From: Yang Shi <shy828301@gmail.com>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Jann Horn <jannh@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
"Zach O'Keefe" <zokeefe@google.com>,
linux-kernel@vger.kernel.org,
David Hildenbrand <david@redhat.com>
Subject: Re: [PATCH] mm/khugepaged: Fix ->anon_vma race
Date: Thu, 12 Jan 2023 19:22:46 -0800 [thread overview]
Message-ID: <CAHbLzkpM3mpOfo_NcH2roJf_WCJZno6CqLvM+FtjLG8d0_fGkA@mail.gmail.com> (raw)
In-Reply-To: <20230113001037.adqha6lxj7lh75at@box.shutemov.name>
On Thu, Jan 12, 2023 at 4:10 PM Kirill A. Shutemov <kirill@shutemov.name> wrote:
>
> On Thu, Jan 12, 2023 at 10:12:53AM -0800, Yang Shi wrote:
> > > This is totally wrong direction. Or I don't understand the race.
> > >
> > > At this point we already paid nearly all price of of pagetable retraction.
> > > I don't see any correctness reason to stop here, except for the assert.
> >
> > Isn't it possible that collapse_and_free_pmd() clear the pmd which may
> > point to a PTE which maps the COW'ed anon page if this race happens?
>
> No. At this point we have huge page in the place in the page cache and it
> is locked. COW fault would serialize on the page lock.
Aha, yeah, I missed the page lock. So IIUC even though anon_vma is set
there should be not any COW'ed anon pages since cow fault would be
blocked by the page lock. If so I tend to agree with you the lockdep
assert seems unnecessary.
>
> --
> Kiryl Shutsemau / Kirill A. Shutemov
next prev parent reply other threads:[~2023-01-13 3:23 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-11 13:33 [PATCH] mm/khugepaged: Fix ->anon_vma race Jann Horn
2023-01-12 1:06 ` Yang Shi
2023-01-13 19:36 ` Jann Horn
2023-01-12 8:56 ` Kirill A. Shutemov
2023-01-12 18:12 ` Yang Shi
2023-01-13 0:10 ` Kirill A. Shutemov
2023-01-13 3:22 ` Yang Shi [this message]
2023-01-13 19:28 ` Jann Horn
2023-01-15 19:06 ` Kirill A. Shutemov
2023-01-16 12:06 ` Jann Horn
2023-01-16 12:34 ` Kirill A. Shutemov
2023-01-16 12:54 ` Jann Horn
2023-01-16 13:07 ` David Hildenbrand
2023-01-16 13:47 ` Kirill A. Shutemov
2023-01-23 11:07 ` David Hildenbrand
2023-01-24 0:51 ` Kirill A. Shutemov
2023-01-24 10:19 ` David Hildenbrand
2023-01-17 18:57 ` Yang Shi
2023-01-17 19:12 ` Jann Horn
2023-01-17 22:55 ` Andrew Morton
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