On Tue, 2006-09-05 at 08:02 +0200, Jan Engelhardt wrote: > > > >I agree that unionfs shouldn't oops, it should handle that situation in > >a more graceful manner, but once the "backing store" is modified > >underneath it, all bets are off for either unionfs or ext2/3 behaving > >"correctly" (where "correctly" doesn't just mean handle the error > >gracefully). > > > >But are you also 100% sure that messing with the underlying backing > >store wouldn't be considered an admin bug as opposed to an administrator > >bug? I mean there's nothing that we can do to prevent an administrator > >from FUBAR'ing their system by > > > >dd if=/dev/random of=/dev/kmem. > > > >where does one draw the line? I agree that stackable file systems make > >this a more pressing issue, as the "backing store" can be visible within > >the file system namespace as a regular file system that people are > >generally accustomed to interacting with. > > So here's an idea. When a branch is added, mount an empty space onto the > branch. (From within the kernel, so it appears as a side-effect of mount(2)) > > mount -t unionfs -o dirs=/a=rw:/b=ro none /union > > should imply something like > > mount --bind /var/lib/empty /a > mount --bind /var/lib/empty /b > > Or better, yet, make them read-only: > > mount --rbind -o ro /a /a > mount --rbind -o ro /b /b > (hope this works as intended?) > > So that no one can tinker with /a and /b while the union is mounted. I thought about that, but that doesn't help you w/ the NFS as branch case. - 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
