[PATCH 3/4 v3] IB/srp: adjust can_queue

[Bart Van Assche <bvanassche-HInyCGIudOg@public.gmane.org>]

The SRP (draft) standard specifies that an SRP initiator must never queue more
than (SRP request limit) - 1 unanswered SRP_CMD information units. This patch
makes sure that the SCSI mid-layer never tries to queue more than (SRP request
limit) - 1 SCSI commands to ib_srp. This improves performance for targets
whose request limit is less than or equal to SRP_SQ_REQ_SIZE (63) by reducing
the number of BUSY responses reported by ib_srp to the SCSI mid-layer.

Signed-off-by: Bart Van Assche <bart.vanassche-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: Roland Dreier <rolandd-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org>
Cc: David Dillow <dave-i1Mk8JYDVaaSihdK6806/g@public.gmane.org>

---
 drivers/infiniband/ulp/srp/ib_srp.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/infiniband/ulp/srp/ib_srp.c b/drivers/infiniband/ulp/srp/ib_srp.c
index 1c40ac3..4efda6c 100644
--- a/drivers/infiniband/ulp/srp/ib_srp.c
+++ b/drivers/infiniband/ulp/srp/ib_srp.c
@@ -1436,7 +1436,7 @@ static int srp_cm_handler(struct ib_cm_id *cm_id, struct ib_cm_event *event)
 			target->max_ti_iu_len = be32_to_cpu(rsp->max_ti_iu_len);
 			target->req_lim       = be32_to_cpu(rsp->req_lim_delta);
 
-			target->scsi_host->can_queue = min(target->req_lim,
+			target->scsi_host->can_queue = min(target->req_lim - 1,
 							   target->scsi_host->can_queue);
 		} else {
 			shost_printk(KERN_WARNING, target->scsi_host,
-- 
1.6.4.2
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