6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Yu Zhao <yuzhao@xxxxxxxxxx> commit c28ac3c7eb945fee6e20f47d576af68fdff1392a upstream. 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(). Link: https://lkml.kernel.org/r/20231223045647.1566043-1-yuzhao@xxxxxxxxxx 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/ Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- mm/vmscan.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -4656,6 +4656,7 @@ void lru_gen_look_around(struct page_vma 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); @@ -4670,11 +4671,15 @@ void lru_gen_look_around(struct page_vma 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) @@ -4699,7 +4704,7 @@ void lru_gen_look_around(struct page_vma 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; @@ -4710,7 +4715,7 @@ void lru_gen_look_around(struct page_vma 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++;
