Re: Way to quickly "revert back" to a snapshot?

[TARUISI Hiroaki <taruishi.hiroak@jp.fujitsu.com>]

I'm trying to make this snapshots/subvolumes listing feature,
I wonder how the interface should be.

I tried to make this feature using ioctl interface, but I don't
know how to notify all subvolume informations because number
of subvolumes are not known before search.
(It may work, that we call number-notify ioctl before subvol-
 listing ioctl itself, or we call subvol-listing ioctl repeatedly
 to last subvolume. But both seem to be not good to me.)

Is there any other idea?

Chris Mason wrote:
> On Sat, Oct 17, 2009 at 01:20:28PM -0400, John Dong wrote:
>> Suppose I want to do test something insane (like a massive OS
>> update) to my system, and create a snapshot before doing so.
>> Afterwards, if I decide my system is hosed and I'd like to revert
>> back to the snapshot and forget any of this actually happened,
>> what's the quickest way of doing it. It seems like by btrfs's design
>> there should be a way to just "set the head" of the filesystem back
>> to the snapshot, like git-reset, right?
> 
> This is near the top of the list of features I want to add for 2.6.33.
> Basically all we need is a way to swap the default subvolume (which is
> just a directory entry) pointer with another subvolume.
> 
> We also want a way to find an snapshot all the subvolumes and snapshots
> underneath a given root.  That way the user won't have to do it
> manually (snapshotting isn't recursive by default).
> 
> If anyone is interested in a coding project, both are fairly easy, just
> let me know.
> 
> -chris
> 
> 
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-- 
taruisi