From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: util-linux-owner@vger.kernel.org Received: from mx1.redhat.com ([209.132.183.28]:39409 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751262Ab1FTO5V (ORCPT ); Mon, 20 Jun 2011 10:57:21 -0400 Date: Mon, 20 Jun 2011 16:57:17 +0200 From: Karel Zak To: John Lindgren Cc: util-linux@vger.kernel.org, Andreas Dilger Subject: Re: blkid: excessive random reads probing for ZFS on NTFS filesystem Message-ID: <20110620145717.GJ17967@nb.net.home> References: <4DF50D58.9020800@tds.net> <20110620111640.GE17967@nb.net.home> <4DFF3613.9050705@tds.net> <20110620124612.GF17967@nb.net.home> <4DFF45A0.1040703@tds.net> <20110620140457.GI17967@nb.net.home> <4DFF5712.4070606@tds.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <4DFF5712.4070606@tds.net> Sender: util-linux-owner@vger.kernel.org List-ID: On Mon, Jun 20, 2011 at 10:20:02AM -0400, John Lindgren wrote: > On 06/20/2011 10:04 AM, Karel Zak wrote: > > On Mon, Jun 20, 2011 at 09:05:36AM -0400, John Lindgren wrote: > >> I did try that; however, blkid checks *all* filesystems, even after it > >> finds a match, just in case two probes turn up positive. Even passing > >> "-n nozfs" doesn't actually prevent it from checking for ZFS. > > The name of the FS in libblkid is zfs_member :-) > > > > blkid -p -o udev -n nozfs_member > > > > Yeah, crazy name, see our TODO file: > > > > - add something like "blkid --list-known" to list all supported > > filesystems/raids Implemented, blkid -k lists all known filesystems/RAIDs now. > Perhaps a "-q/--quick" option could be added to blkid to allow an early > exit once the first positive match is found? That's dangerous, and many times rejected by udev upstream. The mainstream distributions rely on the automatic FS detection on many places. We are not able to control mkfs and partitioning tools, so we are not sure that the device has been properly wiped and there is really only one valid superblock. We already have bad experience with FAT, linux swap, luks, ... some people already lost data. > Then more difficult checks > such as ZFS could be moved to the end of the list, as you suggest, with > a performance benefit. What about to set to blkid (during boot) greater I/O priority than to read-ahead? Karel -- Karel Zak http://karelzak.blogspot.com