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 65075CD4F5B for ; Thu, 5 Sep 2024 08:58:01 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id E8DF86B011E; Thu, 5 Sep 2024 04:58:00 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E16796B0124; Thu, 5 Sep 2024 04:58:00 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C8FC56B0128; Thu, 5 Sep 2024 04:58:00 -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 A886C6B011E for ; Thu, 5 Sep 2024 04:58:00 -0400 (EDT) Received: from smtpin20.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 366E180AE6 for ; Thu, 5 Sep 2024 08:58:00 +0000 (UTC) X-FDA: 82530082320.20.CCE155E Received: from out-181.mta0.migadu.com (out-181.mta0.migadu.com [91.218.175.181]) by imf16.hostedemail.com (Postfix) with ESMTP id 5506B180003 for ; Thu, 5 Sep 2024 08:57:58 +0000 (UTC) Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=hHL2mCMb; spf=pass (imf16.hostedemail.com: domain of muchun.song@linux.dev designates 91.218.175.181 as permitted sender) smtp.mailfrom=muchun.song@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1725526654; 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=CZtqExsDOIYp5HqPgrPdq+CzPwDzSkiYY8yvT9Jxwhw=; b=Oj+4qwcs3CMMgaYD5K0TcKaxc8mJk2VqLYdH7Utp7kKIwpqF3HOD+BClIvJQVvF3lryB3Y uK7fIRcvn1iom7MElPOKW5Kh/Cti6zE5+KiIePuLVkACQUIN+ZG3d6K2wteduSIqGJIMGj 6k7KW+RoBTV8szW7UmwDwbxDENtpj7w= ARC-Authentication-Results: i=1; imf16.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=hHL2mCMb; spf=pass (imf16.hostedemail.com: domain of muchun.song@linux.dev designates 91.218.175.181 as permitted sender) smtp.mailfrom=muchun.song@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1725526654; a=rsa-sha256; cv=none; b=sbJyqNRJ39yIn7t9CpxrjoUKQSPPWaUuT7YFVDYqhYqY9wKh+NduxLZjOYYJbhMoIRLROG XfJ1jdDoZCkt3AApJd1H7Ikc9buz180iyIOXdNieakziwgeoC7f2KlM5lAJn1w8F7YYqOO 2UYNB3RV2+mPON9kShBftBAqqeIT/Ec= Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1725526676; h=from:from: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; bh=CZtqExsDOIYp5HqPgrPdq+CzPwDzSkiYY8yvT9Jxwhw=; b=hHL2mCMbuNK+Hs/O408hs/N7aassZHQuWT3l/9qpf3OwEqwDoq18fUNQy7T4vQkPAhr7Ip KhS7GNRdIL7YXvr4Kwk1nBVf05wbZgGwqSvv3B9YBaijU8YfoK9B1DhEgjDylQD3XI58dx j3oiLIpOO5R1TF/4CpCnFRK2Hn4WWvc= Date: Thu, 5 Sep 2024 16:57:44 +0800 MIME-Version: 1.0 Subject: Re: [PATCH v3 08/14] mm: copy_pte_range() use pte_offset_map_rw_nolock() To: Qi Zheng Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, david@redhat.com, hughd@google.com, willy@infradead.org, vbabka@kernel.org, akpm@linux-foundation.org, rppt@kernel.org, vishal.moola@gmail.com, peterx@redhat.com, ryan.roberts@arm.com, christophe.leroy2@cs-soprasteria.com References: <20240904084022.32728-1-zhengqi.arch@bytedance.com> <20240904084022.32728-9-zhengqi.arch@bytedance.com> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Muchun Song In-Reply-To: <20240904084022.32728-9-zhengqi.arch@bytedance.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Stat-Signature: tbodq36fndpricgm1ywthikgk8nhssu7 X-Rspamd-Queue-Id: 5506B180003 X-Rspamd-Server: rspam11 X-HE-Tag: 1725526678-179508 X-HE-Meta: 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 xqaUQyyP cIZRe36gBQJqUSoJReM0EDWAP1zZ+JumpvRk1RMtYsNNxMcV2ugSdpypbc9t1eUgGgfCOqb9ZFw0vqIxngBL7C1B1WsNdbn6h34Vex5O2p9+e8tNIF4vGetAv6/BSQc8fePqBe1Iz2maHPqgh2tSN40Jo/MlVprTjiqbNf49amg/UQPU9x1upWQrZp3w4eDVlvdVZABFdlXSl8o4CoJZwTSijZuHvwivUVUlg4JPWFICu9jrFXHaxjpXgTC+YTitNTL1F3VzWeSSNX9bj3stStNLFh4x8iOfwO1TZU5UnNe1PzSna5rO6aOvPTw89WHQ1D955 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: On 2024/9/4 16:40, Qi Zheng wrote: > In copy_pte_range(), we may modify the src_pte entry after holding the > src_ptl, so convert it to using pte_offset_map_rw_nolock(). Since we may > free the PTE page in retract_page_tables() without holding the read lock > of mmap_lock, so we still need to get pmdval and do pmd_same() check after > the ptl is held. See commit 3db82b9374ca92, copy_pte_range and retract_page_tables are using vma->anon_vma to be exclusive. retract_page_tables()                    copy_page_range()     vma_interval_tree_foreach()              if (!vma_needs_copy())         if (READ_ONCE(vma->anon_vma))            return 0;             continue;                        copy_pte_range() So I think mmap write lock here is also used for keeping ->anon_vma stable. And we do not need pmd_same(). Muchun, Thanks. > > Signed-off-by: Qi Zheng > --- > Hi Muchun, since the code has changed, I dropped your Reviewed-by tag here. > > mm/memory.c | 18 +++++++++++++++++- > 1 file changed, 17 insertions(+), 1 deletion(-) > > diff --git a/mm/memory.c b/mm/memory.c > index 06674f94b7a4e..47974cc4bd7f2 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -1082,6 +1082,7 @@ copy_pte_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, > struct mm_struct *src_mm = src_vma->vm_mm; > pte_t *orig_src_pte, *orig_dst_pte; > pte_t *src_pte, *dst_pte; > + pmd_t pmdval; > pte_t ptent; > spinlock_t *src_ptl, *dst_ptl; > int progress, max_nr, ret = 0; > @@ -1107,13 +1108,28 @@ copy_pte_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, > ret = -ENOMEM; > goto out; > } > - src_pte = pte_offset_map_nolock(src_mm, src_pmd, addr, &src_ptl); > + > + /* > + * Since we may free the PTE page in retract_page_tables() without > + * holding the read lock of mmap_lock, so we still need to do a > + * pmd_same() check after holding the PTL. > + */ > + src_pte = pte_offset_map_rw_nolock(src_mm, src_pmd, addr, &pmdval, > + &src_ptl); > if (!src_pte) { > pte_unmap_unlock(dst_pte, dst_ptl); > /* ret == 0 */ > goto out; > } > spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING); > + > + if (unlikely(!pmd_same(pmdval, pmdp_get_lockless(src_pmd)))) { > + pte_unmap_unlock(src_pte, src_ptl); > + pte_unmap_unlock(dst_pte, dst_ptl); > + /* ret == 0 */ > + goto out; > + } > + > orig_src_pte = src_pte; > orig_dst_pte = dst_pte; > arch_enter_lazy_mmu_mode();