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/pagelist.c b/fs/nfs/pagelist.c
index 4a31284..ce6440b 100644
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -47,7 +47,7 @@ void nfs_pgheader_init(struct nfs_pageio_descriptor *desc,
 
 	hdr->req = nfs_list_entry(mirror->pg_list.next);
 	hdr->inode = desc->pg_inode;
-	hdr->cred = hdr->req->wb_context->cred;
+	hdr->cred = nfs_req_openctx(hdr->req)->cred;
 	hdr->io_start = req_offset(hdr->req);
 	hdr->good_bytes = mirror->pg_count;
 	hdr->io_completion = desc->pg_io_completion;
@@ -578,7 +578,7 @@ static void nfs_pgio_rpcsetup(struct nfs_pgio_header *hdr,
 	hdr->args.pgbase = req->wb_pgbase;
 	hdr->args.pages  = hdr->page_array.pagevec;
 	hdr->args.count  = count;
-	hdr->args.context = get_nfs_open_context(req->wb_context);
+	hdr->args.context = get_nfs_open_context(nfs_req_openctx(req));
 	hdr->args.lock_context = req->wb_lock_context;
 	hdr->args.stable  = NFS_UNSTABLE;
 	switch (how & (FLUSH_STABLE | FLUSH_COND_STABLE)) {
@@ -935,9 +935,9 @@ static bool nfs_can_coalesce_requests(struct nfs_page *prev,
 	struct file_lock_context *flctx;
 
 	if (prev) {
-		if (!nfs_match_open_context(req->wb_context, prev->wb_context))
+		if (!nfs_match_open_context(nfs_req_openctx(req), nfs_req_openctx(prev)))
 			return false;
-		flctx = d_inode(req->wb_context->dentry)->i_flctx;
+		flctx = d_inode(nfs_req_openctx(req)->dentry)->i_flctx;
 		if (flctx != NULL &&
 		    !(list_empty_careful(&flctx->flc_posix) &&
 		      list_empty_careful(&flctx->flc_flock)) &&