[RFC PATCH 7/8] dax/kmem: add the ltpin opt-in (CAP_LTPIN) for private nodes

[Gregory Price]

Add "ltpin" opt-in setting for NODE_PRIVATE_CAP_LTPIN so long-term GUP
pins (FOLL_LONGTERM) may target the node's folios.

Long-term pins block migration and hot-unplug indefinitely, so they are
refused on a private node unless it explicitly opts in.

Signed-off-by: Gregory Price <gourry@xxxxxxxxxx>
---
 drivers/dax/kmem.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
index 1cb3384c003e3..c33dac5939edd 100644
--- a/drivers/dax/kmem.c
+++ b/drivers/dax/kmem.c
@@ -633,6 +633,7 @@ KMEM_PRIVATE_CAP_ATTR(user_numa, NODE_PRIVATE_CAP_USER_NUMA);
 KMEM_PRIVATE_CAP_ATTR(hotunplug, NODE_PRIVATE_CAP_HOTUNPLUG);
 KMEM_PRIVATE_CAP_ATTR(demotion, NODE_PRIVATE_CAP_DEMOTION);
 KMEM_PRIVATE_CAP_ATTR(numa_balancing, NODE_PRIVATE_CAP_NUMA_BALANCING);
+KMEM_PRIVATE_CAP_ATTR(ltpin, NODE_PRIVATE_CAP_LTPIN);
 
 /* Per-service opt-ins. Visibility toggled by 'private' control */
 static struct attribute *dax_kmem_private_attrs[] = {
@@ -641,6 +642,7 @@ static struct attribute *dax_kmem_private_attrs[] = {
 	&dev_attr_hotunplug.attr,
 	&dev_attr_demotion.attr,
 	&dev_attr_numa_balancing.attr,
+	&dev_attr_ltpin.attr,
 	NULL,
 };
 static const struct attribute_group dax_kmem_private_group = {
-- 
2.53.0-Meta