[RFC V2 09/12] mm: Exclude CDM marked VMAs from auto NUMA

[Anshuman Khandual]

Kernel cannot track device memory accesses behind VMAs containing CDM
memory. Hence all the VM_CDM marked VMAs should not be part of the auto
NUMA migration scheme. This patch also adds a new function is_cdm_vma()
to detect any VMA marked with flag VM_CDM.

Signed-off-by: Anshuman Khandual <khandual@xxxxxxxxxxxxxxxxxx>
---
 include/linux/mempolicy.h | 14 ++++++++++++++
 kernel/sched/fair.c       |  3 ++-
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h
index 5f4d828..ff0c6bc 100644
--- a/include/linux/mempolicy.h
+++ b/include/linux/mempolicy.h
@@ -172,6 +172,20 @@ extern int mpol_parse_str(char *str, struct mempolicy **mpol);
 
 extern void mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol);
 
+#ifdef CONFIG_COHERENT_DEVICE
+static inline bool is_cdm_vma(struct vm_area_struct *vma)
+{
+	if (vma->vm_flags & VM_CDM)
+		return true;
+	return false;
+}
+#else
+static inline bool is_cdm_vma(struct vm_area_struct *vma)
+{
+	return false;
+}
+#endif
+
 /* Check if a vma is migratable */
 static inline bool vma_migratable(struct vm_area_struct *vma)
 {
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 6559d19..523508c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2482,7 +2482,8 @@ void task_numa_work(struct callback_head *work)
 	}
 	for (; vma; vma = vma->vm_next) {
 		if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
-			is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
+			is_vm_hugetlb_page(vma) || is_cdm_vma(vma) ||
+					(vma->vm_flags & VM_MIXEDMAP)) {
 			continue;
 		}
 
-- 
2.9.3