1 files changed, 45 insertions, 19 deletions

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 8c8d7e06b72f..a369e8a70b2c 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2812,39 +2812,65 @@ begin_fwd:
         }
 }
 
-/* Send a fin.  The caller locks the socket for us.  This cannot be
- * allowed to fail queueing a FIN frame under any circumstances.
+/* We allow to exceed memory limits for FIN packets to expedite
+ * connection tear down and (memory) recovery.
+ * Otherwise tcp_send_fin() could be tempted to either delay FIN
+ * or even be forced to close flow without any FIN.
+ */
+static void sk_forced_wmem_schedule(struct sock *sk, int size)
+{
+        int amt, status;
+
+        if (size <= sk->sk_forward_alloc)
+                return;
+        amt = sk_mem_pages(size);
+        sk->sk_forward_alloc += amt * SK_MEM_QUANTUM;
+        sk_memory_allocated_add(sk, amt, &status);
+}
+
+/* Send a FIN. The caller locks the socket for us.
+ * We should try to send a FIN packet really hard, but eventually give up.
  */
 void tcp_send_fin(struct sock *sk)
 {
+        struct sk_buff *skb, *tskb = tcp_write_queue_tail(sk);
         struct tcp_sock *tp = tcp_sk(sk);
-        struct sk_buff *skb = tcp_write_queue_tail(sk);
-        int mss_now;
 
-        /* Optimization, tack on the FIN if we have a queue of
-         * unsent frames.  But be careful about outgoing SACKS
-         * and IP options.
+        /* Optimization, tack on the FIN if we have one skb in write queue and
+         * this skb was not yet sent, or we are under memory pressure.
+         * Note: in the latter case, FIN packet will be sent after a timeout,
+         * as TCP stack thinks it has already been transmitted.
          */
-        mss_now = tcp_current_mss(sk);
-
-        if (tcp_send_head(sk)) {
-                TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_FIN;
-                TCP_SKB_CB(skb)->end_seq++;
+        if (tskb && (tcp_send_head(sk) || sk_under_memory_pressure(sk))) {
+coalesce:
+                TCP_SKB_CB(tskb)->tcp_flags |= TCPHDR_FIN;
+                TCP_SKB_CB(tskb)->end_seq++;
                 tp->write_seq++;
+                if (!tcp_send_head(sk)) {
+                        /* This means tskb was already sent.
+                         * Pretend we included the FIN on previous transmit.
+                         * We need to set tp->snd_nxt to the value it would have
+                         * if FIN had been sent. This is because retransmit path
+                         * does not change tp->snd_nxt.
+                         */
+                        tp->snd_nxt++;
+                        return;
+                }
         } else {
-                /* Socket is locked, keep trying until memory is available. */
-                for (;;) {
-                        skb = sk_stream_alloc_skb(sk, 0, sk->sk_allocation);
-                        if (skb)
-                                break;
-                        yield();
+                skb = alloc_skb_fclone(MAX_TCP_HEADER, sk->sk_allocation);
+                if (unlikely(!skb)) {
+                        if (tskb)
+                                goto coalesce;
+                        return;
                 }
+                skb_reserve(skb, MAX_TCP_HEADER);
+                sk_forced_wmem_schedule(sk, skb->truesize);
                 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
                 tcp_init_nondata_skb(skb, tp->write_seq,
                                      TCPHDR_ACK | TCPHDR_FIN);
                 tcp_queue_skb(sk, skb);
         }
-        __tcp_push_pending_frames(sk, mss_now, TCP_NAGLE_OFF);
+        __tcp_push_pending_frames(sk, tcp_current_mss(sk), TCP_NAGLE_OFF);
 }
 
 /* We get here when a process closes a file descriptor (either due to