cifs: add pid field to cifs_writedata

We'll need this to handle rwpidforward option correctly when we use
async writes in the aio_write op.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: Pavel Shilovsky <piastry@etersoft.ru>
diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index 95ee5a6..9e68340 100644
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -487,6 +487,7 @@
 	struct work_struct		work;
 	struct cifsFileInfo		*cfile;
 	__u64				offset;
+	pid_t				pid;
 	unsigned int			bytes;
 	int				result;
 	unsigned int			nr_pages;