A fixed or non-mm-managed mapping is one which sets VMA_PFNMAP_BIT, VMA_MIXEDMAP_BIT or VMA_DONTEXPAND_BIT, which is precisely what VMA_SPECIAL_FLAGS tests for other than VMA_IO_BIT, which is safe to drop as mm-managed mappings may not set it.
This is equivalent to testing for an mm-backed mapping, except for hugetlb. However, hugetlb folios are never placed on the LRU and lru_gen_look_around() is only called from LRU shrinkers on reclaim so this is fine. Using vma_is_mm_backed() rather than checking VMA_SPECIAL_FLAGS makes the check self-documenting and helps eliminate confusion around 'special flags'. No functional change intended. Reviewed-by: Zi Yan <[email protected]> Acked-by: David Hildenbrand (Arm) <[email protected]> Signed-off-by: Lorenzo Stoakes (ARM) <[email protected]> --- mm/vmscan.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index aecb157bc379..178a5de6c439 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -4417,8 +4417,8 @@ bool lru_gen_look_around(struct page_vma_mapped_walk *pvmw, unsigned int nr) if (spin_is_contended(pvmw->ptl)) return true; - /* exclude special VMAs containing anon pages from COW */ - if (vma->vm_flags & VM_SPECIAL) + /* exclude non-mm-backed VMAs containing anon pages from COW */ + if (!vma_is_mm_backed(vma)) return true; /* avoid taking the LRU lock under the PTL when possible */ -- 2.55.0
