From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp-17.italiaonline.it ([212.48.25.145]:41138 "EHLO libero.it" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751569AbbFNToY (ORCPT ); Sun, 14 Jun 2015 15:44:24 -0400 Message-ID: <557DD993.9080803@inwind.it> Date: Sun, 14 Jun 2015 21:44:19 +0200 From: Goffredo Baroncelli Reply-To: Goffredo Baroncelli MIME-Version: 1.0 To: systemd-devel@lists.freedesktop.org, linux-btrfs , 1i5t5.duncan@cox.net Subject: Re: [systemd-devel] [survey] BTRFS_IOC_DEVICES_READY return status References: <557ADBAE.9040407@oracle.com> <20150612210453.3dee4563@opensuse.site> <557B3C32.9030707@inwind.it> <557BF979.9040106@oracle.com> <557C479F.2070403@libero.it> In-Reply-To: Content-Type: text/plain; charset=utf-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 2015-06-14 06:05, Duncan wrote: > Goffredo Baroncelli posted on Sat, 13 Jun 2015 17:09:19 +0200 as > excerpted: > >> My attempt followed a different idea: the mount helper waits the devices >> if needed, or if it is the case it mounts the filesystem in degraded >> mode. >> All devices are passed as mount arguments (--device=/dev/sdX), there is >> no a device registration: this avoids all these problems. >> >> [*] http://permalink.gmane.org/gmane.comp.file-systems.btrfs/40767 > > But /dev/sdX doesn't always work, because, for instance, my usual /dev/sdb > was slow to respond on my last boot, and currently appears as /dev/sdf, > with sdb/c/d/e being my (multi-type) sdcard, etc, adapter, medialess. Please give a look to my patch. You may mount the filesystem in different way: - by device (/dev/sdxxx) - by UUID (UUID=) - by LABEL (LABEL=) The helper finds the right devices and (eventually) waits for the other devices. When it has collected all the devices, these are passed to the kernel via the "device=/dev/sdx" mount option. So the registration would not be needed anymore. > > Tho if /dev/disk/by-*/* works, I could use that. Tho AFAIK it's udev > that fills that in, so udev would be necessary. I never wrote that udev is not necessary. I think only that relying to udev to handling a multi-volume filesystem is too complicated. The responsibility is spread in too much layer. -- gpg @keyserver.linux.it: Goffredo Baroncelli Key fingerprint BBF5 1610 0B64 DAC6 5F7D 17B2 0EDA 9B37 8B82 E0B5