DragonFly users List (threaded) for 2008-05
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Re: hammer prune explanation

To: Matthew Dillon <dillon@xxxxxxxxxxxxxxxxxxxx>
From: Michael Neumann <mneumann@xxxxxxxx>
Date: Tue, 13 May 2008 15:04:10 +0200

Matthew Dillon wrote:
> :Yeah, I was thinking about wildcarding as well.
> :
> :But is it possible to implement it within cmd_prune.c, or do I have to
> :modify the ioctl kernel code? If done in cmd_prune.c, I somehow have to
> :iterate over all deleted files and call the prune command for it.
> :
> :I thought, it's easier to introduce a check in the kernel, whether the
> :file that should be pruned matches a given pattern. Doesn't sound very
> :hard to do, if it is easy to get the pathname for a given inode.
> :
> :Are you thinking about something like the archive flag?
> I think it is probably best to implement that level of sophistication
> in the utility rather then in the kernel. The pruning ioctl code
> has no concept of files or directories... literally it has no concept.
> All it understands, really, are object id's (aka inode numbers) and
> records.
> The hammer utility on the other hand can actually scan the filesystem
> hierarchy.
> Locating wholely deleted files and directories is not hard to do.
> As-of queries can be used to access earlier versions of a directory.

Hm, how would that work, if I want it to behave like the prune command?
I'd need to traverse a lot of filesystem trees, to just determine which
files were deleted.


compare /mnt with /mnt@1-hour-ago and prune deleted files.

compare /mnt@1-hour-ago with /mnt@2-hours-ago ...

I wouldn't find files that were deleted in between 1-hour-ago and
2-hours-ago. To make it work, I'd need to compare the filesystem trees
of every possible timestamp.

It's probably easier, and more efficient, to have
separate filesystems.

>     We might want to add some kernel support to make it more efficient,
>     for example to make it possible for the hammer utility to have
>     visibility into all deleted directory entries.  It could use that
>     visbility to do as-of accesses and through that mechanic would thus
>     have visibility into all deleted files and directories.

Does this mean, I'd see files like:




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