NFSv4.1/NFSv3: Add pNFS callbacks for nfs3_(read|write|commit)_done()

Enable pNFS callbacks to allow flex files to work correctly with a
NFSv3-enabled data server.
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/nfs3proc.c

@@ -800,6 +800,9 @@ static int nfs3_read_done(struct rpc_task *task, struct nfs_pgio_header *hdr)
 {
 	struct inode *inode = hdr->inode;
 
+	if (hdr->pgio_done_cb != NULL)
+		return hdr->pgio_done_cb(task, hdr);
+
 	if (nfs3_async_handle_jukebox(task, inode))
 		return -EAGAIN;
 
@@ -825,6 +828,9 @@ static int nfs3_write_done(struct rpc_task *task, struct nfs_pgio_header *hdr)
 {
 	struct inode *inode = hdr->inode;
 
+	if (hdr->pgio_done_cb != NULL)
+		return hdr->pgio_done_cb(task, hdr);
+
 	if (nfs3_async_handle_jukebox(task, inode))
 		return -EAGAIN;
 	if (task->tk_status >= 0)
@@ -845,6 +851,9 @@ static void nfs3_proc_commit_rpc_prepare(struct rpc_task *task, struct nfs_commi
 
 static int nfs3_commit_done(struct rpc_task *task, struct nfs_commit_data *data)
 {
+	if (data->commit_done_cb != NULL)
+		return data->commit_done_cb(task, data);
+
 	if (nfs3_async_handle_jukebox(task, data->inode))
 		return -EAGAIN;
 	nfs_refresh_inode(data->inode, data->res.fattr);