From: Qi Zheng <zhengqi.arch@bytedance.com>

After refactoring the move_folios_to_lru(), its caller no longer needs to
hold the lruvec lock, the disabling IRQ is only for __count_vm_events()
and __mod_node_page_state().

On the PREEMPT_RT kernel, the local_irq_disable() cannot be used. To
avoid using local_irq_disable() and reduce the critical section of
disabling IRQ, make all callers of move_folios_to_lru() use IRQ-safed
count_vm_events() and mod_node_page_state().

Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
---
 mm/vmscan.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 28d9b3af47130..49e5661746213 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2021,12 +2021,12 @@ static unsigned long shrink_inactive_list(unsigned long nr_to_scan,
 
 	mod_lruvec_state(lruvec, PGDEMOTE_KSWAPD + reclaimer_offset(sc),
 					stat.nr_demoted);
-	__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
+	mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
 	item = PGSTEAL_KSWAPD + reclaimer_offset(sc);
 	if (!cgroup_reclaim(sc))
-		__count_vm_events(item, nr_reclaimed);
+		count_vm_events(item, nr_reclaimed);
 	count_memcg_events(lruvec_memcg(lruvec), item, nr_reclaimed);
-	__count_vm_events(PGSTEAL_ANON + file, nr_reclaimed);
+	count_vm_events(PGSTEAL_ANON + file, nr_reclaimed);
 
 	lru_note_cost_unlock_irq(lruvec, file, stat.nr_pageout,
 					nr_scanned - nr_reclaimed);
@@ -2171,10 +2171,10 @@ static void shrink_active_list(unsigned long nr_to_scan,
 	nr_activate = move_folios_to_lru(lruvec, &l_active);
 	nr_deactivate = move_folios_to_lru(lruvec, &l_inactive);
 
-	__count_vm_events(PGDEACTIVATE, nr_deactivate);
+	count_vm_events(PGDEACTIVATE, nr_deactivate);
 	count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE, nr_deactivate);
 
-	__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
+	mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
 
 	lru_note_cost_unlock_irq(lruvec, file, 0, nr_rotated);
 	trace_mm_vmscan_lru_shrink_active(pgdat->node_id, nr_taken, nr_activate,
@@ -4751,9 +4751,9 @@ static int evict_folios(unsigned long nr_to_scan, struct lruvec *lruvec,
 
 	item = PGSTEAL_KSWAPD + reclaimer_offset(sc);
 	if (!cgroup_reclaim(sc))
-		__count_vm_events(item, reclaimed);
+		count_vm_events(item, reclaimed);
 	count_memcg_events(memcg, item, reclaimed);
-	__count_vm_events(PGSTEAL_ANON + type, reclaimed);
+	count_vm_events(PGSTEAL_ANON + type, reclaimed);
 
 	spin_unlock_irq(&lruvec->lru_lock);
 
-- 
2.20.1

On Wed, Dec 17, 2025 at 03:27:28PM +0800, Qi Zheng wrote:
> From: Qi Zheng <zhengqi.arch@bytedance.com>
> 
> After refactoring the move_folios_to_lru(), its caller no longer needs to
> hold the lruvec lock, the disabling IRQ is only for __count_vm_events()
> and __mod_node_page_state().
> 
> On the PREEMPT_RT kernel, the local_irq_disable() cannot be used. To
> avoid using local_irq_disable() and reduce the critical section of
> disabling IRQ, make all callers of move_folios_to_lru() use IRQ-safed
> count_vm_events() and mod_node_page_state().
> 
> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>

Acked-by: Shakeel Butt <shakeel.butt@linux.dev>

On 12/17/25 08:27, Qi Zheng wrote:
> From: Qi Zheng <zhengqi.arch@bytedance.com>
> 
> After refactoring the move_folios_to_lru(), its caller no longer needs to
> hold the lruvec lock, the disabling IRQ is only for __count_vm_events()
> and __mod_node_page_state().
> 
> On the PREEMPT_RT kernel, the local_irq_disable() cannot be used. To
> avoid using local_irq_disable() and reduce the critical section of
> disabling IRQ, make all callers of move_folios_to_lru() use IRQ-safed
> count_vm_events() and mod_node_page_state().

The patch description is a bit confusing for me.

I assume you mean something like

"Once we refactor move_folios_to_lru(), its callers will no longer have 
to hold the lruvec lock; disabling IRQs is then only required for 
__count_vm_events() and __mod_node_page_state().

To prepare for that, let's $YOURDETAILSHERE"

-- 
Cheers

David

On 12/18/25 5:04 PM, David Hildenbrand (Red Hat) wrote:
> On 12/17/25 08:27, Qi Zheng wrote:
>> From: Qi Zheng <zhengqi.arch@bytedance.com>
>>
>> After refactoring the move_folios_to_lru(), its caller no longer needs to
>> hold the lruvec lock, the disabling IRQ is only for __count_vm_events()
>> and __mod_node_page_state().
>>
>> On the PREEMPT_RT kernel, the local_irq_disable() cannot be used. To
>> avoid using local_irq_disable() and reduce the critical section of
>> disabling IRQ, make all callers of move_folios_to_lru() use IRQ-safed
>> count_vm_events() and mod_node_page_state().
> 
> The patch description is a bit confusing for me.
> 
> I assume you mean something like
> 
> "Once we refactor move_folios_to_lru(), its callers will no longer have 
> to hold the lruvec lock; disabling IRQs is then only required for 
> __count_vm_events() and __mod_node_page_state().
> 
> To prepare for that, let's $YOURDETAILSHERE"

It is indeed clearer, will do in the next version.

>

On Wed, Dec 17, 2025 at 03:27:28PM +0800, Qi Zheng wrote:
> From: Qi Zheng <zhengqi.arch@bytedance.com>
> 
> After refactoring the move_folios_to_lru(), its caller no longer needs to
> hold the lruvec lock, the disabling IRQ is only for __count_vm_events()
> and __mod_node_page_state().
> 
> On the PREEMPT_RT kernel, the local_irq_disable() cannot be used. To
> avoid using local_irq_disable() and reduce the critical section of
> disabling IRQ, make all callers of move_folios_to_lru() use IRQ-safed
> count_vm_events() and mod_node_page_state().
> 
> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>

Acked-by: Johannes Weiner <hannes@cmpxchg.org>