linux-kernel - Re: [PATCH v2 1/2] mm: Uncharge poisoned pages

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Message-Id: <03a7ec34-106e-3eb6-0b05-f77a40a2d6b9@linux.vnet.ibm.com>
Date:   Mon, 8 May 2017 12:42:28 +0200
From:   Laurent Dufour <ldufour@...ux.vnet.ibm.com>
To:     Balbir Singh <bsingharora@...il.com>,
        Michal Hocko <mhocko@...nel.org>,
        Andi Kleen <andi@...stfloor.org>,
        Johannes Weiner <hannes@...xchg.org>
Cc:     Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        akpm@...ux-foundation.org,
        Vladimir Davydov <vdavydov.dev@...il.com>
Subject: Re: [PATCH v2 1/2] mm: Uncharge poisoned pages

On 04/05/2017 03:21, Balbir Singh wrote:
>> @@ -5527,7 +5527,7 @@ static void uncharge_list(struct list_head *page_list)
>>  		next = page->lru.next;
>>  
>>  		VM_BUG_ON_PAGE(PageLRU(page), page);
>> -		VM_BUG_ON_PAGE(page_count(page), page);
>> +		VM_BUG_ON_PAGE(!PageHWPoison(page) && page_count(page), page);
>>  
>>  		if (!page->mem_cgroup)
>>  			continue;
>> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
>> index 8a6bd3a9eb1e..4497d9619bb4 100644
>> --- a/mm/memory-failure.c
>> +++ b/mm/memory-failure.c
>> @@ -541,6 +541,13 @@ static int delete_from_lru_cache(struct page *p)
>>  		 */
>>  		ClearPageActive(p);
>>  		ClearPageUnevictable(p);
>> +
>> +		/*
>> +		 * Poisoned page might never drop its ref count to 0 so we have to
>> +		 * uncharge it manually from its memcg.
>> +		 */
>> +		mem_cgroup_uncharge(p);
>> +
> 
> Yep, that is the right fix
> 
> https://lkml.org/lkml/2017/4/26/133

Sorry Balbir,

You pointed this out since the beginning but I missed your comment.
My mistake.

Thanks,
Laurent.