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]) by smtp.lore.kernel.org (Postfix) with ESMTP id E3532C7EE29 for ; Fri, 9 Jun 2023 20:06:38 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 815968E0008; Fri, 9 Jun 2023 16:06:38 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7ECA08E0002; Fri, 9 Jun 2023 16:06:38 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6B5298E0008; Fri, 9 Jun 2023 16:06:38 -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 5A1298E0002 for ; Fri, 9 Jun 2023 16:06:38 -0400 (EDT) Received: from smtpin25.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 1F101AF28E for ; Fri, 9 Jun 2023 20:06:38 +0000 (UTC) X-FDA: 80884292076.25.60495F3 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf03.hostedemail.com (Postfix) with ESMTP id 20AF020023 for ; Fri, 9 Jun 2023 20:06:35 +0000 (UTC) Authentication-Results: imf03.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=YqaO5bl3; spf=pass (imf03.hostedemail.com: domain of akpm@linux-foundation.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1686341196; 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=YGPC6XPL5YGiXdg8QM/flJtXTtWJWxe/OKgFadfaR5Q=; b=TBRHH0w3tV9qvvT9wdjbUAJZPys45iJM068JG4Yuuo+O3Nuhx1n4O1hZqpWSHmr3RUPr3R qYLRU6tzVCIGZsJIxLh7nIY98IHYz1z1fnYn84sqnISdzHYfrL1JUKcx6k/em0hGS8h2p0 ivNfjElpIvBJOHNhwOUdbbIgdl5NDFc= ARC-Authentication-Results: i=1; imf03.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=YqaO5bl3; spf=pass (imf03.hostedemail.com: domain of akpm@linux-foundation.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1686341196; a=rsa-sha256; cv=none; b=hdxBxlYVHRguIoHhqsHmLMWa3UekX1cg//8g1EXvIyUJeXj4SvDJ8R4ajRf9uJrUYuLi06 XtWLBQMy7jACpCbIc4x27UH36pm9W/HCgoznLgauOA3JUcCl006I61tXonMMPUGFXnmvXL NJmltZJE6ZkgQiNYIj0TEoDQUQE4pYk= Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 18F8F65997; Fri, 9 Jun 2023 20:06:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4EB81C433EF; Fri, 9 Jun 2023 20:06:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1686341194; bh=I5eLjVvS0j4LRy8nwugVLv1qLrwPGv6yABwGuRiB+w0=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=YqaO5bl3XEMwtnhnotlvPEAgrU3xEt9NSz3dEe6LUBbD5J9rBClfs1UXqaQl2jASA zYO51MdN9A0kxbg86I8m8gM5BK/nbJMwoet5nWMDR+21lql3f94v2/WBHXsb8Mt6qt PnnuYVV0groHs6ywW6cwCI8pR/xRA4fJ9J0LVYuw= Date: Fri, 9 Jun 2023 13:06:32 -0700 From: Andrew Morton To: Hugh Dickins Cc: Mike Kravetz , Mike Rapoport , "Kirill A. Shutemov" , Matthew Wilcox , David Hildenbrand , Suren Baghdasaryan , Qi Zheng , Yang Shi , Mel Gorman , Peter Xu , Peter Zijlstra , Will Deacon , Yu Zhao , Alistair Popple , Ralph Campbell , Ira Weiny , Steven Price , SeongJae Park , Lorenzo Stoakes , Huang Ying , Naoya Horiguchi , Christophe Leroy , Zack Rusin , Jason Gunthorpe , Axel Rasmussen , Anshuman Khandual , Pasha Tatashin , Miaohe Lin , Minchan Kim , Christoph Hellwig , Song Liu , Thomas Hellstrom , Ryan Roberts , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v2 28/32] mm/memory: allow pte_offset_map[_lock]() to fail Message-Id: <20230609130632.ec6ffe72fc5f7952af4a3e54@linux-foundation.org> In-Reply-To: References: X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 20AF020023 X-Rspam-User: X-Stat-Signature: 534fstiunbx17worgqkgznrk7uj5dxhd X-Rspamd-Server: rspam01 X-HE-Tag: 1686341195-544329 X-HE-Meta: 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 /1a55PKo phjXpNihRQcg9VcflInr1MU78jvN8Udy9PWutcVZoSJEUuxTKnM6NFNnb7B+KDNcvIOMA7W2ek9YinHmQKHmic3/UGQyEWB9fxiqaYjplfAJK23bFr8f95AQUrlMWq9JLshLMJu7GTv0DPGFzVRjYzBMFx9NFilYKs3tGRvW+SXYr2ksgtzFnQ/nP0qwM2N2p35EW0G8dlpWvYz/vo98gN7by6gSm09nVYjlMs621UwpwjFPpSLPKL+2zzF6dSQHf1v4zcZaHChNC+dDHk0Z1qq7uWpyNsmVxTGaDU3Awjd7ItTUeBEbgIHdIAdDByrA76BYhntjHWhv7mt3yTv+aE9yCN9lqX6uBjd1Qh2t9zztMCwjLONMQEUKRh5LwmwfJRc920S2dWD0HtOfrBR+biyVlI6xnZHspO4ozX1CpaZU37iOYmE4yNEQZtTHfwHWsLP7sy8GVSMX2JE3GQmpPh1QwwAlOx0AFkciK 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: On Thu, 8 Jun 2023 18:43:38 -0700 (PDT) Hugh Dickins wrote: > copy_pte_range(): use pte_offset_map_nolock(), and allow for it to fail; > but with a comment on some further assumptions that are being made there. > > zap_pte_range() and zap_pmd_range(): adjust their interaction so that > a pte_offset_map_lock() failure in zap_pte_range() leads to a retry in > zap_pmd_range(); remove call to pmd_none_or_trans_huge_or_clear_bad(). > > Allow pte_offset_map_lock() to fail in many functions. Update comment > on calling pte_alloc() in do_anonymous_page(). Remove redundant calls > to pmd_trans_unstable(), pmd_devmap_trans_unstable(), pmd_none() and > pmd_bad(); but leave pmd_none_or_clear_bad() calls in free_pmd_range() > and copy_pmd_range(), those do simplify the next level down. > > ... > > @@ -3728,11 +3737,9 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) > vmf->page = pfn_swap_entry_to_page(entry); > vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, > vmf->address, &vmf->ptl); > - if (unlikely(!pte_same(*vmf->pte, vmf->orig_pte))) { > - spin_unlock(vmf->ptl); > - goto out; > - } > - > + if (unlikely(!vmf->pte || > + !pte_same(*vmf->pte, vmf->orig_pte))) > + goto unlock; > /* > * Get a page reference while we know the page can't be > * freed. This hunk falls afoul of https://lkml.kernel.org/r/20230602092949.545577-5-ryan.roberts@arm.com. I did this: @@ -3729,7 +3738,8 @@ vm_fault_t do_swap_page(struct vm_fault vmf->page = pfn_swap_entry_to_page(entry); vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, vmf->address, &vmf->ptl); - if (unlikely(!pte_same(*vmf->pte, vmf->orig_pte))) + if (unlikely(!vmf->pte || + !pte_same(*vmf->pte, vmf->orig_pte))) goto unlock; /*