From: Laurent Dufour <ldufour@linux.vnet.ibm.com>
To: Balbir Singh <bsingharora@gmail.com>,
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>
Subject: Re: [PATCH v2 1/2] mm: Uncharge poisoned pages
Date: Fri, 28 Apr 2017 11:32:31 +0200 [thread overview]
Message-ID: <f3dce7ae-1209-a6ec-d4ec-49325471fd59@linux.vnet.ibm.com> (raw)
In-Reply-To: <1493197141.16329.1.camel@gmail.com>
On 26/04/2017 10:59, Balbir Singh wrote:
> On Wed, 2017-04-26 at 04:46 +0000, Naoya Horiguchi wrote:
>> On Wed, Apr 26, 2017 at 01:45:00PM +1000, Balbir Singh wrote:
>>>>>> static int delete_from_lru_cache(struct page *p)
>>>>>> {
>>>>>> + if (memcg_kmem_enabled())
>>>>>> + memcg_kmem_uncharge(p, 0);
>>>>>> +
>>>>>
>>>>> The changelog is not quite clear, so we are uncharging a page using
>>>>> memcg_kmem_uncharge for a page in swap cache/page cache?
>>>>
>>>> Hi Balbir,
>>>>
>>>> Yes, in the normal page lifecycle, uncharge is done in page free time.
>>>> But in memory error handling case, in-use pages (i.e. swap cache and page
>>>> cache) are removed from normal path and they don't pass page freeing code.
>>>> So I think that this change is to keep the consistent charging for such a case.
>>>
>>> I agree we should uncharge, but looking at the API name, it seems to
>>> be for kmem pages, why are we not using mem_cgroup_uncharge()? Am I missing
>>> something?
>>
>> Thank you for pointing out.
>> Actually I had the same question and this surely looks strange.
>> But simply calling mem_cgroup_uncharge() here doesn't work because it
>> assumes that page_refcount(p) == 0, which is not true in hwpoison context.
>> We need some other clearer way or at least some justifying comment about
>> why this is ok.
>>
>
> We should call mem_cgroup_uncharge() after isolate_lru_page()/put_page().
Thanks for the review Naoya and Balbir,
I changed the patch to call mem_cgroup_uncharge() once
isolate_lru_page() succeeded, but before calling put_page().
It seems to work fine.
> We could check if page_count() is 0 or force if required (!MF_RECOVERED &&
> !MF_DELAYED). We could even skip the VM_BUG_ON if the page is poisoned.
This doesn't seem to be needed. Am I still missing something here ?
Cheers,
Laurent.
next prev parent reply other threads:[~2017-04-28 9:32 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-25 14:27 [PATCH v2 0/2] BUG raised when onlining HWPoisoned page Laurent Dufour
2017-04-25 14:27 ` [PATCH v2 1/2] mm: Uncharge poisoned pages Laurent Dufour
2017-04-25 23:48 ` Naoya Horiguchi
2017-04-26 1:54 ` Balbir Singh
2017-04-26 2:34 ` Naoya Horiguchi
2017-04-26 3:45 ` Balbir Singh
2017-04-26 4:46 ` Naoya Horiguchi
2017-04-26 8:59 ` Balbir Singh
2017-04-28 9:32 ` Laurent Dufour [this message]
2017-04-27 14:37 ` Michal Hocko
2017-04-27 20:51 ` Andi Kleen
2017-04-28 6:07 ` Michal Hocko
2017-04-28 7:31 ` Michal Hocko
2017-04-28 9:17 ` Laurent Dufour
2017-04-28 13:48 ` Michal Hocko
2017-05-02 14:59 ` Laurent Dufour
2017-05-02 18:55 ` Michal Hocko
2017-05-03 11:34 ` Laurent Dufour
2017-05-04 1:21 ` Balbir Singh
2017-05-08 10:42 ` Laurent Dufour
2017-05-09 1:41 ` Balbir Singh
2017-05-08 2:58 ` Naoya Horiguchi
2017-05-09 9:18 ` Michal Hocko
2017-05-09 22:59 ` Naoya Horiguchi
2017-04-25 14:27 ` [PATCH v2 2/2] mm: skip HWPoisoned pages when onlining pages Laurent Dufour
2017-04-26 2:10 ` Balbir Singh
2017-04-26 3:13 ` Naoya Horiguchi
2017-04-28 2:51 ` Balbir Singh
2017-04-28 6:30 ` Michal Hocko
2017-04-28 6:50 ` Michal Hocko
2017-04-28 6:51 ` Michal Hocko
2017-05-10 7:41 ` Michal Hocko
2018-01-17 23:03 ` Andrew Morton
2018-01-23 18:15 ` Laurent Dufour
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