nfsd41: sessions basic data types

This patch provides basic data structures representing the nfs41
sessions and slots, plus helpers for keeping a reference count
on the session and freeing it.

Note that our server only support a headerpadsz of 0 and
it ignores backchannel attributes at the moment.

Signed-off-by: Benny Halevy <bhalevy@panasas.com>
[nfsd41: remove headerpadsz from channel attributes]
[nfsd41: embed nfsd4_channel in nfsd4_session]
Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
[nfsd41: use bool inuse for slot state]
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
[nfsd41 remove sl_session from nfsd4_slot]
Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

fs/nfsd/nfs4state.c

@@ -382,6 +382,24 @@ static void release_openowner(struct nfs4_stateowner *sop)
 	nfs4_put_stateowner(sop);
 }
 
+static void
+release_session(struct nfsd4_session *ses)
+{
+	list_del(&ses->se_hash);
+	list_del(&ses->se_perclnt);
+	nfsd4_put_session(ses);
+}
+
+void
+free_session(struct kref *kref)
+{
+	struct nfsd4_session *ses;
+
+	ses = container_of(kref, struct nfsd4_session, se_ref);
+	kfree(ses->se_slots);
+	kfree(ses);
+}
+
 static inline void
 renew_client(struct nfs4_client *clp)
 {