Messages in this thread | | | Date | Mon, 21 Jun 2010 19:17:20 -0400 | From | Valerie Aurora <> | Subject | Re: [PATCH 17/38] union-mount: Union mounts documentation |
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On Mon, Jun 21, 2010 at 03:14:35PM +0200, Miklos Szeredi wrote: > On Thu, 17 Jun 2010, Valerie Aurora wrote: > > On Thu, Jun 17, 2010 at 10:01:30AM +0200, Alex Riesen wrote: > > > On Tue, Jun 15, 2010 at 20:39, Valerie Aurora <vaurora@redhat.com> wrote: > > > > +git://git.kernel.org/pub/scm/fs/ext2/val/e2fsprogs.git > > > > + > > > > +Currently, whiteout directory entries are not returned to userland. > > > > +While the directory type for whiteouts, DT_WHT, has been defined for > > > > +many years, very little userland code handles them. ??Userland will > > > > +never see fallthru directory entries. > > > > > > This may be a dumb question (I must admit I did only very little research), > > > but how does one cleanup the topmost layer of whiteouts and fallthroughs, > > > so that the entries of lower layer(s) can be made visible again? > > > > I'm not sure how best to do this. We don't want to add more system > > calls. One thought of mine has been to do this offline, when the file > > system is unmounted. For example, e2fsck could add a feature to > > delete whiteouts and fallthrus. Another option is to add a flag to an > > existing system call. > > One more advantage of doing whiteouts, etc. with hard links and > extended attributes instead of as special filesystem objects. That > way they are visible (unless part of a union) and can be treated as > normal filesystem objects.
This should be reasonably easy to prototype - the whiteout and fallthru patches are pretty well separated from the rest of union mounts.
-VAL
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