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[209.85.167.44]) by smtp.gmail.com with ESMTPSA id m5sm3661416ljb.98.2020.07.12.13.38.34 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 12 Jul 2020 13:38:34 -0700 (PDT) Received: by mail-lf1-f44.google.com with SMTP id k15so6764541lfc.4 for ; Sun, 12 Jul 2020 13:38:34 -0700 (PDT) X-Received: by 2002:ac2:5a5e:: with SMTP id r30mr51001288lfn.30.1594586313808; Sun, 12 Jul 2020 13:38:33 -0700 (PDT) MIME-Version: 1.0 References: <20200712173052.GU12769@casper.infradead.org> In-Reply-To: <20200712173052.GU12769@casper.infradead.org> From: Linus Torvalds Date: Sun, 12 Jul 2020 13:38:18 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: WARNING: at mm/mremap.c:211 move_page_tables in i386 To: Matthew Wilcox Cc: Naresh Kamboju , Joel Fernandes , "Kirill A. Shutemov" , William Kucharski , linux- stable , open list , linux-mm , Arnd Bergmann , Andrew Morton , Roman Gushchin , Michal Hocko , lkft-triage@lists.linaro.org, Chris Down , Michel Lespinasse , Fan Yang , Brian Geffon , Anshuman Khandual , Will Deacon , Catalin Marinas , pugaowei@gmail.com, Jerome Glisse , Greg Kroah-Hartman , Mel Gorman , Hugh Dickins , Al Viro , Tejun Heo , Sasha Levin , Oleg Nesterov Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: CB996180B3C83 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 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 Sun, Jul 12, 2020 at 10:31 AM Matthew Wilcox wrote: > > But I don't see any other way to do it. It's not like I can put THPs > in the page cache before fixing the things that won't work. I agree that sometimes there are bootstrapping issues. Incremental and explanatory commits are still better than one big commit that introduces a whole new feature and enables it. But if at all possible, at least limit the scope of the new feature first, enabling the simplest possible cases as they become possible so that there's some incremental testing, and so that bisection can say "ok, that baseline worked, but then when XYZ happened, things went sideways". And even when it's a new feature - if it needs cleanup patches to other things first, please do that. In fact, please do that as a completely independent series that goes into a previous kernel release entirely, so that the cleanup and preparatory patches can be independently verified by a lot of people who run that _previous_ kernel, so that the baseline of that cleanup phase is something as stable as possible. Linus