7  * Balloon page migration makes use of the general non-lru movable page
10  * page->private is used to reference the responsible balloon device.
11  * page->mapping is used in context of non-lru page migration to reference
12  * the address space operations for page isolation/migration/compaction.
14  * As the page isolation scanning step a compaction thread does is a lockless
15  * procedure (from a page standpoint), it might bring some racy situations while
16  * performing balloon page compaction. In order to sort out these racy scenarios
17  * and safely perform balloon's page compaction and migration we must, always,
20  *   i. when updating a balloon's page ->mapping element, strictly do it under
23  *	    +-page_lock(page);
25  *	            ... page->mapping updates here ...
27  *  ii. isolation or dequeueing procedure must remove the page from balloon
28  *      device page list under b_dev_info->pages_lock.
31  * the aforementioned balloon page corner case, as well as to ensure the simple
40 #include <linux/page-flags.h>
51  * have to cope for page compaction / migration, as well as it serves the
52  * balloon driver as a page book-keeper for its registered balloon devices.
58 	int (*migratepage)(struct balloon_dev_info *, struct page *newpage,
59 			struct page *page, enum migrate_mode mode);
63 extern struct page *balloon_page_alloc(void);
65 				 struct page *page);
66 extern struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info);
83 extern bool balloon_page_isolate(struct page *page,
85 extern void balloon_page_putback(struct page *page);
87 				struct page *newpage,
88 				struct page *page, enum migrate_mode mode);
91  * balloon_page_insert - insert a page into the balloon's page list and make
92  *			 the page->private assignment accordingly.
94  * @page    : page to be assigned as a 'balloon page'
96  * Caller must ensure the page is locked and the spin_lock protecting balloon
97  * pages list is held before inserting a page into the balloon device.
100 				       struct page *page)  in balloon_page_insert()  argument
102 	__SetPageOffline(page);  in balloon_page_insert()
103 	__SetPageMovable(page, balloon->inode->i_mapping);  in balloon_page_insert()
104 	set_page_private(page, (unsigned long)balloon);  in balloon_page_insert()
105 	list_add(&page->lru, &balloon->pages);  in balloon_page_insert()
109  * balloon_page_delete - delete a page from balloon's page list and clear
110  *			 the page->private assignement accordingly.
111  * @page    : page to be released from balloon's page list
113  * Caller must ensure the page is locked and the spin_lock protecting balloon
114  * pages list is held before deleting a page from the balloon device.
116 static inline void balloon_page_delete(struct page *page)  in balloon_page_delete()  argument
118 	__ClearPageOffline(page);  in balloon_page_delete()
119 	__ClearPageMovable(page);  in balloon_page_delete()
120 	set_page_private(page, 0);  in balloon_page_delete()
122 	 * No touch page.lru field once @page has been isolated  in balloon_page_delete()
125 	if (!PageIsolated(page))  in balloon_page_delete()
126 		list_del(&page->lru);  in balloon_page_delete()
131  *			 that enqueues the given page.
133 static inline struct balloon_dev_info *balloon_page_device(struct page *page)  in balloon_page_device()  argument
135 	return (struct balloon_dev_info *)page_private(page);  in balloon_page_device()
146 				       struct page *page)  in balloon_page_insert()  argument
148 	__SetPageOffline(page);  in balloon_page_insert()
149 	list_add(&page->lru, &balloon->pages);  in balloon_page_insert()
152 static inline void balloon_page_delete(struct page *page)  in balloon_page_delete()  argument
154 	__ClearPageOffline(page);  in balloon_page_delete()
155 	list_del(&page->lru);  in balloon_page_delete()
158 static inline bool balloon_page_isolate(struct page *page)  in balloon_page_isolate()  argument
163 static inline void balloon_page_putback(struct page *page)  in balloon_page_putback()  argument
168 static inline int balloon_page_migrate(struct page *newpage,  in balloon_page_migrate()
169 				struct page *page, enum migrate_mode mode)  in balloon_page_migrate()  argument
182  * balloon_page_push - insert a page into a page list.
184  * @page : page to be added
186  * Caller must ensure the page is private and protect the list.
188 static inline void balloon_page_push(struct list_head *pages, struct page *page)  in balloon_page_push()  argument
190 	list_add(&page->lru, pages);  in balloon_page_push()
194  * balloon_page_pop - remove a page from a page list.
196  * @page : page to be added
198  * Caller must ensure the page is private and protect the list.
200 static inline struct page *balloon_page_pop(struct list_head *pages)  in balloon_page_pop()
202 	struct page *page = list_first_entry_or_null(pages, struct page, lru);  in balloon_page_pop()  local
204 	if (!page)  in balloon_page_pop()
207 	list_del(&page->lru);  in balloon_page_pop()
208 	return page;  in balloon_page_pop()