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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 06D87C636D4 for ; Wed, 15 Feb 2023 22:05:53 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 1C52C6B0071; Wed, 15 Feb 2023 17:05:53 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 175BA6B0072; Wed, 15 Feb 2023 17:05:53 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0160D6B0073; Wed, 15 Feb 2023 17:05:52 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id E41A16B0071 for ; Wed, 15 Feb 2023 17:05:52 -0500 (EST) Received: from smtpin19.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id B966E1C69E4 for ; Wed, 15 Feb 2023 22:05:52 +0000 (UTC) X-FDA: 80470909344.19.7D25439 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf10.hostedemail.com (Postfix) with ESMTP id 7B7BCC0023 for ; Wed, 15 Feb 2023 22:05:50 +0000 (UTC) Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=BAaFYrDd; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf10.hostedemail.com: domain of peterx@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=peterx@redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1676498750; 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=qfFNZnFKtWRE4O4MevqHQ5cnOaMIQ6l++58Do45WQus=; b=tr+HjPPINVXK8XnSpsfPugp5UhdJ1KdWzxlvIgKb9YN5sF+4RXWGBNQyj53e1WJrzKr47K +ku9IT+KEzSMTwXtk6dZ16sTtjplVdswUUB+4ps4/Ss51WbmCQHnY4uLydcnM3vZdoSzz5 mmrC8RZDNfyn4dX0nXgj1GuWEmvjfSk= ARC-Authentication-Results: i=1; imf10.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=BAaFYrDd; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf10.hostedemail.com: domain of peterx@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=peterx@redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1676498750; a=rsa-sha256; cv=none; b=N08LLh9mhZ0w3MmwlAlNaDblrq1KG7o9ENX0vqr50S5AkbRRKaUbNd+DKHoKOFkmZ0M43v 0jAJhEhm/FpMdTFXm8cPypcrz3mMleHTUxomzWvGuL2sHlOr0vPY0qhTeJmNs8W1kuD2Zm cBOYzguc+FKgPqSFDJIyjyVaWZnPW0k= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1676498749; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=qfFNZnFKtWRE4O4MevqHQ5cnOaMIQ6l++58Do45WQus=; b=BAaFYrDdizqHVudsImUd+9juat7Y2JYui45JUHujPwVjlby+r/lrpehPU8Y9fDqLCbG4Jx KQv4iUNDyYWFSJoL/tSRzLzGzB1XmJM2iy3NAT2UKX3Z3cuUxfcwKU88tplbBlOMFHX23S XI5jiKKbUiGcryTyz3t1Pso+/PCMw9o= Received: from mail-il1-f198.google.com (mail-il1-f198.google.com [209.85.166.198]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-620-W3AE0-GNPY-X53IpUMVw9g-1; Wed, 15 Feb 2023 17:05:48 -0500 X-MC-Unique: W3AE0-GNPY-X53IpUMVw9g-1 Received: by mail-il1-f198.google.com with SMTP id a4-20020a056e0208a400b003157c7e623cso200237ilt.14 for ; Wed, 15 Feb 2023 14:05:48 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1676498748; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=qfFNZnFKtWRE4O4MevqHQ5cnOaMIQ6l++58Do45WQus=; b=5gaRnCSflISkGjDIX8b1ceEMNXex7rRWdU3VfQPFSIq0+y0HqvrKBx37kcnO7J2lS/ CpsmW65o1o3zwk37TRJDYpsE4/Poe2EWZiIeSLvHwuR8Vx184ArFeqOKKONt81FDpntX 0Ksh5aUlap3IV5S1ys+1zRGUO2yIHaANr/xpQwkouFgmYEGjh32u0viaRrKpSidtDH7F fWo9m7fbQkHTag44fdywomQyLD4uR7FEmOolihof20W9OTipPfo/6ZRQ1EQlSQkVuFjj Rzrg8Z6KMGpAkj0G8utsfhvHtgu4Yq8lzre+cuVKJDadfSzfSbjlCaNfz7SZ23FjUGO/ kUZA== X-Gm-Message-State: AO0yUKXvqbhIBDqb5ngVvTqkuzuXLVYVx3gQh67thnICInx73nq9fUG8 x9gnUbIGMoNieaLUdUWvCrwEeEKPVthVGeBZJv47vjSNfJihzt+dtNXVe0DddOMF4Jyq3btGIck PA+KGX7xyg1o= X-Received: by 2002:a05:6e02:1a64:b0:314:9f2b:f63b with SMTP id w4-20020a056e021a6400b003149f2bf63bmr3412154ilv.2.1676498747892; Wed, 15 Feb 2023 14:05:47 -0800 (PST) X-Google-Smtp-Source: AK7set8sXbg9jtkoGPrpkiuaDU6NHF/TMHj78LHiqYhEfiTkWO2wTHvOJWn3x0YdjWVWMA+Q9HsfkA== X-Received: by 2002:a05:6e02:1a64:b0:314:9f2b:f63b with SMTP id w4-20020a056e021a6400b003149f2bf63bmr3412145ilv.2.1676498747651; Wed, 15 Feb 2023 14:05:47 -0800 (PST) Received: from x1n (bras-base-aurron9127w-grc-56-70-30-145-63.dsl.bell.ca. [70.30.145.63]) by smtp.gmail.com with ESMTPSA id y3-20020a02bb03000000b003b331f0bbdfsm5988459jan.97.2023.02.15.14.05.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Feb 2023 14:05:46 -0800 (PST) Date: Wed, 15 Feb 2023 17:05:45 -0500 From: Peter Xu To: David Stevens Cc: Matthew Wilcox , linux-mm@kvack.org, Andrew Morton , "Kirill A . Shutemov" , Yang Shi , David Hildenbrand , Hugh Dickins , linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] mm/khugepaged: set THP as uptodate earlier for shmem Message-ID: References: <20230214075710.2401855-1-stevensd@google.com> MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Rspamd-Queue-Id: 7B7BCC0023 X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: 7cbrjj9c1rxfzeq9gpmksse6j377arpp X-HE-Tag: 1676498750-757606 X-HE-Meta: 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 807lrk5O Ym46dDZ6FY2RJX+9n28G4Gt4Op9Ad+WliwU0DofwoApJ9uRIoytYEtMlKBy7bExZEnrcUnyLvcaK59+cNQd9YoiDzAhdnPfkztN9b15C04HepT4PIyLzPrIFsS0baeQIgbC+DlRTd/mUp3ewXAe2EoSSIDOpkGD+amXlJMHyl+7+qcCXTEZRociSPpHQSzR+rwAr+bcfGzJxaWHlCrAgr7Tn8vZGdLuQVhba5sfECVKvOxEhJwsyX7HuNOSuxzxMShyePi4d+RoI/YCwgLMpuv7wfOgB8/SkISGMjUaBllMsKyeTMT8AFxfPmUKD1ndpX3TGmSYk8kz7PqurP7gikqUH0eMpJP7hiMwiDf7POR+z+vQAkowxDWisXcqt4lv/FBOmgRKA8g/jXyRJUTRqywqLTI1i3ElXiG6EyoZTHCkAxZRe1cJ/oEH1A5g== 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 Wed, Feb 15, 2023 at 10:33:15AM +0900, David Stevens wrote: > On Wed, Feb 15, 2023 at 12:44 AM Matthew Wilcox wrote: > > > > On Tue, Feb 14, 2023 at 04:57:09PM +0900, David Stevens wrote: > > > /* > > > - * At this point the hpage is locked and not up-to-date. > > > - * It's safe to insert it into the page cache, because nobody would > > > - * be able to map it or use it in another way until we unlock it. > > > + * Mark hpage as up-to-date before inserting it into the page cache to > > > + * prevent it from being mistaken for an fallocated but unwritten page. > > > + * Inserting the unfinished hpage into the page cache is safe because > > > + * it is locked, so nobody can map it or use it in another way until we > > > + * unlock it. > > > > No, that's not true. The data has to be there before we mark it > > uptodate. See filemap_get_pages() for example, used as part of > > read(). We don't lock the page unless we need to bring it uptodate > > ourselves. > > I've been focusing on the shmem case for collapse_file and forgot to > think about the !is_shmem case. As far as I could tell, shmem doesn't > use filemap_get_pages() and everything else in filemap.c/shmem.c that > checks folio_test_uptodate also locks the folio. But yeah, this would > break the !is_shmem case and is kind of sketchy anyway. I'll put > together a better patch. AFAIU we lock the page iff !uptodate and we want to wait it to be uptodate, or as Matthew said when we want to modify !uptodate->uptodate. Take the same example of folio_seek_hole_data() that you mentioned: if (xa_is_value(folio) || folio_test_uptodate(folio)) return seek_data ? start : end; -- Peter Xu