[PATCH v4 3/5] mm: memcg: add per-memcg zswap writeback stat

[Nhat Pham <nphamcs@gmail.com>]

From: Domenico Cerasuolo <cerasuolodomenico@gmail.com>

Since zswap now writes back pages from memcg-specific LRUs, we now need a
new stat to show writebacks count for each memcg.

Suggested-by: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Signed-off-by: Nhat Pham <nphamcs@gmail.com>
---
 include/linux/vm_event_item.h | 1 +
 mm/memcontrol.c               | 1 +
 mm/vmstat.c                   | 1 +
 mm/zswap.c                    | 3 +++
 4 files changed, 6 insertions(+)

diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
index 8abfa1240040..3153359c3841 100644
--- a/include/linux/vm_event_item.h
+++ b/include/linux/vm_event_item.h
@@ -145,6 +145,7 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
 #ifdef CONFIG_ZSWAP
 		ZSWPIN,
 		ZSWPOUT,
+		ZSWP_WB,
 #endif
 #ifdef CONFIG_X86
 		DIRECT_MAP_LEVEL2_SPLIT,
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 61c0c46c2d62..568d9d037a59 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -593,6 +593,7 @@ static const unsigned int memcg_vm_event_stat[] = {
 #if defined(CONFIG_MEMCG_KMEM) && defined(CONFIG_ZSWAP)
 	ZSWPIN,
 	ZSWPOUT,
+	ZSWP_WB,
 #endif
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 	THP_FAULT_ALLOC,
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 359460deb377..5e5572f3b456 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1401,6 +1401,7 @@ const char * const vmstat_text[] = {
 #ifdef CONFIG_ZSWAP
 	"zswpin",
 	"zswpout",
+	"zswp_wb",
 #endif
 #ifdef CONFIG_X86
 	"direct_map_level2_splits",
diff --git a/mm/zswap.c b/mm/zswap.c
index ee8e227e7b0b..b87311e48de9 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -711,6 +711,9 @@ static enum lru_status shrink_memcg_cb(struct list_head *item, struct list_lru_o
 	}
 	zswap_written_back_pages++;
 
+	if (entry->objcg)
+		count_objcg_event(entry->objcg, ZSWP_WB);
+
 	/*
 	 * Writeback started successfully, the page now belongs to the
 	 * swapcache. Drop the entry from zswap - unless invalidate already
-- 
2.34.1