mm: fix comments related to node reclaim

As zone reclaim has been replaced by node reclaim, this patch fixes
related comments.

Link: http://lkml.kernel.org/r/20191126141346.GA22665@haolee.github.ioSigned-off-by: NHao Lee <haolee.swjtu@gmail.com>
Reviewed-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

include/linux/mmzone.h

@@ -758,7 +758,7 @@ typedef struct pglist_data {
 
 #ifdef CONFIG_NUMA
 	/*
-	 * zone reclaim becomes active if more unmapped pages exist.
+	 * node reclaim becomes active if more unmapped pages exist.
 	 */
 	unsigned long		min_unmapped_pages;
 	unsigned long		min_slab_pages;

include/uapi/linux/sysctl.h

@@ -195,7 +195,7 @@ enum
 	VM_MIN_UNMAPPED=32,	/* Set min percent of unmapped pages */
 	VM_PANIC_ON_OOM=33,	/* panic at out-of-memory */
 	VM_VDSO_ENABLED=34,	/* map VDSO into new processes? */
-	VM_MIN_SLAB=35,		 /* Percent pages ignored by zone reclaim */
+	VM_MIN_SLAB=35,		 /* Percent pages ignored by node reclaim */
 };