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>

fs/nfs/client.c

@@ -172,7 +172,6 @@ static struct nfs_client *nfs_alloc_client(const struct nfs_client_initdata *cl_
 	if (err)
 		goto error_cleanup;
 
-	INIT_LIST_HEAD(&clp->cl_delegations);
 	spin_lock_init(&clp->cl_lock);
 	INIT_DELAYED_WORK(&clp->cl_renewd, nfs4_renew_state);
 	rpc_init_wait_queue(&clp->cl_rpcwaitq, "NFS client");
@@ -1040,6 +1039,7 @@ static struct nfs_server *nfs_alloc_server(void)
 	/* Zero out the NFS state stuff */
 	INIT_LIST_HEAD(&server->client_link);
 	INIT_LIST_HEAD(&server->master_link);
+	INIT_LIST_HEAD(&server->delegations);
 
 	atomic_set(&server->active, 0);
 

fs/nfs/delegation.h

@@ -44,6 +44,7 @@ void nfs_expire_all_delegation_types(struct nfs_client *clp, fmode_t flags);
 void nfs_expire_unreferenced_delegations(struct nfs_client *clp);
 void nfs_handle_cb_pathdown(struct nfs_client *clp);
 int nfs_client_return_marked_delegations(struct nfs_client *clp);
+int nfs_delegations_present(struct nfs_client *clp);
 
 void nfs_delegation_mark_reclaim(struct nfs_client *clp);
 void nfs_delegation_reap_unclaimed(struct nfs_client *clp);

fs/nfs/nfs4renewd.c

@@ -80,7 +80,7 @@ nfs4_renew_state(struct work_struct *work)
 		cred = ops->get_state_renewal_cred_locked(clp);
 		spin_unlock(&clp->cl_lock);
 		if (cred == NULL) {
-			if (list_empty(&clp->cl_delegations)) {
+			if (!nfs_delegations_present(clp)) {
 				set_bit(NFS4CLNT_LEASE_EXPIRED, &clp->cl_state);
 				goto out;
 			}

include/linux/nfs_fs_sb.h

@@ -47,7 +47,6 @@ struct nfs_client {
 	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 nfs_server {
 	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 */