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mm/damon: adjust isolated pages stat for DAMOS_MIGRATE_{HOT,COLD}

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Callers of migrate_pages() should adjust NR_MIGRATED_{ANON,FILE} for
isolations and putback of the folios.  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.

Link: https://lore.kernel.org/20260728140404.94476-1-sj@kernel.org
Link: https://github.com/damonitor/damo [1]
Link: https://lore.kernel.org/20260726164356.87940-1-sj@kernel.org [2]
Fixes: b51820ebea ("mm/damon/paddr: introduce DAMOS_MIGRATE_COLD action for demotion")
Signed-off-by: SJ Park <sj@kernel.org>
Cc: Honggyu Kim <honggyu.kim@sk.com>
Cc: Hyeongtak Ji <hyeongtak.ji@sk.com>
Cc: <stable@vger.kernel.org> # 6.11.x
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
SJ Park 2026-07-28 07:04:03 -07:00 committed by Andrew Morton
parent 5deb65c34e
commit 1ec0e6b6f7
3 changed files with 8 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
mm/damon/ops-common.c
View File

@ -375,6 +375,8 @@ 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);
}
@ -397,6 +399,8 @@ unsigned long damon_migrate_pages(struct list_head *folio_list, int target_nid)
struct folio *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);
}
return nr_migrated;

2
mm/damon/paddr.c
View File

@ -350,6 +350,8 @@ 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);

3
mm/damon/vaddr.c
View File

@ -649,7 +649,8 @@ 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]);
}