Ability to discard all changes after a point in time?

Hi,

recently I was searching for a way to discard all changes after a certain point in time -- that is, to rollback filesystem state to a particular checkpoint. I couldn't find a way, is there any?

If not, I'd like to request such functionality. Preferrably selectable at mount time, via an argument to mount (or the `rootflags' kernel parameter).

Something along the lines `rollbackto=<checkpoint-number>'.

The desired effect is to set the indicated checkpoint as the latest one, so all subsequent changes to filesystem are discarded.

What are your thoughts on that?

Regards,

dexen deVries

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Hi,

The feature is indeed one of todo items, and I just have been considering the topic for upcoming LinuxCon Japan.

At present, I made a patchset which can revert only one fully deleted regular file without duplicating data blocks. (This work derives your post titled "It is not possible to restore file from a mounted snapshot using a hardlink" and the successive reflink topic.)

The challenge in the rollback (or revert) feature is to handle lifetime of each disk block, which is maintained for garbage collection. (a disk address table, which we call DAT file, preserves this metadata).

The mount-time whole checkpoint reversion, that is to say rollback, seems rather difficult than this. In my estimation, it would take too long time to rewrite whole DAT file.

But, yes, I think this feature is one of priorities, and have plan to take time for it.

Thanks,
Ryusuke Konishi

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Hi,

At Fri, 27 May 2011 08:28:28 +0200,

I know this is not what you want, but as a partial solution, timebrowse (http://timebrowse.sourceforge.net/) can restore the files or directories of NILFS2 checkpoints from nautilus interface.

Of course, this will merely rsync from the checkpoint to current mount point. Therefore all the history still remain in the log and it may take unreasonable time if the differences are big.

thanks,

regards,

Jiro SEKIBA <[email protected]>
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Hi Jiro,

Thanks, that's a good thing. Btw., is there any KIO slave or application for KDE with similar functionality?

My target usecase was: OS is so mis-configured it won't even boot. I wanted to pass a parameter to kernel to make it discard some recent changes and go on with a slightly older version of files.

Another usecase was: due to bug in older kernel FS had a few recent checkpoints corrupted. It's either back files up and re-format the filesystem, or roll back a few minutes to an older, correct checkpoint.

Regards,

dexen deVries

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Hi, dexen

At Wed, 1 Jun 2011 14:41:12 +0200,

Unfortunately no, or no volunteer yet ;-p.

Timebrowse has two parts, snapshot manager and nautilus add-on.

Snapshot manater keep nilfs checkpoints and alter its to snapshots and mount its specified mount point. In later snapshots will be unmount and sparse or deleted.

While, nautils add-on is completely independent from the manager. It tries to find nilfs checkpoint mount from /proc/mounts and list the checkpoint.

So if you want KIO slave or something similar for KDE, you may be able to utilize the snapshot manager to implement the functionality you want.

If the problem is rather simple, like need to boot correct kernel in the file system in the log boot loader may help it.
#and pray the log roll forward on boot time.

Current grub2 nilfs module only tries to find kernel from latest log. However, implementation itself can specify any checkpoint.
The problem is how to specify the checkpoint from standard grub2 interface. grub2 does not have any parapeter for file system module :(.

regards,

Jiro SEKIBA <[email protected]>
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