[Dev] [RFC] Tizen system rollback

Łukasz Stelmach l.stelmach at samsung.com
Mon Dec 2 12:17:02 GMT 2013


It was <2013-12-02 pon 12:35>, when Aliaksei Katovich wrote:
> hi Łukasz;
>
>> It was <2013-11-29 pią 16:07>, when Aliaksei Katovich wrote:
>> > hi all;
>> >
>> > 	I would like to bring to your attention Tizen system rollback feature.
>> > 	The idea is to provide possibility to roll back Tizen based system to
>> > 	one of several known working configurations. Most obvious use-cases are:
>> >
>> > 	* system update or upgrade failed;
>> > 	* there are regressions introduced by system update;
>> > 	* User does not like features added by system update;
>> > 	* User wants to restore device to first time configuration;
>> > 	* User wants to restore device to factory defaults.
>> >
>> > 	Proposed architecture is based on device-mapper thin-provisioning
>> > 	capabilities. Please find more details in attached document.
>> >
>> > 	Before starting actual implementation of this feature I would like to
>> > 	hear your opinion about presented architecture and the idea in general.
>> 
>> I am not sure if btrfs' "file-system specific" (p. 6) is a falw. Tight
>
> 	Maybe it is not, but what to do with single-device-many-filesystems
> 	setup?

What do you mean?

> 	I am trying to be as generic as possible with rollbacks that's why
> 	block device level was so attractive to start with. Especially if
> 	we think of Tizen as of being not just mobile platform.

As much as I like generic solutions, in situations like this I ask
myself: is there any reason (probably outside of the socpe of my
solution) not to use a "specific" solution instead of a "generic" one?

Is there anything in btrfs (probably its "experimentality", its
performance) that should prevent us from adopting it on all Tizen
devices.

>> integration of snapshots with file-system code *may* (it is yet to be
>> measured) bring better performance. It would also allow for snapshots
>> for /boot (p. 11).
>
> 	How? Teach bootloader to deal with snapshots?

Teach it btrfs. As far as I know btrfs snapshots are simply alternative
root directories (or subvolumes? Is there anyone wiser than me to
help?).  All you have to do is to tell the boot-loader which one to
"mount".

-- 
Łukasz Stelmach
Samsung R&D Institute Poland
Samsung Electronics
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