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[2001:b011:20e0:1b9a:f5f9:665b:715:9cc1]) by smtp.gmail.com with ESMTPSA id t6-20020a17090a3b4600b002098f3b4c67sm137488pjf.34.2022.09.29.12.02.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 29 Sep 2022 12:02:36 -0700 (PDT) Date: Fri, 30 Sep 2022 03:02:29 +0800 From: Chih-En Lin To: Nadav Amit Cc: David Hildenbrand , Andrew Morton , Qi Zheng , 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 9/9] mm: Introduce Copy-On-Write PTE table Message-ID: References: <20220927162957.270460-1-shiyn.lin@gmail.com> <20220927162957.270460-10-shiyn.lin@gmail.com> <3D21021E-490F-4FE0-9C75-BB3A46A66A26@vmware.com> <39c5ef18-1138-c879-2c6d-c013c79fa335@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: ARC-Authentication-Results: i=1; imf20.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b="H6Kx+Ps/"; spf=pass (imf20.hostedemail.com: domain of shiyn.lin@gmail.com designates 209.85.215.169 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=1664478158; a=rsa-sha256; cv=none; b=FDegzm9jRrR4M2YX1hCvcmtJQ6W+CwvBKGVvGVoWzq+lC9hHUEY+bYM1AfCevYfQ35gqfZ YwihBsgw14foq173EPaN7uSJreEFRqFy2+A9kZ4zOCk74FJl6EzDm82Ab2t4rGknrAJvvY aYgPaq4z5EX2KGqNpKNmbZMEOFWAuAQ= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1664478158; 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=VRWMAHYEyCYnit1DgorRCfjCV475mNFdc2il+dM3xyY=; b=6AVkTNLaLrQPDRmWZcf3K6BUEaJBwvIDVPBpCQKWTsClmyChlOmF08cTJ7qw5nMKu79NFK ZmLv7e5EIuGoShA+4qz9+s7h8HK822h0IJr4C0wnuqzORVw29cS36Gxc1P46gC90d9kzU1 KtNQ6AAYEiPNra/3dHo+FmSYto2A9Cs= Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b="H6Kx+Ps/"; spf=pass (imf20.hostedemail.com: domain of shiyn.lin@gmail.com designates 209.85.215.169 as permitted sender) smtp.mailfrom=shiyn.lin@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Rspam-User: X-Stat-Signature: ektyqfdjugu8zth5wwtg1henytma7xd4 X-Rspamd-Queue-Id: 5E3261C0022 X-Rspamd-Server: rspam05 X-HE-Tag: 1664478158-655224 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, Sep 29, 2022 at 06:40:36PM +0000, Nadav Amit wrote: > On Sep 29, 2022, at 11:29 AM, Chih-En Lin wrote: > > > That case could be caught in copy_pte_range(): in case we'd have to allocate > >> a page via page_copy_prealloc(), we'd have to fall back to the ordinary > >> "separate page table for the child" way of doing things. > >> > >> But that looks doable to me. > > > > Sounds good. :) > > Chih-En, I admit I did not fully read the entire correspondence and got deep > into all the details. > > I would note, however, that there are several additional components that I > did not see (and perhaps missed) in your patches. Basically, there are many > page-table manipulations that are done not through the page-fault handler or > reclamation mechanisms. I did not see any of them being addressed. > > So if/when you send a new version, please have a look at mprotect(), > madvise(), soft-dirty, userfaultfd and THP. In these cases, I presume, you > would have to COW-break (aka COW-unshare) the page-tables. > Sure. Before I send the new version I will try to handle all of them. Thank you for the note. Thanks, Chih-En Lin