[PATCH] cifs: smbdirect: use the max_sge the hw reports

[Namjae Jeon <linkinjeon@kernel.org>]

In Soft-iWARP, smbdirect does not work in cifs client.
The hardcoding max_sge is large in cifs, but need smaller value for
soft-iWARP. Add SMBDIRECT_MIN_SGE macro as 6 and use the max_sge
the hw reports instead of hardcoding 16 sge's.

Cc: Tom Talpey <tom@talpey.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Hyunchul Lee <hyc.lee@gmail.com>
Cc: Long Li <longli@microsoft.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
---
 fs/cifs/smbdirect.c | 15 ++++++++++-----
 fs/cifs/smbdirect.h |  3 ++-
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/fs/cifs/smbdirect.c b/fs/cifs/smbdirect.c
index 5fbbec22bcc8..bb68702362f7 100644
--- a/fs/cifs/smbdirect.c
+++ b/fs/cifs/smbdirect.c
@@ -1518,7 +1518,7 @@ static int allocate_caches_and_workqueue(struct smbd_connection *info)
 static struct smbd_connection *_smbd_get_connection(
 	struct TCP_Server_Info *server, struct sockaddr *dstaddr, int port)
 {
-	int rc;
+	int rc, max_sge;
 	struct smbd_connection *info;
 	struct rdma_conn_param conn_param;
 	struct ib_qp_init_attr qp_attr;
@@ -1562,13 +1562,13 @@ static struct smbd_connection *_smbd_get_connection(
 	info->max_receive_size = smbd_max_receive_size;
 	info->keep_alive_interval = smbd_keep_alive_interval;
 
-	if (info->id->device->attrs.max_send_sge < SMBDIRECT_MAX_SGE) {
+	if (info->id->device->attrs.max_send_sge < SMBDIRECT_MIN_SGE) {
 		log_rdma_event(ERR,
 			"warning: device max_send_sge = %d too small\n",
 			info->id->device->attrs.max_send_sge);
 		log_rdma_event(ERR, "Queue Pair creation may fail\n");
 	}
-	if (info->id->device->attrs.max_recv_sge < SMBDIRECT_MAX_SGE) {
+	if (info->id->device->attrs.max_recv_sge < SMBDIRECT_MIN_SGE) {
 		log_rdma_event(ERR,
 			"warning: device max_recv_sge = %d too small\n",
 			info->id->device->attrs.max_recv_sge);
@@ -1593,13 +1593,18 @@ static struct smbd_connection *_smbd_get_connection(
 		goto alloc_cq_failed;
 	}
 
+	max_sge = min3(info->id->device->attrs.max_send_sge,
+		       info->id->device->attrs.max_recv_sge,
+		       SMBDIRECT_MAX_SGE);
+	max_sge = max(max_sge, SMBDIRECT_MIN_SGE);
+
 	memset(&qp_attr, 0, sizeof(qp_attr));
 	qp_attr.event_handler = smbd_qp_async_error_upcall;
 	qp_attr.qp_context = info;
 	qp_attr.cap.max_send_wr = info->send_credit_target;
 	qp_attr.cap.max_recv_wr = info->receive_credit_max;
-	qp_attr.cap.max_send_sge = SMBDIRECT_MAX_SGE;
-	qp_attr.cap.max_recv_sge = SMBDIRECT_MAX_SGE;
+	qp_attr.cap.max_send_sge = max_sge;
+	qp_attr.cap.max_recv_sge = max_sge;
 	qp_attr.cap.max_inline_data = 0;
 	qp_attr.sq_sig_type = IB_SIGNAL_REQ_WR;
 	qp_attr.qp_type = IB_QPT_RC;
diff --git a/fs/cifs/smbdirect.h b/fs/cifs/smbdirect.h
index a87fca82a796..8b81301e4d4c 100644
--- a/fs/cifs/smbdirect.h
+++ b/fs/cifs/smbdirect.h
@@ -225,7 +225,8 @@ struct smbd_buffer_descriptor_v1 {
 	__le32 length;
 } __packed;
 
-/* Default maximum number of SGEs in a RDMA send/recv */
+/* Default maximum/minimum number of SGEs in a RDMA send/recv */
+#define SMBDIRECT_MIN_SGE	6
 #define SMBDIRECT_MAX_SGE	16
 /* The context for a SMBD request */
 struct smbd_request {
-- 
2.25.1