Re: [PATCH][RESEND] tcp: replace hard coded GFP_KERNEL withsk_allocation

From: David Miller
Date: Thu Sep 03 2009 - 02:32:19 EST

From: David Miller <davem@xxxxxxxxxxxxx>
Date: Wed, 02 Sep 2009 23:10:17 -0700 (PDT)

> From: Wu Fengguang <fengguang.wu@xxxxxxxxx>
> Date: Thu, 3 Sep 2009 12:04:07 +0800
>> 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@xxxxxxxxxxxxxxxxxx>
>> CC: David S. Miller <davem@xxxxxxxxxxxxx>
>> CC: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
>> Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
> Applied to net-next-2.6, thanks!

You obviously didn't build test this with TCP MD5 support
enabled, that fails.

I'm fixing it up, but if you're going to go through the motions
of submitting a patch multiple times, at least do a thorough
build test of the code you're changing.
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