Re: [PATCH v2 2/2] overlay: copy-up lowerdir which has opaque xattr set

[Eryu Guan <eguan@redhat.com>]

On Thu, Sep 01, 2016 at 10:22:41AM +1000, Dave Chinner wrote:
> On Tue, Aug 09, 2016 at 07:16:21PM +0800, Eryu Guan wrote:
> > When copying up a directory with opaque xattr set, the xattr was
> > copied up as well, after a remount the opaque flag is honored so the
> > copied-up directory is treated as opaque, which causes files created
> > in the lowerdir to be hidden when using multiple lower directories.
> > 
> > This is fixed by "ovl: don't copy up opaqueness".
> ....
> > +_scratch_mkfs
> > +
> > +# Create multiple lowerdirs and upperdir, workdir, and testdir on lowerdir
> > +lowerdir1=$SCRATCH_DEV/lower1
> > +lowerdir2=$SCRATCH_DEV/lower2
> > +upperdir=$SCRATCH_DEV/upper
> > +workdir=$SCRATCH_DEV/workdir
> > +mkdir -p $lowerdir1 $lowerdir2 $upperdir $workdir
> > +mkdir -p $lowerdir1/testdir/d
> > +
> > +# mount overlay with $lowerdir2 as upperdir, and remove & recreate testdir,
> > +# make testdir on $lowerdir2 opaque
> > +_overlay_mount_dirs $lowerdir1 $lowerdir2 $workdir none $SCRATCH_MNT
> 
> What is the "none" here? If _overlay_mount_dirs() doesn't require
> this parameter to have a specifically valid value, then why are
> we passing it in at all?

It's place-holder for device to be mounted, for overlayfs this can be
any string but cannot be omitted. I probably should use $SCRATCH_DEV
instead, like what _scratch_mount does on overlayfs, so helpers like
_fs_type and _df_device that look for mounted device could work
correctly.

Thanks for the review!

Eryu