NFSv4: Don't use synchronous delegation recall in exception handling

The code needs to be able to work from inside an asynchronous context.
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/delegation.c

@@ -721,14 +721,12 @@ int nfs_async_inode_return_delegation(struct inode *inode,
 	struct nfs_client *clp = server->nfs_client;
 	struct nfs_delegation *delegation;
 
-	filemap_flush(inode->i_mapping);
-
 	rcu_read_lock();
 	delegation = rcu_dereference(NFS_I(inode)->delegation);
 	if (delegation == NULL)
 		goto out_enoent;
-
-	if (!clp->cl_mvops->match_stateid(&delegation->stateid, stateid))
+	if (stateid != NULL &&
+	    !clp->cl_mvops->match_stateid(&delegation->stateid, stateid))
 		goto out_enoent;
 	nfs_mark_return_delegation(server, delegation);
 	rcu_read_unlock();

fs/nfs/nfs4proc.c

@@ -362,11 +362,9 @@ static int nfs4_do_handle_exception(struct nfs_server *server,
 		case -NFS4ERR_DELEG_REVOKED:
 		case -NFS4ERR_ADMIN_REVOKED:
 		case -NFS4ERR_BAD_STATEID:
-			if (inode && nfs4_have_delegation(inode, FMODE_READ)) {
-				nfs4_inode_return_delegation(inode);
-				exception->retry = 1;
-				return 0;
-			}
+			if (inode && nfs_async_inode_return_delegation(inode,
+						NULL) == 0)
+				goto wait_on_recovery;
 			if (state == NULL)
 				break;
 			ret = nfs4_schedule_stateid_recovery(server, state);