linux-kernel - [PATCH 0/2 v2] mm, slab: consolidate KMALLOC_MAX

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Date:   Tue, 20 Dec 2016 14:06:57 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Cristopher Lameter <cl@...ux.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        netdev@...r.kernel.org, <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH 0/2 v2] mm, slab: consolidate KMALLOC_MAX_SIZE

Hi,
this is the second version of the patchset previously posted here [1].
Alexei has insisted on the patches reordering which I've done in this
series. I've also updated the changelog of the second patch to mention
why KMALLOC_SHIFT_MAX has been used.

Andrey has revealed a discrepancy between KMALLOC_MAX_SIZE and the
maximum supported page allocator size [2]. The underlying problem
should be fixed in the ep_write_iter code of course, but I do not feel
qualified to do that. The discrepancy which it reveals (see patch 2)
is worth fixing anyway, though.

While I was looking into the code, I've noticed that the only code which
uses KMALLOC_SHIFT_MAX outside of the slab code is bpf so I've updated
it to use KMALLOC_MAX_SIZE instead. There shouldn't be any real reason
to use KMALLOC_SHIFT_MAX which is a slab internal constant same as
KMALLOC_SHIFT_{LOW,HIGH}

[1] http://lkml.kernel.org/r/20161215164722.21586-1-mhocko@kernel.org
[2] http://lkml.kernel.org/r/CAAeHK+ztusS68DejO8AH3nn-EfiYQpD5FmBwmqKG8BWvoqPNqQ@mail.gm