[PATCHv3 6/7] blk-mq-dma: add support for mapping integrity metadata

[Keith Busch <kbusch@meta.com>]

From: Keith Busch <kbusch@kernel.org>

Provide integrity metadata helpers equivalent to the data payload
helpers for iterating a request for dma setup.

Signed-off-by: Keith Busch <kbusch@kernel.org>
---
 block/blk-mq-dma.c            | 54 +++++++++++++++++++++++++++++++----
 include/linux/blk-integrity.h | 17 +++++++++++
 include/linux/blk-mq-dma.h    |  1 +
 3 files changed, 67 insertions(+), 5 deletions(-)

diff --git a/block/blk-mq-dma.c b/block/blk-mq-dma.c
index 646caa00a0485..708fb6f51efc7 100644
--- a/block/blk-mq-dma.c
+++ b/block/blk-mq-dma.c
@@ -2,9 +2,28 @@
 /*
  * Copyright (C) 2025 Christoph Hellwig
  */
+#include <linux/blk-integrity.h>
 #include <linux/blk-mq-dma.h>
 #include "blk.h"
 
+static bool __blk_map_iter_next(struct blk_map_iter *iter)
+{
+	if (iter->iter.bi_size)
+		return true;
+	if (!iter->bio->bi_next)
+		return false;
+
+	iter->bio = iter->bio->bi_next;
+	if (iter->is_integrity) {
+		iter->iter = iter->bio->bi_integrity->bip_iter;
+		iter->bvec = iter->bio->bi_integrity->bip_vec;
+	} else {
+		iter->iter = iter->bio->bi_iter;
+		iter->bvec = iter->bio->bi_io_vec;
+	}
+	return true;
+}
+
 static bool blk_map_iter_next(struct request *req, struct blk_map_iter *iter)
 {
 	unsigned int max_size;
@@ -31,11 +50,8 @@ static bool blk_map_iter_next(struct request *req, struct blk_map_iter *iter)
 	       (!iter->iter.bi_bvec_done && iter->bio->bi_next)) {
 		struct bio_vec next;
 
-		if (!iter->iter.bi_size) {
-			iter->bio = iter->bio->bi_next;
-			iter->iter = iter->bio->bi_iter;
-			iter->bvec = iter->bio->bi_io_vec;
-		}
+		if (!__blk_map_iter_next(iter))
+			break;
 
 		next = mp_bvec_iter_bvec(iter->bvec, iter->iter);
 		if (bv.bv_len + next.bv_len > max_size ||
@@ -178,6 +194,7 @@ bool blk_rq_dma_map_iter_start(struct request *req, struct device *dma_dev,
 		struct dma_iova_state *state, struct blk_dma_iter *iter)
 {
 	iter->iter.iter = req->bio->bi_iter;
+	iter->iter.is_integrity = false;
 	if (req->rq_flags & RQF_SPECIAL_PAYLOAD)
 		iter->iter.bvec = &req->special_vec;
 	else
@@ -218,6 +235,33 @@ bool blk_rq_dma_map_iter_next(struct request *req, struct device *dma_dev,
 }
 EXPORT_SYMBOL_GPL(blk_rq_dma_map_iter_next);
 
+#ifdef CONFIG_BLK_DEV_INTEGRITY
+bool blk_rq_integrity_dma_map_iter_start(struct request *req,
+		struct device *dma_dev,  struct dma_iova_state *state,
+		struct blk_dma_iter *iter)
+{
+	unsigned len = bio_integrity_bytes(&req->q->limits.integrity,
+					   blk_rq_sectors(req));
+	iter->iter.iter = req->bio->bi_integrity->bip_iter;
+	iter->iter.bvec = req->bio->bi_integrity->bip_vec;
+	iter->iter.is_integrity = true;
+	return blk_dma_map_iter_start(req, dma_dev, state, iter, len);
+}
+EXPORT_SYMBOL_GPL(blk_rq_integrity_dma_map_iter_start);
+
+bool blk_rq_integrity_dma_map_iter_next(struct request *req,
+               struct device *dma_dev, struct blk_dma_iter *iter)
+{
+	if (!blk_map_iter_next(req, &iter->iter))
+		return false;
+
+	if (iter->p2pdma.map == PCI_P2PDMA_MAP_BUS_ADDR)
+		return blk_dma_map_bus(iter);
+	return blk_dma_map_direct(req, dma_dev, iter);
+}
+EXPORT_SYMBOL_GPL(blk_rq_integrity_dma_map_iter_next);
+#endif
+
 static inline struct scatterlist *
 blk_next_sg(struct scatterlist **sg, struct scatterlist *sglist)
 {
diff --git a/include/linux/blk-integrity.h b/include/linux/blk-integrity.h
index c7eae0bfb013f..1ef0c373297b3 100644
--- a/include/linux/blk-integrity.h
+++ b/include/linux/blk-integrity.h
@@ -4,6 +4,7 @@
 
 #include <linux/blk-mq.h>
 #include <linux/bio-integrity.h>
+#include <linux/blk-mq-dma.h>
 
 struct request;
 
@@ -29,6 +30,11 @@ int blk_rq_map_integrity_sg(struct request *, struct scatterlist *);
 int blk_rq_count_integrity_sg(struct request_queue *, struct bio *);
 int blk_rq_integrity_map_user(struct request *rq, void __user *ubuf,
 			      ssize_t bytes);
+bool blk_rq_integrity_dma_map_iter_start(struct request *req,
+		struct device *dma_dev,  struct dma_iova_state *state,
+		struct blk_dma_iter *iter);
+bool blk_rq_integrity_dma_map_iter_next(struct request *req,
+		struct device *dma_dev, struct blk_dma_iter *iter);
 
 static inline bool
 blk_integrity_queue_supports_integrity(struct request_queue *q)
@@ -108,6 +114,17 @@ static inline int blk_rq_integrity_map_user(struct request *rq,
 {
 	return -EINVAL;
 }
+static inline bool blk_rq_integrity_dma_map_iter_start(struct request *req,
+		struct device *dma_dev,  struct dma_iova_state *state,
+		struct blk_dma_iter *iter)
+{
+	return false;
+}
+static inline bool blk_rq_integrity_dma_map_iter_next(struct request *req,
+		struct device *dma_dev, struct blk_dma_iter *iter)
+{
+	return false;
+}
 static inline struct blk_integrity *bdev_get_integrity(struct block_device *b)
 {
 	return NULL;
diff --git a/include/linux/blk-mq-dma.h b/include/linux/blk-mq-dma.h
index aef8d784952ff..4b7b85f9e23e6 100644
--- a/include/linux/blk-mq-dma.h
+++ b/include/linux/blk-mq-dma.h
@@ -11,6 +11,7 @@ struct blk_map_iter {
 	struct bio_vec                  *bvec;
 	struct bvec_iter		iter;
 	struct bio			*bio;
+	bool				is_integrity;
 };
 
 struct blk_dma_iter {
-- 
2.47.3