[PATCH v4 4/4] mm: swap: Count successful mTHP ZSWAP stores in sysfs mTHP stats.

[Kanchana P Sridhar]

If zswap_store() successfully swaps out an mTHP, it will be counted under
the per-order sysfs "zswpout" stats:

/sys/kernel/mm/transparent_hugepage/hugepages-*kB/stats/zswpout

Other block dev/fs mTHP swap-out events will be counted under
the existing sysfs "swpout" stats:

/sys/kernel/mm/transparent_hugepage/hugepages-*kB/stats/swpout

Based on changes made in commit 61e751c01466ffef5dc72cb64349454a691c6bfe
("mm: cleanup count_mthp_stat() definition"), this patch also moves
the call to count_mthp_stat() in count_swpout_vm_event() to be outside
the "ifdef CONFIG_TRANSPARENT_HUGEPAGE".

Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@xxxxxxxxx>
---
 mm/page_io.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/page_io.c b/mm/page_io.c
index a00e2f615118..ac5954149eb9 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -196,6 +196,7 @@ int swap_writepage(struct page *page, struct writeback_control *wbc)
 		return ret;
 	}
 	if (zswap_store(folio)) {
+		count_mthp_stat(folio_order(folio), MTHP_STAT_ZSWPOUT);
 		folio_unlock(folio);
 		return 0;
 	}
@@ -215,8 +216,8 @@ static inline void count_swpout_vm_event(struct folio *folio)
 		count_memcg_folio_events(folio, THP_SWPOUT, 1);
 		count_vm_event(THP_SWPOUT);
 	}
-	count_mthp_stat(folio_order(folio), MTHP_STAT_SWPOUT);
 #endif
+	count_mthp_stat(folio_order(folio), MTHP_STAT_SWPOUT);
 	count_vm_events(PSWPOUT, folio_nr_pages(folio));
 }
 
-- 
2.27.0