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=-6.6 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 404A4C388F9 for ; Mon, 2 Nov 2020 19:12:51 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9129522275 for ; Mon, 2 Nov 2020 19:12:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="C7RVtAPp" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9129522275 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id A84206B0036; Mon, 2 Nov 2020 14:12:49 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id A314B6B005C; Mon, 2 Nov 2020 14:12:49 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8F9ED6B0068; Mon, 2 Nov 2020 14:12:49 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0186.hostedemail.com [216.40.44.186]) by kanga.kvack.org (Postfix) with ESMTP id 583FD6B0036 for ; Mon, 2 Nov 2020 14:12:49 -0500 (EST) Received: from smtpin06.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id DAB3F1EE6 for ; Mon, 2 Nov 2020 19:12:48 +0000 (UTC) X-FDA: 77440425216.06.size89_1307c8f272b2 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin06.hostedemail.com (Postfix) with ESMTP id B39B310035816 for ; Mon, 2 Nov 2020 19:12:48 +0000 (UTC) X-HE-Tag: size89_1307c8f272b2 X-Filterd-Recvd-Size: 4156 Received: from mail-qk1-f170.google.com (mail-qk1-f170.google.com [209.85.222.170]) by imf44.hostedemail.com (Postfix) with ESMTP for ; Mon, 2 Nov 2020 19:12:48 +0000 (UTC) Received: by mail-qk1-f170.google.com with SMTP id z6so12522021qkz.4 for ; Mon, 02 Nov 2020 11:12:48 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=VAQ2TnpJpSVGzs9QxUvU5ZK0uQebk2f7vZtBu6/vXNM=; b=C7RVtAPpyBQzNGUG4jZgFRVUqm/6zBJOG+5P1ElksKEHbVFoTPvq2bqlVA56N8Tl4s riJvl5ka/fXVWurSWnzGygvr+pAPdh01ADBBdUwcU5gw+e/Wc0jvo9muwBSIf42Ajkht GYINzk6IAuEwETE34w7/iJKUWVgzsdtWHDB3whcTZgu1ItEuihstyPwB1dLjmY41P7Tn AhWH0DYOASr8gq7Ne4lEryXfuIqCO55aysNJ+7fNYwTJw1whYADQ1UIByG96m3uy0VxV nymThXqWCRKPp93dYEGj6WF550dQ6z3xkWGBt866aY107P5GApkM+mjOii97ZOJ1w2ry 7GpQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=VAQ2TnpJpSVGzs9QxUvU5ZK0uQebk2f7vZtBu6/vXNM=; b=NmTmUvyt5efXl9zz+O51SgODk0XNy+v+L1A51rUSlQjdqR+JtmhTUKA1+k0lIvWwu5 NRRJwXMw7dTVOWIKM6KVXWXA5KSjLUVqSqWr2Mr6FTLp5CH03yeDwgIqx1gVQNtJdfSV iOeNG1iCZbn4UI8fzB/YnAQh5g6Mv3w/ECUsTMdr+tMc3mX1Cs3MUcf9DGj0JHCk2Rsg 3DNyYIAbR/TZDioWsRhe0SI6NkZQiN6mD9ogIB6fthuQ9S9TUrjCiWPX3koaImDXnUsV ZB2RlasvQSjzWiAt/hb2Iom7bC+EKzXT6aiJxAj7auLXACvl5H9XFoTlcEZKkxXoAfkf f3mQ== X-Gm-Message-State: AOAM53392OgUuPugruk0BUHu544jhiuwE1GxL6SjAuhG2pgrAsnN6RrN 7o5tneL1OYun5HrefJ+akRS2XdgeDPbA X-Google-Smtp-Source: ABdhPJz2PnUt91CU8Wz3Tgul0hHG7qTSVyvEDt74rVFK3OUq9oPNC48D5ZESNB3AAt4tVwKWvvfJXw== X-Received: by 2002:a37:664a:: with SMTP id a71mr10555111qkc.370.1604344367822; Mon, 02 Nov 2020 11:12:47 -0800 (PST) Received: from moria.home.lan (c-73-219-103-14.hsd1.vt.comcast.net. [73.219.103.14]) by smtp.gmail.com with ESMTPSA id a206sm5606583qkb.64.2020.11.02.11.12.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Nov 2020 11:12:47 -0800 (PST) Date: Mon, 2 Nov 2020 14:12:45 -0500 From: Kent Overstreet To: "Matthew Wilcox (Oracle)" Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, hch@lst.de Subject: Re: [PATCH 04/17] mm/filemap: Support readpage splitting a page Message-ID: <20201102191245.GI2123636@moria.home.lan> References: <20201102184312.25926-1-willy@infradead.org> <20201102184312.25926-5-willy@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201102184312.25926-5-willy@infradead.org> 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, Nov 02, 2020 at 06:42:59PM +0000, Matthew Wilcox (Oracle) wrote: > For page splitting to succeed, the thread asking to split the > page has to be the only one with a reference to the page. Calling > wait_on_page_locked() while holding a reference to the page will > effectively prevent this from happening with sufficient threads waiting > on the same page. Use put_and_wait_on_page_locked() to sleep without > holding a reference to the page, then retry the page lookup after the > page is unlocked. > > Since we now get the page lock a little earlier in filemap_update_page(), > we can eliminate a number of duplicate checks. The original intent > (commit ebded02788b5 ("avoid unnecessary calls to lock_page when waiting > for IO to complete during a read")) behind getting the page lock later > was to avoid re-locking the page after it has been brought uptodate by > another thread. We still avoid that because we go through the normal > lookup path again after the winning thread has brought the page uptodate. > > Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: Kent Overstreet