mm/page_isolation.c: add new tracepoint, test_pages_isolated

cma allocation should be guranteeded to succeed.  But sometimes it can
fail in the current implementation.  To track down the problem, we need
to know which page is problematic and this new tracepoint will report
it.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/page_isolation.c

@@ -9,6 +9,9 @@
 #include <linux/hugetlb.h>
 #include "internal.h"
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/page_isolation.h>
+
 static int set_migratetype_isolate(struct page *page,
 				bool skip_hwpoisoned_pages)
 {
@@ -268,6 +271,8 @@ int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn,
 						skip_hwpoisoned_pages);
 	spin_unlock_irqrestore(&zone->lock, flags);
 
+	trace_test_pages_isolated(start_pfn, end_pfn, pfn);
+
 	return pfn < end_pfn ? -EBUSY : 0;
 }