From mboxrd@z Thu Jan  1 00:00:00 1970
From: chas williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Subject: Re: [PATCH net-next] atm: use SKB_TRUESIZE() in
 atm_guess_pdu2truesize()
Date: Tue, 22 Nov 2011 17:42:05 -0500
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To: Eric Dumazet <eric.dumazet@gmail.com>
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On Tue, 22 Nov 2011 21:33:54 +0100
Eric Dumazet <eric.dumazet@gmail.com> wrote:

> Le mardi 22 novembre 2011 =C3=A0 15:22 -0500, chas williams - CONTRAC=
TOR a
> =C3=A9crit :
> > it doesnt seem like a good idea to create a wrapper for a one to on=
e
> > call.  perhaps this whole bit of nonsense should be removed.  the
> > iphase driver should be returning skb->truesize like everyone. =20
> >=20
> > if atm_alloc_charge() just uses SKB_TRUESIZE() then we konw that gu=
ess
> > will be the same as skb->truesize and atm_alloc_charge() can be
> > simplified by removing atomic_add(skb->truesize - guess, which will=
 be
> > 0 in all cases.
> >=20
>=20
> Please note I didnt create a wrapper, only correct existing one :)
>=20
> Feel free to send a (tested) patch, but be warned that following code=
 is
> not correct :
>=20
> int size =3D something;
>=20
> struct sk_buff *skb =3D skb_alloc(size);
>=20
> ASSERT(skb->truesize =3D=3D SKB_TRUESIZE(size));
>=20
> (It might be true with SLOB only)

perhaps it is best to say that you discovered an inadvertent wrapper.

given skb->truesize !=3D SKB_TRUESIZE() for all cases, it is certainly
wrong in the iphase driver to return the guessed value.  it should be
returning skb->truesize.  i will send along a patch shortly to just get
rid of this function.