tcp: replace hard coded GFP_KERNEL with sk_allocation

This fixed a lockdep warning which appeared when doing stress
memory tests over NFS:

	inconsistent {RECLAIM_FS-ON-W} -> {IN-RECLAIM_FS-W} usage.

	page reclaim => nfs_writepage => tcp_sendmsg => lock sk_lock

	mount_root => nfs_root_data => tcp_close => lock sk_lock =>
			tcp_send_fin => alloc_skb_fclone => page reclaim

David raised a concern that if the allocation fails in tcp_send_fin(), and it's
GFP_ATOMIC, we are going to yield() (which sleeps) and loop endlessly waiting
for the allocation to succeed.

But fact is, the original GFP_KERNEL also sleeps. GFP_ATOMIC+yield() looks
weird, but it is no worse the implicit sleep inside GFP_KERNEL. Both could
loop endlessly under memory pressure.

CC: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
CC: David S. Miller <davem@davemloft.net>
CC: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 2 deletions

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 4e004424d400..5200aab0ca97 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2135,7 +2135,8 @@ void tcp_send_fin(struct sock *sk)
         } else {
                 /* Socket is locked, keep trying until memory is available. */
                 for (;;) {
-                        skb = alloc_skb_fclone(MAX_TCP_HEADER, GFP_KERNEL);
+                        skb = alloc_skb_fclone(MAX_TCP_HEADER,
+                                               sk->sk_allocation);
                         if (skb)
                                 break;
                         yield();
@@ -2388,7 +2389,7 @@ int tcp_connect(struct sock *sk)
         sk->sk_wmem_queued += buff->truesize;
         sk_mem_charge(sk, buff->truesize);
         tp->packets_out += tcp_skb_pcount(buff);
-        tcp_transmit_skb(sk, buff, 1, GFP_KERNEL);
+        tcp_transmit_skb(sk, buff, 1, sk->sk_allocation);
 
         /* We change tp->snd_nxt after the tcp_transmit_skb() call
          * in order to make this packet get counted in tcpOutSegs.