netdev - Re: [PATCH 1/2] bpf: do not use KMALLOC_SHIFT

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Message-ID: <20161216232340.GA99159@ast-mbp.thefacebook.com>
Date:   Fri, 16 Dec 2016 15:23:42 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     linux-mm@...ck.org, Cristopher Lameter <cl@...ux.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexei Starovoitov <ast@...nel.org>, netdev@...r.kernel.org,
        Daniel Borkmann <daniel@...earbox.net>
Subject: Re: [PATCH 1/2] bpf: do not use KMALLOC_SHIFT_MAX

On Fri, Dec 16, 2016 at 11:02:35PM +0100, Michal Hocko wrote:
> On Fri 16-12-16 10:02:10, Alexei Starovoitov wrote:
> > On Thu, Dec 15, 2016 at 05:47:21PM +0100, Michal Hocko wrote:
> > > From: Michal Hocko <mhocko@...e.com>
> > > 
> > > 01b3f52157ff ("bpf: fix allocation warnings in bpf maps and integer
> > > overflow") has added checks for the maximum allocateable size. It
> > > (ab)used KMALLOC_SHIFT_MAX for that purpose. While this is not incorrect
> > > it is not very clean because we already have KMALLOC_MAX_SIZE for this
> > > very reason so let's change both checks to use KMALLOC_MAX_SIZE instead.
> > > 
> > > Cc: Alexei Starovoitov <ast@...nel.org>
> > > Signed-off-by: Michal Hocko <mhocko@...e.com>
> > 
> > Nack until the patches 1 and 2 are reversed.
> 
> I do not insist on ordering. The thing is that it shouldn't matter all
> that much. Or are you worried about bisectability?

This patch 1 strongly depends on patch 2 !
Therefore order matters.
The patch 1 by itself is broken.
The commit log is saying
'(ab)used KMALLOC_SHIFT_MAX for that purpose .. use KMALLOC_MAX_SIZE instead'
that is also incorrect. We cannot do that until KMALLOC_MAX_SIZE is fixed.
So please change the order and fix the commit log to say that KMALLOC_MAX_SIZE
is actually valid limit now.