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t=1791578191; bh=qsvSQTb/mkLW7ftqjoW8EveuRC0YRtADluZX056tD6s=; h=Date:Subject:From:To:Cc:References:In-Reply-To; b=GLg1cnuJ6do1U7xESKZK430UTlifVgIdS04Wit5vk4OfnCoWthVvEQWbUXYt8mX30 0/IFQUAJXsPkfEYmpvaVVmc07kPx74p5T2FLl26XFDkliiFbqCIdI6Frhu9gN3S5q/ lqswPDyNyFXCYw+5XjMSu4eeohk7I6KZAPNJsVZnTc9fKvCU4ZOQR03N9jY7p8Cu3s QuqPJ0VKJBXqgMvfaaumrRgQIgbFjfBiYdyiKYvH1Hx+iXrWt5Ykyhcd/2pPgyrBJD EN6OBqmIGEix8m1WtBV5guB1BJuQDWtbOW+cnvJpNVemIC52kNxFo4rAONufCe3C+7 UjLoQted9mjXw== Message-ID: <39ae6c48-7fcc-41d5-bfaf-fe626071861e@kernel.org> Date: Fri, 9 Oct 2026 22:36:21 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/4] x86/mm: fix missing pgtable destructor for vmemmap tables From: "David Hildenbrand (Arm)" To: Muchun Song , akpm@linux-foundation.org Cc: linux-mm@kvack.org, stable@vger.kernel.org, osalvador@suse.de, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, tglx@kernel.org, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com, linux-arm-kernel@lists.infradead.org, pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu, alex@ghiti.fr, linux-riscv@lists.infradead.org, agordeev@linux.ibm.com, kevin.brodsky@arm.com, bjorn@rivosinc.com, apopple@nvidia.com, linux-kernel@vger.kernel.org, muchun.song@linux.dev References: <20261008073021.2512665-1-songmuchun@bytedance.com> <20261008073021.2512665-2-songmuchun@bytedance.com> Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 192A3C0003 X-Stat-Signature: 9xsjitaqjmftw7chg1xfx6mr639utrzz X-HE-Tag: 1791578192-899909 X-HE-Meta: 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 eh78/vCZ LG3s2admuRzjPjVqUVLnbSV9ewn0VeoCWC+EEgAMtBey8lYUhKoRwVV1jqh3r7i8ActwK7KkdIYZJmpyJhbEptukxWMpJfhONz/xLJwLthU8XO6NiXE/pPu9hLPG5YXlYDuGpt5lYXNDzjoNqVzRpCfwNr1HWbn3tFG72/lTH2ZO0N9zUOVEkg+Iyyn5uO2b6qPaZuhZf9TXn2fhjcQuC9rDsJlu127YFYDKwIGu7/gIr/LQHEteO0sqOTCl2hQS5yMurWa6j23os5UBvzj9/MfxUgj9g8xD2Y3H4s3kN22iotv8EZ+FAjPDz4w== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 10/9/26 22:33, David Hildenbrand (Arm) wrote: > On 10/8/26 09:30, Muchun Song wrote: >> Since commit 49f599666420 ("mm: call ctor/dtor for kernel PTEs"), >> pte_alloc_one_kernel() runs the page-table constructor for kernel PTE >> tables. >> >> HugeTLB vmemmap optimization uses pte_alloc_one_kernel() when splitting >> a PMD. Restoring the vmemmap backing pages does not collapse the PTE >> table, so a later memory hot-remove eventually frees that table through >> free_pagetable(). That path currently calls pagetable_free() directly >> without decrementing NR_PAGETABLE. >> >> Use PageTable() to identify constructor-backed tables and run the >> matching destructor before freeing them. Keep reserved and >> constructor-free tables on their existing paths. This also prepares >> vmemmap teardown for generic runtime allocations through the normal >> pgalloc helpers. >> >> Fixes: 49f599666420 ("mm: call ctor/dtor for kernel PTEs") >> Cc: stable@vger.kernel.org >> Assisted-by: LLM >> Signed-off-by: Muchun Song >> --- >> arch/x86/mm/init_64.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c >> index 70e682180291..a3ea627157ab 100644 >> --- a/arch/x86/mm/init_64.c >> +++ b/arch/x86/mm/init_64.c >> @@ -1003,6 +1003,8 @@ static void __meminit free_pagetable(struct page *page) >> { >> if (PageReserved(page)) >> free_reserved_page(page); >> + else if (PageTable(page)) >> + pagetable_dtor_free(page_ptdesc(page)); >> else >> pagetable_free(page_ptdesc(page)); >> } > > pagetable_free() will do ptdesc_test_kernel(pt) -> pagetable_free_kernel(pt) -> > pagetable_dtor_free(). Ah, behavior depends on CONFIG_ASYNC_KERNEL_PGTABLE_FREE$ ... Why not do the right thing in pagetable_free() instead? -- Cheers, David