nfs: modify pg_test interface to return size_t

This is a step toward allowing pg_test to inform the the
coalescing code to reduce the size of requests so they may fit in
whatever scheme the pg_test callback wants to define.

For now, just return the size of the request if there is space, or 0
if there is not.  This shouldn't change any behavior as it acts
the same as when the pg_test functions returned bool.

Signed-off-by: Weston Andros Adamson <dros@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
diff --git a/include/linux/nfs_page.h b/include/linux/nfs_page.h
index be0b098..13d59af 100644
--- a/include/linux/nfs_page.h
+++ b/include/linux/nfs_page.h
@@ -46,7 +46,8 @@
 struct nfs_pageio_descriptor;
 struct nfs_pageio_ops {
 	void	(*pg_init)(struct nfs_pageio_descriptor *, struct nfs_page *);
-	bool	(*pg_test)(struct nfs_pageio_descriptor *, struct nfs_page *, struct nfs_page *);
+	size_t	(*pg_test)(struct nfs_pageio_descriptor *, struct nfs_page *,
+			   struct nfs_page *);
 	int	(*pg_doio)(struct nfs_pageio_descriptor *);
 };
 
@@ -102,7 +103,7 @@
 				   struct nfs_page *);
 extern	void nfs_pageio_complete(struct nfs_pageio_descriptor *desc);
 extern	void nfs_pageio_cond_complete(struct nfs_pageio_descriptor *, pgoff_t);
-extern bool nfs_generic_pg_test(struct nfs_pageio_descriptor *desc,
+extern size_t nfs_generic_pg_test(struct nfs_pageio_descriptor *desc,
 				struct nfs_page *prev,
 				struct nfs_page *req);
 extern  int nfs_wait_on_request(struct nfs_page *);