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>
diff --git a/block/bio.c b/block/bio.c
index bb55b94..b35356c 100644
--- a/block/bio.c
+++ b/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);
 }
@@ -1681,8 +1684,7 @@ 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_release_pages(bio);
 		bio_put(bio);
 	}
 }
@@ -1698,8 +1700,7 @@ void bio_check_pages_dirty(struct bio *bio)
 			goto defer;
 	}
 
-	if (!bio_flagged(bio, BIO_NO_PAGE_REF))
-		bio_release_pages(bio);
+	bio_release_pages(bio);
 	bio_put(bio);
 	return;
 defer: