From: Yu Zhao <yuzhao@google.com>
To: Ryan Roberts <ryan.roberts@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
SeongJae Park <sj@kernel.org>,
Christoph Hellwig <hch@infradead.org>,
"Matthew Wilcox (Oracle)" <willy@infradead.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Lorenzo Stoakes <lstoakes@gmail.com>,
Uladzislau Rezki <urezki@gmail.com>, Zi Yan <ziy@nvidia.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
damon@lists.linux.dev
Subject: Re: [PATCH v2 2/5] mm: damon must atomically clear young on ptes and pmds
Date: Thu, 18 May 2023 17:19:48 -0600 [thread overview]
Message-ID: <CAOUHufYXuH+mUNAtiRbAqqKTKO-nGR248Z2MVgGzMJqYu8yawQ@mail.gmail.com> (raw)
In-Reply-To: <20230518110727.2106156-3-ryan.roberts@arm.com>
On Thu, May 18, 2023 at 5:07 AM Ryan Roberts <ryan.roberts@arm.com> wrote:
>
> It is racy to non-atomically read a pte, then clear the young bit, then
> write it back as this could discard dirty information. Further, it is
> bad practice to directly set a pte entry within a table. Instead
> clearing young must go through the arch-provided helper,
> ptep_test_and_clear_young() to ensure it is modified atomically and to
> give the arch code visibility and allow it to check (and potentially
> modify) the operation.
>
> Fixes: 46c3a0accdc4 ("mm/damon/vaddr: separate commonly usable functions")
This should be a separate patch, since it's independent from what the
series tries to do.
And that patch should cc stable, since it fixes user data corruption.
> Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
> Reviewed-by: Zi Yan <ziy@nvidia.com>
> ---
> mm/damon/ops-common.c | 16 ++++++----------
> mm/damon/ops-common.h | 4 ++--
> mm/damon/paddr.c | 4 ++--
> mm/damon/vaddr.c | 4 ++--
> 4 files changed, 12 insertions(+), 16 deletions(-)
>
> diff --git a/mm/damon/ops-common.c b/mm/damon/ops-common.c
> index cc63cf953636..acc264b97903 100644
> --- a/mm/damon/ops-common.c
> +++ b/mm/damon/ops-common.c
> @@ -37,7 +37,7 @@ struct folio *damon_get_folio(unsigned long pfn)
> return folio;
> }
>
> -void damon_ptep_mkold(pte_t *pte, struct mm_struct *mm, unsigned long addr)
> +void damon_ptep_mkold(pte_t *pte, struct vm_area_struct *vma, unsigned long addr)
> {
> bool referenced = false;
> struct folio *folio = damon_get_folio(pte_pfn(*pte));
> @@ -45,13 +45,11 @@ void damon_ptep_mkold(pte_t *pte, struct mm_struct *mm, unsigned long addr)
> if (!folio)
> return;
>
> - if (pte_young(*pte)) {
> + if (ptep_test_and_clear_young(vma, addr, pte))
> referenced = true;
> - *pte = pte_mkold(*pte);
> - }
>
> #ifdef CONFIG_MMU_NOTIFIER
> - if (mmu_notifier_clear_young(mm, addr, addr + PAGE_SIZE))
> + if (mmu_notifier_clear_young(vma->vm_mm, addr, addr + PAGE_SIZE))
> referenced = true;
> #endif /* CONFIG_MMU_NOTIFIER */
Use ptep_clear_young_notify(). Similar below.
next prev parent reply other threads:[~2023-05-18 23:20 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-18 11:07 [PATCH v2 0/5] Encapsulate PTE contents from non-arch code Ryan Roberts
2023-05-18 11:07 ` [PATCH v2 1/5] mm: vmalloc must set pte via arch code Ryan Roberts
2023-05-19 12:09 ` Uladzislau Rezki
2023-05-24 18:47 ` Mike Rapoport
2023-05-18 11:07 ` [PATCH v2 2/5] mm: damon must atomically clear young on ptes and pmds Ryan Roberts
2023-05-18 17:13 ` SeongJae Park
2023-05-19 8:53 ` Ryan Roberts
2023-05-18 23:19 ` Yu Zhao [this message]
2023-05-19 9:02 ` Ryan Roberts
2023-05-19 19:54 ` SeongJae Park
2023-05-22 8:53 ` Ryan Roberts
2023-05-24 18:49 ` Mike Rapoport
2023-05-18 11:07 ` [PATCH v2 3/5] mm: Fix failure to unmap pte on highmem systems Ryan Roberts
2023-05-24 18:59 ` Mike Rapoport
2023-05-18 11:07 ` [PATCH v2 4/5] mm: Add new ptep_deref() helper to fully encapsulate pte_t Ryan Roberts
2023-05-18 19:28 ` Yu Zhao
2023-05-19 9:12 ` Ryan Roberts
2023-05-25 9:08 ` Ryan Roberts
2023-05-26 2:02 ` Yu Zhao
2023-05-24 19:06 ` Mike Rapoport
2023-05-24 19:11 ` Ryan Roberts
2023-05-18 11:07 ` [PATCH v2 5/5] mm: ptep_deref() conversion Ryan Roberts
2023-05-18 12:08 ` Jason Gunthorpe
2023-05-18 17:22 ` SeongJae Park
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