qcacmn: Reject scan after a max number of scans are received

Currently the driver enques any number of scans it receives
from the NL, or vendor scan path, which can lead to lower
throughputs of the connected profile ( any vdev ), as
antennas would be used by the MAC for scanning, and if
the number of scans are too much, this will lead to a
bad user experience.

Fix is to have a max check of number of scans, and then only
enque a particular scan request.

Change-Id: Iacdb1294ff5e7e20cd30dd328c6ea2b6f7899cda
CRs-Fixed: 2392883

os_if/linux/scan/src/wlan_cfg80211_scan.c

@@ -669,7 +669,7 @@ static int wlan_scan_request_enqueue(struct wlan_objmgr_pdev *pdev,
 	struct osif_scan_pdev *osif_scan;
 
 	scan_req = qdf_mem_malloc(sizeof(*scan_req));
-	if (NULL == scan_req) {
+	if (!scan_req) {
 		cfg80211_alert("malloc failed for Scan req");
 		return -ENOMEM;
 	}
@@ -683,11 +683,15 @@ static int wlan_scan_request_enqueue(struct wlan_objmgr_pdev *pdev,
 	scan_req->dev = req->wdev->netdev;
 
 	qdf_mutex_acquire(&osif_scan->scan_req_q_lock);
-	status = qdf_list_insert_back(&osif_scan->scan_req_q,
-					&scan_req->node);
+	if (qdf_list_size(&osif_scan->scan_req_q) < WLAN_MAX_SCAN_COUNT)
+		status = qdf_list_insert_back(&osif_scan->scan_req_q,
+					      &scan_req->node);
+	else
+		status = QDF_STATUS_E_RESOURCES;
 	qdf_mutex_release(&osif_scan->scan_req_q_lock);
-	if (QDF_STATUS_SUCCESS != status) {
-		cfg80211_err("Failed to enqueue Scan Req");
+	if (QDF_IS_STATUS_ERROR(status)) {
+		cfg80211_debug_rl("Failed to enqueue Scan Req as max scan %d already queued",
+			          qdf_list_size(&osif_scan->scan_req_q));
 		qdf_mem_free(scan_req);
 		return -EINVAL;
 	}
@@ -1342,6 +1346,14 @@ int wlan_cfg80211_scan(struct wlan_objmgr_vdev *vdev,
 	req->scan_req.scan_id = scan_id;
 	req->scan_req.scan_req_id = req_id;
 
+	/* Enqueue the scan request */
+	ret = wlan_scan_request_enqueue(pdev, request, params->source,
+					req->scan_req.scan_id);
+	if (ret) {
+		qdf_mem_free(req);
+		return ret;
+	}
+
 	/* Update scan policy type flags according to cfg scan request */
 	wlan_cfg80211_update_scan_policy_type_flags(request,
 					     &req->scan_req);
@@ -1429,7 +1441,7 @@ int wlan_cfg80211_scan(struct wlan_objmgr_vdev *vdev,
 #endif
 		if (!chl) {
 			ret = -ENOMEM;
-			goto end;
+			goto err;
 		}
 		for (i = 0; i < request->n_channels; i++) {
 			channel = request->channels[i]->hw_value;
@@ -1451,7 +1463,7 @@ int wlan_cfg80211_scan(struct wlan_objmgr_vdev *vdev,
 					qdf_mem_free(chl);
 					chl = NULL;
 					ret = -EINVAL;
-					goto end;
+					goto err;
 				}
 				if (!ok)
 					continue;
@@ -1477,9 +1489,8 @@ int wlan_cfg80211_scan(struct wlan_objmgr_vdev *vdev,
 	}
 	if (!num_chan) {
 		cfg80211_err("Received zero non-dsrc channels");
-		qdf_mem_free(req);
 		ret = -EINVAL;
-		goto end;
+		goto err;
 	}
 	req->scan_req.chan_list.num_chan = num_chan;
 
@@ -1491,8 +1502,7 @@ int wlan_cfg80211_scan(struct wlan_objmgr_vdev *vdev,
 		if (!req->scan_req.extraie.ptr) {
 			cfg80211_err("Failed to allocate memory");
 			ret = -ENOMEM;
-			qdf_mem_free(req);
-			goto end;
+			goto err;
 		}
 		req->scan_req.extraie.len = request->ie_len;
 		qdf_mem_copy(req->scan_req.extraie.ptr, request->ie,
@@ -1503,8 +1513,7 @@ int wlan_cfg80211_scan(struct wlan_objmgr_vdev *vdev,
 		if (!req->scan_req.extraie.ptr) {
 			cfg80211_err("Failed to allocate memory");
 			ret = -ENOMEM;
-			qdf_mem_free(req);
-			goto end;
+			goto err;
 		}
 		req->scan_req.extraie.len = params->default_ie.len;
 		qdf_mem_copy(req->scan_req.extraie.ptr, params->default_ie.ptr,
@@ -1523,10 +1532,6 @@ int wlan_cfg80211_scan(struct wlan_objmgr_vdev *vdev,
 	if (request->flags & NL80211_SCAN_FLAG_FLUSH)
 		ucfg_scan_flush_results(pdev, NULL);
 
-	/* Enqueue the scan request */
-	wlan_scan_request_enqueue(pdev, request, params->source,
-				  req->scan_req.scan_id);
-
 	/*
 	 * Acquire wakelock to handle the case where APP's send scan to connect.
 	 * If suspend is received during scan scan will be aborted and APP will
@@ -1554,9 +1559,13 @@ int wlan_cfg80211_scan(struct wlan_objmgr_vdev *vdev,
 				&osif_priv->osif_scan->scan_wake_lock);
 		}
 	}
-	ret = qdf_status_to_os_return(qdf_status);
 
-end:
+	return qdf_status_to_os_return(qdf_status);
+
+err:
+	qdf_mem_free(req);
+	wlan_scan_request_dequeue(pdev, scan_id, &request,
+				  &params->source, &netdev);
 	return ret;
 }