block/scsi: Provide a limit on the number of integrity segments

Some controllers have a hardware limit on the number of protection
information scatter-gather list segments they can handle.

Introduce a max_integrity_segments limit in the block layer and provide
a new scsi_host_template setting that allows HBA drivers to provide a
value suitable for the hardware.

Add support for honoring the integrity segment limit when merging both
bios and requests.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <axboe@carl.home.kernel.dk>

block/blk-integrity.c

@@ -32,24 +32,37 @@ static struct kmem_cache *integrity_cachep;
 
 /**
  * blk_rq_count_integrity_sg - Count number of integrity scatterlist elements
- * @rq:		request with integrity metadata attached
+ * @q:		request queue
+ * @bio:	bio with integrity metadata attached
  *
  * Description: Returns the number of elements required in a
- * scatterlist corresponding to the integrity metadata in a request.
+ * scatterlist corresponding to the integrity metadata in a bio.
  */
-int blk_rq_count_integrity_sg(struct request *rq)
+int blk_rq_count_integrity_sg(struct request_queue *q, struct bio *bio)
 {
-	struct bio_vec *iv, *ivprv;
-	struct req_iterator iter;
-	unsigned int segments;
+	struct bio_vec *iv, *ivprv = NULL;
+	unsigned int segments = 0;
+	unsigned int seg_size = 0;
+	unsigned int i = 0;
 
-	ivprv = NULL;
-	segments = 0;
+	bio_for_each_integrity_vec(iv, bio, i) {
 
-	rq_for_each_integrity_segment(iv, rq, iter) {
+		if (ivprv) {
+			if (!BIOVEC_PHYS_MERGEABLE(ivprv, iv))
+				goto new_segment;
 
-		if (!ivprv || !BIOVEC_PHYS_MERGEABLE(ivprv, iv))
+			if (!BIOVEC_SEG_BOUNDARY(q, ivprv, iv))
+				goto new_segment;
+
+			if (seg_size + iv->bv_len > queue_max_segment_size(q))
+				goto new_segment;
+
+			seg_size += iv->bv_len;
+		} else {
+new_segment:
 			segments++;
+			seg_size = iv->bv_len;
+		}
 
 		ivprv = iv;
 	}
@@ -60,30 +73,34 @@ EXPORT_SYMBOL(blk_rq_count_integrity_sg);
 
 /**
  * blk_rq_map_integrity_sg - Map integrity metadata into a scatterlist
- * @rq:		request with integrity metadata attached
+ * @q:		request queue
+ * @bio:	bio with integrity metadata attached
  * @sglist:	target scatterlist
  *
  * 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().
  */
-int blk_rq_map_integrity_sg(struct request *rq, struct scatterlist *sglist)
+int blk_rq_map_integrity_sg(struct request_queue *q, struct bio *bio,
+			    struct scatterlist *sglist)
 {
-	struct bio_vec *iv, *ivprv;
-	struct req_iterator iter;
-	struct scatterlist *sg;
-	unsigned int segments;
+	struct bio_vec *iv, *ivprv = NULL;
+	struct scatterlist *sg = NULL;
+	unsigned int segments = 0;
+	unsigned int i = 0;
 
-	ivprv = NULL;
-	sg = NULL;
-	segments = 0;
-
-	rq_for_each_integrity_segment(iv, rq, iter) {
+	bio_for_each_integrity_vec(iv, bio, i) {
 
 		if (ivprv) {
 			if (!BIOVEC_PHYS_MERGEABLE(ivprv, iv))
 				goto new_segment;
 
+			if (!BIOVEC_SEG_BOUNDARY(q, ivprv, iv))
+				goto new_segment;
+
+			if (sg->length + iv->bv_len > queue_max_segment_size(q))
+				goto new_segment;
+
 			sg->length += iv->bv_len;
 		} else {
 new_segment:
@@ -162,6 +179,40 @@ int blk_integrity_compare(struct gendisk *gd1, struct gendisk *gd2)
 }
 EXPORT_SYMBOL(blk_integrity_compare);
 
+int blk_integrity_merge_rq(struct request_queue *q, struct request *req,
+			   struct request *next)
+{
+	if (blk_integrity_rq(req) != blk_integrity_rq(next))
+		return -1;
+
+	if (req->nr_integrity_segments + next->nr_integrity_segments >
+	    q->limits.max_integrity_segments)
+		return -1;
+
+	return 0;
+}
+EXPORT_SYMBOL(blk_integrity_merge_rq);
+
+int blk_integrity_merge_bio(struct request_queue *q, struct request *req,
+			    struct bio *bio)
+{
+	int nr_integrity_segs;
+	struct bio *next = bio->bi_next;
+
+	bio->bi_next = NULL;
+	nr_integrity_segs = blk_rq_count_integrity_sg(q, bio);
+	bio->bi_next = next;
+
+	if (req->nr_integrity_segments + nr_integrity_segs >
+	    q->limits.max_integrity_segments)
+		return -1;
+
+	req->nr_integrity_segments += nr_integrity_segs;
+
+	return 0;
+}
+EXPORT_SYMBOL(blk_integrity_merge_bio);
+
 struct integrity_sysfs_entry {
 	struct attribute attr;
 	ssize_t (*show)(struct blk_integrity *, char *);

block/blk-merge.c

@@ -205,12 +205,11 @@ static inline int ll_new_hw_segment(struct request_queue *q,
 {
 	int nr_phys_segs = bio_phys_segments(q, bio);
 
-	if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q)) {
-		req->cmd_flags |= REQ_NOMERGE;
-		if (req == q->last_merge)
-			q->last_merge = NULL;
-		return 0;
-	}
+	if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q))
+		goto no_merge;
+
+	if (bio_integrity(bio) && blk_integrity_merge_bio(q, req, bio))
+		goto no_merge;
 
 	/*
 	 * This will form the start of a new hw segment.  Bump both
@@ -218,6 +217,12 @@ static inline int ll_new_hw_segment(struct request_queue *q,
 	 */
 	req->nr_phys_segments += nr_phys_segs;
 	return 1;
+
+no_merge:
+	req->cmd_flags |= REQ_NOMERGE;
+	if (req == q->last_merge)
+		q->last_merge = NULL;
+	return 0;
 }
 
 int ll_back_merge_fn(struct request_queue *q, struct request *req,
@@ -301,6 +306,9 @@ static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
 	if (total_phys_segments > queue_max_segments(q))
 		return 0;
 
+	if (blk_integrity_rq(req) && blk_integrity_merge_rq(q, req, next))
+		return 0;
+
 	/* Merge is OK... */
 	req->nr_phys_segments = total_phys_segments;
 	return 1;
@@ -372,9 +380,6 @@ static int attempt_merge(struct request_queue *q, struct request *req,
 	    || next->special)
 		return 0;
 
-	if (blk_integrity_rq(req) != blk_integrity_rq(next))
-		return 0;
-
 	/*
 	 * If we are allowed to merge, then append bio list
 	 * from next to rq and release next. merge_requests_fn

block/blk-settings.c

@@ -111,6 +111,7 @@ EXPORT_SYMBOL_GPL(blk_queue_lld_busy);
 void blk_set_default_limits(struct queue_limits *lim)
 {
 	lim->max_segments = BLK_MAX_SEGMENTS;
+	lim->max_integrity_segments = 0;
 	lim->seg_boundary_mask = BLK_SEG_BOUNDARY_MASK;
 	lim->max_segment_size = BLK_MAX_SEGMENT_SIZE;
 	lim->max_sectors = BLK_DEF_MAX_SECTORS;
@@ -509,6 +510,8 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
 					    b->seg_boundary_mask);
 
 	t->max_segments = min_not_zero(t->max_segments, b->max_segments);
+	t->max_integrity_segments = min_not_zero(t->max_integrity_segments,
+						 b->max_integrity_segments);
 
 	t->max_segment_size = min_not_zero(t->max_segment_size,
 					   b->max_segment_size);

block/blk-sysfs.c

@@ -112,6 +112,11 @@ static ssize_t queue_max_segments_show(struct request_queue *q, char *page)
 	return queue_var_show(queue_max_segments(q), (page));
 }
 
+static ssize_t queue_max_integrity_segments_show(struct request_queue *q, char *page)
+{
+	return queue_var_show(q->limits.max_integrity_segments, (page));
+}
+
 static ssize_t queue_max_segment_size_show(struct request_queue *q, char *page)
 {
 	if (test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags))
@@ -288,6 +293,11 @@ static struct queue_sysfs_entry queue_max_segments_entry = {
 	.show = queue_max_segments_show,
 };
 
+static struct queue_sysfs_entry queue_max_integrity_segments_entry = {
+	.attr = {.name = "max_integrity_segments", .mode = S_IRUGO },
+	.show = queue_max_integrity_segments_show,
+};
+
 static struct queue_sysfs_entry queue_max_segment_size_entry = {
 	.attr = {.name = "max_segment_size", .mode = S_IRUGO },
 	.show = queue_max_segment_size_show,
@@ -375,6 +385,7 @@ static struct attribute *default_attrs[] = {
 	&queue_max_hw_sectors_entry.attr,
 	&queue_max_sectors_entry.attr,
 	&queue_max_segments_entry.attr,
+	&queue_max_integrity_segments_entry.attr,
 	&queue_max_segment_size_entry.attr,
 	&queue_iosched_entry.attr,
 	&queue_hw_sector_size_entry.attr,

block/blk.h

@@ -132,14 +132,6 @@ static inline int queue_congestion_off_threshold(struct request_queue *q)
 	return q->nr_congestion_off;
 }
 
-#if defined(CONFIG_BLK_DEV_INTEGRITY)
-
-#define rq_for_each_integrity_segment(bvl, _rq, _iter)		\
-	__rq_for_each_bio(_iter.bio, _rq)			\
-		bip_for_each_vec(bvl, _iter.bio->bi_integrity, _iter.i)
-
-#endif /* BLK_DEV_INTEGRITY */
-
 static inline int blk_cpu_to_group(int cpu)
 {
 #ifdef CONFIG_SCHED_MC