2 files changed, 27 insertions, 1 deletions

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 9db8bab27fa2..c2d585c4f7c5 100644
--- 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);
diff --git a/net/netlink/af_netlink.h b/net/netlink/af_netlink.h
index acbd774eeb7c..ed13a790b00e 100644
--- a/net/netlink/af_netlink.h
+++ b/net/netlink/af_netlink.h
@@ -31,6 +31,7 @@ struct netlink_sock {
         u32                     ngroups;
         unsigned long           *groups;
         unsigned long           state;
+        size_t                  max_recvmsg_len;
         wait_queue_head_t       wait;
         bool                    cb_running;
         struct netlink_callback cb;