From: Wei Yang <richard.weiyang@linux.alibaba.com>
To: David Hildenbrand <david@redhat.com>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>,
Alexander Duyck <alexander.h.duyck@linux.intel.com>,
akpm@linux-foundation.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm/page_reporting: the "page" must not be the list head
Date: Tue, 18 Aug 2020 16:41:21 +0800 [thread overview]
Message-ID: <20200818084121.GA33710@L-31X9LVDL-1304.local> (raw)
In-Reply-To: <9656b6cb-23c7-7875-85e7-6aeea7c9dc2c@redhat.com>
On Tue, Aug 18, 2020 at 09:23:12AM +0200, David Hildenbrand wrote:
>On 18.08.20 05:05, Wei Yang wrote:
>> On Mon, Aug 17, 2020 at 07:07:04PM +0200, David Hildenbrand wrote:
>>> On 17.08.20 18:05, Alexander Duyck wrote:
>>>>
>>>>
>>>> On 8/17/2020 2:35 AM, David Hildenbrand wrote:
>>>>> On 17.08.20 10:48, Wei Yang wrote:
>>>>>> If "page" is the list head, list_for_each_entry_safe() would stop
>>>>>> iteration.
>>>>>>
>>>>>> Signed-off-by: Wei Yang <richard.weiyang@linux.alibaba.com>
>>>>>> ---
>>>>>> mm/page_reporting.c | 2 +-
>>>>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>>
>>>>>> diff --git a/mm/page_reporting.c b/mm/page_reporting.c
>>>>>> index 3bbd471cfc81..aaaa3605123d 100644
>>>>>> --- a/mm/page_reporting.c
>>>>>> +++ b/mm/page_reporting.c
>>>>>> @@ -178,7 +178,7 @@ page_reporting_cycle(struct page_reporting_dev_info *prdev, struct zone *zone,
>>>>>> * the new head of the free list before we release the
>>>>>> * zone lock.
>>>>>> */
>>>>>> - if (&page->lru != list && !list_is_first(&page->lru, list))
>>>>>> + if (!list_is_first(&page->lru, list))
>>>>>> list_rotate_to_front(&page->lru, list);
>>>>>>
>>>>>> /* release lock before waiting on report processing */
>>>>>>
>>>>>
>>>>> Is this a fix or a cleanup? If it's a fix, can this be reproduced easily
>>>>> and what ere the effects?
>>>>>
>>>>
>>>> This should be a clean-up. Since the &page->lru != list will always be true.
>>>>
>>>
>>> Makes sense, maybe we can make that a little bit clearer in the patch
>>> description.
>>>
>>
>> Ok, do you have some suggestion on the description?
>>
>> A clean-up for commit xxx?
>>
>> I would appreciate your suggestion :-)
>>
>
>I'd go with something like
>
>"
>mm/page_reporting: drop stale list head check in page_reporting_cycle
>
>list_for_each_entry_safe() guarantees that we will never stumble over
>the list head; "&page->lru != list" will always evaluate to true. Let's
>simplify.
>"
>
Looks really better than mine. Thanks a lot.
>to stress that this is a pure simplifcation.
>
>Reviewed-by: David Hildenbrand <david@redhat.com>
>
>>>> If I recall at some point the that was a check for &next->lru != list
>>>> but I think I pulled out an additional conditional check somewhere so
>>>> that we just go through the start of the loop again and iterate over
>>>> reported pages until we are guaranteed to have a non-reported page to
>>>> rotate to the top of the list with the general idea being that we wanted
>>>> the allocator to pull non-reported pages before reported pages.
>>>
>>> --
>>> Thanks,
>>>
>>> David / dhildenb
>>
>
>
>--
>Thanks,
>
>David / dhildenb
--
Wei Yang
Help you, Help me
next prev parent reply other threads:[~2020-08-18 8:41 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-17 8:48 [PATCH] mm/page_reporting: the "page" must not be the list head Wei Yang
2020-08-17 9:35 ` David Hildenbrand
2020-08-17 16:05 ` Alexander Duyck
2020-08-17 17:07 ` David Hildenbrand
2020-08-18 3:05 ` Wei Yang
2020-08-18 7:23 ` David Hildenbrand
2020-08-18 8:41 ` Wei Yang [this message]
2020-08-18 3:22 ` Wei Yang
2020-08-18 14:58 ` Alexander Duyck
2020-08-18 3:03 ` Wei Yang
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