Multi-gen LRU: fix can_swap in lru_gen_look_around()

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).

Link: https://lkml.kernel.org/r/20230802025606.346758-3-kaleshsingh@google.com
Fixes: 018ee47f1489 ("mm: multi-gen LRU: exploit locality in rmap")
Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
Tested-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com> [mediatek]
Tested-by: Charan Teja Kalla <quic_charante@quicinc.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Aneesh Kumar K V <aneesh.kumar@linux.ibm.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Brian Geffon <bgeffon@google.com>
Cc: Jan Alexander Steffens (heftig) <heftig@archlinux.org>
Cc: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: Oleksandr Natalenko <oleksandr@natalenko.name>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Steven Barrett <steven@liquorix.net>
Cc: Suleiman Souhlal <suleiman@google.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 6eecd291756cde383a9004ddf15fe5c46d022046..b4329f93a682e3e8dc88f3ced920db204b057929 100644 (file)
--- 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;