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That for migration succeeded folios is done by migrate_pages(), in migrate_folio_done(). That for MR_DEMOTION reason is an exception though. DAMOS_MIGRATE_{HOT,COLD} call migrate_pages() but mistakenly not doing the stat adjustment. As a result, use of DAMOS_MIGRATE_{HOT,COLD} could corrupt the stat. It could confuse too_many_isolated(), make compaction and reclaim to behave in unexpected ways. The stat corruption can be reproduced and confirmed using DAMON user-space tool [1] on NUMA systems, like below. $ numactl --hardware available: 2 nodes (0-1) [...] $ sudo ./damo start --damos_action migrate_hot 1 $ sudo cat /proc/sys/vm/stat_refresh $ sudo dmesg [...] [ 80.215554] vmstat_refresh: nr_isolated_anon -5578 [ 80.216842] vmstat_refresh: nr_isolated_file -34400 This issue was discovered [2] by Sashiko. [1] https://github.com/damonitor/damo [2] https://lore.kernel.org/20260726164356.87940-1-sj@kernel.org Fixes: b51820ebea65 ("mm/damon/paddr: introduce DAMOS_MIGRATE_COLD action for demotion") Cc: # 6.11.x Signed-off-by: SJ Park --- mm/damon/ops-common.c | 2 ++ mm/damon/paddr.c | 2 ++ mm/damon/vaddr.c | 3 ++- 3 files changed, 6 insertions(+), 1 deletion(-) diff --git a/mm/damon/ops-common.c b/mm/damon/ops-common.c index e59f77eca83b2..9809fa12b09a8 100644 --- a/mm/damon/ops-common.c +++ b/mm/damon/ops-common.c @@ -374,6 +374,8 @@ static unsigned int damon_migrate_folio_list(struct list_head *folio_list, while (!list_empty(folio_list)) { folio = lru_to_folio(folio_list); list_del(&folio->lru); + node_stat_sub_folio(folio, NR_ISOLATED_ANON + + folio_is_file_lru(folio)); folio_putback_lru(folio); } diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c index 5a6a78054784a..5c6c3a597fd0b 100644 --- a/mm/damon/paddr.c +++ b/mm/damon/paddr.c @@ -346,6 +346,8 @@ static unsigned long damon_pa_migrate(struct damon_region *r, if (!folio_isolate_lru(folio)) goto put_folio; + node_stat_add_folio(folio, NR_ISOLATED_ANON + + folio_is_file_lru(folio)); list_add(&folio->lru, &folio_list); put_folio: addr += folio_size(folio); diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c index 4976775fe2762..0648400b2d65b 100644 --- a/mm/damon/vaddr.c +++ b/mm/damon/vaddr.c @@ -627,7 +627,8 @@ static void damos_va_migrate_dests_add(struct folio *folio, isolate: if (!folio_isolate_lru(folio)) return; - + node_stat_add_folio(folio, NR_ISOLATED_ANON + + folio_is_file_lru(folio)); list_add(&folio->lru, &migration_lists[i]); } base-commit: 1e15fbef3a3c465a6a2db0f38e3980d75420bd6d -- 2.47.3