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

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Message-Id: <F89E7123-C21C-41AA-8084-1DB4C832D7BD@gmail.com>
Date:   Mon, 15 Jul 2019 10:01:00 -0500
From:   Catalin Marinas <catalin.marinas@...il.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Yang Shi <yang.shi@...ux.alibaba.com>,
        "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 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. 

Catalin