From: Vlastimil Babka <vbabka@suse.cz>
To: Michal Hocko <mhocko@kernel.org>
Cc: linux-mm@kvack.org, Michael Ellerman <mpe@ellerman.id.au>,
Andrew Morton <akpm@linux-foundation.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Reza Arbab <arbab@linux.vnet.ibm.com>,
Yasuaki Ishimatsu <yasu.isimatu@gmail.com>,
qiuxishi@huawei.com, Igor Mammedov <imammedo@redhat.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/2] mm, page_alloc: fail has_unmovable_pages when seeing reserved pages
Date: Tue, 17 Oct 2017 15:03:30 +0200 [thread overview]
Message-ID: <7d389744-13c9-4f01-106a-902af61643e1@suse.cz> (raw)
In-Reply-To: <20171013120756.jeopthigbmm3c7bl@dhcp22.suse.cz>
On 10/13/2017 02:07 PM, Michal Hocko wrote:
> On Fri 13-10-17 14:04:08, Vlastimil Babka wrote:
>> On 10/13/2017 02:00 PM, Michal Hocko wrote:
>>> From: Michal Hocko <mhocko@suse.com>
>>>
>>> Reserved pages should be completely ignored by the core mm because they
>>> have a special meaning for their owners. has_unmovable_pages doesn't
>>> check those so we rely on other tests (reference count, or PageLRU) to
>>> fail on such pages. Althought this happens to work it is safer to simply
>>> check for those explicitly and do not rely on the owner of the page
>>> to abuse those fields for special purposes.
>>>
>>> Please note that this is more of a further fortification of the code
>>> rahter than a fix of an existing issue.
>>>
>>> Signed-off-by: Michal Hocko <mhocko@suse.com>
>>> ---
>>> mm/page_alloc.c | 3 +++
>>> 1 file changed, 3 insertions(+)
>>>
>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>>> index ad0294ab3e4f..a8800b0a5619 100644
>>> --- a/mm/page_alloc.c
>>> +++ b/mm/page_alloc.c
>>> @@ -7365,6 +7365,9 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count,
>>>
>>> page = pfn_to_page(check);
>>>
>>> + if (PageReferenced(page))
>>
>> "Referenced" != "Reserved"
>
> Dohh, you are right of course. I blame auto-completion ;) but I am lame
> in fact...
> ---
> From 44b20bdb03846bc5fd79c883d16b8f3aa436878f Mon Sep 17 00:00:00 2001
> From: Michal Hocko <mhocko@suse.com>
> Date: Fri, 13 Oct 2017 13:55:21 +0200
> Subject: [PATCH] mm, page_alloc: fail has_unmovable_pages when seeing reserved
> pages
>
> Reserved pages should be completely ignored by the core mm because they
> have a special meaning for their owners. has_unmovable_pages doesn't
> check those so we rely on other tests (reference count, or PageLRU) to
> fail on such pages. Althought this happens to work it is safer to simply
> check for those explicitly and do not rely on the owner of the page
> to abuse those fields for special purposes.
>
> Please note that this is more of a further fortification of the code
> rahter than a fix of an existing issue.
>
> Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
> ---
> mm/page_alloc.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index ad0294ab3e4f..5b4d85ae445c 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -7365,6 +7365,9 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count,
>
> page = pfn_to_page(check);
>
> + if (PageReserved(page))
> + return true;
> +
> /*
> * Hugepages are not in LRU lists, but they're movable.
> * We need not scan over tail pages bacause we don't
>
--
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next prev parent reply other threads:[~2017-10-17 13:03 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-18 7:08 [PATCH v2 0/2] mm, memory_hotplug: redefine memory offline retry logic Michal Hocko
2017-09-18 7:08 ` [PATCH 1/2] mm, memory_hotplug: do not fail offlining too early Michal Hocko
2017-10-10 12:05 ` Michael Ellerman
2017-10-10 12:27 ` Michal Hocko
2017-10-11 2:37 ` Michael Ellerman
2017-10-11 5:19 ` Michael Ellerman
2017-10-11 14:05 ` Anshuman Khandual
2017-10-11 14:16 ` Michal Hocko
2017-10-11 6:51 ` Michal Hocko
2017-10-11 8:04 ` Vlastimil Babka
2017-10-11 8:13 ` Michal Hocko
2017-10-11 11:17 ` Vlastimil Babka
2017-10-11 11:24 ` Michal Hocko
2017-10-13 11:42 ` Michael Ellerman
2017-10-13 11:58 ` Michal Hocko
2017-10-13 12:00 ` [PATCH 1/2] mm: drop migrate type checks from has_unmovable_pages Michal Hocko
2017-10-13 12:00 ` [PATCH 2/2] mm, page_alloc: fail has_unmovable_pages when seeing reserved pages Michal Hocko
2017-10-13 12:04 ` Vlastimil Babka
2017-10-13 12:07 ` Michal Hocko
2017-10-17 13:03 ` Vlastimil Babka [this message]
2017-10-17 11:41 ` [PATCH 1/2] mm: drop migrate type checks from has_unmovable_pages Michael Ellerman
2017-10-17 12:03 ` Michal Hocko
2017-10-17 13:02 ` Vlastimil Babka
2017-10-19 2:51 ` Joonsoo Kim
2017-10-19 7:15 ` Michal Hocko
2017-10-19 7:33 ` Joonsoo Kim
2017-10-19 8:20 ` Michal Hocko
2017-10-19 12:21 ` Michal Hocko
2017-10-20 2:13 ` Joonsoo Kim
2017-10-20 5:59 ` Michal Hocko
2017-10-20 6:50 ` Joonsoo Kim
2017-10-20 7:02 ` Michal Hocko
2017-10-23 5:23 ` Joonsoo Kim
2017-10-23 8:10 ` Michal Hocko
2017-10-24 4:44 ` Joonsoo Kim
2017-10-24 7:44 ` Michal Hocko
2017-10-24 8:12 ` Vlastimil Babka
2017-10-24 12:25 ` Michal Hocko
2017-10-26 2:47 ` Joonsoo Kim
2017-10-26 7:41 ` Michal Hocko
2017-10-20 7:22 ` Xishi Qiu
2017-10-20 8:17 ` Michal Hocko
2017-10-23 5:26 ` Joonsoo Kim
2017-10-26 13:04 ` Vlastimil Babka
2017-10-26 13:59 ` Michal Hocko
2017-09-18 7:08 ` [PATCH 2/2] mm, memory_hotplug: remove timeout from __offline_memory Michal Hocko
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