mm: mempolicy: skip non-migratable VMAs when setting MPOL_MF_LAZY

MPOL_MF_LAZY is not visible from userspace since a720094 ("mm:
mempolicy: Hide MPOL_NOOP and MPOL_MF_LAZY from userspace for now"), but
it should still skip non-migratable VMAs such as VM_IO, VM_PFNMAP, and
VM_HUGETLB VMAs, and avoid useless overhead of minor faults.

Signed-off-by: Liang Chen <[email protected]>
Signed-off-by: Gavin Guo <[email protected]>
Acked-by: Rik van Riel <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Naoya Horiguchi <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: LiangChen77

mm/mempolicy.c

@@ -644,7 +644,8 @@ static int queue_pages_test_walk(unsigned long start, unsigned long end,
 
 	if (flags & MPOL_MF_LAZY) {
 		/* Similar to task_numa_work, skip inaccessible VMAs */
-		if (vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))
+		if (vma_migratable(vma) &&
+			vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))
 			change_prot_numa(vma, start, endvma);
 		return 1;
 	}