Re: Default to read-only on snapshot creation and have a flag if snapshot should be writable (was: [PATCH 0/5] btrfs: Readonly snapshots)

[Andrey Kuzmin <andrey.v.kuzmin@gmail.com>]

This may sound excessive as any new concept introduction that late in
development, but readonly/writable snapshots could be further
differentiated by naming the latter clones. This way end-user would
naturally perceive snapsot as read-only PIT fs image, while clone
would naturally refer to (writable) head fork.

Regards,
Andrey




On Tue, Nov 30, 2010 at 12:08 AM, Mike Fedyk <mfedyk@mikefedyk.com> wro=
te:
> On Mon, Nov 29, 2010 at 12:41 PM, David Arendt <admin@prnet.org> wrot=
e:
>> On 11/29/10 21:02, Mike Fedyk wrote:
>>>
>>> On Mon, Nov 29, 2010 at 12:02 AM, Li Zefan<lizf@cn.fujitsu.com> =C2=
=A0wrote:
>>>>
>>>> (Cc: Sage Weil<sage@newdream.net> =C2=A0for changes in async snaps=
hots)
>>>>
>>>> This patchset adds readonly-snapshots support. You can create a
>>>> readonly snapshot, and you can also set a snapshot readonly/writab=
le
>>>> on the fly.
>>>>
>>>> A few readonly checks are added in setattr, permission, remove_xat=
tr
>>>> and set_xattr callbacks, as well as in some ioctls.
>>>>
>>> Great work!
>>>
>>> I have a suggestion on defaults when snapshots are created. =C2=A0I=
 think
>>> they should default to being read-only and if they are meant to be
>>> read-write a flag can be set at creation time (and changable at a
>>> later time as well of course).
>>>
>>> This way user/admin preconceptions of a snapshot being read-only ca=
n
>>> be enforced by default, and the exception when you want a read-writ=
e
>>> snapshot can be available with a switch at the cli level (and proba=
bly
>>> a flag at the ioctl level).
>>>
>>> It gives one more natural distinction between a snapshot and a
>>> subvolume at the user conceptual level.
>>>
>>> What do you think?
>>>
>> I completely agree with you. I think lots of people use snapshots fo=
r backup
>> purposes and these ones shouldn't be writable.
>>
> .... by default.
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