[PATCH 4.7 157/186] IB/srpt: Limit the number of SG elements per work request

[Greg Kroah-Hartman]

4.7-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Bart Van Assche <bart.vanassche@xxxxxxxxxxx>

commit 30c6d8773de06878f920666d8c945f81cb2081b3 upstream.

Limit the number of SG elements per work request to what the HCA
and the queue pair support.

Fixes: 34693573fde0 ("IB/srpt: Reduce QP buffer size")
Reported-by: Parav Pandit <pandit.parav@xxxxxxxxx>
Signed-off-by: Bart Van Assche <bart.vanassche@xxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Sagi Grimberg <sagi@xxxxxxxxxxx>
Cc: Steve Wise <swise@xxxxxxxxxxxxxxxxxxxxx>
Cc: Parav Pandit <pandit.parav@xxxxxxxxx>
Cc: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
Cc: Laurence Oberman <loberman@xxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Doug Ledford <dledford@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/infiniband/ulp/srpt/ib_srpt.c |    3 ++-
 drivers/infiniband/ulp/srpt/ib_srpt.h |    6 +++++-
 2 files changed, 7 insertions(+), 2 deletions(-)

--- a/drivers/infiniband/ulp/srpt/ib_srpt.c
+++ b/drivers/infiniband/ulp/srpt/ib_srpt.c
@@ -1601,6 +1601,7 @@ static int srpt_create_ch_ib(struct srpt
 	struct ib_qp_init_attr *qp_init;
 	struct srpt_port *sport = ch->sport;
 	struct srpt_device *sdev = sport->sdev;
+	const struct ib_device_attr *attrs = &sdev->device->attrs;
 	u32 srp_sq_size = sport->port_attrib.srp_sq_size;
 	int ret;
 
@@ -1638,7 +1639,7 @@ retry:
 	 */
 	qp_init->cap.max_send_wr = srp_sq_size / 2;
 	qp_init->cap.max_rdma_ctxs = srp_sq_size / 2;
-	qp_init->cap.max_send_sge = SRPT_DEF_SG_PER_WQE;
+	qp_init->cap.max_send_sge = min(attrs->max_sge, SRPT_MAX_SG_PER_WQE);
 	qp_init->port_num = ch->sport->port;
 
 	ch->qp = ib_create_qp(sdev->pd, qp_init);
--- a/drivers/infiniband/ulp/srpt/ib_srpt.h
+++ b/drivers/infiniband/ulp/srpt/ib_srpt.h
@@ -106,7 +106,11 @@ enum {
 	SRP_LOGIN_RSP_MULTICHAN_MAINTAINED = 0x2,
 
 	SRPT_DEF_SG_TABLESIZE = 128,
-	SRPT_DEF_SG_PER_WQE = 16,
+	/*
+	 * An experimentally determined value that avoids that QP creation
+	 * fails due to "swiotlb buffer is full" on systems using the swiotlb.
+	 */
+	SRPT_MAX_SG_PER_WQE = 16,
 
 	MIN_SRPT_SQ_SIZE = 16,
 	DEF_SRPT_SQ_SIZE = 4096,