From: Ding Hui <dinghui@sangfor.com.cn>
To: "HORIGUCHI NAOYA(堀口 直也)" <naoya.horiguchi@nec.com>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
Andrew Morton <akpm@linux-foundation.org>,
David Hildenbrand <david@redhat.com>,
Oscar Salvador <osalvador@suse.de>,
Michal Hocko <mhocko@suse.com>, Tony Luck <tony.luck@intel.com>,
"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v1 2/6] mm/hwpoison: remove race consideration
Date: Wed, 16 Jun 2021 08:40:58 +0800 [thread overview]
Message-ID: <7b8f576b-b61b-ad68-c84b-476c96f89156@sangfor.com.cn> (raw)
In-Reply-To: <20210616001141.GA1924716@hori.linux.bs1.fc.nec.co.jp>
On 2021/6/16 8:11, HORIGUCHI NAOYA(堀口 直也) wrote:
> On Tue, Jun 15, 2021 at 08:57:06PM +0800, Ding Hui wrote:
>> On 2021/6/14 10:12, Naoya Horiguchi wrote:
>>> @@ -1956,17 +1938,6 @@ int unpoison_memory(unsigned long pfn)
>>> goto unlock_mutex;
>>> }
>>> - /*
>>> - * unpoison_memory() can encounter thp only when the thp is being
>>> - * worked by memory_failure() and the page lock is not held yet.
>>> - * In such case, we yield to memory_failure() and make unpoison fail.
>>> - */
>>> - if (!PageHuge(page) && PageTransHuge(page)) {
>>> - unpoison_pr_info("Unpoison: Memory failure is now running on %#lx\n",
>>> - pfn, &unpoison_rs);
>>> - goto unlock_mutex;
>>> - }
>>> -
>>
>> if a huge page is in process of alloc or free, HUGETLB_PAGE_DTOR can be set
>> after __SetPageHead() or be cleared before __ClearPageHead(), so this
>> condition may be true in racy.
>
> Hi Ding,
>
> We confirm PageHWPoison() before reaching this if-block and hwpoisoned pages
> are prohibited from allocation, so it seems to me that this check never
> races with hugetlb allocation.
>
> And according to the original patch introduced this if-block (0cea3fdc416d:
> "mm/hwpoison: fix race against poison thp"), this if-block intended to close
> the race between memory_failure() and unpoison_memory(), so that's no longer
> necessary due to mf_mutex.
>
I got it and thanks for your explanation.
>> Do we need the racy test for this situation?
>
> I'm not sure, but I think that we need more stress/fuzz testing focusing on
> this subsystem, and "unpoison vs allocation" race can be covered in the topic.
>
> Thank you,
> Naoya Horiguchi
>
--
Thanks,
- Ding Hui
next prev parent reply other threads:[~2021-06-16 0:41 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-14 2:12 [PATCH v1 0/6] mm/hwpoison: fix unpoison_memory() Naoya Horiguchi
2021-06-14 2:12 ` [PATCH v1 1/6] mm/hwpoison: mf_mutex for soft offline and unpoison Naoya Horiguchi
2021-06-15 11:41 ` Ding Hui
2021-06-15 11:55 ` HORIGUCHI NAOYA(堀口 直也)
2021-06-15 12:42 ` Miaohe Lin
2021-06-16 0:41 ` HORIGUCHI NAOYA(堀口 直也)
2021-06-16 3:14 ` Miaohe Lin
2021-06-14 2:12 ` [PATCH v1 2/6] mm/hwpoison: remove race consideration Naoya Horiguchi
2021-06-15 12:57 ` Ding Hui
2021-06-16 0:11 ` HORIGUCHI NAOYA(堀口 直也)
2021-06-16 0:40 ` Ding Hui [this message]
2021-06-14 2:12 ` [PATCH v1 3/6] mm/hwpoison: introduce MF_MSG_PAGETABLE Naoya Horiguchi
2021-06-14 3:06 ` Matthew Wilcox
2021-06-14 3:55 ` HORIGUCHI NAOYA(堀口 直也)
2021-06-14 2:12 ` [PATCH v1 4/6] mm/hwpoison: remove MF_MSG_BUDDY_2ND and MF_MSG_POISONED_HUGE Naoya Horiguchi
2021-06-14 2:12 ` [PATCH v1 5/6] mm/hwpoison: make some kernel pages handlable Naoya Horiguchi
2021-07-28 10:59 ` Ding Hui
2021-07-29 6:54 ` HORIGUCHI NAOYA(堀口 直也)
2021-06-14 2:12 ` [PATCH v1 6/6] mm/hwpoison: fix unpoison_memory() Naoya Horiguchi
2021-06-17 10:00 ` Ding Hui
2021-06-18 8:36 ` HORIGUCHI NAOYA(堀口 直也)
2021-06-19 12:22 ` Ding Hui
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