From: Geliang Tang <tanggeliang@kylinos.cn>

With the help of get_addr(), we can refactor dump_addr() interfaces to
reuse send_nlmsg code between the netlink PM and userspace PM.

The current dump_addr() flow looks like this:

	lock();
	for_each_entry(entry)
		send_nlmsg(entry);
	unlock();

After holding the lock, get every entry by walking the address list,
send each one looply, and finally release the lock.

This set changes the process by copying the address list to an id
bitmap while holding the lock, then release the lock immediately.
After that, without locking, walking the copied id bitmap to get
every copy of entry by using get_addr(), and send each one looply.

This patch is the first part of refactoring dump_addr().

Without changing the position of the locks, the dump process is split
into two parts: copying the ID bitmap first, and then traversing the
ID bitmap, use lookup_addr_by_id() to get the entry, then send each
one through nlmsg:

	lock();
	for_each_entry(entry)
		set_bit(bitmap);
	for_each_bit(bitmap) {
		entry = lookup_addr_by_id();
		send_nlmsg(entry);
	}
	unlock();

Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
---
 net/mptcp/pm_netlink.c   |  6 ++++-
 net/mptcp/pm_userspace.c | 54 +++++++++++++++++++++++++++++-----------
 2 files changed, 45 insertions(+), 15 deletions(-)

diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index 2ab966393c55..9d502ab4d91d 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -1868,16 +1868,20 @@ static int mptcp_pm_nl_dump_addr(struct sk_buff *msg,
 {
 	struct net *net = sock_net(msg->sk);
 	struct mptcp_pm_addr_entry *entry;
+	struct mptcp_id_bitmap *bitmap;
 	struct pm_nl_pernet *pernet;
 	int id = cb->args[0];
 	void *hdr;
 	int i;
 
+	bitmap = (struct mptcp_id_bitmap *)cb->ctx;
 	pernet = pm_nl_get_pernet(net);
 
 	spin_lock_bh(&pernet->lock);
+	if (!id)
+		bitmap_copy(bitmap->map, pernet->id_bitmap.map, MPTCP_PM_MAX_ADDR_ID + 1);
 	for (i = id; i < MPTCP_PM_MAX_ADDR_ID + 1; i++) {
-		if (test_bit(i, pernet->id_bitmap.map)) {
+		if (test_bit(i, bitmap->map)) {
 			entry = __lookup_addr_by_id(pernet, i);
 			if (!entry)
 				break;
diff --git a/net/mptcp/pm_userspace.c b/net/mptcp/pm_userspace.c
index 373ff0186bee..2f1afb719ecf 100644
--- a/net/mptcp/pm_userspace.c
+++ b/net/mptcp/pm_userspace.c
@@ -582,6 +582,21 @@ int mptcp_userspace_pm_set_flags(struct genl_info *info)
 	return ret;
 }
 
+static int mptcp_userspace_pm_set_bitmap(struct mptcp_sock *msk,
+					 struct mptcp_id_bitmap *bitmap)
+{
+	struct mptcp_pm_addr_entry *entry;
+
+	list_for_each_entry(entry, &msk->pm.userspace_pm_local_addr_list, list) {
+		if (test_bit(entry->addr.id, bitmap->map))
+			continue;
+
+		__set_bit(entry->addr.id, bitmap->map);
+	}
+
+	return 0;
+}
+
 int mptcp_userspace_pm_dump_addr(struct sk_buff *msg,
 				 struct netlink_callback *cb)
 {
@@ -589,9 +604,11 @@ int mptcp_userspace_pm_dump_addr(struct sk_buff *msg,
 	struct mptcp_pm_addr_entry *entry;
 	struct mptcp_id_bitmap *bitmap;
 	struct mptcp_sock *msk;
+	int id = cb->args[0];
 	int ret = -EINVAL;
 	struct sock *sk;
 	void *hdr;
+	int i;
 
 	bitmap = (struct mptcp_id_bitmap *)cb->ctx;
 
@@ -603,24 +620,33 @@ int mptcp_userspace_pm_dump_addr(struct sk_buff *msg,
 
 	lock_sock(sk);
 	spin_lock_bh(&msk->pm.lock);
-	list_for_each_entry(entry, &msk->pm.userspace_pm_local_addr_list, list) {
-		if (test_bit(entry->addr.id, bitmap->map))
-			continue;
+	if (!id)
+		ret = mptcp_userspace_pm_set_bitmap(msk, bitmap);
+	for (i = id; i < MPTCP_PM_MAX_ADDR_ID + 1; i++) {
+		if (test_bit(i, bitmap->map)) {
+			entry = mptcp_userspace_pm_lookup_addr_by_id(msk, i);
+			if (!entry)
+				break;
+
+			if (id && entry->addr.id <= id)
+				continue;
 
-		hdr = genlmsg_put(msg, NETLINK_CB(cb->skb).portid,
-				  cb->nlh->nlmsg_seq, &mptcp_genl_family,
-				  NLM_F_MULTI, MPTCP_PM_CMD_GET_ADDR);
-		if (!hdr)
-			break;
+			hdr = genlmsg_put(msg, NETLINK_CB(cb->skb).portid,
+					  cb->nlh->nlmsg_seq, &mptcp_genl_family,
+					  NLM_F_MULTI, MPTCP_PM_CMD_GET_ADDR);
+			if (!hdr)
+				break;
 
-		if (mptcp_nl_fill_addr(msg, entry) < 0) {
-			genlmsg_cancel(msg, hdr);
-			break;
-		}
+			if (mptcp_nl_fill_addr(msg, entry) < 0) {
+				genlmsg_cancel(msg, hdr);
+				break;
+			}
 
-		__set_bit(entry->addr.id, bitmap->map);
-		genlmsg_end(msg, hdr);
+			id = entry->addr.id;
+			genlmsg_end(msg, hdr);
+		}
 	}
+	cb->args[0] = id;
 	spin_unlock_bh(&msk->pm.lock);
 	release_sock(sk);
 	ret = msg->len;
-- 
2.43.0