IB/srpt: Limit the number of SG elements per work request

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@gmail.com>
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Sagi Grimberg <sagi@grimberg.me>
Cc: Steve Wise <swise@opengridcomputing.com>
Cc: Parav Pandit <pandit.parav@gmail.com>
Cc: Nicholas Bellinger <nab@linux-iscsi.org>
Cc: Laurence Oberman <loberman@redhat.com>
Cc: <stable@vger.kernel.org> #v4.7+
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Doug Ledford <dledford@redhat.com>

diff --git a/drivers/infiniband/ulp/srpt/ib_srpt.c b/drivers/infiniband/ulp/srpt/ib_srpt.c
index 4a41556..9a3b954 100644 (file)
--- 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_rdma_ch *ch)
        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);

diff --git a/drivers/infiniband/ulp/srpt/ib_srpt.h b/drivers/infiniband/ulp/srpt/ib_srpt.h
index 3890304..5818787 100644 (file)
--- 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,