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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 7E2FBC2BA83 for ; Fri, 14 Feb 2020 16:39:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5A58524650 for ; Fri, 14 Feb 2020 16:39:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389958AbgBNQjC (ORCPT ); Fri, 14 Feb 2020 11:39:02 -0500 Received: from mx2.suse.de ([195.135.220.15]:45750 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404422AbgBNQi7 (ORCPT ); Fri, 14 Feb 2020 11:38:59 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 4621BB011; Fri, 14 Feb 2020 16:38:58 +0000 (UTC) Received: by ds.suse.cz (Postfix, from userid 10065) id A5C95DA703; Fri, 14 Feb 2020 17:38:43 +0100 (CET) Date: Fri, 14 Feb 2020 17:38:42 +0100 From: David Sterba To: Qu Wenruo Cc: linux-btrfs@vger.kernel.org Subject: Re: [PATCH] btrfs: relocation: Remove is_cowonly_root() Message-ID: <20200214163842.GB2902@twin.jikos.cz> Reply-To: dsterba@suse.cz Mail-Followup-To: dsterba@suse.cz, Qu Wenruo , linux-btrfs@vger.kernel.org References: <20200212074331.32800-1-wqu@suse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200212074331.32800-1-wqu@suse.com> User-Agent: Mutt/1.5.23.1-rc1 (2014-03-12) Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Wed, Feb 12, 2020 at 03:43:31PM +0800, Qu Wenruo wrote: > This function is only used in read_fs_root(), which is just a wrapper of > btrfs_get_fs_root(). > > For all the mentioned essential roots except log root tree, > btrfs_get_fs_root() has its own quick path to grab them from fs_info > directly, thus no need for key.offset modification. > > For subvolume trees, btrfs_get_fs_root() with key.offset == -1 is > completely fine. > > For log trees and log root tree, it's impossible to hit them, as for > relocation all backrefs are fetched from commit root, which never > records log tree blocks. > > Log tree blocks either get freed in regular transaction commit, or > replayed at mount time. At runtime we should never hit an backref for > log tree in extent tree. > > Signed-off-by: Qu Wenruo Added to misc-next, thanks.