sunrpc/cache: avoid variable over-loading in cache_defer_req

In cache_defer_req, 'dreq' is used for two significantly different
values that happen to be of the same type.

This is both confusing, and makes it hard to extend the range of one of
the values as we will in the next patch.
So introduce 'discard' to take one of the values.

Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index 4a32a30..d6eee29 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -500,7 +500,7 @@
 
 static int cache_defer_req(struct cache_req *req, struct cache_head *item)
 {
-	struct cache_deferred_req *dreq;
+	struct cache_deferred_req *dreq, *discard;
 	int hash = DFR_HASH(item);
 
 	if (cache_defer_cnt >= DFR_MAX) {
@@ -525,20 +525,20 @@
 	list_add(&dreq->hash, &cache_defer_hash[hash]);
 
 	/* it is in, now maybe clean up */
-	dreq = NULL;
+	discard = NULL;
 	if (++cache_defer_cnt > DFR_MAX) {
-		dreq = list_entry(cache_defer_list.prev,
-				  struct cache_deferred_req, recent);
-		list_del_init(&dreq->recent);
-		list_del_init(&dreq->hash);
+		discard = list_entry(cache_defer_list.prev,
+				     struct cache_deferred_req, recent);
+		list_del_init(&discard->recent);
+		list_del_init(&discard->hash);
 		cache_defer_cnt--;
 	}
 	spin_unlock(&cache_defer_lock);
 
-	if (dreq) {
+	if (discard)
 		/* there was one too many */
-		dreq->revisit(dreq, 1);
-	}
+		discard->revisit(discard, 1);
+
 	if (!test_bit(CACHE_PENDING, &item->flags)) {
 		/* must have just been validated... */
 		cache_revisit_request(item);