bcache: Move keylist out of btree_op

Slowly working on pruning struct btree_op - the aim is for it to only
contain things that are actually necessary for traversing the btree.

Signed-off-by: Kent Overstreet <kmo@daterainc.com>
diff --git a/drivers/md/bcache/request.h b/drivers/md/bcache/request.h
index 1f1b59d3..7d02ac5 100644
--- a/drivers/md/bcache/request.h
+++ b/drivers/md/bcache/request.h
@@ -25,8 +25,10 @@
 	short			error;
 	unsigned long		start_time;
 
-	/* Anything past op->keys won't get zeroed in do_bio_hook */
 	struct btree_op		op;
+
+	/* Anything past this point won't get zeroed in search_alloc() */
+	struct keylist		insert_keys;
 };
 
 void bch_cache_read_endio(struct bio *, int);