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b=AFXG7GwmXhucIfzukLXOgDvZlVmnV9j9ty1ByoXrpRN1ioDyphHHOHlrVv1gakqUg KTlxAHcEq8++l4cHTAc330eModcJymsBYpvtBM2qCbji3PeNjnKxwNrdqyii6EH3K0 FhzHHvfdF2Kjq+f8G3BnISidcHkCMQLL93qInxxEkHqXghsN3WFRFDy4CNl0Jte+K8 6UMNMQnhTlbRb9LZOYQFes0x9AaJ+T7wRMG6KhTwmG87PnXKQozeUgmUGGXvhbjRd+ HcJl+37dRYS5su40Rb/zEoPXIb6vDzDHiWzLnciUTKCGNF8vZQ+/S2JO2Dboz89Q/M NE/JwmRFRRunw== Message-ID: <6f6e6998-7dd2-469d-852f-4ff7bbb768b9@kernel.org> Date: Sun, 31 May 2026 21:29:21 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] arm64: mm: call pagetable dtor when freeing hot-removed page tables To: Kevin Brodsky , 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: "David Hildenbrand (Arm)" 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-Queue-Id: 23DEA140002 X-Stat-Signature: iziyn19tg8733kcdyhdjffy8m96s3f6i X-Rspamd-Server: rspam06 X-HE-Tag: 1780255765-447720 X-HE-Meta: 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 KNTL0ZLu Z/iKLOAhyUNmqK/DYzDh1urn62RFDCAPW4fdVXrTQkRAxOlHW6nQVX7ZCsXm32eyt0eXlPoATAArbem767jn3nyORTR+qe0FXWM6NErYcjiAP0KiXYo0+06jz1AryMrsVcJgbAyqPMEwLBbkY2f82oyUFyGsuq/HPunPNCozjmmPTBxso66srsD4tz5r+LKlycGSKdoeiRU/K7pi+FC6W87TYHb3dk4KHm9bgfGOLkzWGw0HngP6Mzvzpo8RXwUZS/GkQMdDgNXLRoajc4p7r4EA2+hZaeRLsZgaeFdzSccVdTBxwAbRxbNWid5rsZs5vpGlVaw9dOoyUo7s= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 5/27/26 09:34, Kevin Brodsky wrote: > On 26/05/2026 14:31, David Hildenbrand (Arm) wrote: >> On 5/26/26 13:54, Kevin Brodsky wrote: >>> 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(). We started running into the wrong direction, and now have to undo all the wrong things we already did :) In the current design Willy has in mind, doing a page_folio() will later return NULL if it's not actually a folio. -- Cheers, David