From b9306a796cad8a65f4d21779524e73fe0745bae1 Mon Sep 17 00:00:00 2001
From: Yang Shi <yang.shi@linux.alibaba.com>
Date: Thu, 6 Aug 2020 23:19:55 -0700
Subject: [PATCH] mm: filemap: clear idle flag for writes
Git-commit: b9306a796cad8a65f4d21779524e73fe0745bae1
Patch-mainline: v5.9-rc1
References: bsc#1175769

Since commit bbddabe2e436aa ("mm: filemap: only do access activations on
reads"), mark_page_accessed() is called for reads only.  But the idle flag
is cleared by mark_page_accessed() so the idle flag won't get cleared if
the page is write accessed only.

Basically idle page tracking is used to estimate workingset size of
workload, noticeable size of workingset might be missed if the idle flag
is not maintained correctly.

It seems good enough to just clear idle flag for write operations.

Fixes: bbddabe2e436 ("mm: filemap: only do access activations on reads")
Reported-by: Gang Deng <gavin.dg@linux.alibaba.com>
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Rik van Riel <riel@surriel.com>
Link: http://lkml.kernel.org/r/1593020612-13051-1-git-send-email-yang.shi@linux.alibaba.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Jan Kara <jack@suse.cz>

---
 mm/filemap.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -37,6 +37,7 @@
 #include <linux/cleancache.h>
 #include <linux/shmem_fs.h>
 #include <linux/rmap.h>
+#include <linux/page_idle.h>
 #include "internal.h"
 
 #define CREATE_TRACE_POINTS
@@ -1634,6 +1635,11 @@ repeat:
 
 	if (page && (fgp_flags & FGP_ACCESSED))
 		mark_page_accessed(page);
+	else if (fgp_flags & FGP_WRITE) {
+		/* Clear idle flag for buffer write */
+		if (page_is_idle(page))
+			clear_page_idle(page);
+	}
 
 no_page:
 	if (!page && (fgp_flags & FGP_CREAT)) {