[PATCH] mm: disable numa migration faults for dax vmas

[Dan Williams]

Mark dax vmas as not migratable to exclude them from task_numa_work().
This is especially relevant for device-dax which wants to ensure
predictable access latency and not incur periodic faults.

Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Reported-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
 include/linux/mempolicy.h |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h
index 5e5b2969d931..d72c691afaa6 100644
--- a/include/linux/mempolicy.h
+++ b/include/linux/mempolicy.h
@@ -7,6 +7,7 @@
 
 
 #include <linux/mmzone.h>
+#include <linux/dax.h>
 #include <linux/slab.h>
 #include <linux/rbtree.h>
 #include <linux/spinlock.h>
@@ -177,6 +178,9 @@ static inline bool vma_migratable(struct vm_area_struct *vma)
 	if (vma->vm_flags & (VM_IO | VM_PFNMAP))
 		return false;
 
+	if (vma_is_dax(vma))
+		return false;
+
 #ifndef CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION
 	if (vma->vm_flags & VM_HUGETLB)
 		return false;