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>

1 files changed, 14 insertions, 9 deletions

diff --git a/block/blk-merge.c b/block/blk-merge.c
index 3b0cd4249671..6a725461654d 100644
--- a/block/blk-merge.c
+++ b/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