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Rafael Aquini18468d92012-12-11 16:02:38 -08001/*
2 * include/linux/balloon_compaction.h
3 *
4 * Common interface definitions for making balloon pages movable by compaction.
5 *
6 * Despite being perfectly possible to perform ballooned pages migration, they
7 * make a special corner case to compaction scans because balloon pages are not
8 * enlisted at any LRU list like the other pages we do compact / migrate.
9 *
10 * As the page isolation scanning step a compaction thread does is a lockless
11 * procedure (from a page standpoint), it might bring some racy situations while
12 * performing balloon page compaction. In order to sort out these racy scenarios
13 * and safely perform balloon's page compaction and migration we must, always,
14 * ensure following these three simple rules:
15 *
16 * i. when updating a balloon's page ->mapping element, strictly do it under
17 * the following lock order, independently of the far superior
18 * locking scheme (lru_lock, balloon_lock):
19 * +-page_lock(page);
20 * +--spin_lock_irq(&b_dev_info->pages_lock);
21 * ... page->mapping updates here ...
22 *
23 * ii. before isolating or dequeueing a balloon page from the balloon device
24 * pages list, the page reference counter must be raised by one and the
25 * extra refcount must be dropped when the page is enqueued back into
26 * the balloon device page list, thus a balloon page keeps its reference
27 * counter raised only while it is under our special handling;
28 *
29 * iii. after the lockless scan step have selected a potential balloon page for
Konstantin Khlebnikovd6d86c02014-10-09 15:29:27 -070030 * isolation, re-test the PageBalloon mark and the PagePrivate flag
Rafael Aquini18468d92012-12-11 16:02:38 -080031 * under the proper page lock, to ensure isolating a valid balloon page
32 * (not yet isolated, nor under release procedure)
33 *
Konstantin Khlebnikovd6d86c02014-10-09 15:29:27 -070034 * iv. isolation or dequeueing procedure must clear PagePrivate flag under
35 * page lock together with removing page from balloon device page list.
36 *
Rafael Aquini18468d92012-12-11 16:02:38 -080037 * The functions provided by this interface are placed to help on coping with
38 * the aforementioned balloon page corner case, as well as to ensure the simple
39 * set of exposed rules are satisfied while we are dealing with balloon pages
40 * compaction / migration.
41 *
42 * Copyright (C) 2012, Red Hat, Inc. Rafael Aquini <aquini@redhat.com>
43 */
44#ifndef _LINUX_BALLOON_COMPACTION_H
45#define _LINUX_BALLOON_COMPACTION_H
46#include <linux/pagemap.h>
47#include <linux/page-flags.h>
48#include <linux/migrate.h>
49#include <linux/gfp.h>
50#include <linux/err.h>
51
52/*
53 * Balloon device information descriptor.
54 * This struct is used to allow the common balloon compaction interface
55 * procedures to find the proper balloon device holding memory pages they'll
56 * have to cope for page compaction / migration, as well as it serves the
57 * balloon driver as a page book-keeper for its registered balloon devices.
58 */
59struct balloon_dev_info {
Rafael Aquini18468d92012-12-11 16:02:38 -080060 unsigned long isolated_pages; /* # of isolated pages for migration */
61 spinlock_t pages_lock; /* Protection to pages list */
62 struct list_head pages; /* Pages enqueued & handled to Host */
Konstantin Khlebnikov9d1ba802014-10-09 15:29:29 -070063 int (*migratepage)(struct balloon_dev_info *, struct page *newpage,
64 struct page *page, enum migrate_mode mode);
Rafael Aquini18468d92012-12-11 16:02:38 -080065};
66
67extern struct page *balloon_page_enqueue(struct balloon_dev_info *b_dev_info);
68extern struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info);
Rafael Aquini18468d92012-12-11 16:02:38 -080069
Konstantin Khlebnikov9d1ba802014-10-09 15:29:29 -070070static inline void balloon_devinfo_init(struct balloon_dev_info *balloon)
Rafael Aquini18468d92012-12-11 16:02:38 -080071{
Konstantin Khlebnikov9d1ba802014-10-09 15:29:29 -070072 balloon->isolated_pages = 0;
73 spin_lock_init(&balloon->pages_lock);
74 INIT_LIST_HEAD(&balloon->pages);
75 balloon->migratepage = NULL;
Rafael Aquini18468d92012-12-11 16:02:38 -080076}
77
Rafael Aquini18468d92012-12-11 16:02:38 -080078#ifdef CONFIG_BALLOON_COMPACTION
79extern bool balloon_page_isolate(struct page *page);
80extern void balloon_page_putback(struct page *page);
81extern int balloon_page_migrate(struct page *newpage,
82 struct page *page, enum migrate_mode mode);
Rafael Aquini18468d92012-12-11 16:02:38 -080083
84/*
Konstantin Khlebnikovd6d86c02014-10-09 15:29:27 -070085 * __is_movable_balloon_page - helper to perform @page PageBalloon tests
Rafael Aquini18468d92012-12-11 16:02:38 -080086 */
87static inline bool __is_movable_balloon_page(struct page *page)
88{
Konstantin Khlebnikovd6d86c02014-10-09 15:29:27 -070089 return PageBalloon(page);
Rafael Aquini18468d92012-12-11 16:02:38 -080090}
91
92/*
Konstantin Khlebnikovd6d86c02014-10-09 15:29:27 -070093 * balloon_page_movable - test PageBalloon to identify balloon pages
94 * and PagePrivate to check that the page is not
95 * isolated and can be moved by compaction/migration.
Rafael Aquini18468d92012-12-11 16:02:38 -080096 *
97 * As we might return false positives in the case of a balloon page being just
Konstantin Khlebnikovd6d86c02014-10-09 15:29:27 -070098 * released under us, this need to be re-tested later, under the page lock.
Rafael Aquini18468d92012-12-11 16:02:38 -080099 */
100static inline bool balloon_page_movable(struct page *page)
101{
Konstantin Khlebnikovd6d86c02014-10-09 15:29:27 -0700102 return PageBalloon(page) && PagePrivate(page);
Rafael Aquini18468d92012-12-11 16:02:38 -0800103}
104
105/*
Rafael Aquini117aad12013-09-30 13:45:16 -0700106 * isolated_balloon_page - identify an isolated balloon page on private
107 * compaction/migration page lists.
Rafael Aquini117aad12013-09-30 13:45:16 -0700108 */
109static inline bool isolated_balloon_page(struct page *page)
110{
Konstantin Khlebnikovd6d86c02014-10-09 15:29:27 -0700111 return PageBalloon(page);
Rafael Aquini117aad12013-09-30 13:45:16 -0700112}
113
114/*
Rafael Aquini18468d92012-12-11 16:02:38 -0800115 * balloon_page_insert - insert a page into the balloon's page list and make
Konstantin Khlebnikov9d1ba802014-10-09 15:29:29 -0700116 * the page->private assignment accordingly.
117 * @balloon : pointer to balloon device
Rafael Aquini18468d92012-12-11 16:02:38 -0800118 * @page : page to be assigned as a 'balloon page'
Rafael Aquini18468d92012-12-11 16:02:38 -0800119 *
120 * Caller must ensure the page is locked and the spin_lock protecting balloon
121 * pages list is held before inserting a page into the balloon device.
122 */
Konstantin Khlebnikov9d1ba802014-10-09 15:29:29 -0700123static inline void balloon_page_insert(struct balloon_dev_info *balloon,
124 struct page *page)
Rafael Aquini18468d92012-12-11 16:02:38 -0800125{
Konstantin Khlebnikovd6d86c02014-10-09 15:29:27 -0700126 __SetPageBalloon(page);
127 SetPagePrivate(page);
Konstantin Khlebnikov9d1ba802014-10-09 15:29:29 -0700128 set_page_private(page, (unsigned long)balloon);
129 list_add(&page->lru, &balloon->pages);
Rafael Aquini18468d92012-12-11 16:02:38 -0800130}
131
132/*
133 * balloon_page_delete - delete a page from balloon's page list and clear
Konstantin Khlebnikov9d1ba802014-10-09 15:29:29 -0700134 * the page->private assignement accordingly.
Rafael Aquini18468d92012-12-11 16:02:38 -0800135 * @page : page to be released from balloon's page list
136 *
137 * Caller must ensure the page is locked and the spin_lock protecting balloon
138 * pages list is held before deleting a page from the balloon device.
139 */
140static inline void balloon_page_delete(struct page *page)
141{
Konstantin Khlebnikovd6d86c02014-10-09 15:29:27 -0700142 __ClearPageBalloon(page);
Konstantin Khlebnikov9d1ba802014-10-09 15:29:29 -0700143 set_page_private(page, 0);
Konstantin Khlebnikovd6d86c02014-10-09 15:29:27 -0700144 if (PagePrivate(page)) {
145 ClearPagePrivate(page);
146 list_del(&page->lru);
147 }
Rafael Aquini18468d92012-12-11 16:02:38 -0800148}
149
150/*
151 * balloon_page_device - get the b_dev_info descriptor for the balloon device
152 * that enqueues the given page.
153 */
154static inline struct balloon_dev_info *balloon_page_device(struct page *page)
155{
Konstantin Khlebnikov9d1ba802014-10-09 15:29:29 -0700156 return (struct balloon_dev_info *)page_private(page);
Rafael Aquini18468d92012-12-11 16:02:38 -0800157}
158
159static inline gfp_t balloon_mapping_gfp_mask(void)
160{
161 return GFP_HIGHUSER_MOVABLE;
162}
163
Rafael Aquini18468d92012-12-11 16:02:38 -0800164#else /* !CONFIG_BALLOON_COMPACTION */
165
Konstantin Khlebnikov9d1ba802014-10-09 15:29:29 -0700166static inline void balloon_page_insert(struct balloon_dev_info *balloon,
167 struct page *page)
Rafael Aquini18468d92012-12-11 16:02:38 -0800168{
Konstantin Khlebnikov09316c02014-10-09 15:29:32 -0700169 __SetPageBalloon(page);
Konstantin Khlebnikov9d1ba802014-10-09 15:29:29 -0700170 list_add(&page->lru, &balloon->pages);
Rafael Aquini18468d92012-12-11 16:02:38 -0800171}
172
173static inline void balloon_page_delete(struct page *page)
174{
Konstantin Khlebnikov09316c02014-10-09 15:29:32 -0700175 __ClearPageBalloon(page);
Rafael Aquini18468d92012-12-11 16:02:38 -0800176 list_del(&page->lru);
177}
178
Konstantin Khlebnikovd6d86c02014-10-09 15:29:27 -0700179static inline bool __is_movable_balloon_page(struct page *page)
180{
181 return false;
182}
183
Rafael Aquini18468d92012-12-11 16:02:38 -0800184static inline bool balloon_page_movable(struct page *page)
185{
186 return false;
187}
188
Rafael Aquini117aad12013-09-30 13:45:16 -0700189static inline bool isolated_balloon_page(struct page *page)
190{
191 return false;
192}
193
Rafael Aquini18468d92012-12-11 16:02:38 -0800194static inline bool balloon_page_isolate(struct page *page)
195{
196 return false;
197}
198
199static inline void balloon_page_putback(struct page *page)
200{
201 return;
202}
203
204static inline int balloon_page_migrate(struct page *newpage,
205 struct page *page, enum migrate_mode mode)
206{
207 return 0;
208}
209
210static inline gfp_t balloon_mapping_gfp_mask(void)
211{
212 return GFP_HIGHUSER;
213}
214
Rafael Aquini18468d92012-12-11 16:02:38 -0800215#endif /* CONFIG_BALLOON_COMPACTION */
216#endif /* _LINUX_BALLOON_COMPACTION_H */