openwrt/target/linux/bcm27xx/patches-6.6/950-1261-mm-vmscan-Maintain-TLB-coherency-in-LRU-code.patch

From 536f2097dc397e4ebd0566e8f00219c02d7c8073 Mon Sep 17 00:00:00 2001
From: Phil Elwell <phil@raspberrypi.com>
Date: Thu, 12 Sep 2024 10:06:50 +0100
Subject: [PATCH 1261/1350] mm/vmscan: Maintain TLB coherency in LRU code

As a workaround (and possibly a fix) for CPU spins observed on BCM2837,
use ptep_clear_flush_young instead of ptep_test_and_clear_young inside
lru_gen_look_around in order to expose PTE changes to the MMU. Note that
on architectures that don't require an explicit flush,
ptep_clear_flush_young just calls ptep_test_and_clear_young.

Signed-off-by: Phil Elwell <phil@raspberrypi.com>
---
 mm/vmscan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -4716,7 +4716,7 @@ void lru_gen_look_around(struct page_vma
 		if (!folio)
 			continue;
 
-		if (!ptep_test_and_clear_young(vma, addr, pte + i))
+		if (!ptep_clear_flush_young(vma, addr, pte + i))
 			VM_WARN_ON_ONCE(true);
 
 		young++;