[PATCH V4 5/5] RDMA/isert: Limit read depth based on the device max_sge_rd capability

Steve Wise
2015-07-02T15:16:30Z

Use the device's max_sge_rd capability to compute the target's read sge
depth. Save both the read and write max_sge values in the isert_conn
struct, and use these when creating RDMA_WRITE/READ work requests.

Signed-off-by: Steve Wise <swise-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org>
Reviewed-by: Sagi Grimberg <sagig-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
---
drivers/infiniband/ulp/isert/ib_isert.c | 31 +++++++++++++++++++++++--------
drivers/infiniband/ulp/isert/ib_isert.h | 3 ++-
2 files changed, 25 insertions(+), 9 deletions(-)

diff --git a/drivers/infiniband/ulp/isert/ib_isert.c b/drivers/infiniband/ulp/isert/ib_isert.c
index 2737ade..c2c7037 100644
--- a/drivers/infiniband/ulp/isert/ib_isert.c
+++ b/drivers/infiniband/ulp/isert/ib_isert.c
@@ -163,7 +163,9 @@ isert_create_qp(struct isert_conn *isert_conn,
* outgoing control PDU responses.
*/
attr.cap.max_send_sge = max(2, device->dev_attr.max_sge - 2);
- isert_conn->max_sge = attr.cap.max_send_sge;
+ isert_conn->max_write_sge = attr.cap.max_send_sge;
+ isert_conn->max_read_sge = min_t(u32, device->dev_attr.max_sge_rd,
+ attr.cap.max_send_sge);

attr.cap.max_recv_sge = 1;
attr.sq_sig_type = IB_SIGNAL_REQ_WR;
@@ -2376,7 +2378,7 @@ isert_put_text_rsp(struct iscsi_cmd *cmd, struct iscsi_conn *conn)
static int
isert_build_rdma_wr(struct isert_conn *isert_conn, struct isert_cmd *isert_cmd,
struct ib_sge *ib_sge, struct ib_send_wr *send_wr,
- u32 data_left, u32 offset)
+ u32 data_left, u32 offset, u32 max_sge)
{
struct iscsi_cmd *cmd = isert_cmd->iscsi_cmd;
struct scatterlist *sg_start, *tmp_sg;
@@ -2387,7 +2389,7 @@ isert_build_rdma_wr(struct isert_conn *isert_conn, struct isert_cmd *isert_cmd,

sg_off = offset / PAGE_SIZE;
sg_start = &cmd->se_cmd.t_data_sg[sg_off];
- sg_nents = min(cmd->se_cmd.t_data_nents - sg_off, isert_conn->max_sge);
+ sg_nents = min(cmd->se_cmd.t_data_nents - sg_off, max_sge);
page_off = offset % PAGE_SIZE;

send_wr->sg_list = ib_sge;
@@ -2431,8 +2433,9 @@ isert_map_rdma(struct iscsi_conn *conn, struct iscsi_cmd *cmd,
struct isert_data_buf *data = &wr->data;
struct ib_send_wr *send_wr;
struct ib_sge *ib_sge;
- u32 offset, data_len, data_left, rdma_write_max, va_offset = 0;
+ u32 offset, data_len, data_left, rdma_max_len, va_offset = 0;
int ret = 0, i, ib_sge_cnt;
+ u32 max_sge;

isert_cmd->tx_desc.isert_cmd = isert_cmd;

@@ -2454,7 +2457,12 @@ isert_map_rdma(struct iscsi_conn *conn, struct iscsi_cmd *cmd,
}
wr->ib_sge = ib_sge;

- wr->send_wr_num = DIV_ROUND_UP(data->nents, isert_conn->max_sge);
+ if (wr->iser_ib_op == ISER_IB_RDMA_WRITE)
+ max_sge = isert_conn->max_write_sge;
+ else
+ max_sge = isert_conn->max_read_sge;
+
+ wr->send_wr_num = DIV_ROUND_UP(data->nents, max_sge);
wr->send_wr = kzalloc(sizeof(struct ib_send_wr) * wr->send_wr_num,
GFP_KERNEL);
if (!wr->send_wr) {
@@ -2464,11 +2472,11 @@ isert_map_rdma(struct iscsi_conn *conn, struct iscsi_cmd *cmd,
}

wr->isert_cmd = isert_cmd;
- rdma_write_max = isert_conn->max_sge * PAGE_SIZE;
+ rdma_max_len = max_sge * PAGE_SIZE;

for (i = 0; i < wr->send_wr_num; i++) {
send_wr = &isert_cmd->rdma_wr.send_wr[i];
- data_len = min(data_left, rdma_write_max);
+ data_len = min(data_left, rdma_max_len);

send_wr->send_flags = 0;
if (wr->iser_ib_op == ISER_IB_RDMA_WRITE) {
@@ -2490,7 +2498,7 @@ isert_map_rdma(struct iscsi_conn *conn, struct iscsi_cmd *cmd,
}

ib_sge_cnt = isert_build_rdma_wr(isert_conn, isert_cmd, ib_sge,
- send_wr, data_len, offset);
+ send_wr, data_len, offset, max_sge);
ib_sge += ib_sge_cnt;

offset += data_len;
@@ -2619,6 +2627,13 @@ isert_fast_reg_mr(struct isert_conn *isert_conn,
fr_wr.wr.fast_reg.rkey = mr->rkey;
fr_wr.wr.fast_reg.access_flags = IB_ACCESS_LOCAL_WRITE;

+ /*
+ * IWARP transports need REMOTE_WRITE for MRs used as the target of
+ * an RDMA_READ.
+ */
+ if (rdma_protocol_iwarp(ib_dev, isert_conn->cm_id->port_num))
+ fr_wr.wr.fast_reg.access_flags |= IB_ACCESS_REMOTE_WRITE;
+
if (!wr)
wr = &fr_wr;
else
diff --git a/drivers/infiniband/ulp/isert/ib_isert.h b/drivers/infiniband/ulp/isert/ib_isert.h
index 9ec23a7..29fde27 100644
--- a/drivers/infiniband/ulp/isert/ib_isert.h
+++ b/drivers/infiniband/ulp/isert/ib_isert.h
@@ -152,7 +152,8 @@ struct isert_conn {
u32 responder_resources;
u32 initiator_depth;
bool pi_support;
- u32 max_sge;
+ u32 max_write_sge;
+ u32 max_read_sge;
char *login_buf;
char *login_req_buf;
char *login_rsp_buf;