mm: Cleanup __put_devmap_managed_page() vs ->page_free()

[linux-2.6-microblaze.git] / mm / memremap.c

diff --git a/mm/memremap.c b/mm/memremap.c
index c51c6bd..f915d07 100644 (file)
--- a/mm/memremap.c
+++ b/mm/memremap.c
@@ -27,7 +27,8 @@ static void devmap_managed_enable_put(void)
 
 static int devmap_managed_enable_get(struct dev_pagemap *pgmap)
 {
-       if (!pgmap->ops || !pgmap->ops->page_free) {
+       if (pgmap->type == MEMORY_DEVICE_PRIVATE &&
+           (!pgmap->ops || !pgmap->ops->page_free)) {
                WARN(1, "Missing page_free method\n");
                return -EINVAL;
        }
@@ -414,44 +415,51 @@ void __put_devmap_managed_page(struct page *page)
 {
        int count = page_ref_dec_return(page);
 
-       /*
-        * If refcount is 1 then page is freed and refcount is stable as nobody
-        * holds a reference on the page.
-        */
-       if (count == 1) {
-               /* Clear Active bit in case of parallel mark_page_accessed */
-               __ClearPageActive(page);
-               __ClearPageWaiters(page);
+       /* still busy */
+       if (count > 1)
+               return;
 
-               mem_cgroup_uncharge(page);
+       /* only triggered by the dev_pagemap shutdown path */
+       if (count == 0) {
+               __put_page(page);
+               return;
+       }
 
-               /*
-                * When a device_private page is freed, the page->mapping field
-                * may still contain a (stale) mapping value. For example, the
-                * lower bits of page->mapping may still identify the page as
-                * an anonymous page. Ultimately, this entire field is just
-                * stale and wrong, and it will cause errors if not cleared.
-                * One example is:
-                *
-                *  migrate_vma_pages()
-                *    migrate_vma_insert_page()
-                *      page_add_new_anon_rmap()
-                *        __page_set_anon_rmap()
-                *          ...checks page->mapping, via PageAnon(page) call,
-                *            and incorrectly concludes that the page is an
-                *            anonymous page. Therefore, it incorrectly,
-                *            silently fails to set up the new anon rmap.
-                *
-                * For other types of ZONE_DEVICE pages, migration is either
-                * handled differently or not done at all, so there is no need
-                * to clear page->mapping.
-                */
-               if (is_device_private_page(page))
-                       page->mapping = NULL;
+       /* notify page idle for dax */
+       if (!is_device_private_page(page)) {
+               wake_up_var(&page->_refcount);
+               return;
+       }
 
-               page->pgmap->ops->page_free(page);
-       } else if (!count)
-               __put_page(page);
+       /* Clear Active bit in case of parallel mark_page_accessed */
+       __ClearPageActive(page);
+       __ClearPageWaiters(page);
+
+       mem_cgroup_uncharge(page);
+
+       /*
+        * When a device_private page is freed, the page->mapping field
+        * may still contain a (stale) mapping value. For example, the
+        * lower bits of page->mapping may still identify the page as an
+        * anonymous page. Ultimately, this entire field is just stale
+        * and wrong, and it will cause errors if not cleared.  One
+        * example is:
+        *
+        *  migrate_vma_pages()
+        *    migrate_vma_insert_page()
+        *      page_add_new_anon_rmap()
+        *        __page_set_anon_rmap()
+        *          ...checks page->mapping, via PageAnon(page) call,
+        *            and incorrectly concludes that the page is an
+        *            anonymous page. Therefore, it incorrectly,
+        *            silently fails to set up the new anon rmap.
+        *
+        * For other types of ZONE_DEVICE pages, migration is either
+        * handled differently or not done at all, so there is no need
+        * to clear page->mapping.
+        */
+       page->mapping = NULL;
+       page->pgmap->ops->page_free(page);
 }
 EXPORT_SYMBOL(__put_devmap_managed_page);
 #endif /* CONFIG_DEV_PAGEMAP_OPS */