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;