FAILED: patch "[PATCH] mm/damon: adjust isolated pages stat for" failed to apply to 6.12-stable tree

The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x 1ec0e6b6f7321feb769f50d2f094a0aa6c2eda63
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026081758-bagged-engaged-79ec@gregkh' --subject-prefix 'PATCH 6.12.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 1ec0e6b6f7321feb769f50d2f094a0aa6c2eda63 Mon Sep 17 00:00:00 2001
From: SJ Park <[email protected]>
Date: Tue, 28 Jul 2026 07:04:03 -0700
Subject: [PATCH] mm/damon: adjust isolated pages stat for
DAMOS_MIGRATE_{HOT,COLD}

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.

index 9c178c175832..0bcad6b1e5b9 100644
@@ -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;

index 5c2da45f988c..f7613ce279a2 100644
@@ -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);

index e73ec1ce016e..2c1c1952c008 100644
@@ -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]);
 }
 

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.

---
NOTE: This patch should be applied after the manual backport [1] of 5deb65c34e68 ("mm/damon/ops-common: putback folios on invalid migrate nid").

[1] https://lore.kernel.org/[email protected]

 mm/damon/paddr.c | 6 ++++++
 1 file changed, 6 insertions(+)

index 884042856f7ea..d4a4d51750f5f 100644
@@ -414,6 +414,8 @@ static unsigned int damon_pa_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);
 	}
 

@@ -437,6 +439,8 @@ static unsigned long damon_pa_migrate_pages(struct list_head *folio_list,
 			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;

@@ -487,6 +491,8 @@ static unsigned long damon_pa_migrate(struct damon_region *r, struct damos *s)
 
 		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);

2.47.3

Queued for 6.12, thanks - it went in after the ops-common backport, as your note asked.

Thanks,
Sasha