NFS: Add a helper to return a pointer to the open context of a struct nfs_page

Add a helper for when we remove the explicit pointer to the open
context.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
diff --git a/fs/nfs/pnfs.h b/fs/nfs/pnfs.h
index c0420b9..f15609c 100644
--- a/fs/nfs/pnfs.h
+++ b/fs/nfs/pnfs.h
@@ -459,7 +459,7 @@
 pnfs_mark_request_commit(struct nfs_page *req, struct pnfs_layout_segment *lseg,
 			 struct nfs_commit_info *cinfo, u32 ds_commit_idx)
 {
-	struct inode *inode = d_inode(req->wb_context->dentry);
+	struct inode *inode = d_inode(nfs_req_openctx(req)->dentry);
 	struct pnfs_layoutdriver_type *ld = NFS_SERVER(inode)->pnfs_curr_ld;
 
 	if (lseg == NULL || ld->mark_request_commit == NULL)
@@ -471,7 +471,7 @@
 static inline bool
 pnfs_clear_request_commit(struct nfs_page *req, struct nfs_commit_info *cinfo)
 {
-	struct inode *inode = d_inode(req->wb_context->dentry);
+	struct inode *inode = d_inode(nfs_req_openctx(req)->dentry);
 	struct pnfs_layoutdriver_type *ld = NFS_SERVER(inode)->pnfs_curr_ld;
 
 	if (ld == NULL || ld->clear_request_commit == NULL)