[RFC 5/8] mm: Add new flag VM_CDM for coherent device memory

[Anshuman Khandual <khandual@linux.vnet.ibm.com>]

VMAs containing coherent device memory should be marked with VM_CDM. These
VMAs need to be identified in various core kernel paths and this new flag
will help in this regard.

Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
---
 include/linux/mm.h |  5 +++++
 mm/mempolicy.c     | 43 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 3a19185..acee4d1 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -182,6 +182,11 @@ extern unsigned int kobjsize(const void *objp);
 #define VM_ACCOUNT	0x00100000	/* Is a VM accounted object */
 #define VM_NORESERVE	0x00200000	/* should the VM suppress accounting */
 #define VM_HUGETLB	0x00400000	/* Huge TLB Page VM */
+
+#ifdef CONFIG_COHERENT_DEVICE
+#define VM_CDM		0x00800000	/* Contains coherent device memory */
+#endif
+
 #define VM_ARCH_1	0x01000000	/* Architecture-specific flag */
 #define VM_ARCH_2	0x02000000
 #define VM_DONTDUMP	0x04000000	/* Do not include in the core dump */
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index cb1ba01..b983cea 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -174,6 +174,47 @@ static void mpol_relative_nodemask(nodemask_t *ret, const nodemask_t *orig,
 	nodes_onto(*ret, tmp, *rel);
 }
 
+#ifdef CONFIG_COHERENT_DEVICE
+static bool nodemask_contains_cdm(nodemask_t *nodes)
+{
+	int weight, nid, i;
+	nodemask_t mask;
+
+
+	if (!nodes)
+		return false;
+
+	mask = *nodes;
+	weight = nodes_weight(mask);
+	nid = first_node(mask);
+	for (i = 0; i < weight; i++) {
+		if (isolated_cdm_node(nid))
+			return true;
+		nid = next_node(nid, mask);
+	}
+	return false;
+}
+
+static void update_coherent_vma_flag(nodemask_t *nmask,
+		struct page *page, struct vm_area_struct *vma)
+{
+	if (!page)
+		return;
+
+	if (nodemask_contains_cdm(nmask)) {
+		if (!(vma->vm_flags & VM_CDM)) {
+			if (isolated_cdm_node(page_to_nid(page)))
+				vma->vm_flags |= VM_CDM;
+		}
+	}
+}
+#else
+static void update_coherent_vma_flag(nodemask_t *nmask,
+		struct page *page, struct vm_area_struct *vma)
+{
+}
+#endif
+
 static int mpol_new_interleave(struct mempolicy *pol, const nodemask_t *nodes)
 {
 	if (nodes_empty(*nodes))
@@ -2045,6 +2086,8 @@ alloc_pages_vma(gfp_t gfp, int order, struct vm_area_struct *vma,
 	zl = policy_zonelist(gfp, pol, node);
 	mpol_cond_put(pol);
 	page = __alloc_pages_nodemask(gfp, order, zl, nmask);
+	update_coherent_vma_flag(nmask, page, vma);
+
 out:
 	if (unlikely(!page && read_mems_allowed_retry(cpuset_mems_cookie)))
 		goto retry_cpuset;
-- 
2.1.0