mm: multi-gen LRU: fix two warnings in evict_folios()

evict_folios() does not take lruvec lock before calling
reset_batch_size(), leading to a warning:

  WARNING: CPU: 19 PID: 235 at include/linux/mm_inline.h:44 reset_batch_size+0x1aa/0x1f0
  [...]
  Call Trace:
   <TASK>
   ? evict_folios+0x25e/0x8c0
   evict_folios+0x83e/0x8c0
   try_to_shrink_lruvec+0x195/0x2c0
   shrink_one+0x107/0x1c0
   shrink_many+0x1e6/0x900
   ? shrink_many+0x73/0x900
   shrink_node+0x3e3/0x440
   ? balance_pgdat+0xdb/0x7d0
   balance_pgdat+0x2d7/0x7d0
   kswapd+0x114/0x1e0
   ? __pfx_kswapd+0x10/0x10
   kthread+0xd6/0x110
   ? __pfx_kthread+0x10/0x10
   ret_from_fork+0x34/0x50
   ? __pfx_kthread+0x10/0x10
   ret_from_fork_asm+0x1a/0x30
   </TASK>

Fix this by taking the lock.

Also, both reset_batch_size() and __mod_lruvec_state() should be called
with irq disabled. Not disabling irq causes another warning:

  WARNING: CPU: 19 PID: 235 at mm/vmstat.c:393 __mod_node_page_state+0x84/0xd0
  [...]
  Call Trace:
   <TASK>
   __mod_lruvec_state+0x26/0x50
   evict_folios+0x65a/0x8c0
   try_to_shrink_lruvec+0x195/0x2c0
   shrink_one+0x107/0x1c0
   shrink_many+0x1e6/0x900
   ? shrink_many+0x73/0x900
   shrink_node+0x3e3/0x440
   ? balance_pgdat+0xdb/0x7d0
   balance_pgdat+0x2d7/0x7d0
   kswapd+0x114/0x1e0
   ? __pfx_kswapd+0x10/0x10
   kthread+0xd6/0x110
   ? __pfx_kthread+0x10/0x10
   ret_from_fork+0x34/0x50
   ? __pfx_kthread+0x10/0x10
   ret_from_fork_asm+0x1a/0x30
   </TASK>

Disable IRQ before reset_batch_size() and __mod_lruvec_state().

These two issues appear to be a mistake in commit d6530a1
("mm: vmscan: rework move_pages_to_lru()"). The latest version [1]
of Muchun's lruvec reparenting series handles this correctly.

Orabug: 37997618

Link: https://lore.kernel.org/linux-mm/[email protected] [1]
Fixes: d6530a1 ("mm: vmscan: rework move_pages_to_lru()")
Reviewed-by: Sidhartha Kumar <[email protected]>
Reviewed-by: Imran Khan <[email protected]>
Signed-off-by: Harry Yoo <[email protected]>

Author: Harry Yoo

mm/vmscan.c

@@ -4641,16 +4641,18 @@ static int evict_folios(struct lruvec *lruvec, struct scan_control *sc, int swap
 
 	move_folios_to_lru(&list);
 
+	local_irq_disable();
 	walk = current->reclaim_state->mm_walk;
 	if (walk && walk->batched) {
 		walk->lruvec = lruvec;
+		spin_lock(&lruvec->lru_lock);
 		reset_batch_size(walk);
+		spin_unlock(&lruvec->lru_lock);
 	}
 
 	__mod_lruvec_state(lruvec, PGDEMOTE_KSWAPD + reclaimer_offset(),
 					stat.nr_demoted);
 
-	local_irq_disable();
 	item = PGSTEAL_KSWAPD + reclaimer_offset();
 	if (!cgroup_reclaim(sc))
 		__count_vm_events(item, reclaimed);