[PATCH 3/4] block: don't bother iter advancing a fully done bio

[Jens Axboe <axboe@kernel.dk>]

If we're completing nbytes and nbytes is the size of the bio, don't bother
with calling into the iterator increment helpers. Just clear the bio
size and we're done.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 block/bio.c         |  4 ++--
 include/linux/bio.h | 13 +++++++++++--
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index a3c9ff23a036..874ff235aff7 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1289,7 +1289,7 @@ EXPORT_SYMBOL(submit_bio_wait);
  *
  * @bio will then represent the remaining, uncompleted portion of the io.
  */
-void bio_advance(struct bio *bio, unsigned bytes)
+void __bio_advance(struct bio *bio, unsigned bytes)
 {
 	if (bio_integrity(bio))
 		bio_integrity_advance(bio, bytes);
@@ -1297,7 +1297,7 @@ void bio_advance(struct bio *bio, unsigned bytes)
 	bio_crypt_advance(bio, bytes);
 	bio_advance_iter(bio, &bio->bi_iter, bytes);
 }
-EXPORT_SYMBOL(bio_advance);
+EXPORT_SYMBOL(__bio_advance);
 
 void bio_copy_data_iter(struct bio *dst, struct bvec_iter *dst_iter,
 			struct bio *src, struct bvec_iter *src_iter)
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 62d684b7dd4c..44b543e7baf6 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -119,6 +119,17 @@ static inline void bio_advance_iter_single(const struct bio *bio,
 		bvec_iter_advance_single(bio->bi_io_vec, iter, bytes);
 }
 
+extern void __bio_advance(struct bio *, unsigned);
+
+static inline void bio_advance(struct bio *bio, unsigned int nbytes)
+{
+	if (nbytes == bio->bi_iter.bi_size) {
+		bio->bi_iter.bi_size = 0;
+		return;
+	}
+	__bio_advance(bio, nbytes);
+}
+
 #define __bio_for_each_segment(bvl, bio, iter, start)			\
 	for (iter = (start);						\
 	     (iter).bi_size &&						\
@@ -381,8 +392,6 @@ static inline int bio_iov_vecs_to_alloc(struct iov_iter *iter, int max_segs)
 struct request_queue;
 
 extern int submit_bio_wait(struct bio *bio);
-extern void bio_advance(struct bio *, unsigned);
-
 extern void bio_init(struct bio *bio, struct bio_vec *table,
 		     unsigned short max_vecs);
 extern void bio_uninit(struct bio *);
-- 
2.33.0