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tcp: replace hard coded GFP_KERNEL with sk_allocation

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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>
This commit is contained in:
Wu Fengguang
2009-09-02 23:45:45 -07:00
committed by David S. Miller
parent 05c6a8d7a7
commit aa1330766c
6 changed files with 15 additions and 13 deletions
Download Patch File Download Diff File Expand all files Collapse all files

5
net/ipv4/tcp_output.c
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@@ -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.