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 C104DD68BD5 for ; Sun, 21 Dec 2025 09:26:54 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 2C5D26B00AC; Sun, 21 Dec 2025 04:26:54 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 2709B6B00AD; Sun, 21 Dec 2025 04:26:54 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1AA336B00AE; Sun, 21 Dec 2025 04:26:54 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 0A42A6B00AC for ; Sun, 21 Dec 2025 04:26:54 -0500 (EST) Received: from smtpin20.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id BA78A8B7E4 for ; Sun, 21 Dec 2025 09:26:53 +0000 (UTC) X-FDA: 84242948706.20.1278AE8 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf03.hostedemail.com (Postfix) with ESMTP id 049D520002 for ; Sun, 21 Dec 2025 09:26:51 +0000 (UTC) Authentication-Results: imf03.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=Nb+bP8zK; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf03.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1766309212; a=rsa-sha256; cv=none; b=J5bHbkLhC8aPZ8zEoK4aWd7VTYyecS6pkMF6J2H9dWnI8jD9QS7KU9MEqhVOB/jOuK7pTO rGxPT7+m/LML7Dbmko6M2Pfq3ZTsyDY1YXvjziqdiyvfmCZgfWiTurSqSk6qSCjggWJWbm taQ4udd2DNVZDNPvi4BPiT7iO2GrtJ4= ARC-Authentication-Results: i=1; imf03.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=Nb+bP8zK; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf03.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=1766309212; 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=DToSSkcTtui14uU0FGAHMQ5atcuUt3CMQP6j7IV4mOM=; b=195lWQu40F2fdraHE32a/5Dlx7NGZe2b/Fqy1CP4Saot00Jo2f5uofCP04ILI3F8RZYu9G FFruzRgeumXf+9qrOjzR/Npb2hKsr2ovupD6fZiMRz1r50I/Jk9OTDZFXyG8lzr8mkNowt CS6S3rk7t1u1o9uMPSSsrKwY92D+Lpo= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id F375A42D77; Sun, 21 Dec 2025 09:26:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D2618C4CEFB; Sun, 21 Dec 2025 09:26:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1766309210; bh=r/HnyZxm1R6JN5eoXSIU5zr+Fo96rUTb1s7oPXl32Hg=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=Nb+bP8zKsVe13MWjC6VhGiVGWuX60q75WG3ymxPHxQaQNoEZt9X07AZMW8bQYGoBo 832booaCYWwk80iWMWOGT8IZWy7QQo9K0ejIQ0DGqlYu2UNbDi1hcLCNklnidfZoYy zj7y96b5+kig2ITg8FMHuXwFAxDC9QfAy3QjqOIuFQKFEugl4FMh0SkMzlCRvkFbPU YsjizVCeShvDzjdpMJXhtIViD6WdPOL2tnDOyOa0fXAO3qKPo8QmR5wRj1CLn7ExRd lgx7qQezmlLjeaZopnMLDrw2AGK8qUb2AHKBbIMGKzpcKWSZeZ5kcwekoiRAnADcZ4 eaJJnZ546eleA== Message-ID: Date: Sun, 21 Dec 2025 10:26:42 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/4] mm/hugetlb: fix two comments related to huge_pmd_unshare() To: Nadav Amit Cc: Harry Yoo , Linux Kernel Mailing List , linux-arch@vger.kernel.org, "open list:MEMORY MANAGEMENT" , Will Deacon , "Aneesh Kumar K.V" , Andrew Morton , Nick Piggin , Peter Zijlstra , Arnd Bergmann , Muchun Song , Oscar Salvador , "Liam R. Howlett" , Lorenzo Stoakes , Vlastimil Babka , Jann Horn , Pedro Falcato , Rik van Riel , Laurence Oberman , Prakash Sangappa , Liu Shixin References: <20251212071019.471146-1-david@kernel.org> <20251212071019.471146-3-david@kernel.org> <506fef86-5c3b-490e-94f9-2eb6c9c47834@kernel.org> <2bbe1e49-95ba-42ea-b6af-5eeb61d68c4c@kernel.org> <3D7F0E85-2509-4925-BDD5-149E9E8D5C1F@gmail.com> From: "David Hildenbrand (Red Hat)" Content-Language: en-US In-Reply-To: <3D7F0E85-2509-4925-BDD5-149E9E8D5C1F@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 049D520002 X-Stat-Signature: eq3nxk5xicnebejqkk6mypoxzueactor X-Rspam-User: X-HE-Tag: 1766309211-450853 X-HE-Meta: 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 8Tvz13dG vIp90Z9uufqryPtZZIR3jsxQQ1wNiBw66uT+1pVuMILlXH1I/g9RzpHjYuJLcLnbVHoNzErUtBo9WAWPDvcQq/wiyNhmNEqE+UUh9SzF3ABFK+lnNLTwiVb92Y/B8eJPRrhk+juDEHsOujOP+FfhR3jF/WqCV2ltxWhFj1wQ6TB81UTHduwQ920J7BoIX/sdmqy/JvfeyTKKPQ8VrrGPVO2F7+Jiz4plh0gv0X1CQRlqAT/uMrUucgsalBbop7jGPjwOAZyO8pEm5o6Y6/2L0I0R0gIuh1we9FqJzmdS/Togh7hsbZsYW0UBq1+Ad1UQ7HXtnnZBUr8crhZr1vDf+QJh5/iWC2QhZuVdRiEO+ixw1+LK2Oi9DQF/KN6mbFaf1eUjk1X+Y8I1zqRwfYngFTWYrfQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: >>>> >>>> Whoever is the last owner of a (previously) shared page table must unmap any >>>> contained pages (adjust mapcount/ref, sync a/d bit, ...). >>> Right. >>>> So it's not just a matter of deferring the freeing, because these page tables >>>> will still contain content. >>> I was (and maybe still) bit confused while reading the old comment as >>> it implied (or maybe I just misread) that by deferring freeing of page tables >>> we don't have to flush TLB in __unmap_hugepage_range() and can flush later >>> instead. >> >> Yeah, I am also confused by the old comment. I think the idea there was to drop the reference only later and thereby deferred-free the page. > > My bad. I looked again, and the comment indeed doesn’t make much sense. Thanks for fixing it. No worries, thanks for taking a look! -- Cheers David