[PATCH v3 1/3] mm: mprotect: always skip dma pinned folio in prot_numa_skip()

[Kefeng Wang <wangkefeng.wang@huawei.com>]

If the folio(even not CoW folio) is dma pinned, it can't be
migrated, so always skip pinned folio to avoid a waste of cycles
when folios migration.

Reviewed-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
---
 mm/mprotect.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/mm/mprotect.c b/mm/mprotect.c
index 113b48985834..bb59a42809b8 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -136,9 +136,12 @@ static bool prot_numa_skip(struct vm_area_struct *vma, unsigned long addr,
 	if (folio_is_zone_device(folio) || folio_test_ksm(folio))
 		goto skip;
 
-	/* Also skip shared copy-on-write pages */
-	if (is_cow_mapping(vma->vm_flags) &&
-	    (folio_maybe_dma_pinned(folio) || folio_maybe_mapped_shared(folio)))
+	/* Also skip shared copy-on-write folios */
+	if (is_cow_mapping(vma->vm_flags) && folio_maybe_mapped_shared(folio))
+		goto skip;
+
+	/* Folios are pinned and can't be migrated */
+	if (folio_maybe_dma_pinned(folio))
 		goto skip;
 
 	/*
-- 
2.27.0