NFS: new idmapper

This patch creates a new idmapper system that uses the request-key function to
place a call into userspace to map user and group ids to names.  The old
idmapper was single threaded, which prevented more than one request from running
at a single time.  This means that a user would have to wait for an upcall to
finish before accessing a cached result.

The upcall result is stored on a keyring of type id_resolver.  See the file
Documentation/filesystems/nfs/idmapper.txt for instructions.

Signed-off-by: Bryan Schumaker <bjschuma@netapp.com>
[Trond: fix up the return value of nfs_idmap_lookup_name and clean up code]
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/fs/nfs/Kconfig b/fs/nfs/Kconfig
index 6c2aad49d731..3f69752d6f18 100644
--- a/fs/nfs/Kconfig
+++ b/fs/nfs/Kconfig
@@ -116,3 +116,14 @@ config NFS_USE_KERNEL_DNS
         select DNS_RESOLVER
         select KEYS
         default y
+
+config NFS_USE_NEW_IDMAPPER
+        bool "Use the new idmapper upcall routine"
+        depends on NFS_V4 && KEYS
+        help
+          Say Y here if you want NFS to use the new idmapper upcall functions.
+          You will need /sbin/request-key (usually provided by the keyutils
+          package).  For details, read
+          <file:Documentation/filesystems/nfs/idmapper.txt>.
+
+          If you are unsure, say N.