From: Long Li <longli@xxxxxxxxxxxxx>
SMB client and server maintain a credit system on the SMBD transport. Credits are used to tell when the client or server can send a packet to the peer, based on current memory or resource usage.
Signed-off-by: Long Li <longli@xxxxxxxxxxxxx>
---
fs/cifs/cifsrdma.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 45 insertions(+)
diff --git a/fs/cifs/cifsrdma.c b/fs/cifs/cifsrdma.c
index eb48651..97cde3f 100644
--- a/fs/cifs/cifsrdma.c
+++ b/fs/cifs/cifsrdma.c
@@ -575,6 +575,46 @@ static int cifs_rdma_post_send_negotiate_req(struct cifs_rdma_info *info)
}
/*
+ * Extend the credits to remote peer
+ * This implements [MS-SMBD] 3.1.5.9
+ * The idea is that we should extend credits to remote peer as quickly as
+ * it's allowed, to maintain data flow. We allocate as much as receive
+ * buffer as possible, and extend the receive credits to remote peer
+ * return value: the new credtis being granted.
+ */
+static int manage_credits_prior_sending(struct cifs_rdma_info *info)
+{
+ int ret = 0;
+ struct cifs_rdma_response *response;
+ int rc;
+
+ if (atomic_read(&info->receive_credit_target) >
+ atomic_read(&info->receive_credits)) {
+ while (true) {
+ response = get_receive_buffer(info);
+ if (!response)
+ break;
+
+ response->type = SMBD_TRANSFER_DATA;
+ response->first_segment = false;
+ rc = cifs_rdma_post_recv(info, response);
+ if (rc) {
+ log_rdma_recv("post_recv failed rc=%d\n", rc);
+ put_receive_buffer(info, response);
+ break;
+ }
+
+ ret++;
+ }
+ }
+
+ atomic_add(ret, &info->receive_credits);
+ log_transport_credit(info);
+
+ return ret;
+}
+
+/*
* Send a page
* page: the page to send
* offset: offset in the page to send
@@ -607,6 +647,8 @@ static int cifs_rdma_post_send_page(struct cifs_rdma_info *info, struct page *pa
packet = (struct smbd_data_transfer *) request->packet;
packet->credits_requested = cpu_to_le16(info->send_credit_target);
+ packet->credits_granted =
+ cpu_to_le16(manage_credits_prior_sending(info));
packet->flags = cpu_to_le16(0);
packet->reserved = cpu_to_le16(0);
@@ -718,6 +760,8 @@ static int cifs_rdma_post_send_empty(struct cifs_rdma_info *info)
request->info = info;
packet = (struct smbd_data_transfer_no_data *) request->packet;
+ credits_granted = manage_credits_prior_sending(info);
+
/* nothing to do? */
if (credits_granted==0 && flags==0) {
mempool_free(request, info->request_mempool);
@@ -827,6 +871,7 @@ static int cifs_rdma_post_send_data(
packet = (struct smbd_data_transfer *) request->packet;
packet->credits_requested = cpu_to_le16(info->send_credit_target);
+ packet->credits_granted = cpu_to_le16(manage_credits_prior_sending(info));
packet->flags = cpu_to_le16(0);
packet->reserved = cpu_to_le16(0);
--
2.7.4
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