[SCSI] add use_sg_chaining option to scsi_host_template

This option is true if a low-level driver can support sg
chaining. This will be removed eventually when all the drivers are
converted to support sg chaining. q->max_phys_segments is set to
SCSI_MAX_SG_SEGMENTS if false.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index c75cb6ad6d94..b6e6d801768b 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1645,7 +1645,10 @@ struct request_queue *__scsi_alloc_queue(struct Scsi_Host *shost,
          * converted, so better keep it safe.
          */
 #ifdef ARCH_HAS_SG_CHAIN
-        blk_queue_max_phys_segments(q, SCSI_MAX_SG_CHAIN_SEGMENTS);
+        if (shost->use_sg_chaining)
+                blk_queue_max_phys_segments(q, SCSI_MAX_SG_CHAIN_SEGMENTS);
+        else
+                blk_queue_max_phys_segments(q, SCSI_MAX_SG_SEGMENTS);
 #else
         blk_queue_max_phys_segments(q, SCSI_MAX_SG_SEGMENTS);
 #endif