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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 7F9A9C10F13 for ; Thu, 11 Apr 2019 16:58:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4F4022075B for ; Thu, 11 Apr 2019 16:58:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726595AbfDKQ62 (ORCPT ); Thu, 11 Apr 2019 12:58:28 -0400 Received: from mx2.suse.de ([195.135.220.15]:44658 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726014AbfDKQ62 (ORCPT ); Thu, 11 Apr 2019 12:58:28 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 99FEFACBD; Thu, 11 Apr 2019 16:58:27 +0000 (UTC) Received: by ds.suse.cz (Postfix, from userid 10065) id A2649DA85B; Thu, 11 Apr 2019 18:59:35 +0200 (CEST) Date: Thu, 11 Apr 2019 18:59:35 +0200 From: David Sterba To: Johannes Thumshirn Cc: David Sterba , Linux BTRFS Mailinglist Subject: Re: [PATCH] btrfs: simplify read_extent_buffer_pages a bit Message-ID: <20190411165935.GA3476@twin.jikos.cz> Reply-To: dsterba@suse.cz Mail-Followup-To: dsterba@suse.cz, Johannes Thumshirn , David Sterba , Linux BTRFS Mailinglist References: <20190411164059.4981-1-jthumshirn@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190411164059.4981-1-jthumshirn@suse.de> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Thu, Apr 11, 2019 at 06:40:59PM +0200, Johannes Thumshirn wrote: > Currently read_extent_buffer_pages() uses a 4 pass algorithm to read an > extent buffer's pages from disk, all 4 stages looping over all pages of > the extent buffer. > > 1) Loop over all pages and lock them. > 2) Loop over all pages and see if one is not marked as PageUptodate, so we > can break out of the function early. > 3) Loop over all pages and if the page is !PageUptodate read the page, > otherwise unlock the page. > 4) Loop over all pages and wait for stable pages. > > Unify the 1st two for loops, we can count the number of uptodate pages > after we have locked them without the need for re-starting the loop. Effectively reverting 2571e739677f1e4c0c63f5ed49adcc0857923625 that fixed a bug. Please have a look if something has really changed so that the split loops are no longer necessary.