+ mm-vmscan-accumulate-nr_demoted-for-accurate-demotion-statistics.patch added to mm-hotfixes-unstable branch

+ mm-vmscan-accumulate-nr_demoted-for-accurate-demotion-statistics.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm/vmscan: accumulate nr_demoted for accurate demotion statistics
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     mm-vmscan-accumulate-nr_demoted-for-accurate-demotion-statistics.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-vmscan-accumulate-nr_demoted-for-accurate-demotion-statistics.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Li Zhijian <lizhijian@fujitsu.com>
Subject: mm/vmscan: accumulate nr_demoted for accurate demotion statistics
Date: Fri, 10 Jan 2025 20:21:32 +0800

In shrink_folio_list(), demote_folio_list() can be called multiple times,
which can lead to inaccurate demotion statistics if the number of demoted
pages is not accumulated correctly.

Accumulate the nr_demoted count across multiple calls to
demote_folio_list(), ensuring accurate reporting of demotion statistics.

Link: https://lkml.kernel.org/r/20250110122133.423481-1-lizhijian@fujitsu.com
Fixes: f77f0c751478 ("mm,memcg: provide per-cgroup counters for NUMA balancing operations")
Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
Acked-by: Kaiyang Zhao <kaiyang2@cs.cmu.edu>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/vmscan.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/vmscan.c~mm-vmscan-accumulate-nr_demoted-for-accurate-demotion-statistics
+++ a/mm/vmscan.c
@@ -1522,7 +1522,7 @@ keep:
 	/* 'folio_list' is always empty here */
 
 	/* Migrate folios selected for demotion */
-	stat->nr_demoted = demote_folio_list(&demote_folios, pgdat);
+	stat->nr_demoted += demote_folio_list(&demote_folios, pgdat);
 	nr_reclaimed += stat->nr_demoted;
 	/* Folios that could not be demoted are still in @demote_folios */
 	if (!list_empty(&demote_folios)) {
_

Patches currently in -mm which might be from lizhijian@fujitsu.com are

mm-vmscan-accumulate-nr_demoted-for-accurate-demotion-statistics.patch
selftests-mm-add-a-few-missing-gitignore-files.patch