Special VMAs like VM_PFNMAP can contain anon pages from COW. There
isn't much profit in doing lookaround on them. Besides, they can
trigger the pte_special() warning in get_pte_pfn().
Skip them in lru_gen_look_around().
Fixes: 018ee47f1489 ("mm: multi-gen LRU: exploit locality in rmap")
Signed-off-by: Yu Zhao <yuzhao@xxxxxxxxxx>
Reported-by: syzbot+03fd9b3f71641f0ebf2d@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://lore.kernel.org/000000000000f9ff00060d14c256@xxxxxxxxxx/
---
mm/vmscan.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index b4ca3563bcf4..3cf7066d627f 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3959,6 +3959,7 @@ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw)
int young = 0;
pte_t *pte = pvmw->pte;
unsigned long addr = pvmw->address;
+ struct vm_area_struct *vma = pvmw->vma;
struct folio *folio = pfn_folio(pvmw->pfn);
bool can_swap = !folio_is_file_lru(folio);
struct mem_cgroup *memcg = folio_memcg(folio);
@@ -3973,11 +3974,15 @@ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw)
if (spin_is_contended(pvmw->ptl))
return;
+ /* exclude special VMAs containing anon pages from COW */
+ if (vma->vm_flags & VM_SPECIAL)
+ return;
+
/* avoid taking the LRU lock under the PTL when possible */
walk = current->reclaim_state ? current->reclaim_state->mm_walk : NULL;
- start = max(addr & PMD_MASK, pvmw->vma->vm_start);
- end = min(addr | ~PMD_MASK, pvmw->vma->vm_end - 1) + 1;
+ start = max(addr & PMD_MASK, vma->vm_start);
+ end = min(addr | ~PMD_MASK, vma->vm_end - 1) + 1;
if (end - start > MIN_LRU_BATCH * PAGE_SIZE) {
if (addr - start < MIN_LRU_BATCH * PAGE_SIZE / 2)
@@ -4002,7 +4007,7 @@ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw)
unsigned long pfn;
pte_t ptent = ptep_get(pte + i);
- pfn = get_pte_pfn(ptent, pvmw->vma, addr);
+ pfn = get_pte_pfn(ptent, vma, addr);
if (pfn == -1)
continue;
@@ -4013,7 +4018,7 @@ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw)
if (!folio)
continue;
- if (!ptep_test_and_clear_young(pvmw->vma, addr, pte + i))
+ if (!ptep_test_and_clear_young(vma, addr, pte + i))
VM_WARN_ON_ONCE(true);
young++;
--
2.43.0.472.g3155946c3a-goog
