linux-ext4 - Re: How to run xfstests against multipath disks on SuSE?

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Message-ID: <20121127031438.GK6434@dastard>
Date:	Tue, 27 Nov 2012 14:14:38 +1100
From:	Dave Chinner <david@...morbit.com>
To:	Ryan Wang <openspace.wang@...il.com>
Cc:	Theodore Ts'o <tytso@....edu>,
	Lukáš Czerner <lczerner@...hat.com>,
	linux-ext4@...r.kernel.org, xfs@....sgi.com
Subject: Re: How to run xfstests against multipath disks on SuSE?

On Tue, Nov 27, 2012 at 09:20:47AM +0800, Ryan Wang wrote:
> 2012/11/26 Theodore Ts'o <tytso@....edu>:
> > On Mon, Nov 26, 2012 at 02:43:40PM +0100, Lukáš Czerner wrote:
> >> > The I checked the script common.rc, and found that it uses
> >> > df to determine the filesystem type and it uses the realpath
> >> > "/dev/dm-0" instead of "/dev/mapper/mpatha", while df always
> >> > shows "devtmpfs" instead of "ext4" for /dev/dm-0.
> >> >
> >> > I run "mount" and found that devtmpfs is mount on /dev/ on opensuse
> >> > ***by default***. Even though  I run "mount -t btrfs /dev/dm-0 /somedir",
> >> > df still showed devtmpfs.
> >> >
> >> > Any ideas to kick off the xfstests?
> >
> > At least with the df which ships with Debian Testing, df will display
> > the file system in use if it matches the device name which is
> > /etc/mtab.  It looks the issue is that mount is canonicalizing the
> > device name to be the human friendly version:
> >
> > # ls -l /dev/mapper/closure-bigscratch
> > 0 lrwxrwxrwx 1 root root 7 Nov 16 15:15 /dev/mapper/closure-bigscratch -> ../dm-7
> > <tytso.root@...sure> {/home/tytso/bin}, level 2
> > # mount /dev/dm-7 /u2
> > # df /u2
> > Filesystem                     1K-blocks   Used Available Use% Mounted on
> > /dev/mapper/closure-bigscratch  52403200 224772  52178428   1% /u2
> > # grep /u2 /etc/mtab
> > /dev/mapper/closure-bigscratch /u2 xfs rw,relatime,attr2,inode64,noquota 0 0
> >
> > So the simplest solution is to just use /dev/mapper/mpatha instead of
> > insisting on using /dev/dm-0.  That's what I do....
> 
> In xfstests/common.rc, it will use realpath to obtain /dev/dm-0, even if you
> specified /dev/mapper/mpatha.
> My problem is in SuSE, the devtmpfs is mounted on /dev by default, seems
> used by udev. And df reports devtmpfs on /dev/dm-0, instead of ext4.

What version of xfstests are you using? Do you have a
"README.device-mapper" file in the base directory? If not, upgrade
to the latest version and retry.

$ gl -n 1 -p 0a81886
commit 0a818862bb74932e15971ec8bedb55765ec3a3f6
Author: Christoph Hellwig <hch@....de>
Date:   Wed May 4 16:28:32 2011 +0200

    xfstests: support post-udev device mapper nodes

    Because of udevs complaining device mapper now creates /dev/dm-N as the real
    device nodes, and just symlinks the /dev/mapper/ names to it.  This would be
    easy if everything used the /dev/mapper clear names, but most system utilities
    translate them back to the /dev/mapper/ names and thus confuse various test
    cases.  Add support to _is_block_dev to read symlinks, and add documentation
    on how to run xfstests on device mapper volumes.

    Signed-off-by: Christoph Hellwig <hch@....de>
    Reviewed-by: Alex Elder <aelder@....com>

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com
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