Re: [PATCH 0/8] Introduce offline fsid/chunk tree uuid change for btrfstune.

[Qu Wenruo <quwenruo@cn.fujitsu.com>]

-------- Original Message  --------
Subject: Re: [PATCH 0/8] Introduce offline fsid/chunk tree uuid change 
for btrfstune.
From: David Sterba <dsterba@suse.cz>
To: Qu Wenruo <quwenruo@cn.fujitsu.com>
Date: 2015年05月12日 00:24

> On Fri, May 08, 2015 at 04:57:14PM +0800, Qu Wenruo wrote:
>>> Respecting the current syntax, the way to set the uuid is:
>>>
>>>    btrfs prop set -t filesytem /dev/sdx uuid ...UUID...
>>>
>>> In this special case, the property handler should check if the device is
>>> unmounted (and is a btrfs filesystem) and then do the rest.
>> This is one good idea, but I'm afraid it may still be confusing.
>> And things may get even worse when we try to move everything into
>> btrfs-prop,
>> E.g. if we auto move seeding flag to prop, we must give a quite detailed
>> explain on which property is offline.
>>
>> So I prefer to add a new type called offline, and put uuid change with
>> other btrfstune function into this type.
>> IMHO this should provide a good explain on which is online and which is
>> offline.
>>
>> How do you think about this method?
>
> I don't think that 'offline' is a good choice. The type should denote
> the modified object, ie device, inode, filesystem. What's 'offline' in
> this context?
Right, 'offline' type here is just a easy trick for me to code, not a 
meaningful type.
>
> The property interface can be used to modify other features both for
> mounted and unmounted filesystem, I agree that this should be done in a
> way that's not confusing. There are operations that are allowed on an
> unmounted fs (seeding), mounted + unmounted (extref feature) etc. so I
> think we could add options like --check-unmounted that would not allow
> to act on a mounted filesystem.

Nice idea, but i prefer a option like "--offline" to enable the usage of 
offline operations.
E.g, for normal online operations, nothing is changed.

And for "btrfs prop set <DEV> uuid <UUID>", "--offline" must be 
specified to work.
Or a message will be output to info user.

What about this one?

Thanks,
Qu