qcacmn: Optimize scm_age_out_entries()

To check if a scan entry is a non-Tx VAP of our connected BSS, the current
implementation of scm_age_out_entries() searches through all scan entries
to find out our connected BSS. This check takes O(n) time where n = number
of scan entries. Running this check in the main loop of
scm_age_out_entries() results in an overall time complexity of O(square(n))

Time complexity can be improved if we do one iteration over scan entries
to find out our connected BSS, and save it in a local variable, and then
use that local variable in the main loop of scm_age_out_entries().
With this approach, we just do two iterations over scan entries
instead of nested iterations.

CRs-Fixed: 2877884
Change-Id: I51be764f4aa6f65ba9068d46eaa42791ac0f8d97

umac/scan/core/src/wlan_scan_cache_db.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017-2020 The Linux Foundation. All rights reserved.
+ * Copyright (c) 2017-2021 The Linux Foundation. All rights reserved.
  *
  * Permission to use, copy, modify, and/or distribute this software for
  * any purpose with or without fee is hereby granted, provided that the
@@ -439,39 +439,33 @@ static bool scm_bss_is_connected(struct scan_cache_entry *entry)
 	return false;
 }
 
-static bool scm_bss_is_nontx_of_conn_bss(struct scan_cache_entry *entry,
-					 struct scan_dbs *scan_db)
+/**
+ * scm_get_conn_node() - Get the scan cache entry node of the connected BSS
+ * @scan_db: scan DB pointer
+ *
+ * Return: scan cache entry node of connected BSS if exists, NULL otherwise
+ */
+static
+struct scan_cache_node *scm_get_conn_node(struct scan_dbs *scan_db)
 {
 	int i;
 	struct scan_cache_node *cur_node = NULL;
 	struct scan_cache_node *next_node = NULL;
 
-	if (!entry->mbssid_info.profile_num)
-		return false;
-
 	for (i = 0 ; i < SCAN_HASH_SIZE; i++) {
 		cur_node = scm_get_next_node(scan_db,
-					     &scan_db->scan_hash_tbl[i], NULL);
+			&scan_db->scan_hash_tbl[i], NULL);
 		while (cur_node) {
-			if (!memcmp(entry->mbssid_info.trans_bssid,
-				    cur_node->entry->bssid.bytes,
-				    QDF_MAC_ADDR_SIZE)) {
-				if (scm_bss_is_connected(cur_node->entry)) {
-					scm_scan_entry_put_ref(scan_db,
-							       cur_node,
-							       true);
-					return true;
-				}
-			}
-
+			if (scm_bss_is_connected(cur_node->entry))
+				return cur_node;
 			next_node = scm_get_next_node(scan_db,
-					&scan_db->scan_hash_tbl[i], cur_node);
+				&scan_db->scan_hash_tbl[i], cur_node);
 			cur_node = next_node;
 			next_node = NULL;
 		}
 	}
 
-	return false;
+	return NULL;
 }
 
 void scm_age_out_entries(struct wlan_objmgr_psoc *psoc,
@@ -480,6 +474,7 @@ void scm_age_out_entries(struct wlan_objmgr_psoc *psoc,
 	int i;
 	struct scan_cache_node *cur_node = NULL;
 	struct scan_cache_node *next_node = NULL;
+	struct scan_cache_node *conn_node = NULL;
 	struct scan_default_params *def_param;
 
 	def_param = wlan_scan_psoc_get_def_params(psoc);
@@ -488,21 +483,31 @@ void scm_age_out_entries(struct wlan_objmgr_psoc *psoc,
 		return;
 	}
 
+	conn_node = scm_get_conn_node(scan_db);
 	for (i = 0 ; i < SCAN_HASH_SIZE; i++) {
 		cur_node = scm_get_next_node(scan_db,
 			&scan_db->scan_hash_tbl[i], NULL);
 		while (cur_node) {
-			if (!scm_bss_is_connected(cur_node->entry) &&
-			    !scm_bss_is_nontx_of_conn_bss(cur_node->entry,
-							  scan_db))
+			if (!conn_node /* if there is no connected node */ ||
+			    /* OR cur_node is not part of the MBSSID of the
+			     * connected node
+			     */
+			    memcmp(conn_node->entry->mbssid_info.trans_bssid,
+				   cur_node->entry->mbssid_info.trans_bssid,
+				   QDF_MAC_ADDR_SIZE)
+			   ) {
 				scm_check_and_age_out(scan_db, cur_node,
 					def_param->scan_cache_aging_time);
+			}
 			next_node = scm_get_next_node(scan_db,
 				&scan_db->scan_hash_tbl[i], cur_node);
 			cur_node = next_node;
 			next_node = NULL;
 		}
 	}
+
+	if (conn_node)
+		scm_scan_entry_put_ref(scan_db, conn_node, true);
 }
 
 /**