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[2001:b011:20e0:1b32:d148:19d6:82fa:6094]) by smtp.gmail.com with ESMTPSA id w198-20020a627bcf000000b0052d2b55be32sm2161147pfc.171.2022.09.27.11.23.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 Sep 2022 11:23:32 -0700 (PDT) Date: Wed, 28 Sep 2022 02:23:25 +0800 From: Chih-En Lin To: Nadav Amit Cc: Andrew Morton , Qi Zheng , David Hildenbrand , Matthew Wilcox , Christophe Leroy , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , Luis Chamberlain , Kees Cook , Iurii Zaikin , Vlastimil Babka , William Kucharski , "Kirill A . Shutemov" , Peter Xu , Suren Baghdasaryan , Arnd Bergmann , Tong Tiangen , Pasha Tatashin , Li kunyu , Anshuman Khandual , Minchan Kim , Yang Shi , Song Liu , Miaohe Lin , Thomas Gleixner , Sebastian Andrzej Siewior , Andy Lutomirski , Fenghua Yu , Dinglan Peng , Pedro Fonseca , Jim Huang , Huichun Feng Subject: Re: [RFC PATCH v2 3/9] mm, pgtable: Add ownership to PTE table Message-ID: References: <20220927162957.270460-1-shiyn.lin@gmail.com> <20220927162957.270460-4-shiyn.lin@gmail.com> <2A6CA595-1F8D-4A83-9E85-E2C4392395CB@vmware.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2A6CA595-1F8D-4A83-9E85-E2C4392395CB@vmware.com> ARC-Authentication-Results: i=1; imf03.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=YG1XIdYw; spf=pass (imf03.hostedemail.com: domain of shiyn.lin@gmail.com designates 209.85.216.49 as permitted sender) smtp.mailfrom=shiyn.lin@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1664303014; a=rsa-sha256; cv=none; b=bjskTm67cDmgiAspQH7nJt3KFGQzkW9n+yClrVcyjgdd1zjdcpDhfUpWaN0ElgzP9nWhQ9 R5FidI1RqDBox8MLlSfUxh0iKd8zoN5ikH49j/H1i1FOUVaYPkJcQq799wQoiCgN4mIaBM ylPHAuyQ4FmTy/n5DwvnKp7auNIcdvk= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1664303014; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=RixpraDw2SxLEdK6PC2PZsHmmx7TUNCjtnumQde8TDs=; b=IF4GWXzI9eFPL6ku6+Z65U4ZYMkLmc8YI/Vs8CkXeyRylyKxFA8fo5KvvFyyDaAtdoCOhn tNdg3XsKMCBob3crXNSq7cnMn+vC6OM4M+Y6GoCc+r+whGXT/LPppNDFPqd7zGh7a+MAw2 4BgiPo6llDjx9aboxXR38egG1qmGGIc= X-Stat-Signature: ow5cm3fs34pwm54frsxqru9tu15k7iyz X-Rspamd-Queue-Id: 4589120009 Authentication-Results: imf03.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=YG1XIdYw; spf=pass (imf03.hostedemail.com: domain of shiyn.lin@gmail.com designates 209.85.216.49 as permitted sender) smtp.mailfrom=shiyn.lin@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1664303014-555616 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 Tue, Sep 27, 2022 at 05:30:39PM +0000, Nadav Amit wrote: > > +static inline void set_cow_pte_owner(pmd_t *pmd, pmd_t *owner) > > +{ > > + smp_store_release(&pmd_page(*pmd)->cow_pte_owner, owner); > > +} > > + > > +static inline bool cow_pte_owner_is_same(pmd_t *pmd, pmd_t *owner) > > +{ > > + return smp_load_acquire(&pmd_page(*pmd)->cow_pte_owner) == owner; > > +} > > Hiding synchronization primitives in such manner, and especially without > proper comments, makes it hard to understand what the ordering is supposed > to achieve. > It ensures that every time we write into the pointer, the reader will ebserve the newest one. I will add the comments. Thanks, Chih-En Lin