NFS: Ensure rpc_run_task() cannot fail in nfs_async_rename()

Ensure the call to rpc_run_task() cannot fail by preallocating the
rpc_task.

Fixes: 910ad386 ("NFS: Fix memory allocation in rpc_alloc_task()")
Signed-off-by: NTrond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/unlink.c

@@ -347,6 +347,7 @@ nfs_async_rename(struct inode *old_dir, struct inode *new_dir,
 	data = kzalloc(sizeof(*data), GFP_KERNEL);
 	if (data == NULL)
 		return ERR_PTR(-ENOMEM);
+	task_setup_data.task = &data->task;
 	task_setup_data.callback_data = data;
 
 	data->cred = get_current_cred();

include/linux/nfs_xdr.h

@@ -1694,6 +1694,7 @@ struct nfs_unlinkdata {
 struct nfs_renamedata {
 	struct nfs_renameargs	args;
 	struct nfs_renameres	res;
+	struct rpc_task		task;
 	const struct cred	*cred;
 	struct inode		*old_dir;
 	struct dentry		*old_dentry;