linux-kernel - Re: [PATCH] mm: page_alloc: document kmemleak's non-blockable __GFP

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Date:   Mon, 15 Jul 2019 09:58:14 -0700
From:   Yang Shi <yang.shi@...ux.alibaba.com>
To:     Qian Cai <cai@....pw>, Catalin Marinas <catalin.marinas@...il.com>,
        Michal Hocko <mhocko@...nel.org>
Cc:     "dvyukov@...gle.com" <dvyukov@...gle.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: page_alloc: document kmemleak's non-blockable
 __GFP_NOFAIL case



On 7/15/19 8:18 AM, Qian Cai wrote:
> On Mon, 2019-07-15 at 10:01 -0500, Catalin Marinas wrote:
>> On 15 Jul 2019, at 08:17, Michal Hocko <mhocko@...nel.org> wrote:
>>> On Sat 13-07-19 04:49:04, Yang Shi wrote:
>>>> When running ltp's oom test with kmemleak enabled, the below warning was
>>>> triggerred since kernel detects __GFP_NOFAIL & ~__GFP_DIRECT_RECLAIM is
>>>> passed in:
>>> kmemleak is broken and this is a long term issue. I thought that
>>> Catalin had something to address this.
>> What needs to be done in the short term is revert commit
>> d9570ee3bd1d4f20ce63485f5ef05663866fe6c0. Longer term the solution is to embed
>> kmemleak metadata into the slab so that we don’t have the situation where the
>> primary slab allocation success but the kmemleak metadata fails.
>>
>> I’m on holiday for one more week with just a phone to reply from but feel free
>> to revert the above commit. I’ll follow up with a better solution.
> Well, the reverting will only make the situation worst for the kmemleak under
> memory pressure. In the meantime, if someone wants to push for the mempool

I think this is expected by reverting that commit since kmemleak 
metadata could fail. But, it could fail too even though that commit is 
not reverted if the context is non-blockable.

> solution with tunable pool sizes along with the reverting, that could be an
> improvement.
>
> https://lore.kernel.org/linux-mm/20190328145917.GC10283@arrakis.emea.arm.com/