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    SubjectRe: [ANNOUNCE] Btrfs: a copy on write, snapshotting FS
    On 6/13/07, Chris Mason <> wrote:
    > On Wed, Jun 13, 2007 at 12:14:40PM -0400, Albert Cahalan wrote:
    > > On 6/13/07, Chris Mason <> wrote:
    > > >On Wed, Jun 13, 2007 at 01:45:28AM -0400, Albert Cahalan wrote:

    > > >> * secure delete via destruction of per-file or per-block random crypto
    > > >keys
    > > >
    > > >I'd rather keep secure delete as a userland problem (or a layered FS
    > > >problem). When you take backups and other copies of the file into
    > > >account, it's a bigger problem than btrfs wants to tackle right now.
    > >
    > > It can't be a userland problem if you allow disk blocks to move.
    > > Volume resizing, logging/journalling, etc. -- they combine to make
    > > the userland solution essentially impossible. (one could wipe the
    > > whole partition, or maybe fill ALL space on the volume)
    > Right about here is where I would insert a long story about ecryptfs, or
    > encryption solutions that happen all in userland. At any rate, it is
    > outside the scope of v1.0, even though I definitely agree it is an
    > important problem for some people.

    I'm sure you do have a nice long story, and I'm sure it seems
    correct, but there is something not quite right about the add-on

    BTW, I'm suggesting that this be about deletion, not protection
    of data you wish to keep. It covers more than just file bodies.
    It covers inode data, block allocations, etc.

    > > >> * atomic creation of copy-on-write directory trees
    > > >
    > > >Do you mean something more fine grained than the current snapshotting
    > > >system?
    > >
    > > I believe so. Example: I have a linux-2.6 directory. It's not
    > > a mount point or anything special like that. I want to copy
    > > it to a new directory called wip, without actually copying
    > > all the blocks. To all the normal POSIX API stuff, this copy
    > > should look like the result of "cp -a", not hard links.
    > This would be a snapshot, which has to be done on a subvolume right now.
    > It is not as nice as being able to pick a random directory, but I've
    > only been able to get this far by limiting the feature scope
    > significantly. What I did do was make subvolumes very cheap...just make
    > a bunch of them.

    Can a regular user create and use a subvolume? If not, then
    this doesn't work. (if so, then I have other concerns...)
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