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, 3 insertions, 0 deletions

diff --git a/block/blk-settings.c b/block/blk-settings.c
index 8d592b559bd3..f8f2ddf20613 100644
--- a/block/blk-settings.c
+++ b/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);