[PATCH 4.9 21/91] mm/zsmalloc.c: fix the migrated zspage statistics.

[Greg Kroah-Hartman]

From: Chanho Min <chanho.min@xxxxxxx>

commit ac8f05da5174c560de122c499ce5dfb5d0dfbee5 upstream.

When zspage is migrated to the other zone, the zone page state should be
updated as well, otherwise the NR_ZSPAGE for each zone shows wrong
counts including proc/zoneinfo in practice.

Link: http://lkml.kernel.org/r/1575434841-48009-1-git-send-email-chanho.min@xxxxxxx
Fixes: 91537fee0013 ("mm: add NR_ZSMALLOC to vmstat")
Signed-off-by: Chanho Min <chanho.min@xxxxxxx>
Signed-off-by: Jinsuk Choi <jjinsuk.choi@xxxxxxx>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
Acked-by: Minchan Kim <minchan@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>        [4.9+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 mm/zsmalloc.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -2138,6 +2138,11 @@ int zs_page_migrate(struct address_space
 		zs_pool_dec_isolated(pool);
 	}
 
+	if (page_zone(newpage) != page_zone(page)) {
+		dec_zone_page_state(page, NR_ZSPAGES);
+		inc_zone_page_state(newpage, NR_ZSPAGES);
+	}
+
 	reset_page(page);
 	put_page(page);
 	page = newpage;