[dm-devel] Re: [RFC PATCH 2/2] Add timeout feature

Hi,

David Chinner wrote:
>> Exactly my timeout feature is only for an application, not for
>> freeze_bdev().
>> I think it is needed for the situation we can't unfreeze from
userspace.
>> (e.g. Freezing the root filesystem)
>
> Ummm - why can't you unfreeze the root fs from userspace? freezing
> only prevents modification to the filesystem. A frozen filesystem is
> effectively a read-only filesystem...
>
> On XFS:
>
> # xfs_freeze -f /
> # echo $?
> 0
> # xfs_freeze -u /
> # echo $?
> 0

Yes. If we have already logged in, we can unfreeze as above.
But if not, we cannot log in and unfreeze because the modification
of /var/log/wtmp is blocked in the log-in procedure.
The timeout feature will work in such case.

Cheers, Takashi