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);
62 extern struct page *balloon_page_alloc(void);
64 				 struct page *page);
65 extern struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info);
83  * balloon_page_insert - insert a page into the balloon's page list and make
84  *			 the page->private assignment accordingly.
86  * @page    : page to be assigned as a 'balloon page'
88  * Caller must ensure the page is locked and the spin_lock protecting balloon
89  * pages list is held before inserting a page into the balloon device.
92 				       struct page *page)  in balloon_page_insert()  argument
94 	__SetPageOffline(page);  in balloon_page_insert()
95 	__SetPageMovable(page, &balloon_mops);  in balloon_page_insert()
96 	set_page_private(page, (unsigned long)balloon);  in balloon_page_insert()
97 	list_add(&page->lru, &balloon->pages);  in balloon_page_insert()
101  * balloon_page_delete - delete a page from balloon's page list and clear
102  *			 the page->private assignement accordingly.
103  * @page    : page to be released from balloon's page list
105  * Caller must ensure the page is locked and the spin_lock protecting balloon
106  * pages list is held before deleting a page from the balloon device.
108 static inline void balloon_page_delete(struct page *page)  in balloon_page_delete()  argument
110 	__ClearPageOffline(page);  in balloon_page_delete()
111 	__ClearPageMovable(page);  in balloon_page_delete()
112 	set_page_private(page, 0);  in balloon_page_delete()
114 	 * No touch page.lru field once @page has been isolated  in balloon_page_delete()
117 	if (!PageIsolated(page))  in balloon_page_delete()
118 		list_del(&page->lru);  in balloon_page_delete()
123  *			 that enqueues the given page.
125 static inline struct balloon_dev_info *balloon_page_device(struct page *page)  in balloon_page_device()  argument
127 	return (struct balloon_dev_info *)page_private(page);  in balloon_page_device()
138 				       struct page *page)  in balloon_page_insert()  argument
140 	__SetPageOffline(page);  in balloon_page_insert()
141 	list_add(&page->lru, &balloon->pages);  in balloon_page_insert()
144 static inline void balloon_page_delete(struct page *page)  in balloon_page_delete()  argument
146 	__ClearPageOffline(page);  in balloon_page_delete()
147 	list_del(&page->lru);  in balloon_page_delete()
158  * balloon_page_push - insert a page into a page list.
160  * @page : page to be added
162  * Caller must ensure the page is private and protect the list.
164 static inline void balloon_page_push(struct list_head *pages, struct page *page)  in balloon_page_push()  argument
166 	list_add(&page->lru, pages);  in balloon_page_push()
170  * balloon_page_pop - remove a page from a page list.
172  * @page : page to be added
174  * Caller must ensure the page is private and protect the list.
176 static inline struct page *balloon_page_pop(struct list_head *pages)  in balloon_page_pop()
178 	struct page *page = list_first_entry_or_null(pages, struct page, lru);  in balloon_page_pop()  local
180 	if (!page)  in balloon_page_pop()
183 	list_del(&page->lru);  in balloon_page_pop()
184 	return page;  in balloon_page_pop()