 
-/**
- * bch_bio_split - split a bio
- * @bio:        bio to split
- * @sectors:    number of sectors to split from the front of @bio
- * @gfp:        gfp mask
- * @bs:         bio set to allocate from
- *
- * Allocates and returns a new bio which represents @sectors from the start of
- * @bio, and updates @bio to represent the remaining sectors.
- *
- * If bio_sectors(@bio) was less than or equal to @sectors, returns @bio
- * unchanged.
- *
- * The newly allocated bio will point to @bio's bi_io_vec, if the split was on a
- * bvec boundry; it is the caller's responsibility to ensure that @bio is not
- * freed before the split.
- */
-struct bio *bch_bio_split(struct bio *bio, int sectors,
-                          gfp_t gfp, struct bio_set *bs)
-{
-        unsigned vcnt = 0, nbytes = sectors << 9;
-        struct bio_vec bv;
-        struct bvec_iter iter;
-        struct bio *ret = NULL;
-
-        BUG_ON(sectors <= 0);
-
-        if (sectors >= bio_sectors(bio))
-                return bio;
-
-        if (bio->bi_rw & REQ_DISCARD) {
-                ret = bio_alloc_bioset(gfp, 1, bs);
-                if (!ret)
-                        return NULL;
-                goto out;
-        }
-
-        bio_for_each_segment(bv, bio, iter) {
-                vcnt++;
-
-                if (nbytes <= bv.bv_len)
-                        break;
-
-                nbytes -= bv.bv_len;
-        }
-
-        ret = bio_alloc_bioset(gfp, vcnt, bs);
-        if (!ret)
-                return NULL;
-
-        bio_for_each_segment(bv, bio, iter) {
-                ret->bi_io_vec[ret->bi_vcnt++] = bv;
-
-                if (ret->bi_vcnt == vcnt)
-                        break;
-        }
-
-        ret->bi_io_vec[ret->bi_vcnt - 1].bv_len = nbytes;
-out:
-        ret->bi_bdev    = bio->bi_bdev;
-        ret->bi_iter.bi_sector  = bio->bi_iter.bi_sector;
-        ret->bi_iter.bi_size    = sectors << 9;
-        ret->bi_rw      = bio->bi_rw;
-
-        if (bio_integrity(bio)) {
-                if (bio_integrity_clone(ret, bio, gfp)) {
-                        bio_put(ret);
-                        return NULL;
-                }
-
-                bio_integrity_trim(ret, 0, bio_sectors(ret));
-        }
-
-        bio_advance(bio, ret->bi_iter.bi_size);
-
-        return ret;
-}
-
 static unsigned bch_bio_max_sectors(struct bio *bio)
 {
         struct request_queue *q = bdev_get_queue(bio->bi_bdev);
@@ -172,8 +94,8 @@ void bch_generic_make_request(struct bio *bio, struct bio_split_pool *p)
         bio_get(bio);
 
         do {
-                n = bch_bio_split(bio, bch_bio_max_sectors(bio),
-                                  GFP_NOIO, s->p->bio_split);
+                n = bio_next_split(bio, bch_bio_max_sectors(bio),
+                                   GFP_NOIO, s->p->bio_split);
 
                 n->bi_end_io    = bch_bio_submit_split_endio;
                 n->bi_private   = &s->cl;
diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c
index 63451c724781..5878cdb39529 100644
--- a/drivers/md/bcache/request.c
+++ b/drivers/md/bcache/request.c
@@ -371,7 +371,7 @@ static void bch_data_insert_start(struct closure *cl)
                                        op->writeback))
                         goto err;
 
-                n = bch_bio_split(bio, KEY_SIZE(k), GFP_NOIO, split);
+                n = bio_next_split(bio, KEY_SIZE(k), GFP_NOIO, split);
 
                 n->bi_end_io    = bch_data_insert_endio;
                 n->bi_private   = cl;
@@ -679,9 +679,9 @@ static int cache_lookup_fn(struct btree_op *op, struct btree *b, struct bkey *k)
         if (KEY_DIRTY(k))
                 s->read_dirty_data = true;
 
-        n = bch_bio_split(bio, min_t(uint64_t, INT_MAX,
-                                     KEY_OFFSET(k) - bio->bi_iter.bi_sector),
-                          GFP_NOIO, s->d->bio_split);
+        n = bio_next_split(bio, min_t(uint64_t, INT_MAX,
+                                      KEY_OFFSET(k) - bio->bi_iter.bi_sector),
+                           GFP_NOIO, s->d->bio_split);
 
         bio_key = &container_of(n, struct bbio, bio)->key;
         bch_bkey_copy_single_ptr(bio_key, k, ptr);
@@ -920,7 +920,7 @@ static int cached_dev_cache_miss(struct btree *b, struct search *s,
         struct bio *miss, *cache_bio;
 
         if (s->cache_miss || s->iop.bypass) {
-                miss = bch_bio_split(bio, sectors, GFP_NOIO, s->d->bio_split);
+                miss = bio_next_split(bio, sectors, GFP_NOIO, s->d->bio_split);
                 ret = miss == bio ? MAP_DONE : MAP_CONTINUE;
                 goto out_submit;
         }
@@ -943,7 +943,7 @@ static int cached_dev_cache_miss(struct btree *b, struct search *s,
 
         s->iop.replace = true;
 
-        miss = bch_bio_split(bio, sectors, GFP_NOIO, s->d->bio_split);
+        miss = bio_next_split(bio, sectors, GFP_NOIO, s->d->bio_split);
 
         /* btree_search_recurse()'s btree iterator is no good anymore */
         ret = miss == bio ? MAP_DONE : -EINTR;