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 X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1B3F7C433E4 for ; Sun, 12 Jul 2020 17:31:22 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id D4F70206F0 for ; Sun, 12 Jul 2020 17:31:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="EpxDrpEA" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D4F70206F0 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 52F8C6B0027; Sun, 12 Jul 2020 13:31:21 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4DFE16B0028; Sun, 12 Jul 2020 13:31:21 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3F5EB8D0001; Sun, 12 Jul 2020 13:31:21 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0200.hostedemail.com [216.40.44.200]) by kanga.kvack.org (Postfix) with ESMTP id 2A79D6B0027 for ; Sun, 12 Jul 2020 13:31:21 -0400 (EDT) Received: from smtpin05.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 9EB0A181AC9CC for ; Sun, 12 Jul 2020 17:31:20 +0000 (UTC) X-FDA: 77030115120.05.drum49_170352126ee1 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin05.hostedemail.com (Postfix) with ESMTP id 7625E1802CCB4 for ; Sun, 12 Jul 2020 17:31:20 +0000 (UTC) X-HE-Tag: drum49_170352126ee1 X-Filterd-Recvd-Size: 4237 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf13.hostedemail.com (Postfix) with ESMTP for ; Sun, 12 Jul 2020 17:31:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=0lZACZlm7hp7p3AuwMaMc3pMQx+Gf0OKUy9R5BwWajc=; b=EpxDrpEAuVkfls1cofHEt/ntsC hHzEneuO2eVxHcRPwBtIExjx8O4Z/1xHFraQYVBrYFT3o9pwMaPdtIuEVvVTD+GrePjU5HdJBDyLU ikdn0vwlBsmBCokv3BN6qLdTLdmkWygYGG9qmT0UvJOsGkjHujcq6vtI9ElBoFhqHTNjF3WyBpLHJ lLlsuggQuh8TTZAUo5T7erp/SKaCGf91TAcho55w0gd5+j89GqUA1Zv2tlS+FOPj9xigaGs5N8Gma Bf1E67MFWlMnvI+LHlTYI5GZ8VMDabrgeDnmRMoffKnq9ZjIEdICBMEIqXZOj8TsyHfEHn12gkl79 Ce8OXG8w==; Received: from willy by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jufoS-0002Yv-FD; Sun, 12 Jul 2020 17:30:52 +0000 Date: Sun, 12 Jul 2020 18:30:52 +0100 From: Matthew Wilcox To: Linus Torvalds 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 Subject: Re: WARNING: at mm/mremap.c:211 move_page_tables in i386 Message-ID: <20200712173052.GU12769@casper.infradead.org> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 7625E1802CCB4 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 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 Sat, Jul 11, 2020 at 11:12:58AM -0700, Linus Torvalds wrote: > Yeah, that's just the commit that enables the code, not the commit > that introduces the fundamental problem. > > That said, this is a prime example of why I absolutely detest patch > series that do this kind of thing, and are several patches that create > new functionality, followed by one patch to enable it. > > If you can't get things working incrementally, maybe you shouldn't do > them at all. Doing a big series of "hidden work" and then enabling it > later is wrong. I'm struggling with exactly this for my current THP-in-pagecache patches. There are about fifty patches, each fixing something that won't work if the page is a THP. And then there's the one patch which actually starts creating THPs, and that's the one patch any bisect will point to. 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. This probably wasn't the kind of thing you had in mind when you wrote the above, but if you had some advice for my situation, I'd welcome it.