On Tue, Jan 09, 2007 at 09:49:35AM +0000, Christoph Hellwig wrote: > On Mon, Jan 08, 2007 at 06:25:16PM -0500, Josef Sipek wrote: > > > There's no such problem with bind mounts. It's surprising to see such a > > > restriction with union mounts. > > > > Bind mounts are a purely VFS level construct. Unionfs is, as the name > > implies, a filesystem. Last year at OLS, it seemed that a lot of people > > agreed that unioning is neither purely a fs construct, nor purely a vfs > > construct. > > > > I'm using Unionfs (and ecryptfs) as guinea pigs to make linux fs stacking > > friendly - a topic to be discussed at LSF in about a month. > > And unionfs is the wrong thing do use for this. Unioning is a complex > namespace operation and needs to be implemented in the VFS or at least > needs a lot of help from the VFS. Getting namespace cache coherency > and especially locking right is imposisble with out that. What I meant was that I use them as an example for a linear and fanout stacking examples. While unioning itself is a complex operation, the general idea of one set of vfs objects (dentry, inode, etc.) pointing to several lower ones is very generic and applies to all fan-out stackable fs. Josef "Jeff" Sipek. -- Linux, n.: Generous programmers from around the world all join forces to help you shoot yourself in the foot for free. - 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
