mm/page_owner: record single timestamp value for high order allocations

When allocating a high-order page, separate allocation timestamp is
recorded for each sub-page resulting in different timestamp values between
them.

This behavior is not consistent with the behavior when recording free
timestamp and caused confusion when analyzing memory dumps.  Record single
timestamp for the entire allocation, aligning with the behavior for free
timestamps.

Link: https://lkml.kernel.org/r/20230121165054.520507-1-42.hyeyoo@gmail.comSigned-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/page_owner.c

@@ -163,6 +163,7 @@ static inline void __set_page_owner_handle(struct page_ext *page_ext,
 {
 	struct page_owner *page_owner;
 	int i;
+	u64 ts_nsec = local_clock();
 
 	for (i = 0; i < (1 << order); i++) {
 		page_owner = get_page_owner(page_ext);
@@ -172,7 +173,7 @@ static inline void __set_page_owner_handle(struct page_ext *page_ext,
 		page_owner->last_migrate_reason = -1;
 		page_owner->pid = current->pid;
 		page_owner->tgid = current->tgid;
-		page_owner->ts_nsec = local_clock();
+		page_owner->ts_nsec = ts_nsec;
 		strscpy(page_owner->comm, current->comm,
 			sizeof(page_owner->comm));
 		__set_bit(PAGE_EXT_OWNER, &page_ext->flags);