linux-kernel - Re: [RFC PATCH] hwpoison, memory_hotplug: allow hwpoisoned pages to be offlined

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Date:   Thu, 06 Dec 2018 09:40:23 +0100
From:   osalvador@...e.de
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        Oscar Salvador <OSalvador@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dan Williams <dan.j.williams@...il.com>,
        Pavel Tatashin <pasha.tatashin@...een.com>, linux-mm@...ck.org,
        LKML <linux-kernel@...r.kernel.org>,
        Stable tree <stable@...r.kernel.org>, owner-linux-mm@...ck.org
Subject: Re: [RFC PATCH] hwpoison, memory_hotplug: allow hwpoisoned pages to
 be offlined

>> This commit adds shake_page() for mlocked pages to make sure that the 
>> target
>> page is flushed out from LRU cache. Without this shake_page(), 
>> subsequent
>> delete_from_lru_cache() (from me_pagecache_clean()) fails to isolate 
>> it and
>> the page will finally return back to LRU list.  So this scenario leads 
>> to
>> "hwpoisoned by still linked to LRU list" page.
> 
> OK, I see. So does that mean that the LRU handling is no longer needed
> and there is a guanratee that all kernels with the above commit cannot
> ever get an LRU page?

For the sake of completeness:

I made a quick test reverting 286c469a988 on upstream kernel.
As expected, the poisoned page is in LRU when it hits do_migrate_range,
and so, the migration path is taken and I see the exact failure I saw 
on. 4.4


Oscar Salvador
---
Suse L3