Fix genarate thousand kworker on Linux Kernel 4.7

mm_slab_setup_bug_fix_on_4.7.x.patch

# Re: [Bug 172981] New: [bisected] SLAB: extreme load averages and over 2000 kworker threads
# Joonsoo Kim
# http://www.spinics.net/lists/linux-mm/msg114252.html

# Usage
# cd linux-X.X.X
# patch -p1 < this.patch

diff --git a/mm/slab.c b/mm/slab.c
index cc8bbc1..be4c7fa 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -964,7 +964,7 @@ static int setup_kmem_cache_node(struct kmem_cache *cachep,
 	 * guaranteed to be valid until irq is re-enabled, because it will be
 	 * freed after synchronize_sched().
 	 */
-	if (force_change)
+	if (old_shared && force_change)
 		synchronize_sched();
 
 fail: