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>,
Yang Shi <shy828301@gmail.com>,
Wang Yugui <wangyugui@e16-tech.com>,
Matthew Wilcox <willy@infradead.org>,
Naoya Horiguchi <naoya.horiguchi@nec.com>,
Alistair Popple <apopple@nvidia.com>,
Ralph Campbell <rcampbell@nvidia.com>, Zi Yan <ziy@nvidia.com>,
Miaohe Lin <linmiaohe@huawei.com>,
Minchan Kim <minchan@kernel.org>, Jue Wang <juew@google.com>,
Peter Xu <peterx@redhat.com>, Jan Kara <jack@suse.cz>,
Shakeel Butt <shakeelb@google.com>,
Oscar Salvador <osalvador@suse.de>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 02/10] mm/thp: make is_huge_zero_pmd() safe and quicker
Date: Wed, 9 Jun 2021 13:22:46 +0300 [thread overview]
Message-ID: <20210609102246.hgw23tsqyw7jxts3@box.shutemov.name> (raw)
In-Reply-To: <21ea9ca-a1f5-8b90-5e88-95fb1c49bbfa@google.com>
On Tue, Jun 08, 2021 at 09:08:09PM -0700, Hugh Dickins wrote:
> Most callers of is_huge_zero_pmd() supply a pmd already verified present;
> but a few (notably zap_huge_pmd()) do not - it might be a pmd migration
> entry, in which the pfn is encoded differently from a present pmd: which
> might pass the is_huge_zero_pmd() test (though not on x86, since L1TF
> forced us to protect against that); or perhaps even crash in pmd_page()
> applied to a swap-like entry.
>
> Make it safe by adding pmd_present() check into is_huge_zero_pmd() itself;
> and make it quicker by saving huge_zero_pfn, so that is_huge_zero_pmd()
> will not need to do that pmd_page() lookup each time.
>
> __split_huge_pmd_locked() checked pmd_trans_huge() before: that worked,
> but is unnecessary now that is_huge_zero_pmd() checks present.
>
> Fixes: e71769ae5260 ("mm: enable thp migration for shmem thp")
> Signed-off-by: Hugh Dickins <hughd@google.com>
> Cc: <stable@vger.kernel.org>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
--
Kirill A. Shutemov
next prev parent reply other threads:[~2021-06-09 10:22 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <af88612-1473-2eaa-903-8d1a448b26@google.com>
2021-06-09 4:08 ` [PATCH v2 02/10] mm/thp: make is_huge_zero_pmd() safe and quicker Hugh Dickins
2021-06-09 10:22 ` Kirill A. Shutemov [this message]
2021-06-09 16:56 ` Yang Shi
2021-06-09 4:14 ` [PATCH v2 04/10] mm/thp: fix vma_address() if virtual address below file offset Hugh Dickins
2021-06-09 4:16 ` [PATCH v2 05/10] mm/thp: fix page_address_in_vma() on file THP tails Hugh Dickins
2021-06-09 4:19 ` [PATCH v2 06/10] mm/thp: unmap_mapping_page() to fix THP truncate_cleanup_page() Hugh Dickins
2021-06-09 17:02 ` Yang Shi
2021-06-09 21:11 ` Hugh Dickins
2021-06-09 21:16 ` [PATCH v3 " Hugh Dickins
2021-06-09 21:51 ` Yang Shi
2021-06-09 4:22 ` [PATCH v2 07/10] mm: thp: replace DEBUG_VM BUG with VM_WARN when unmap fails for split Hugh Dickins
2021-06-09 4:25 ` [PATCH v2 08/10] mm: rmap: make try_to_unmap() void function Hugh Dickins
2021-06-10 7:57 ` HORIGUCHI NAOYA(堀口 直也)
2021-06-09 4:27 ` [PATCH v2 09/10] mm/thp: remap_page() is only needed on anonymous THP Hugh Dickins
2021-06-09 4:30 ` [PATCH v2 10/10] mm: hwpoison_user_mappings() try_to_unmap() with TTU_SYNC Hugh Dickins
2021-06-09 10:27 ` Kirill A. Shutemov
2021-06-10 7:38 ` HORIGUCHI NAOYA(堀口 直也)
[not found] ` <20210610151505.d0124033e55bda07fa3d4408@linux-foundation.org>
[not found] ` <2014832.e7zRqyNrDn@nvdebian>
2021-06-11 0:15 ` [PATCH v2 00/10] mm/thp: fix THP splitting unmap BUGs and related Hugh Dickins
2021-06-11 7:28 ` Alistair Popple
2021-06-11 20:56 ` Hugh Dickins
2021-06-12 7:34 ` Alistair Popple
2021-06-12 8:20 ` Hugh Dickins
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