Date:	Tue, 27 Nov 2012 11:08:30 -0600
From:	Eric Sandeen <sandeen@...hat.com>
To:	Dave Chinner <david@...morbit.com>
CC:	Ryan Wang <openspace.wang@...il.com>,
	"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 11/26/12 9:14 PM, Dave Chinner wrote:
> 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.
> 

Recent "realpath" changes also went in:

b03c662399956609934ff063e9064e15dc7459ac xfstests: fix to build src/realpath and the correct the existence of target devices
d5ea873fcbf00b841f0511a26fb341364a5c6425 xfstests: resolve symlinked devices to real paths

so either of those could have broken and/or fixed it for you :)

-Eric
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