This avoids an indirect call in the VFS for each path component lookup.

Well, at least as long as you own the directory in question, and the ACL
check is unnecessary.
Reviewed-by: NJames Morris <jmorris@namei.org>
Acked-by: NSerge Hallyn <serue@us.ibm.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>