[PATCH 4/4] mm: Add PGREUSE counter

[Peter Xu <peterx@redhat.com>]

This accounts for wp_page_reuse() case, where we reused a page for COW.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 include/linux/vm_event_item.h | 1 +
 mm/memory.c                   | 1 +
 mm/vmstat.c                   | 1 +
 3 files changed, 3 insertions(+)

diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
index 2e6ca53b9bbd..18e75974d4e3 100644
--- a/include/linux/vm_event_item.h
+++ b/include/linux/vm_event_item.h
@@ -30,6 +30,7 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
 		PGFAULT, PGMAJFAULT,
 		PGLAZYFREED,
 		PGREFILL,
+		PGREUSE,
 		PGSTEAL_KSWAPD,
 		PGSTEAL_DIRECT,
 		PGSCAN_KSWAPD,
diff --git a/mm/memory.c b/mm/memory.c
index cb9006189d22..148eafb8cbb1 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2622,6 +2622,7 @@ static inline void wp_page_reuse(struct vm_fault *vmf)
 	if (ptep_set_access_flags(vma, vmf->address, vmf->pte, entry, 1))
 		update_mmu_cache(vma, vmf->address, vmf->pte);
 	pte_unmap_unlock(vmf->pte, vmf->ptl);
+	count_vm_event(PGREUSE);
 }
 
 /*
diff --git a/mm/vmstat.c b/mm/vmstat.c
index e670f910cd2f..4f7b4ee6aa12 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1241,6 +1241,7 @@ const char * const vmstat_text[] = {
 	"pglazyfreed",
 
 	"pgrefill",
+	"pgreuse",
 	"pgsteal_kswapd",
 	"pgsteal_direct",
 	"pgscan_kswapd",
-- 
2.26.2