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

[Mike Fedyk <mfedyk@mikefedyk.com>]

On Mon, Nov 29, 2010 at 12:41 PM, David Arendt <admin@prnet.org> wrote:
> 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=A0=
wrote:
>>>
>>> (Cc: Sage Weil<sage@newdream.net> =C2=A0for changes in async snapsh=
ots)
>>>
>>> This patchset adds readonly-snapshots support. You can create a
>>> readonly snapshot, and you can also set a snapshot readonly/writabl=
e
>>> on the fly.
>>>
>>> A few readonly checks are added in setattr, permission, remove_xatt=
r
>>> 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 can
>> be enforced by default, and the exception when you want a read-write
>> snapshot can be available with a switch at the cli level (and probab=
ly
>> 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 for=
 backup
> purposes and these ones shouldn't be writable.
>
=2E... by default.
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