SUNRPC: remove BUG_ON from bc_malloc

Replace BUG_ON() with WARN_ON_ONCE() and NULL return - the caller will handle
this like a memory allocation failure.

Signed-off-by: Weston Andros Adamson <dros@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index 46c1a879..6db26e5 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -2330,9 +2330,11 @@
 	struct page *page;
 	struct rpc_buffer *buf;
 
-	BUG_ON(size > PAGE_SIZE - sizeof(struct rpc_buffer));
-	page = alloc_page(GFP_KERNEL);
+	WARN_ON_ONCE(size > PAGE_SIZE - sizeof(struct rpc_buffer));
+	if (size > PAGE_SIZE - sizeof(struct rpc_buffer))
+		return NULL;
 
+	page = alloc_page(GFP_KERNEL);
 	if (!page)
 		return NULL;