On Wed, Aug 06, 2014 at 07:41:31AM -0400, Greg Troxel wrote:
> u-codalist-z149_at_aetey.se writes:
> > ls <conflict>/.codactl/replicas/
> > diff <conflict>/.codactl/replicas/{server1,server2}
> > diff <conflict>/.codactl/replicas/server1 <conflict>/.codactl/local
> > echo server2 > <conflict>/.codactl/prefer
> >
> > Which could possibly be worth to be available even if <conflict> is not a
> > conflict but a healthy file or directory, just in case, like "cfs expand".
> 
> That in concept sounds good.

In concept, but in practice you now have a directory hardlink between
<conflict> and <conflict>/.codactl/local, and as such a path of infinite
recursion.

cfs expand does some tricky stuff to avoid this, under the covers it
tries to do the following (not actual steps since it can do this
atomically under the covers):

    mkdir .tmp_conflict
    cfs mkm .tmp_conflict/server1 @server1.object.replica
    cfs mkm .tmp_conflict/server2 @server1.object.replica
    mv <conflict> .tmp_conflict/localhost
    mv .tmp_conflict <conflict>

This way there is no directory hardlink and in theory any open
references to files in <conflict> can stay open. (the problem for
active references is the step where we try to collapse <conflict>
into a dangling symlink to indicate that there is a conflict.

> I don't understand the notion of using xattr for control.  They are
> extra properties stored on files, and it seems semantically abusive to
> write them as a control operation.   (Having .codactl is also a bit
> abusive, but it's s single clean break.)

Not all are appropriate but from a quick scan the following would fit
very nicely with the concept of properties on files and/or volumes:

    cfs setacl/listacl  other filesystems also use xattrs for these
    cfs getfid          get the fid
    cfs whereis         get the replica server names/addresses
    cfs listvol         get the volume information
    cfs getmountpoint   get the nearest ancestor volume mount?
    cfs lsmount         read the contents of the covered mountlink
    cfs listlocal       show volume CML

Jan