From: Li Zhijian <lizhijian@xxxxxxxxxxx> commit a479b078fddb0ad7f9e3c6da22d9cf8f2b5c7799 upstream. In shrink_folio_list(), demote_folio_list() can be called 2 times. Currently stat->nr_demoted will only store the last nr_demoted( the later nr_demoted is always zero, the former nr_demoted will get lost), as a result number of demoted pages is not accurate. Accumulate the nr_demoted count across multiple calls to demote_folio_list(), ensuring accurate reporting of demotion statistics. [lizhijian@xxxxxxxxxxx: introduce local nr_demoted to fix nr_reclaimed double counting] Link: https://lkml.kernel.org/r/20250111015253.425693-1-lizhijian@xxxxxxxxxxx Link: https://lkml.kernel.org/r/20250110122133.423481-1-lizhijian@xxxxxxxxxxx Fixes: f77f0c751478 ("mm,memcg: provide per-cgroup counters for NUMA balancing operations") Signed-off-by: Li Zhijian <lizhijian@xxxxxxxxxxx> Acked-by: Kaiyang Zhao <kaiyang2@xxxxxxxxxx> Tested-by: Donet Tom <donettom@xxxxxxxxxxxxx> Reviewed-by: Donet Tom <donettom@xxxxxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- mm/vmscan.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1053,7 +1053,7 @@ static unsigned int shrink_folio_list(st struct folio_batch free_folios; LIST_HEAD(ret_folios); LIST_HEAD(demote_folios); - unsigned int nr_reclaimed = 0; + unsigned int nr_reclaimed = 0, nr_demoted = 0; unsigned int pgactivate = 0; bool do_demote_pass; struct swap_iocb *plug = NULL; @@ -1522,8 +1522,9 @@ keep: /* 'folio_list' is always empty here */ /* Migrate folios selected for demotion */ - stat->nr_demoted = demote_folio_list(&demote_folios, pgdat); - nr_reclaimed += stat->nr_demoted; + nr_demoted = demote_folio_list(&demote_folios, pgdat); + nr_reclaimed += nr_demoted; + stat->nr_demoted += nr_demoted; /* Folios that could not be demoted are still in @demote_folios */ if (!list_empty(&demote_folios)) { /* Folios which weren't demoted go back on @folio_list */ Patches currently in stable-queue which might be from lizhijian@xxxxxxxxxxx are queue-6.12/mm-vmscan-accumulate-nr_demoted-for-accurate-demotion-statistics.patch
