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>
diff --git a/Documentation/filesystems/nfs/00-INDEX b/Documentation/filesystems/nfs/00-INDEX
index 2f68cd6..3225a56 100644
--- a/Documentation/filesystems/nfs/00-INDEX
+++ b/Documentation/filesystems/nfs/00-INDEX
@@ -14,3 +14,5 @@
- short guide on setting up a diskless box with NFS root filesystem.
rpc-cache.txt
- introduction to the caching mechanisms in the sunrpc layer.
+idmapper.txt
+ - information for configuring request-keys to be used by idmapper
diff --git a/Documentation/filesystems/nfs/idmapper.txt b/Documentation/filesystems/nfs/idmapper.txt
new file mode 100644
index 0000000..c385204
--- /dev/null
+++ b/Documentation/filesystems/nfs/idmapper.txt
@@ -0,0 +1,67 @@
+
+=========
+ID Mapper
+=========
+Id mapper is used by NFS to translate user and group ids into names, and to
+translate user and group names into ids. Part of this translation involves
+performing an upcall to userspace to request the information. Id mapper will
+user request-key to perform this upcall and cache the result. The program
+/usr/sbin/nfs.upcall should be called by request-key, and will perform the
+translation and initialize a key with the resulting information.
+
+ NFS_USE_NEW_IDMAPPER must be selected when configuring the kernel to use this
+ feature.
+
+===========
+Configuring
+===========
+The file /etc/request-key.conf will need to be modified so /sbin/request-key can
+direct the upcall. The following line should be added:
+
+#OP TYPE DESCRIPTION CALLOUT INFO PROGRAM ARG1 ARG2 ARG3 ...
+#====== ======= =============== =============== ===============================
+create id_resolver * * /usr/sbin/nfs.upcall %k %d 600
+
+This will direct all id_resolver requests to the program /usr/sbin/nfs.upcall.
+The last parameter, 600, defines how many seconds into the future the key will
+expire. This parameter is optional for /usr/sbin/nfs.upcall. When the timeout
+is not specified, nfs.upcall will default to 600 seconds.
+
+id mapper uses for key descriptions:
+ uid: Find the UID for the given user
+ gid: Find the GID for the given group
+ user: Find the user name for the given UID
+ group: Find the group name for the given GID
+
+You can handle any of these individually, rather than using the generic upcall
+program. If you would like to use your own program for a uid lookup then you
+would edit your request-key.conf so it look similar to this:
+
+#OP TYPE DESCRIPTION CALLOUT INFO PROGRAM ARG1 ARG2 ARG3 ...
+#====== ======= =============== =============== ===============================
+create id_resolver uid:* * /some/other/program %k %d 600
+create id_resolver * * /usr/sbin/nfs.upcall %k %d 600
+
+Notice that the new line was added above the line for the generic program.
+request-key will find the first matching line and corresponding program. In
+this case, /some/other/program will handle all uid lookups and
+/usr/sbin/nfs.upcall will handle gid, user, and group lookups.
+
+See <file:Documentation/keys-request-keys.txt> for more information about the
+request-key function.
+
+
+==========
+nfs.upcall
+==========
+nfs.upcall is designed to be called by request-key, and should not be run "by
+hand". This program takes two arguments, a serialized key and a key
+description. The serialized key is first converted into a key_serial_t, and
+then passed as an argument to keyctl_instantiate (both are part of keyutils.h).
+
+The actual lookups are performed by functions found in nfsidmap.h. nfs.upcall
+determines the correct function to call by looking at the first part of the
+description string. For example, a uid lookup description will appear as
+"uid:user@domain".
+
+nfs.upcall will return 0 if the key was instantiated, and non-zero otherwise.