Add support for caching negative dentries.
Up till now, ->d_revalidate() always forced a new lookup on these. Now let
the lookup method return a zero node ID (not used for anything else) meaning a
negative entry, but with a positive cache timeout. The old way of signaling
negative entry (replying ENOENT) still works.
Userspace should check the ABI minor version to see whether sending a zero ID
is allowed by the kernel or not.
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
8cbdf1e6f6