block: remove bio_clone_bioset_partial()

commit c18a1e0(block: introduce bio_clone_bioset_partial()) introduced
bio_clone_bioset_partial() for raid1 write behind IO. Now the write behind is
rewritten by Ming. We don't need the API any more, so revert the commit.

Cc: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jens Axboe <axboe@fb.com>
Reviewed-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Shaohua Li <shli@fb.com>
diff --git a/block/bio.c b/block/bio.c
index 1ccff0d..0364359 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -631,20 +631,21 @@ struct bio *bio_clone_fast(struct bio *bio, gfp_t gfp_mask, struct bio_set *bs)
 }
 EXPORT_SYMBOL(bio_clone_fast);
 
-static struct bio *__bio_clone_bioset(struct bio *bio_src, gfp_t gfp_mask,
-				      struct bio_set *bs, int offset,
-				      int size)
+/**
+ * 	bio_clone_bioset - clone a bio
+ * 	@bio_src: bio to clone
+ *	@gfp_mask: allocation priority
+ *	@bs: bio_set to allocate from
+ *
+ *	Clone bio. Caller will own the returned bio, but not the actual data it
+ *	points to. Reference count of returned bio will be one.
+ */
+struct bio *bio_clone_bioset(struct bio *bio_src, gfp_t gfp_mask,
+			     struct bio_set *bs)
 {
 	struct bvec_iter iter;
 	struct bio_vec bv;
 	struct bio *bio;
-	struct bvec_iter iter_src = bio_src->bi_iter;
-
-	/* for supporting partial clone */
-	if (offset || size != bio_src->bi_iter.bi_size) {
-		bio_advance_iter(bio_src, &iter_src, offset);
-		iter_src.bi_size = size;
-	}
 
 	/*
 	 * Pre immutable biovecs, __bio_clone() used to just do a memcpy from
@@ -668,8 +669,7 @@ static struct bio *__bio_clone_bioset(struct bio *bio_src, gfp_t gfp_mask,
 	 *    __bio_clone_fast() anyways.
 	 */
 
-	bio = bio_alloc_bioset(gfp_mask, __bio_segments(bio_src,
-			       &iter_src), bs);
+	bio = bio_alloc_bioset(gfp_mask, bio_segments(bio_src), bs);
 	if (!bio)
 		return NULL;
 	bio->bi_bdev		= bio_src->bi_bdev;
@@ -686,7 +686,7 @@ static struct bio *__bio_clone_bioset(struct bio *bio_src, gfp_t gfp_mask,
 		bio->bi_io_vec[bio->bi_vcnt++] = bio_src->bi_io_vec[0];
 		break;
 	default:
-		__bio_for_each_segment(bv, bio_src, iter, iter_src)
+		bio_for_each_segment(bv, bio_src, iter)
 			bio->bi_io_vec[bio->bi_vcnt++] = bv;
 		break;
 	}
@@ -705,44 +705,9 @@ static struct bio *__bio_clone_bioset(struct bio *bio_src, gfp_t gfp_mask,
 
 	return bio;
 }
-
-/**
- * 	bio_clone_bioset - clone a bio
- * 	@bio_src: bio to clone
- *	@gfp_mask: allocation priority
- *	@bs: bio_set to allocate from
- *
- *	Clone bio. Caller will own the returned bio, but not the actual data it
- *	points to. Reference count of returned bio will be one.
- */
-struct bio *bio_clone_bioset(struct bio *bio_src, gfp_t gfp_mask,
-			     struct bio_set *bs)
-{
-	return __bio_clone_bioset(bio_src, gfp_mask, bs, 0,
-				  bio_src->bi_iter.bi_size);
-}
 EXPORT_SYMBOL(bio_clone_bioset);
 
 /**
- * 	bio_clone_bioset_partial - clone a partial bio
- * 	@bio_src: bio to clone
- *	@gfp_mask: allocation priority
- *	@bs: bio_set to allocate from
- *	@offset: cloned starting from the offset
- *	@size: size for the cloned bio
- *
- *	Clone bio. Caller will own the returned bio, but not the actual data it
- *	points to. Reference count of returned bio will be one.
- */
-struct bio *bio_clone_bioset_partial(struct bio *bio_src, gfp_t gfp_mask,
-				     struct bio_set *bs, int offset,
-				     int size)
-{
-	return __bio_clone_bioset(bio_src, gfp_mask, bs, offset, size);
-}
-EXPORT_SYMBOL(bio_clone_bioset_partial);
-
-/**
  *	bio_add_pc_page	-	attempt to add page to bio
  *	@q: the target queue
  *	@bio: destination bio