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[209.85.208.177]) by smtp.gmail.com with ESMTPSA id t7sm2489007lfg.115.2021.12.20.13.28.05 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 20 Dec 2021 13:28:06 -0800 (PST) Received: by mail-lj1-f177.google.com with SMTP id z8so18081319ljz.9 for ; Mon, 20 Dec 2021 13:28:05 -0800 (PST) X-Received: by 2002:adf:d1a6:: with SMTP id w6mr35633wrc.274.1640035674847; Mon, 20 Dec 2021 13:27:54 -0800 (PST) MIME-Version: 1.0 References: <4D97206A-3B32-4818-9980-8F24BC57E289@vmware.com> <5A7D771C-FF95-465E-95F6-CD249FE28381@vmware.com> In-Reply-To: From: Linus Torvalds Date: Mon, 20 Dec 2021 13:27:38 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v1 06/11] mm: support GUP-triggered unsharing via FAULT_FLAG_UNSHARE (!hugetlb) To: Matthew Wilcox Cc: David Hildenbrand , Nadav Amit , Jason Gunthorpe , Linux Kernel Mailing List , Andrew Morton , Hugh Dickins , David Rientjes , Shakeel Butt , John Hubbard , Mike Kravetz , Mike Rapoport , Yang Shi , "Kirill A . Shutemov" , Vlastimil Babka , Jann Horn , Michal Hocko , Rik van Riel , Roman Gushchin , Andrea Arcangeli , Peter Xu , Donald Dutile , Christoph Hellwig , Oleg Nesterov , Jan Kara , Linux-MM , "open list:KERNEL SELFTEST FRAMEWORK" , "open list:DOCUMENTATION" Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 41A821C0027 X-Stat-Signature: kh19wtxs9e453w5jefe5mxxytjjaccx6 Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=google header.b=BlcnCZc5; spf=pass (imf20.hostedemail.com: domain of torvalds@linuxfoundation.org designates 209.85.208.175 as permitted sender) smtp.mailfrom=torvalds@linuxfoundation.org; dmarc=none X-HE-Tag: 1640035684-925019 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 Mon, Dec 20, 2021 at 1:02 PM Matthew Wilcox wrote: > > Hah, that was actually how I did it originally (without actually > committing at each step, and with a few "Oh, hang on, now we can avoid > calculating this too" stops and restarts along the way), but I thought > it all hung together logically as a single change. It's hard to see > things from the other person's perspective at times. In just about any other area, I wouldn't mind one bigger patch that just removes code that isn't used. But when it's in the vm code, and it's pretty grotty, I do prefer seeing three patches that individually are much easier to see that "yeah, this doesn't actually change anything at all". The combined patch may be exactly the same thing, it's just much harder to see that "oh, now it's not used any more". That was perhaps especially true since a number of the changes also ended up doing statement simplification when the old layout made no sense any more with part of the results not used. So your 3-patch series was much easier to look at and go "Yeah, I believe each of these patches is a no-op". So ACK on all those patches. Linus