NFS: Move cl_delegations to the nfs_server struct

Delegations are per-inode, not per-nfs_client.  When a server file
system is migrated, delegations on the client must be moved from the
source to the destination nfs_server.  Make it easier to manage a
mount point's delegation list across a migration event by moving the
list to the nfs_server struct.

Clean up: I added documenting comments to public functions I changed
in this patch.  For consistency I added comments to all the other
public functions in fs/nfs/delegation.c.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h
index 27255ff..b197563 100644
--- a/include/linux/nfs_fs_sb.h
+++ b/include/linux/nfs_fs_sb.h
@@ -47,7 +47,6 @@
 	u64			cl_clientid;	/* constant */
 	unsigned long		cl_state;
 
-	struct list_head	cl_delegations;
 	spinlock_t		cl_lock;
 
 	unsigned long		cl_lease_time;
@@ -152,6 +151,7 @@
 	struct rb_root		openowner_id;
 	struct rb_root		lockowner_id;
 #endif
+	struct list_head	delegations;
 	void (*destroy)(struct nfs_server *);
 
 	atomic_t active; /* Keep trace of any activity to this server */