ipc: define the slab_memory_callback priority as a constant

This is a trivial patch that defines the priority of slab_memory_callback in
the callback chain as a constant.  This is to prepare for next patch in the
series.
Signed-off-by: Nadia Derbey <Nadia.Derbey@bull.net>
Cc: Yasunori Goto <y-goto@jp.fujitsu.com>
Cc: Matt Helsley <matthltc@us.ibm.com>
Cc: Mingming Cao <cmm@us.ibm.com>
Cc: Pierre Peiffer <pierre.peiffer@bull.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/memory.h

@@ -53,6 +53,12 @@ struct memory_notify {
 struct notifier_block;
 struct mem_section;
 
+/*
+ * Priorities for the hotplug memory callback routines (stored in decreasing
+ * order in the callback chain)
+ */
+#define SLAB_CALLBACK_PRI       1
+
 #ifndef CONFIG_MEMORY_HOTPLUG_SPARSE
 static inline int memory_dev_init(void)
 {

mm/slub.c

@@ -2978,7 +2978,7 @@ void __init kmem_cache_init(void)
 	kmalloc_caches[0].refcount = -1;
 	caches++;
 
-	hotplug_memory_notifier(slab_memory_callback, 1);
+	hotplug_memory_notifier(slab_memory_callback, SLAB_CALLBACK_PRI);
 #endif
 
 	/* Able to allocate the per node structures */