Re: [PATCH] zerocopy NFS for 2.5.36

From: David S. Miller (
Date: Wed Sep 18 2002 - 18:00:57 EST

   From: Hirokazu Takahashi <>
   Date: Wed, 18 Sep 2002 17:14:31 +0900 (JST)
   This patch enables HW-checksum against outgoing packets including UDP frames.
Can you explain the TCP parts? They look very wrong.

It was discussed long ago that csum_and_copy_from_user() performs
better than plain copy_from_user() on x86. I do not remember all
details, but I do know that using copy_from_user() is not a real
improvement at least on x86 architecture.

The rest of the changes (ie. the getfrag() logic to set
skb->ip_summed) looks fine.

   This patch fixes the problem of x86 csum_partilal() routines which
   can't handle odd addressed buffers.
I've sent Linus this fix already.
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