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Date:   Tue,  1 Aug 2023 19:56:04 -0700
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Subject: [PATCH v2 3/3] mm-unstable: Multi-gen LRU: Fix can_swap in lru_gen_look_around()
From:   Kalesh Singh <kaleshsingh@google.com>
To:     yuzhao@google.com, akpm@linux-foundation.org
Cc:     surenb@google.com, android-mm@google.com, kernel-team@android.com,
        Kalesh Singh <kaleshsingh@google.com>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>,
        Suleiman Souhlal <suleiman@google.com>,
        Steven Barrett <steven@liquorix.net>,
        Oleksandr Natalenko <oleksandr@natalenko.name>,
        "Jan Alexander Steffens (heftig)" <heftig@archlinux.org>,
        Qi Zheng <zhengqi.arch@bytedance.com>,
        Brian Geffon <bgeffon@google.com>,
        Barry Song <baohua@kernel.org>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org
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Precedence: bulk

walk->can_swap might be invalid since it's not guaranteed to be
initialized for the particular lruvec. Instead deduce it from the folio
type (anon/file).

Fixes: 018ee47f1489 ("mm: multi-gen LRU: exploit locality in rmap")
Cc: Yu Zhao <yuzhao@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
---

Changes in v2:
  - Add Fixes tag

 mm/vmscan.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 6eecd291756c..b4329f93a682 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -4656,6 +4656,7 @@ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw)
 	pte_t *pte = pvmw->pte;
 	unsigned long addr = pvmw->address;
 	struct folio *folio = pfn_folio(pvmw->pfn);
+	bool can_swap = !folio_is_file_lru(folio);
 	struct mem_cgroup *memcg = folio_memcg(folio);
 	struct pglist_data *pgdat = folio_pgdat(folio);
 	struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
@@ -4704,7 +4705,7 @@ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw)
 		if (!pte_young(ptent))
 			continue;
 
-		folio = get_pfn_folio(pfn, memcg, pgdat, !walk || walk->can_swap);
+		folio = get_pfn_folio(pfn, memcg, pgdat, can_swap);
 		if (!folio)
 			continue;
 
-- 
2.41.0.255.g8b1d071c50-goog