ksmbd: improve credits management

* Requests except READ, WRITE, IOCTL, INFO, QUERY
DIRECOTRY, CANCEL must consume one credit.
* If client's granted credits are insufficient,
refuse to handle requests.
* Windows server 2016 or later grant up to 8192
credits to clients at once.

Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Hyunchul Lee <hyc.lee@gmail.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/ksmbd/connection.c

@@ -61,6 +61,8 @@ struct ksmbd_conn *ksmbd_conn_alloc(void)
 		conn->local_nls = load_nls_default();
 	atomic_set(&conn->req_running, 0);
 	atomic_set(&conn->r_count, 0);
+	conn->total_credits = 1;
+
 	init_waitqueue_head(&conn->req_running_q);
 	INIT_LIST_HEAD(&conn->conns_list);
 	INIT_LIST_HEAD(&conn->sessions);

fs/ksmbd/smb2misc.c

@@ -284,11 +284,13 @@ static inline int smb2_ioctl_resp_len(struct smb2_ioctl_req *h)
 		le32_to_cpu(h->MaxOutputResponse);
 }
 
-static int smb2_validate_credit_charge(struct smb2_hdr *hdr)
+static int smb2_validate_credit_charge(struct ksmbd_conn *conn,
+				       struct smb2_hdr *hdr)
 {
-	int req_len = 0, expect_resp_len = 0, calc_credit_num, max_len;
-	int credit_charge = le16_to_cpu(hdr->CreditCharge);
+	unsigned int req_len = 0, expect_resp_len = 0, calc_credit_num, max_len;
+	unsigned short credit_charge = le16_to_cpu(hdr->CreditCharge);
 	void *__hdr = hdr;
+	int ret;
 
 	switch (hdr->Command) {
 	case SMB2_QUERY_INFO:
@@ -310,21 +312,37 @@ static int smb2_validate_credit_charge(struct smb2_hdr *hdr)
 		req_len = smb2_ioctl_req_len(__hdr);
 		expect_resp_len = smb2_ioctl_resp_len(__hdr);
 		break;
-	default:
+	case SMB2_CANCEL:
 		return 0;
+	default:
+		req_len = 1;
+		break;
 	}
 
-	credit_charge = max(1, credit_charge);
-	max_len = max(req_len, expect_resp_len);
+	credit_charge = max_t(unsigned short, credit_charge, 1);
+	max_len = max_t(unsigned int, req_len, expect_resp_len);
 	calc_credit_num = DIV_ROUND_UP(max_len, SMB2_MAX_BUFFER_SIZE);
 
 	if (credit_charge < calc_credit_num) {
-		pr_err("Insufficient credit charge, given: %d, needed: %d\n",
-		       credit_charge, calc_credit_num);
+		ksmbd_debug(SMB, "Insufficient credit charge, given: %d, needed: %d\n",
+			    credit_charge, calc_credit_num);
+		return 1;
+	} else if (credit_charge > conn->max_credits) {
+		ksmbd_debug(SMB, "Too large credit charge: %d\n", credit_charge);
 		return 1;
 	}
 
-	return 0;
+	spin_lock(&conn->credits_lock);
+	if (credit_charge <= conn->total_credits) {
+		conn->total_credits -= credit_charge;
+		ret = 0;
+	} else {
+		ksmbd_debug(SMB, "Insufficient credits granted, given: %u, granted: %u\n",
+			    credit_charge, conn->total_credits);
+		ret = 1;
+	}
+	spin_unlock(&conn->credits_lock);
+	return ret;
 }
 
 int ksmbd_smb2_check_message(struct ksmbd_work *work)
@@ -383,7 +401,7 @@ int ksmbd_smb2_check_message(struct ksmbd_work *work)
 	}
 
 	if ((work->conn->vals->capabilities & SMB2_GLOBAL_CAP_LARGE_MTU) &&
-	    smb2_validate_credit_charge(hdr)) {
+	    smb2_validate_credit_charge(work->conn, hdr)) {
 		work->conn->ops->set_rsp_status(work, STATUS_INVALID_PARAMETER);
 		return 1;
 	}

fs/ksmbd/smb2pdu.c

@@ -292,22 +292,6 @@ int init_smb2_neg_rsp(struct ksmbd_work *work)
 	return 0;
 }
 
-static int smb2_consume_credit_charge(struct ksmbd_work *work,
-				      unsigned short credit_charge)
-{
-	struct ksmbd_conn *conn = work->conn;
-	unsigned int rsp_credits = 1;
-
-	if (!conn->total_credits)
-		return 0;
-
-	if (credit_charge > 0)
-		rsp_credits = credit_charge;
-
-	conn->total_credits -= rsp_credits;
-	return rsp_credits;
-}
-
 /**
  * smb2_set_rsp_credits() - set number of credits in response buffer
  * @work:	smb work containing smb response buffer
@@ -317,49 +301,43 @@ int smb2_set_rsp_credits(struct ksmbd_work *work)
 	struct smb2_hdr *req_hdr = ksmbd_req_buf_next(work);
 	struct smb2_hdr *hdr = ksmbd_resp_buf_next(work);
 	struct ksmbd_conn *conn = work->conn;
-	unsigned short credits_requested = le16_to_cpu(req_hdr->CreditRequest);
-	unsigned short credit_charge = 1, credits_granted = 0;
-	unsigned short aux_max, aux_credits, min_credits;
-	int rsp_credit_charge;
+	unsigned short credits_requested;
+	unsigned short credit_charge, credits_granted = 0;
+	unsigned short aux_max, aux_credits;
 
-	if (hdr->Command == SMB2_CANCEL)
-		goto out;
+	if (work->send_no_response)
+		return 0;
 
-	/* get default minimum credits by shifting maximum credits by 4 */
-	min_credits = conn->max_credits >> 4;
+	hdr->CreditCharge = req_hdr->CreditCharge;
 
-	if (conn->total_credits >= conn->max_credits) {
+	if (conn->total_credits > conn->max_credits) {
+		hdr->CreditRequest = 0;
 		pr_err("Total credits overflow: %d\n", conn->total_credits);
-		conn->total_credits = min_credits;
-	}
-
-	rsp_credit_charge =
-		smb2_consume_credit_charge(work, le16_to_cpu(req_hdr->CreditCharge));
-	if (rsp_credit_charge < 0)
 		return -EINVAL;
+	}
 
-	hdr->CreditCharge = cpu_to_le16(rsp_credit_charge);
+	credit_charge = max_t(unsigned short,
+			      le16_to_cpu(req_hdr->CreditCharge), 1);
+	credits_requested = max_t(unsigned short,
+				  le16_to_cpu(req_hdr->CreditRequest), 1);
 
-	if (credits_requested > 0) {
-		aux_credits = credits_requested - 1;
-		aux_max = 32;
-		if (hdr->Command == SMB2_NEGOTIATE)
-			aux_max = 0;
-		aux_credits = (aux_credits < aux_max) ? aux_credits : aux_max;
-		credits_granted = aux_credits + credit_charge;
+	/* according to smb2.credits smbtorture, Windows server
+	 * 2016 or later grant up to 8192 credits at once.
+	 *
+	 * TODO: Need to adjuct CreditRequest value according to
+	 * current cpu load
+	 */
+	aux_credits = credits_requested - 1;
+	if (hdr->Command == SMB2_NEGOTIATE)
+		aux_max = 0;
+	else
+		aux_max = conn->max_credits - credit_charge;
+	aux_credits = min_t(unsigned short, aux_credits, aux_max);
+	credits_granted = credit_charge + aux_credits;
 
-		/* if credits granted per client is getting bigger than default
-		 * minimum credits then we should wrap it up within the limits.
-		 */
-		if ((conn->total_credits + credits_granted) > min_credits)
-			credits_granted = min_credits -	conn->total_credits;
-		/*
-		 * TODO: Need to adjuct CreditRequest value according to
-		 * current cpu load
-		 */
-	} else if (conn->total_credits == 0) {
-		credits_granted = 1;
-	}
+	if (conn->max_credits - conn->total_credits < credits_granted)
+		credits_granted = conn->max_credits -
+			conn->total_credits;
 
 	conn->total_credits += credits_granted;
 	work->credits_granted += credits_granted;
@@ -368,7 +346,6 @@ int smb2_set_rsp_credits(struct ksmbd_work *work)
 		/* Update CreditRequest in last request */
 		hdr->CreditRequest = cpu_to_le16(work->credits_granted);
 	}
-out:
 	ksmbd_debug(SMB,
 		    "credits: requested[%d] granted[%d] total_granted[%d]\n",
 		    credits_requested, credits_granted,