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

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Date:   Mon, 15 Jul 2019 11:18:02 -0400
From:   Qian Cai <cai@....pw>
To:     Catalin Marinas <catalin.marinas@...il.com>,
        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 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
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/