[RFC PATCH 5/5] mm: changes to unref pages with Generic type

[Felix Kuehling]

From: Alex Sierra <alex.sierra at amd.com>

pages in device mapping refcounts are 1-based, instead
of 0-based. If refcount 1, means it can be freed.
This logic is not set for Generic memory type. Therefore,
its release is threated as a normal page, instead of
the callback device driver release it.

Signed-off-by: Alex Sierra <alex.sierra at amd.com>
---
 include/linux/mm.h | 1 +
 mm/memremap.c      | 5 ++++-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 1af7b9b76948..83bd2f3e111b 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1130,6 +1130,7 @@ static inline bool page_is_devmap_managed(struct page *page)
 	switch (page->pgmap->type) {
 	case MEMORY_DEVICE_PRIVATE:
 	case MEMORY_DEVICE_FS_DAX:
+	case MEMORY_DEVICE_GENERIC:
 		return true;
 	default:
 		break;
diff --git a/mm/memremap.c b/mm/memremap.c
index 16b2fb482da1..d2563fbcf987 100644
--- a/mm/memremap.c
+++ b/mm/memremap.c
@@ -44,6 +44,7 @@ EXPORT_SYMBOL(devmap_managed_key);
 static void devmap_managed_enable_put(struct dev_pagemap *pgmap)
 {
 	if (pgmap->type == MEMORY_DEVICE_PRIVATE ||
+	    pgmap->type == MEMORY_DEVICE_GENERIC ||
 	    pgmap->type == MEMORY_DEVICE_FS_DAX)
 		static_branch_dec(&devmap_managed_key);
 }
@@ -51,6 +52,7 @@ static void devmap_managed_enable_put(struct dev_pagemap *pgmap)
 static void devmap_managed_enable_get(struct dev_pagemap *pgmap)
 {
 	if (pgmap->type == MEMORY_DEVICE_PRIVATE ||
+	    pgmap->type == MEMORY_DEVICE_GENERIC ||
 	    pgmap->type == MEMORY_DEVICE_FS_DAX)
 		static_branch_inc(&devmap_managed_key);
 }
@@ -480,7 +482,8 @@ EXPORT_SYMBOL_GPL(get_dev_pagemap);
 void free_devmap_managed_page(struct page *page)
 {
 	/* notify page idle for dax */
-	if (!is_device_private_page(page)) {
+	if (!(is_device_private_page(page) ||
+	    is_device_generic_page(page))) {
 		wake_up_var(&page->_refcount);
 		return;
 	}
-- 
2.31.1