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From: "Luck, Tony" <tony.luck@intel.com>
To: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>,
	Muchun Song <songmuchun@bytedance.com>,
	Mike Kravetz <mike.kravetz@oracle.com>,
	linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
	Michal Hocko <mhocko@suse.com>,
	Naoya Horiguchi <naoya.horiguchi@nec.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v6 1/2] mm,hwpoison: fix race with hugetlb page allocation
Date: Wed, 11 Aug 2021 21:28:13 -0700	[thread overview]
Message-ID: <20210812042813.GA1576603@agluck-desk2.amr.corp.intel.com> (raw)
In-Reply-To: <20210603233632.2964832-2-nao.horiguchi@gmail.com>

On Fri, Jun 04, 2021 at 08:36:31AM +0900, Naoya Horiguchi wrote:
> From: Naoya Horiguchi <naoya.horiguchi@nec.com>
> 
> When hugetlb page fault (under overcommitting situation) and
> memory_failure() race, VM_BUG_ON_PAGE() is triggered by the following race:
> 
>     CPU0:                           CPU1:
> 
>                                     gather_surplus_pages()
>                                       page = alloc_surplus_huge_page()
>     memory_failure_hugetlb()
>       get_hwpoison_page(page)
>         __get_hwpoison_page(page)
>           get_page_unless_zero(page)
>                                       zero = put_page_testzero(page)
>                                       VM_BUG_ON_PAGE(!zero, page)
>                                       enqueue_huge_page(h, page)
>       put_page(page)
> 
> __get_hwpoison_page() only checks the page refcount before taking an
> additional one for memory error handling, which is not enough because
> there's a time window where compound pages have non-zero refcount during
> hugetlb page initialization.
> 
> So make __get_hwpoison_page() check page status a bit more for hugetlb
> pages with get_hwpoison_huge_page(). Checking hugetlb-specific flags
> under hugetlb_lock makes sure that the hugetlb page is not transitive.
> It's notable that another new function, HWPoisonHandlable(), is helpful
> to prevent a race against other transitive page states (like a generic
> compound page just before PageHuge becomes true).

I'm seeing some strange results when doing a simple injection/recovery.

Current upstream often fails to offline the page with messages like:

	"high-order kernel page"
or
	"unknown page"

Things were working in v5.12. Broken in v5.13.

Bisect says that:

25182f05ffed ("mm,hwpoison: fix race with hugetlb page allocation")

is the culprit (though it is possible that there is more than one
issue ... failure symptoms changed a bit during the bisection).

This commit doesn't revert automatically from upstream. But it
does revert from v5.13. Running with this reverted from v5.13
gives kernel that recovers normally[1] from hundreds of consecutive
error injections.

-Tony

[1] Almost normally. My test catches SIGBUS and prints the virtual
address from the siginfo_t structure. Sometimes the address is correct
other times it is NULL.

  parent reply	other threads:[~2021-08-12  4:28 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-03 23:36 [PATCH v6 0/2] hwpoison: " Naoya Horiguchi
2021-06-03 23:36 ` [PATCH v6 1/2] mm,hwpoison: " Naoya Horiguchi
2021-06-04 23:55   ` Mike Kravetz
2021-08-12  4:28   ` Luck, Tony [this message]
2021-08-12  9:03     ` HORIGUCHI NAOYA(堀口 直也)
2021-08-12 15:25       ` Luck, Tony
2021-08-13  6:29         ` HORIGUCHI NAOYA(堀口 直也)
2021-08-13 15:07           ` Luck, Tony
2021-08-16 17:12             ` Naoya Horiguchi
2021-08-16 17:56               ` Luck, Tony
2021-08-17  5:40                 ` HORIGUCHI NAOYA(堀口 直也)
2021-06-03 23:36 ` [PATCH v6 2/2] mm,hwpoison: make get_hwpoison_page() call get_any_page() Naoya Horiguchi

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