On Fri, 28 Nov 2008, Bharata B Rao wrote: > On Fri, Nov 28, 2008 at 12:01:32PM +0100, Miklos Szeredi wrote: > > I've been doing some small fixing/cleanup work on the union directory > > patches by Jan, and just noticed there's a thread about the union > > mounts on LKML, so I thought publicizing won't hurt. > > Interesting that you call it "union directory", do you have plans to go > the Plan 9's way of union directories ? I think yes, although I never tried Plan9 and don't know the details of the union directory semantics. At first we thought of providing completely read-only unioning (no whiteouts, no object creation/removal). This gets rid of a _lot_ of complexity. > > It's still a work in progress, notably the readdir code currently only > > works on a few specific filesystem types. > > readdir was one of the things on which we couldn't reach a consensus > on how to do it the right way. We were suggested that we move the > duplicate elimination into user space and an effort towards this was > also done (Ref: http://lkml.org/lkml/2008/4/29/248) by moving this > to glibc readdir. But we weren't sure how this could work for NFS and > were told that it is required to get the NFS side of things > sorted out first. So that's where readdir effort stands now afaik. > Do you have any ideas/plans on this front ? The plan is to get a simple kernel implementation first which caches the directory in 'struct file'. Long term we'll see. Maybe the userspace implementation is worth persuing as well for a more "kernel memory friendly" implementation. Thanks, Miklos -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
