block: move the BIO_NO_PAGE_REF check into bio_release_pages

Move the BIO_NO_PAGE_REF check into bio_release_pages instead of
duplicating it in both callers.

Also make the function available outside of bio.c so that we can
reuse it in other direct I/O implementations.
Reviewed-by: Minwoo Im <minwoo.im.dev@gmail.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/bio.c

@@ -845,11 +845,14 @@ static void bio_get_pages(struct bio *bio)
 		get_page(bvec->bv_page);
 }
 
-static void bio_release_pages(struct bio *bio)
+void bio_release_pages(struct bio *bio)
 {
 	struct bvec_iter_all iter_all;
 	struct bio_vec *bvec;
 
+	if (bio_flagged(bio, BIO_NO_PAGE_REF))
+		return;
+
 	bio_for_each_segment_all(bvec, bio, iter_all)
 		put_page(bvec->bv_page);
 }
@@ -1681,7 +1684,6 @@ static void bio_dirty_fn(struct work_struct *work)
 		next = bio->bi_private;
 
 		bio_set_pages_dirty(bio);
-		if (!bio_flagged(bio, BIO_NO_PAGE_REF))
 		bio_release_pages(bio);
 		bio_put(bio);
 	}
@@ -1698,7 +1700,6 @@ void bio_check_pages_dirty(struct bio *bio)
 			goto defer;
 	}
 
-	if (!bio_flagged(bio, BIO_NO_PAGE_REF))
 	bio_release_pages(bio);
 	bio_put(bio);
 	return;

include/linux/bio.h

@@ -426,6 +426,7 @@ bool __bio_try_merge_page(struct bio *bio, struct page *page,
 void __bio_add_page(struct bio *bio, struct page *page,
 		unsigned int len, unsigned int off);
 int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter);
+void bio_release_pages(struct bio *bio);
 struct rq_map_data;
 extern struct bio *bio_map_user_iov(struct request_queue *,
 				    struct iov_iter *, gfp_t);