linux-kernel - Re: [PATCH] mm/khugepaged: Fix ->anon

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Message-ID: <20230115190654.mehtlyz2rxtg34sl@box.shutemov.name>
Date:   Sun, 15 Jan 2023 22:06:54 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Jann Horn <jannh@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Zach O'Keefe <zokeefe@...gle.com>,
        linux-kernel@...r.kernel.org, David Hildenbrand <david@...hat.com>,
        Yang Shi <shy828301@...il.com>
Subject: Re: [PATCH] mm/khugepaged: Fix ->anon_vma race

On Fri, Jan 13, 2023 at 08:28:59PM +0100, Jann Horn wrote:
> No, that lockdep assert has to be there. Page table traversal is
> allowed under any one of the mmap lock, the anon_vma lock (if the VMA
> is associated with an anon_vma), and the mapping lock (if the VMA is
> associated with a mapping); and so to be able to remove page tables,
> we must hold all three of them.

Okay, that's fair. I agree with the patch now. Maybe adjust the commit
message a bit?

Anyway:

Acked-by: Kirill A. Shutemov <kirill.shutemov@...el.linux.com>

BTW, I've noticied that you recently added tlb_remove_table_sync_one().
I'm not sure why it is needed. Why IPI in pmdp_collapse_flush() in not
good enough to serialize against GUP fast?

-- 
  Kiryl Shutsemau / Kirill A. Shutemov