New hammer utility feature in HEAD: 'hammer cleanup'

Matthew Dillon dillon at
Sun Sep 28 10:56:40 PDT 2008

:>     It should be.  I've gone over that code several times and it restricts
:>     the scan to a single PFS, but I haven't actually tested that it works
:>     as advertised.
:>From practical experience with ZFS (which permits what are 
:effectively nested PFSs), an operation that permits atomic snapshots 
:across a set of filesystems would be very handy.
:jan grant, ISYS, University of Bristol.

    Well, the hammer snapshot code syncs the whole filesystem,
    meaning all the PFS's get synced so the transaction id will in
    fact apply to all PFSs.  It only creates the softlink in one
    place, so the next pruning operation will only prune around
    the snapshot in that particular PFS.  Of course, one could duplicate
    the softlink in all the PFSs.  It's just a softlink with a special
    string so its easy to do from userland.

					Matthew Dillon 
					<dillon at>

More information about the Kernel mailing list