netlink: autosize skb lengthes

[cascardo/linux.git] / net / netlink / af_netlink.c

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 9db8bab..c2d585c 100644 (file)
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -2343,6 +2343,11 @@ static int netlink_recvmsg(struct kiocb *kiocb, struct socket *sock,
        }
 #endif
 
+       /* Record the max length of recvmsg() calls for future allocations */
+       nlk->max_recvmsg_len = max(nlk->max_recvmsg_len, len);
+       nlk->max_recvmsg_len = min_t(size_t, nlk->max_recvmsg_len,
+                                    16384);
+
        copied = data_skb->len;
        if (len < copied) {
                msg->msg_flags |= MSG_TRUNC;
@@ -2587,7 +2592,27 @@ static int netlink_dump(struct sock *sk)
        if (!netlink_rx_is_mmaped(sk) &&
            atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf)
                goto errout_skb;
-       skb = netlink_alloc_skb(sk, alloc_size, nlk->portid, GFP_KERNEL);
+
+       /* NLMSG_GOODSIZE is small to avoid high order allocations being
+        * required, but it makes sense to _attempt_ a 16K bytes allocation
+        * to reduce number of system calls on dump operations, if user
+        * ever provided a big enough buffer.
+        */
+       if (alloc_size < nlk->max_recvmsg_len) {
+               skb = netlink_alloc_skb(sk,
+                                       nlk->max_recvmsg_len,
+                                       nlk->portid,
+                                       GFP_KERNEL |
+                                       __GFP_NOWARN |
+                                       __GFP_NORETRY);
+               /* available room should be exact amount to avoid MSG_TRUNC */
+               if (skb)
+                       skb_reserve(skb, skb_tailroom(skb) -
+                                        nlk->max_recvmsg_len);
+       }
+       if (!skb)
+               skb = netlink_alloc_skb(sk, alloc_size, nlk->portid,
+                                       GFP_KERNEL);
        if (!skb)
                goto errout_skb;
        netlink_skb_set_owner_r(skb, sk);