nfs: introduce pg_cleanup op for pgio descriptors

Add a new operation to nfs_pageio_ops that is called on nfs_pageio_complete.
Signed-off-by: Weston Andros Adamson <dros@primarydata.com>

fs/nfs/pagelist.c

@@ -1050,7 +1050,7 @@ int nfs_pageio_resend(struct nfs_pageio_descriptor *desc,
 EXPORT_SYMBOL_GPL(nfs_pageio_resend);
 
 /**
- * nfs_pageio_complete - Complete I/O on an nfs_pageio_descriptor
+ * nfs_pageio_complete - Complete I/O then cleanup an nfs_pageio_descriptor
  * @desc: pointer to io descriptor
  */
 void nfs_pageio_complete(struct nfs_pageio_descriptor *desc)
@@ -1062,6 +1062,9 @@ void nfs_pageio_complete(struct nfs_pageio_descriptor *desc)
 		if (!nfs_do_recoalesce(desc))
 			break;
 	}
+
+	if (desc->pg_ops->pg_cleanup)
+		desc->pg_ops->pg_cleanup(desc);
 }
 
 /**

include/linux/nfs_page.h

@@ -58,6 +58,7 @@ struct nfs_pageio_ops {
 	size_t	(*pg_test)(struct nfs_pageio_descriptor *, struct nfs_page *,
 			   struct nfs_page *);
 	int	(*pg_doio)(struct nfs_pageio_descriptor *);
+	void	(*pg_cleanup)(struct nfs_pageio_descriptor *);
 };
 
 struct nfs_rw_ops {