blk-integrity: improved sg segment mapping

Make the integrity mapping more like data mapping, blk_rq_map_sg. Use
the request to validate the segment count, and update the callers so
they don't have to.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Link: https://lore.kernel.org/r/20240913191746.2628196-1-kbusch@meta.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: keithbusch

block/blk-integrity.c

@@ -62,19 +62,20 @@ int blk_rq_count_integrity_sg(struct request_queue *q, struct bio *bio)
  *
  * Description: Map the integrity vectors in request into a
  * scatterlist.  The scatterlist must be big enough to hold all
- * elements.  I.e. sized using blk_rq_count_integrity_sg().
+ * elements.  I.e. sized using blk_rq_count_integrity_sg() or
+ * rq->nr_integrity_segments.
  */
-int blk_rq_map_integrity_sg(struct request_queue *q, struct bio *bio,
-			    struct scatterlist *sglist)
+int blk_rq_map_integrity_sg(struct request *rq, struct scatterlist *sglist)
 {
 	struct bio_vec iv, ivprv = { NULL };
+	struct request_queue *q = rq->q;
 	struct scatterlist *sg = NULL;
+	struct bio *bio = rq->bio;
 	unsigned int segments = 0;
 	struct bvec_iter iter;
 	int prev = 0;
 
 	bio_for_each_integrity_vec(iv, bio, iter) {
-
 		if (prev) {
 			if (!biovec_phys_mergeable(q, &ivprv, &iv))
 				goto new_segment;
@@ -102,6 +103,12 @@ int blk_rq_map_integrity_sg(struct request_queue *q, struct bio *bio,
 	if (sg)
 		sg_mark_end(sg);
 
+	/*
+	 * Something must have been wrong if the figured number of segment
+	 * is bigger than number of req's physical integrity segments
+	 */
+	BUG_ON(segments > rq->nr_integrity_segments);
+	BUG_ON(segments > queue_max_integrity_segments(q));
 	return segments;
 }
 EXPORT_SYMBOL(blk_rq_map_integrity_sg);

drivers/nvme/host/rdma.c

@@ -1504,8 +1504,8 @@ static int nvme_rdma_dma_map_req(struct ib_device *ibdev, struct request *rq,
 			goto out_unmap_sg;
 		}
 
-		req->metadata_sgl->nents = blk_rq_map_integrity_sg(rq->q,
-				rq->bio, req->metadata_sgl->sg_table.sgl);
+		req->metadata_sgl->nents = blk_rq_map_integrity_sg(rq,
+				req->metadata_sgl->sg_table.sgl);
 		*pi_count = ib_dma_map_sg(ibdev,
 					  req->metadata_sgl->sg_table.sgl,
 					  req->metadata_sgl->nents,

drivers/scsi/scsi_lib.c

@@ -1163,7 +1163,6 @@ blk_status_t scsi_alloc_sgtables(struct scsi_cmnd *cmd)
 
 	if (blk_integrity_rq(rq)) {
 		struct scsi_data_buffer *prot_sdb = cmd->prot_sdb;
-		int ivecs;
 
 		if (WARN_ON_ONCE(!prot_sdb)) {
 			/*
@@ -1175,19 +1174,15 @@ blk_status_t scsi_alloc_sgtables(struct scsi_cmnd *cmd)
 			goto out_free_sgtables;
 		}
 
-		ivecs = rq->nr_integrity_segments;
-		if (sg_alloc_table_chained(&prot_sdb->table, ivecs,
+		if (sg_alloc_table_chained(&prot_sdb->table,
+				rq->nr_integrity_segments,
 				prot_sdb->table.sgl,
 				SCSI_INLINE_PROT_SG_CNT)) {
 			ret = BLK_STS_RESOURCE;
 			goto out_free_sgtables;
 		}
 
-		count = blk_rq_map_integrity_sg(rq->q, rq->bio,
-						prot_sdb->table.sgl);
-		BUG_ON(count > ivecs);
-		BUG_ON(count > queue_max_integrity_segments(rq->q));
-
+		count = blk_rq_map_integrity_sg(rq, prot_sdb->table.sgl);
 		cmd->prot_sdb = prot_sdb;
 		cmd->prot_sdb->table.nents = count;
 	}

include/linux/blk-integrity.h

@@ -25,8 +25,7 @@ static inline bool queue_limits_stack_integrity_bdev(struct queue_limits *t,
 }
 
 #ifdef CONFIG_BLK_DEV_INTEGRITY
-int blk_rq_map_integrity_sg(struct request_queue *, struct bio *,
-				   struct scatterlist *);
+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, u32 seed);
@@ -98,8 +97,7 @@ static inline int blk_rq_count_integrity_sg(struct request_queue *q,
 {
 	return 0;
 }
-static inline int blk_rq_map_integrity_sg(struct request_queue *q,
-					  struct bio *b,
+static inline int blk_rq_map_integrity_sg(struct request *q,
 					  struct scatterlist *s)
 {
 	return 0;