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=-5.5 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 EB0CDC433DF for ; Thu, 2 Jul 2020 13:36:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CF132207CD for ; Thu, 2 Jul 2020 13:36:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729277AbgGBNgh (ORCPT ); Thu, 2 Jul 2020 09:36:37 -0400 Received: from mx2.suse.de ([195.135.220.15]:40700 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729199AbgGBNgg (ORCPT ); Thu, 2 Jul 2020 09:36:36 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id AB8C2AC6E; Thu, 2 Jul 2020 13:36:35 +0000 (UTC) Received: by ds.suse.cz (Postfix, from userid 10065) id 367CFDA781; Thu, 2 Jul 2020 15:36:19 +0200 (CEST) Date: Thu, 2 Jul 2020 15:36:18 +0200 From: David Sterba To: Josef Bacik Cc: Nikolay Borisov , linux-btrfs@vger.kernel.org Subject: Re: [PATCH 8/8] btrfs: sysfs: Add bdi link to the fsid dir Message-ID: <20200702133618.GN27795@twin.jikos.cz> Reply-To: dsterba@suse.cz Mail-Followup-To: dsterba@suse.cz, Josef Bacik , Nikolay Borisov , linux-btrfs@vger.kernel.org References: <20200702122335.9117-1-nborisov@suse.com> <20200702122335.9117-9-nborisov@suse.com> <8469fe54-2641-9873-c845-8355932fccef@toxicpanda.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8469fe54-2641-9873-c845-8355932fccef@toxicpanda.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 Thu, Jul 02, 2020 at 09:25:30AM -0400, Josef Bacik wrote: > On 7/2/20 8:23 AM, Nikolay Borisov wrote: > > Since BTRFS uses a private bdi it makes sense to create a link to this > > bdi under /sys/fs/btrfs//bdi. This allows size of read ahead to > > be controlled. Without this patch it's not possible to uniquely identify > > which bdi pertains to which btrfs filesystem in the fase of multiple > > btrfs filesystem. > > > > Signed-off-by: Nikolay Borisov > > Was confused why we needed to make sure the link existed before removing it, > since other things sysfs is smart enough to figure out. Apparently it has a > WARN_ON() if the parent isn't initialized, so the check is necessary, albeit > annoying. There must be a better way, this is just too weird. We can check if objects have been initialized by peeking to kobject::state_initialized and we use that already for fsid_kobj in __btrfs_sysfs_remove_fsid or btrfs_sysfs_feature_update.