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Sat, 10 Oct 2026 03:50:15 +0000 X-Mizu-Trace-ID: 9484aa877343ee44 X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3901.100.1.1.12\)) Subject: Re: [PATCH 1/4] x86/mm: fix missing pgtable destructor for vmemmap tables From: Muchun Song In-Reply-To: <39ae6c48-7fcc-41d5-bfaf-fe626071861e@kernel.org> Date: Sat, 10 Oct 2026 11:49:57 +0800 Cc: Muchun Song , akpm@linux-foundation.org, 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 Content-Transfer-Encoding: quoted-printable Message-Id: <98481914-D123-4F58-97FA-C2F34469D34C@linux.dev> References: <20261008073021.2512665-1-songmuchun@bytedance.com> <20261008073021.2512665-2-songmuchun@bytedance.com> <39ae6c48-7fcc-41d5-bfaf-fe626071861e@kernel.org> To: "David Hildenbrand (Arm)" X-Mailer: Apple Mail (2.3901.100.1.1.12) X-Stat-Signature: mnyfn588g9dqw1gbiomcz47c1yk8kt46 X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 8241CC0002 X-HE-Tag: 1791604239-96779 X-HE-Meta: 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 BFaypvep bFVx2Eywb0TxVb9VDHbwwZfvtDBu35L1XniS/qNuHG+3hi44dgljyZgfsmM/jomUVAIRcniF0dC/p9WXCV+7NmQ/1R2JsRjm0JzjXtfy+ajDI+0fqPnNA0pnMHIscpspISwFEgYpbWTXLQLmIZ4Rk9m41S/ae6a/CjJaaT2xRRN6gatijOqoH9g1yaG0NfhcbgiwvXmnVLJOpChJdkV7gobNJkCwznyvVDUd41Vcnlk1Jqy35FyFHIEsTk3pu12h/5as/6M6SftCsHfoYACTtORQkYndZNtC4frkrR+GJRZBJI1CnNUl8ZncpVg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > On Oct 10, 2026, at 04:36, David Hildenbrand (Arm) = wrote: >=20 > 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. >>>=20 >>> 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. >>>=20 >>> 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. >>>=20 >>> 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(+) >>>=20 >>> 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)); >>> } >>=20 >> pagetable_free() will do ptdesc_test_kernel(pt) -> = pagetable_free_kernel(pt) -> >> pagetable_dtor_free(). >=20 > Ah, behavior depends on CONFIG_ASYNC_KERNEL_PGTABLE_FREE$ ... >=20 > Why not do the right thing in pagetable_free() instead? Good point. More easy to this issue on different architecture. I'll fix pagetable_free next version. Thanks, Muchun >=20 > --=20 > Cheers, >=20 > David