mm, sched/numa: Remove remaining traces of NUMA rate-limiting

Remove the leftover pglist_data::numabalancing_migrate_lock and its
initialization, we stopped using this lock with:

  efaffc5e ("mm, sched/numa: Remove rate-limiting of automatic NUMA balancing migration")

[ mingo: Rewrote the changelog. ]
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Linux-MM <linux-mm@kvack.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1538824999-31230-1-git-send-email-srikar@linux.vnet.ibm.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

include/linux/mmzone.h

@@ -667,10 +667,6 @@ typedef struct pglist_data {
 	enum zone_type kcompactd_classzone_idx;
 	wait_queue_head_t kcompactd_wait;
 	struct task_struct *kcompactd;
-#endif
-#ifdef CONFIG_NUMA_BALANCING
-	/* Lock serializing the migrate rate limiting window */
-	spinlock_t numabalancing_migrate_lock;
 #endif
 	/*
 	 * This is a per-node reserve of pages that are not available

mm/page_alloc.c

@@ -6193,15 +6193,6 @@ static unsigned long __init calc_memmap_size(unsigned long spanned_pages,
 	return PAGE_ALIGN(pages * sizeof(struct page)) >> PAGE_SHIFT;
 }
 
-#ifdef CONFIG_NUMA_BALANCING
-static void pgdat_init_numabalancing(struct pglist_data *pgdat)
-{
-	spin_lock_init(&pgdat->numabalancing_migrate_lock);
-}
-#else
-static void pgdat_init_numabalancing(struct pglist_data *pgdat) {}
-#endif
-
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 static void pgdat_init_split_queue(struct pglist_data *pgdat)
 {
@@ -6226,7 +6217,6 @@ static void __meminit pgdat_init_internals(struct pglist_data *pgdat)
 {
 	pgdat_resize_init(pgdat);
 
-	pgdat_init_numabalancing(pgdat);
 	pgdat_init_split_queue(pgdat);
 	pgdat_init_kcompactd(pgdat);