[tipc-discussion] [PATCH net-next v3 09/12] tipc: convert tipc_bearers array to pointer array

[Ying X. <yin...@wi...>]

As tipc_bearers will be protected by RCU lock, tipc_bearers is
defined as static array where the data of tipc_bearer struct is
located in each array element. But since static array has not seen
with RCU, tipc_bearers should be redefined to a pointer array where
a pointer pointed to dynamically allocated instance of tipc_bearer
struct is located in each array element, allowing the pointer
array to be protected with RCU.

Signed-off-by: Ying Xue <yin...@wi...>
---
 net/tipc/bcast.c  |    6 +++---
 net/tipc/bearer.c |   53 ++++++++++++++++++++++++++++++++++++++---------------
 net/tipc/bearer.h |    2 +-
 3 files changed, 42 insertions(+), 19 deletions(-)

diff --git a/net/tipc/bcast.c b/net/tipc/bcast.c
index c78f30c..0378fda 100644
--- a/net/tipc/bcast.c
+++ b/net/tipc/bcast.c
@@ -660,6 +660,7 @@ void tipc_bcbearer_sort(void)
 {
 	struct tipc_bcbearer_pair *bp_temp = bcbearer->bpairs_temp;
 	struct tipc_bcbearer_pair *bp_curr;
+	struct tipc_bearer *b;
 	int b_index;
 	int pri;
 
@@ -669,9 +670,8 @@ void tipc_bcbearer_sort(void)
 	memset(bp_temp, 0, sizeof(bcbearer->bpairs_temp));
 
 	for (b_index = 0; b_index < MAX_BEARERS; b_index++) {
-		struct tipc_bearer *b = &tipc_bearers[b_index];
-
-		if (!b->active || !b->nodes.count)
+		b = bearer_list[b_index];
+		if (!b || !b->active || !b->nodes.count)
 			continue;
 
 		if (!bp_temp[b->priority].primary)
diff --git a/net/tipc/bearer.c b/net/tipc/bearer.c
index 5dd587b..5b32254 100644
--- a/net/tipc/bearer.c
+++ b/net/tipc/bearer.c
@@ -42,10 +42,9 @@
 #define MAX_ADDR_STR 60
 
 static struct tipc_media *media_list[MAX_MEDIA];
+struct tipc_bearer *bearer_list[MAX_BEARERS];
 static u32 media_count;
 
-struct tipc_bearer tipc_bearers[MAX_BEARERS];
-
 static void bearer_disable(struct tipc_bearer *b_ptr);
 
 /**
@@ -228,8 +227,9 @@ struct tipc_bearer *tipc_bearer_find(const char *name)
 	struct tipc_bearer *b_ptr;
 	u32 i;
 
-	for (i = 0, b_ptr = tipc_bearers; i < MAX_BEARERS; i++, b_ptr++) {
-		if (b_ptr->active && (!strcmp(b_ptr->name, name)))
+	for (i = 0; i < MAX_BEARERS; i++) {
+		b_ptr = bearer_list[i];
+		if (b_ptr && b_ptr->active && (!strcmp(b_ptr->name, name)))
 			return b_ptr;
 	}
 	return NULL;
@@ -244,8 +244,9 @@ struct tipc_bearer *tipc_bearer_find_interface(const char *if_name)
 	char *b_if_name;
 	u32 i;
 
-	for (i = 0, b_ptr = tipc_bearers; i < MAX_BEARERS; i++, b_ptr++) {
-		if (!b_ptr->active)
+	for (i = 0; i < MAX_BEARERS; i++) {
+		b_ptr = bearer_list[i];
+		if (!b_ptr || !b_ptr->active)
 			continue;
 		b_if_name = strchr(b_ptr->name, ':') + 1;
 		if (!strcmp(b_if_name, if_name))
@@ -270,7 +271,9 @@ struct sk_buff *tipc_bearer_get_names(void)
 	read_lock_bh(&tipc_net_lock);
 	for (i = 0; i < media_count; i++) {
 		for (j = 0; j < MAX_BEARERS; j++) {
-			b_ptr = &tipc_bearers[j];
+			b_ptr = bearer_list[j];
+			if (!b_ptr)
+				continue;
 			if (b_ptr->active && (b_ptr->media == media_list[i])) {
 				tipc_cfg_append_tlv(buf, TIPC_TLV_BEARER_NAME,
 						    b_ptr->name,
@@ -354,17 +357,17 @@ restart:
 	bearer_id = MAX_BEARERS;
 	with_this_prio = 1;
 	for (i = MAX_BEARERS; i-- != 0; ) {
-		if (!tipc_bearers[i].active) {
+		b_ptr = bearer_list[i];
+		if (!b_ptr || !b_ptr->active) {
 			bearer_id = i;
 			continue;
 		}
-		if (!strcmp(name, tipc_bearers[i].name)) {
+		if (!strcmp(name, b_ptr->name)) {
 			pr_warn("Bearer <%s> rejected, already enabled\n",
 				name);
 			goto exit;
 		}
-		if ((tipc_bearers[i].priority == priority) &&
-		    (++with_this_prio > 2)) {
+		if ((b_ptr->priority == priority) && (++with_this_prio > 2)) {
 			if (priority-- == 0) {
 				pr_warn("Bearer <%s> rejected, duplicate priority\n",
 					name);
@@ -381,7 +384,12 @@ restart:
 		goto exit;
 	}
 
-	b_ptr = &tipc_bearers[bearer_id];
+	b_ptr = kzalloc(sizeof(*b_ptr), GFP_ATOMIC);
+	if (!b_ptr) {
+		res = -ENOMEM;
+		goto exit;
+	}
+
 	strcpy(b_ptr->name, name);
 	atomic_set(&b_ptr->blocked, 0);
 	smp_mb();
@@ -409,6 +417,9 @@ restart:
 			name);
 		goto exit;
 	}
+
+	bearer_list[bearer_id] = b_ptr;
+
 	pr_info("Enabled bearer <%s>, discovery domain %s, priority %u\n",
 		name,
 		tipc_addr_string_fill(addr_string, disc_domain), priority);
@@ -449,9 +460,17 @@ static void bearer_disable(struct tipc_bearer *b_ptr)
 	struct tipc_link *l_ptr;
 	struct tipc_link *temp_l_ptr;
 	struct tipc_link_req *temp_req;
+	u32 i;
 
 	pr_info("Disabling bearer <%s>\n", b_ptr->name);
 	atomic_add_unless(&b_ptr->blocked, 1, 1);
+	for (i = 0; i < MAX_BEARERS; i++) {
+		if (b_ptr == bearer_list[i]) {
+			bearer_list[i] = NULL;
+			break;
+		}
+	}
+
 	spin_lock_bh(&b_ptr->lock);
 	b_ptr->media->disable_media(b_ptr);
 	list_for_each_entry_safe(l_ptr, temp_l_ptr, &b_ptr->links, link_list) {
@@ -464,7 +483,7 @@ static void bearer_disable(struct tipc_bearer *b_ptr)
 	if (temp_req)
 		tipc_disc_delete(temp_req);
 
-	memset(b_ptr, 0, sizeof(struct tipc_bearer));
+	kfree(b_ptr);
 }
 
 int tipc_disable_bearer(const char *name)
@@ -487,11 +506,15 @@ int tipc_disable_bearer(const char *name)
 
 void tipc_bearer_stop(void)
 {
+	struct tipc_bearer *b_ptr;
 	u32 i;
 
 	for (i = 0; i < MAX_BEARERS; i++) {
-		if (tipc_bearers[i].active)
-			bearer_disable(&tipc_bearers[i]);
+		b_ptr = bearer_list[i];
+		if (b_ptr && b_ptr->active) {
+			bearer_disable(b_ptr);
+			bearer_list[i] = NULL;
+		}
 	}
 	media_count = 0;
 }
diff --git a/net/tipc/bearer.h b/net/tipc/bearer.h
index 280c23d..757eda9 100644
--- a/net/tipc/bearer.h
+++ b/net/tipc/bearer.h
@@ -154,7 +154,7 @@ struct tipc_bearer_names {
 
 struct tipc_link;
 
-extern struct tipc_bearer tipc_bearers[];
+extern struct tipc_bearer *bearer_list[];
 
 /*
  * TIPC routines available to supported media types
-- 
1.7.9.5