[DEBUG 19/21] mm: Add migrate_virtual_range migration interface

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

Currently there is no interface to be called by a driver for user process
virtual range migration. This adds one function and exports to be then
used by drivers.

Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
---
 include/linux/mempolicy.h |  2 ++
 mm/mempolicy.c            | 45 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h
index ff0c6bc..b07d6dc 100644
--- a/include/linux/mempolicy.h
+++ b/include/linux/mempolicy.h
@@ -153,6 +153,8 @@ extern bool init_nodemask_of_mempolicy(nodemask_t *mask);
 extern bool mempolicy_nodemask_intersects(struct task_struct *tsk,
 				const nodemask_t *mask);
 extern unsigned int mempolicy_slab_node(void);
+extern int migrate_virtual_range(int pid, unsigned long vaddr,
+			unsigned long size, int nid);
 
 extern enum zone_type policy_zone;
 
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 4482140..13cd5eb 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2919,3 +2919,48 @@ void mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol)
 		p += scnprintf(p, buffer + maxlen - p, ":%*pbl",
 			       nodemask_pr_args(&nodes));
 }
+
+/*
+ * migrate_virtual_range - migrate all pages of a process faulted within
+ * a virtual address range to a specified node. This function is also
+ * exported to be used by device drivers dealing with CDM memory.
+ *
+ * @pid:	Process ID of the target process
+ * @start:	Start address of virtual range
+ * @end:	End address of virtual range
+ * @nid:	Target node for migration
+ *
+ * Returns number of pages that were not migrated in case of failure else
+ * returns 0 when its successful.
+ */
+int migrate_virtual_range(int pid, unsigned long start,
+			unsigned long end, int nid)
+{
+	struct mm_struct *mm;
+	int ret = 0;
+
+	LIST_HEAD(mlist);
+
+	if ((!start) || (!end)) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	rcu_read_lock();
+	mm = find_task_by_vpid(pid)->mm;
+	rcu_read_unlock();
+
+	down_write(&mm->mmap_sem);
+	queue_pages_range(mm, start, end, &node_states[N_MEMORY],
+			MPOL_MF_MOVE_ALL | MPOL_MF_DISCONTIG_OK, &mlist);
+	if (!list_empty(&mlist)) {
+		ret = migrate_pages(&mlist, new_node_page, NULL,
+					nid, MIGRATE_SYNC, MR_NUMA_MISPLACED);
+		if (ret)
+			putback_movable_pages(&mlist);
+	}
+	up_write(&mm->mmap_sem);
+out:
+	return ret;
+}
+EXPORT_SYMBOL(migrate_virtual_range);
-- 
2.9.3

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