pnfs: alloc and free layout_hdr layoutdriver methods

[gfp_flags]
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
diff --git a/fs/nfs/pnfs.h b/fs/nfs/pnfs.h
index f37ab35..925d6ef 100644
--- a/fs/nfs/pnfs.h
+++ b/fs/nfs/pnfs.h
@@ -73,6 +73,10 @@
 	const u32 id;
 	const char *name;
 	struct module *owner;
+
+	struct pnfs_layout_hdr * (*alloc_layout_hdr) (struct inode *inode, gfp_t gfp_flags);
+	void (*free_layout_hdr) (struct pnfs_layout_hdr *);
+
 	struct pnfs_layout_segment * (*alloc_lseg) (struct pnfs_layout_hdr *layoutid, struct nfs4_layoutget_res *lgr, gfp_t gfp_flags);
 	void (*free_lseg) (struct pnfs_layout_segment *lseg);