linux-kernel - Re: WARNING: kmalloc bug in input_mt_init

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Date:   Mon, 24 Sep 2018 17:18:25 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Christopher Lameter <cl@...ux.com>
Cc:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        syzbot+87829a10073277282ad1@...kaller.appspotmail.com,
        Pekka Enberg <penberg@...nel.org>,
        "linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Henrik Rydberg <rydberg@...math.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Linux-MM <linux-mm@...ck.org>
Subject: Re: WARNING: kmalloc bug in input_mt_init_slots

On Mon, Sep 24, 2018 at 5:08 PM, Christopher Lameter <cl@...ux.com> wrote:
> On Sun, 23 Sep 2018, Dmitry Vyukov wrote:
>
>> What was the motivation behind that WARNING about large allocations in
>> kmalloc? Why do we want to know about them? Is the general policy that
>> kmalloc calls with potentially large size requests need to use NOWARN?
>> If this WARNING still considered useful? Or we should change it to
>> pr_err?
>
> In general large allocs should be satisfied by the page allocator. The
> slab allocators are used for allocating and managing small objects. The
> page allocator has mechanisms to deal with large objects (compound pages,
> multiple page sized allocs etc).

I am asking more about the status of this warning. If it fires in
input_mt_init_slots(), does it mean that input_mt_init_slots() needs
to be fixed? If not, then we need to change this warning to something
else.