From: Goffredo Baroncelli <kreijack@libero.it>
To: Arnd Hannemann <arnd@arndnet.de>
Cc: Christian Robert <christian.robert@polymtl.ca>,
linux-btrfs@vger.kernel.org
Subject: Re: 3.5.0-rc6: btrfs and LVM snapshots -> wrong devicename in /proc/mounts
Date: Tue, 10 Jul 2012 20:42:09 +0200 [thread overview]
Message-ID: <4FFC7781.5020002@libero.it> (raw)
In-Reply-To: <4FFC6C89.6030303@libero.it>
Hi Arnd,
I am trying to reproduce this bug. Which kernel version are you using ?
BR
G.Baroncelli
On 07/10/2012 07:55 PM, Goffredo Baroncelli wrote:
> On 07/10/2012 10:52 AM, Arnd Hannemann wrote:
>> Hi,
>>
>> Am 10.07.2012 05:30, schrieb Christian Robert:
>>> I agree with you, but you should never mount a snapshot of a btrfs filesystem at the same time the original is,
>>> because both the original and the snapshot had same "device fsid 5c3e8ca2-da56-4ade-9fef-103a6a8a70c2"
>
> I think that the kernel should be smarter in this regard.
>
> At kernel level, as golden rule it should be not possible to add a
> duplicate fsid if the previous one is mounted. "btrfs dev scan" MUST
> return an error in this case. This in any case is an error.
>
> Today it seems that if a device with the same fsid is already
> registered, the new one overwrites the old one (or almost the name is
> overwritten). This could be acceptable if the filesystem is unmounted. I
> think that it is a serious error otherwise.
>
>>>
>>> the kernel will tkink twice and fold back to the same device.
>>
>> If that is correct the bug is that the kernel lets me mount the same device fsid on different devices twice.
>>
>>>
>>> btrsf does not behave like other filesystems, you can't snapshot a btrfs filesystem
>>> and hope to mount the snapshot somewhere else.
>>
>>> snapsoot also duplicate lots of things internally that have no sence in a snapshot (like raid level, single or multiple devies ...)
>>
>> I see. However, I expect a "simple" btrfs to just work or fail gracefully.
>>
>> Best regards,
>> Arnd
>>
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>
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next prev parent reply other threads:[~2012-07-10 18:42 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-09 22:22 3.5.0-rc6: btrfs and LVM snapshots -> wrong devicename in /proc/mounts Arnd Hannemann
2012-07-09 22:49 ` cwillu
2012-07-10 9:03 ` Arnd Hannemann
[not found] ` <4FFBA1C8.9020502@polymtl.ca>
2012-07-10 8:52 ` Arnd Hannemann
2012-07-10 17:55 ` Goffredo Baroncelli
2012-07-10 18:42 ` Goffredo Baroncelli [this message]
2012-07-10 20:09 ` Arnd Hannemann
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