Actually, the bulk of autofs *is* in userspace. However, amd has
constant problems, both performance- and correctness wise, due to its
emulating an NFS server. amd requires a context switch on every
access that crosses the automount point, which leads to very poor
performance, and the necessity for using a secondary mount point
rather than mounting directly on the automount point proper is a
constant source of failures. The kernel stub allows for the common
case (which is, no mounting/umounting needed) to not invoke userspace,
and to provide a clean interface to the VFS, while the hard stuff
(mounting, umounting) is done in userspace.
This is, in fact, analogous to saying that device nodes are kernel
concepts (which they are), but the management of them (which doesn't
need to be fast) belongs in userspace.
-hpa
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu
Please read the FAQ at http://www.altern.org/andrebalsa/doc/lkml-faq.html