[PATCH V4 07/12] block: prepare for supporting bio_list via other link

[Ming Lei <ming.lei@redhat.com>]

So far bio list helpers always use .bi_next to traverse the list, we
will support to link bios by other bio field.

Prepare for such support by adding a macro so that users can define
another helpers for linking bios by other bio field.

Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 include/linux/bio.h | 132 +++++++++++++++++++++++---------------------
 1 file changed, 68 insertions(+), 64 deletions(-)

diff --git a/include/linux/bio.h b/include/linux/bio.h
index d0246c92a6e8..619edd26a6c0 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -608,75 +608,11 @@ static inline unsigned bio_list_size(const struct bio_list *bl)
 	return sz;
 }
 
-static inline void bio_list_add(struct bio_list *bl, struct bio *bio)
-{
-	bio->bi_next = NULL;
-
-	if (bl->tail)
-		bl->tail->bi_next = bio;
-	else
-		bl->head = bio;
-
-	bl->tail = bio;
-}
-
-static inline void bio_list_add_head(struct bio_list *bl, struct bio *bio)
-{
-	bio->bi_next = bl->head;
-
-	bl->head = bio;
-
-	if (!bl->tail)
-		bl->tail = bio;
-}
-
-static inline void bio_list_merge(struct bio_list *bl, struct bio_list *bl2)
-{
-	if (!bl2->head)
-		return;
-
-	if (bl->tail)
-		bl->tail->bi_next = bl2->head;
-	else
-		bl->head = bl2->head;
-
-	bl->tail = bl2->tail;
-}
-
-static inline void bio_list_merge_head(struct bio_list *bl,
-				       struct bio_list *bl2)
-{
-	if (!bl2->head)
-		return;
-
-	if (bl->head)
-		bl2->tail->bi_next = bl->head;
-	else
-		bl->tail = bl2->tail;
-
-	bl->head = bl2->head;
-}
-
 static inline struct bio *bio_list_peek(struct bio_list *bl)
 {
 	return bl->head;
 }
 
-static inline struct bio *bio_list_pop(struct bio_list *bl)
-{
-	struct bio *bio = bl->head;
-
-	if (bio) {
-		bl->head = bl->head->bi_next;
-		if (!bl->head)
-			bl->tail = NULL;
-
-		bio->bi_next = NULL;
-	}
-
-	return bio;
-}
-
 static inline struct bio *bio_list_get(struct bio_list *bl)
 {
 	struct bio *bio = bl->head;
@@ -686,6 +622,74 @@ static inline struct bio *bio_list_get(struct bio_list *bl)
 	return bio;
 }
 
+#define BIO_LIST_HELPERS(_pre, link)					\
+									\
+static inline void _pre##_add(struct bio_list *bl, struct bio *bio)	\
+{									\
+	bio->bi_##link = NULL;						\
+									\
+	if (bl->tail)							\
+		bl->tail->bi_##link = bio;				\
+	else								\
+		bl->head = bio;						\
+									\
+	bl->tail = bio;							\
+}									\
+									\
+static inline void _pre##_add_head(struct bio_list *bl, struct bio *bio) \
+{									\
+	bio->bi_##link = bl->head;					\
+									\
+	bl->head = bio;							\
+									\
+	if (!bl->tail)							\
+		bl->tail = bio;						\
+}									\
+									\
+static inline void _pre##_merge(struct bio_list *bl, struct bio_list *bl2) \
+{									\
+	if (!bl2->head)							\
+		return;							\
+									\
+	if (bl->tail)							\
+		bl->tail->bi_##link = bl2->head;			\
+	else								\
+		bl->head = bl2->head;					\
+									\
+	bl->tail = bl2->tail;						\
+}									\
+									\
+static inline void _pre##_merge_head(struct bio_list *bl,		\
+				       struct bio_list *bl2)		\
+{									\
+	if (!bl2->head)							\
+		return;							\
+									\
+	if (bl->head)							\
+		bl2->tail->bi_##link = bl->head;			\
+	else								\
+		bl->tail = bl2->tail;					\
+									\
+	bl->head = bl2->head;						\
+}									\
+									\
+static inline struct bio *_pre##_pop(struct bio_list *bl)		\
+{									\
+	struct bio *bio = bl->head;					\
+									\
+	if (bio) {							\
+		bl->head = bl->head->bi_##link;				\
+		if (!bl->head)						\
+			bl->tail = NULL;				\
+									\
+		bio->bi_##link = NULL;					\
+	}								\
+									\
+	return bio;							\
+}									\
+
+BIO_LIST_HELPERS(bio_list, next);
+
 /*
  * Increment chain count for the bio. Make sure the CHAIN flag update
  * is visible before the raised count.
-- 
2.29.2