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From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Hugh Dickins <hughd@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Song Liu <songliubraving@fb.com>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH] khugepaged: collapse_pte_mapped_thp() flush the right range
Date: Mon, 3 Aug 2020 00:07:38 +0300	[thread overview]
Message-ID: <20200802210738.i4trrpq5b77yaxzw@box> (raw)
In-Reply-To: <alpine.LSU.2.11.2008021204390.27773@eggly.anvils>

On Sun, Aug 02, 2020 at 12:12:42PM -0700, Hugh Dickins wrote:
> pmdp_collapse_flush() should be given the start address at which the huge
> page is mapped, haddr: it was given addr, which at that point has been
> used as a local variable, incremented to the end address of the extent.
> 
> Found by source inspection while chasing a hugepage locking bug, which
> I then could not explain by this. At first I thought this was very bad;
> then saw that all of the page translations that were not flushed would
> actually still point to the right pages afterwards, so harmless; then
> realized that I know nothing of how different architectures and models
> cache intermediate paging structures, so maybe it matters after all -
> particularly since the page table concerned is immediately freed.
> 
> Much easier to fix than to think about.
> 
> Fixes: 27e1f8273113 ("khugepaged: enable collapse pmd for pte-mapped THP")
> Signed-off-by: Hugh Dickins <hughd@google.com>
> Cc: stable@vger.kernel.org # v5.4+

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

-- 
 Kirill A. Shutemov

      parent reply	other threads:[~2020-08-02 21:07 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-02 19:12 Hugh Dickins
2020-08-02 19:12 ` Hugh Dickins
2020-08-02 19:15 ` [PATCH] khugepaged: collapse_pte_mapped_thp() protect the pmd lock Hugh Dickins
2020-08-02 19:15   ` Hugh Dickins
2020-08-02 21:23   ` Kirill A. Shutemov
2020-08-02 19:16 ` [PATCH] khugepaged: retract_page_tables() remember to test exit Hugh Dickins
2020-08-02 19:16   ` Hugh Dickins
2020-08-02 21:44   ` Kirill A. Shutemov
2020-08-03  0:35     ` Hugh Dickins
2020-08-03  0:35       ` Hugh Dickins
2020-08-03  8:59       ` Kirill A. Shutemov
2020-08-02 19:18 ` [PATCH] khugepaged: khugepaged_test_exit() check mmget_still_valid() Hugh Dickins
2020-08-02 19:18   ` Hugh Dickins
2020-08-14 22:13   ` [PATCH] khugepaged: adjust VM_BUG_ON_MM() in __khugepaged_enter() Hugh Dickins
2020-08-14 22:13     ` Hugh Dickins
2020-08-17 20:50     ` Yang Shi
2020-08-17 20:50       ` Yang Shi
2020-08-02 21:07 ` Kirill A. Shutemov [this message]

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