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h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=lhpGYhy9mzLM0aQ1LmEdrgC7rB9SgaM2E0euQSb2IyT0zWRqzHJdbHCQvPWYTWPEz P7TxGZIzx/4bnsXReJ1v8DM+/x5k4r9aS3DnmQY5y6dTDxqa0kFbXyRop06qe/gjVs u16UwYDXRXQBF7Yv8VbCdByU0IIzdtVpVZ2FuHmg= Message-ID: Date: Wed, 27 May 2026 09:34:19 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] arm64: mm: call pagetable dtor when freeing hot-removed page tables To: "David Hildenbrand (Arm)" , Vishal Moola , Catalin Marinas Cc: Andrew Morton , Alistair Popple , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, will@kernel.org References: <20260521032730.2104017-1-apopple@nvidia.com> <20260521153130.d7d5cd060f7522f894252333@linux-foundation.org> <92450154-e1ab-46e4-b23d-eaa59c9cdd3b@arm.com> <1be38262-53de-4a27-9841-393e12fc1475@kernel.org> From: Kevin Brodsky Content-Language: en-GB In-Reply-To: <1be38262-53de-4a27-9841-393e12fc1475@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam12 X-Stat-Signature: 7jneykk9eoaghx4g31ha7tfwpbfqkth8 X-Rspam-User: X-Rspamd-Queue-Id: 0A98A10000F X-HE-Tag: 1779867265-515124 X-HE-Meta: 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 73YEqOLV CTyUkdGK58sYIAaGYG0eW3JHWKiV4hKLSd0DdV+qIuKxu1owLrWf+iRy2gncr6ajFPcDwpX+eDWj/7nwLn5EYSDNzUOWJCRhSqhy/i1mueRM4zKeRom0hyoaHeGN7cIGfLW2ChSizyqBHeid5Z6kEkHV0qyrIpTtLl1Saw6jzt5vW5/Y/2a1bL69Uo51fi/ncKpDjbqEN+wnEqMMibgZNpDUGuyB7envFToSdEVmlO2J+UGJLpowc61WlOvBR6ZAIgfIugC5yOxXIDsPosEhkwluyFI1cIeq/rH4kBUllVhsHM2opQZsMB4oK/P/RjAWivlBQjWy3pVB3hkTjfawX6o+rkg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 26/05/2026 14:31, David Hildenbrand (Arm) wrote: > On 5/26/26 13:54, Kevin Brodsky wrote: >> On 22/05/2026 11:36, Vishal Moola wrote: >>>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c >>>> index 4c8959153ac4..9d42cbddce27 100644 >>>> --- a/arch/arm64/mm/mmu.c >>>> +++ b/arch/arm64/mm/mmu.c >>>> @@ -1441,6 +1441,9 @@ static void free_hotplug_page_range(struct page *page, size_t size, >>>> >>>> static void free_hotplug_pgtable_page(struct page *page) >>>> { >>>> + if (folio_test_pgtable(page_folio(page))) >>> This should work. >>> >>>> + pagetable_dtor(page_ptdesc(page)); >>>> + >>>> free_hotplug_page_range(page, PAGE_SIZE, NULL); >>> In the case we presumably have a page table page (ptdesc) at this >>> point, we should really be freeing it with pagetable_free() as well. >> Agreed, I think this is the right thing to do, something like: >> >> if (folio_test_pgtable(page_folio(page))) >> pagetable_dtor_free(page_ptdesc(page)); else >> free_hotplug_page_range(page, PAGE_SIZE, NULL); > That code pattern is wrong. > > folio_test_pgtable() shouldn't exist. > > In the future, something is either a pgtable or a folio, not both. > > So check the type against the page, not the folio. In other words use PageTable(page) instead? Interestingly I can see a few calls to folio_test_pgtable() across the kernel but none to PageTable(), maybe just an antipattern then? The ctor/dtor also use __folio_{set,clear}_pgtable(). - Kevin