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Message-ID: <CAJd=RBC9wN_M6T=vxmw+HxwxJF8Me1pq+UwZGEGoxto+HmG-3Q@mail.gmail.com>
Date: Thu, 22 Mar 2012 21:21:22 +0800
From: Hillf Danton <dhillf@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Linux-MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>,
Michal Hocko <mhocko@...e.cz>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
Hugh Dickins <hughd@...gle.com>
Subject: Re: [PATCH] mm: hugetlb: bail out unmapping after serving reference page
On Thu, Mar 22, 2012 at 5:00 AM, Andrew Morton
<akpm@...ux-foundation.org> wrote:
> On Thu, 23 Feb 2012 12:12:38 -0800
> Andrew Morton <akpm@...ux-foundation.org> wrote:
>
>> On Thu, 23 Feb 2012 21:05:41 +0800
>> Hillf Danton <dhillf@...il.com> wrote:
>>
>> > and a follow-up cleanup also attached.
>>
>> Please, never put more than one patches in an email - it is rather a
>> pain to manually unpick everything.
>>
>> > When unmapping given VM range, a couple of code duplicate, such as pte_page()
>> > and huge_pte_none(), so a cleanup needed to compact them together.
>> >
>> > Signed-off-by: Hillf Danton <dhillf@...il.com>
>> > ---
>> >
>> > --- a/mm/hugetlb.c Thu Feb 23 20:13:06 2012
>> > +++ b/mm/hugetlb.c Thu Feb 23 20:30:16 2012
>> > @@ -2245,16 +2245,23 @@ void __unmap_hugepage_range(struct vm_ar
>> > if (huge_pmd_unshare(mm, &address, ptep))
>> > continue;
>> >
>> > + pte = huge_ptep_get(ptep);
>> > + if (huge_pte_none(pte))
>> > + continue;
>> > +
>> > + /*
>> > + * HWPoisoned hugepage is already unmapped and dropped reference
>> > + */
>> > + if (unlikely(is_hugetlb_entry_hwpoisoned(pte)))
>> > + continue;
>> > +
>> > + page = pte_page(pte);
>> > /*
>> > * If a reference page is supplied, it is because a specific
>> > * page is being unmapped, not a range. Ensure the page we
>> > * are about to unmap is the actual page of interest.
>> > */
>> > if (ref_page) {
>> > - pte = huge_ptep_get(ptep);
>> > - if (huge_pte_none(pte))
>> > - continue;
>> > - page = pte_page(pte);
>> > if (page != ref_page)
>> > continue;
>> >
>> > @@ -2267,16 +2274,6 @@ void __unmap_hugepage_range(struct vm_ar
>> > }
>> >
>> > pte = huge_ptep_get_and_clear(mm, address, ptep);
>> > - if (huge_pte_none(pte))
>> > - continue;
>> > -
>> > - /*
>> > - * HWPoisoned hugepage is already unmapped and dropped reference
>> > - */
>> > - if (unlikely(is_hugetlb_entry_hwpoisoned(pte)))
>> > - continue;
>> > -
>> > - page = pte_page(pte);
>> > if (pte_dirty(pte))
>> > set_page_dirty(page);
>> > list_add(&page->lru, &page_list);
>>
>> This changes behaviour when ref_page refers to a hwpoisoned page.
>
> Respond, please?
First say sorry to you, Andrew.
The comment says, HWPoisoned hugepage is already unmapped;
and even if ref_page == HWPoisoned page, it is not added onto
page_list and no page_remove_rmap() is issued for it, so we end
up with no behavior change.
Thanks
-hd
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