From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B5306FF8864 for ; Mon, 27 Apr 2026 20:59:39 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 2A33C6B0088; Mon, 27 Apr 2026 16:59:39 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 252DE6B008A; Mon, 27 Apr 2026 16:59:39 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 142B96B008C; Mon, 27 Apr 2026 16:59:39 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id F3B386B0088 for ; Mon, 27 Apr 2026 16:59:38 -0400 (EDT) Received: from smtpin05.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay01.hostedemail.com (Postfix) with ESMTP id AC2AA1C0383 for ; Mon, 27 Apr 2026 20:59:38 +0000 (UTC) X-FDA: 84705552036.05.E5D73F3 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf01.hostedemail.com (Postfix) with ESMTP id A896C40017 for ; Mon, 27 Apr 2026 20:59:36 +0000 (UTC) Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=fB0MsEdR; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf01.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1777323576; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=W0xbzX9wZmv42XHV/ZmZTyw6S9VYjXqDsMwKLwQ2JuE=; b=Nfxw3/qz02k45tIz2NTgDSy90Tc7YBkZt5quCovh48MFfM7RhGpJjj7tIs7Q7QQwvHrax0 GYTmR8Hodk+5ajWD89p4XfqwlB01ClKL6x0ZgSzChORitM2ijVoJghTV8mqJTFsg30+bnt Ug03EPUHm9DBPhvqCLBbUZOWfxLeUJE= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1777323576; a=rsa-sha256; cv=none; b=SJ3R6ItEeNqvHnQ8hde1T6YecycR89dzpxrhpEESeLrEiW0mLsdPaHds/+0ClAtMuGOMag cm+pJPt6vASYsaTOH+2dOq7NeHfDwbZTZvLLczitaO26pPpth8NdR0nTf2NhQ/l20rkKvK 1wEcniES58yaqBdJ0GX6dFNjBNtzUPE= ARC-Authentication-Results: i=1; imf01.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=fB0MsEdR; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf01.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 9D5B6401AE; Mon, 27 Apr 2026 20:59:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A52FFC19425; Mon, 27 Apr 2026 20:59:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777323575; bh=4fCdoQX9tOKa3DEv8CT8f6q/tReZla5dySYrHKOPds8=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=fB0MsEdRgoihroZKswclQKQK7DSaYaBeTbYgcnwk+cGwwMNHZs+Ewrbsx8gMZ3CyM QtJzJG7vGabw1+iCAwGf0eeEzwn4VwU6nVQ3BOASjmOtgG9H5rY8QhX2YWlZAfPVNo zoz0HYLK/I5mosk9uxs6yULiL2WCKuks9JvwOebp4t60hFYZEACArzvOGq1sLEAm6t H4DtPpdc96HIPXtY7h0zoyvunWqXabnlUPE25QE3718JB7KMtR/87czjxFFJIj5lo1 D6BQLhkgCE5rpeS8GUVhFAPr3DDqFGeq9eMkxXKmYNzBOJebAuAgqyooYpqY16Qyr5 Ag0QFqf0GI2fw== Message-ID: <97192ac3-643d-4393-87ef-53a9f3ddaf95@kernel.org> Date: Mon, 27 Apr 2026 22:59:24 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/3] mm: remove page_mapped() To: Yoshinori Sato , Rich Felker , John Paul Adrian Glaubitz , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Kumar Kartikeya Dwivedi , Song Liu , Yonghong Song , Jiri Olsa , Andrew Morton , Lorenzo Stoakes , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Rik van Riel , Harry Yoo , Jann Horn , Matthew Wilcox , "Liam R. Howlett" Cc: linux-sh@vger.kernel.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, linux-mm@kvack.org References: <20260427-page_mapped-v1-0-e89c3592c74c@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20260427-page_mapped-v1-0-e89c3592c74c@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: A896C40017 X-Rspamd-Server: rspam04 X-Stat-Signature: u7p3gg9df7ae5ki6bkgei6yypo1x6e6s X-HE-Tag: 1777323576-89407 X-HE-Meta: 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 oqjHeTu1 2Fk8Rhfxgp10t+fjQvB3WOuukVOdOytTfoMS7viGHb5/KIaqbPbt9+QFWjgHnuat8QPvhAEsjkjEzEHn8x8bCIfoKjSYpAnEunydY0XC93d8iLR1EwqLjtjIQyJmDofH3nc/Pf5W1kdFT+yUUMmo717l/+oBZlh95C703dJuOi6lFajNvYg6mpCDEqBD9f7uz0Emur+Ndx9+KFXDGNtnLYwYpYW+YXl1zdeONU2PuzY777bn/LajHlsVEZhP28t+mAa31J3+tCn+/ag9yeGQeJHyBCMVy4Mk4TLPRubBxZSVI6pPohGQx/36l/3z8bdvirSg0yLMOGpqMHLQ= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/27/26 13:43, David Hildenbrand (Arm) wrote: > While preparing my slides for an LSF/MM talk, I realized that I did not > yet remove page_mapped(). > > So let's do that. In the BPF arena code it's unclear which memdesc we > would want to allocate in the future: certainly something with a > refcount, but likely none with a mapcount. So let's just rely on > the page refcount instead to decide whether we want to try zapping the > page from user page tables. > > Signed-off-by: David Hildenbrand (Arm) > --- I scanned AI review and I think it founds something that is not related to this patch. We use the page_mapped()->page_ref_count() check as an optimization to avoid calling zap_vma_range(). We must be able to call it even without that optimization. Just like the bulk zap call earlier if (page_cnt > 1) /* bulk zap if multiple pages being freed */ zap_pages(arena, full_uaddr, page_cnt); It talks about concurrent "munmap(), unmap_region() executes unmap_vmas()" racing with our zap_vma_range(). Looking into the details, arena_map_mmap() calls remember_vma(). We reject mremap and VMA split. arena_vm_close() removes the VMA from the list. The arena->lock protects our VMA list. So in zap_pages, the VMA cannot go away. If we find a VMA, ->close could not have been called yet. In vma.c, we call remove_vma() after vms_clear_pte(). So after unmapping the pages and freeing the page tables. So munmap() can indeed race with zap_vma_range(), and the page_mapped() check would not have changed anything about that really. @BPF folks: does BPF take anywhere the mmap lock in read mode before calling zap_vma_range()? It should do that. -- Cheers, David