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b2441318 | 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
18468d93 RA |
2 | /* |
3 | * include/linux/balloon_compaction.h | |
4 | * | |
5 | * Common interface definitions for making balloon pages movable by compaction. | |
6 | * | |
7 | * Despite being perfectly possible to perform ballooned pages migration, they | |
8 | * make a special corner case to compaction scans because balloon pages are not | |
9 | * enlisted at any LRU list like the other pages we do compact / migrate. | |
10 | * | |
11 | * As the page isolation scanning step a compaction thread does is a lockless | |
12 | * procedure (from a page standpoint), it might bring some racy situations while | |
13 | * performing balloon page compaction. In order to sort out these racy scenarios | |
14 | * and safely perform balloon's page compaction and migration we must, always, | |
15 | * ensure following these three simple rules: | |
16 | * | |
17 | * i. when updating a balloon's page ->mapping element, strictly do it under | |
18 | * the following lock order, independently of the far superior | |
19 | * locking scheme (lru_lock, balloon_lock): | |
20 | * +-page_lock(page); | |
21 | * +--spin_lock_irq(&b_dev_info->pages_lock); | |
22 | * ... page->mapping updates here ... | |
23 | * | |
24 | * ii. before isolating or dequeueing a balloon page from the balloon device | |
25 | * pages list, the page reference counter must be raised by one and the | |
26 | * extra refcount must be dropped when the page is enqueued back into | |
27 | * the balloon device page list, thus a balloon page keeps its reference | |
28 | * counter raised only while it is under our special handling; | |
29 | * | |
30 | * iii. after the lockless scan step have selected a potential balloon page for | |
d6d86c0a | 31 | * isolation, re-test the PageBalloon mark and the PagePrivate flag |
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32 | * under the proper page lock, to ensure isolating a valid balloon page |
33 | * (not yet isolated, nor under release procedure) | |
34 | * | |
d6d86c0a KK |
35 | * iv. isolation or dequeueing procedure must clear PagePrivate flag under |
36 | * page lock together with removing page from balloon device page list. | |
37 | * | |
18468d93 RA |
38 | * The functions provided by this interface are placed to help on coping with |
39 | * the aforementioned balloon page corner case, as well as to ensure the simple | |
40 | * set of exposed rules are satisfied while we are dealing with balloon pages | |
41 | * compaction / migration. | |
42 | * | |
43 | * Copyright (C) 2012, Red Hat, Inc. Rafael Aquini <aquini@redhat.com> | |
44 | */ | |
45 | #ifndef _LINUX_BALLOON_COMPACTION_H | |
46 | #define _LINUX_BALLOON_COMPACTION_H | |
47 | #include <linux/pagemap.h> | |
48 | #include <linux/page-flags.h> | |
dd4123f3 | 49 | #include <linux/migrate.h> |
18468d93 RA |
50 | #include <linux/gfp.h> |
51 | #include <linux/err.h> | |
b1123ea6 | 52 | #include <linux/fs.h> |
c7cdff0e | 53 | #include <linux/list.h> |
18468d93 RA |
54 | |
55 | /* | |
56 | * Balloon device information descriptor. | |
57 | * This struct is used to allow the common balloon compaction interface | |
58 | * procedures to find the proper balloon device holding memory pages they'll | |
59 | * have to cope for page compaction / migration, as well as it serves the | |
60 | * balloon driver as a page book-keeper for its registered balloon devices. | |
61 | */ | |
62 | struct balloon_dev_info { | |
18468d93 RA |
63 | unsigned long isolated_pages; /* # of isolated pages for migration */ |
64 | spinlock_t pages_lock; /* Protection to pages list */ | |
65 | struct list_head pages; /* Pages enqueued & handled to Host */ | |
9d1ba805 KK |
66 | int (*migratepage)(struct balloon_dev_info *, struct page *newpage, |
67 | struct page *page, enum migrate_mode mode); | |
b1123ea6 | 68 | struct inode *inode; |
18468d93 RA |
69 | }; |
70 | ||
c7cdff0e MT |
71 | extern struct page *balloon_page_alloc(void); |
72 | extern void balloon_page_enqueue(struct balloon_dev_info *b_dev_info, | |
73 | struct page *page); | |
18468d93 | 74 | extern struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info); |
18468d93 | 75 | |
9d1ba805 | 76 | static inline void balloon_devinfo_init(struct balloon_dev_info *balloon) |
18468d93 | 77 | { |
9d1ba805 KK |
78 | balloon->isolated_pages = 0; |
79 | spin_lock_init(&balloon->pages_lock); | |
80 | INIT_LIST_HEAD(&balloon->pages); | |
81 | balloon->migratepage = NULL; | |
b1123ea6 | 82 | balloon->inode = NULL; |
18468d93 RA |
83 | } |
84 | ||
18468d93 | 85 | #ifdef CONFIG_BALLOON_COMPACTION |
b1123ea6 MK |
86 | extern const struct address_space_operations balloon_aops; |
87 | extern bool balloon_page_isolate(struct page *page, | |
88 | isolate_mode_t mode); | |
18468d93 | 89 | extern void balloon_page_putback(struct page *page); |
b1123ea6 MK |
90 | extern int balloon_page_migrate(struct address_space *mapping, |
91 | struct page *newpage, | |
18468d93 | 92 | struct page *page, enum migrate_mode mode); |
18468d93 | 93 | |
18468d93 RA |
94 | /* |
95 | * balloon_page_insert - insert a page into the balloon's page list and make | |
9d1ba805 KK |
96 | * the page->private assignment accordingly. |
97 | * @balloon : pointer to balloon device | |
18468d93 | 98 | * @page : page to be assigned as a 'balloon page' |
18468d93 RA |
99 | * |
100 | * Caller must ensure the page is locked and the spin_lock protecting balloon | |
101 | * pages list is held before inserting a page into the balloon device. | |
102 | */ | |
9d1ba805 KK |
103 | static inline void balloon_page_insert(struct balloon_dev_info *balloon, |
104 | struct page *page) | |
18468d93 | 105 | { |
d6d86c0a | 106 | __SetPageBalloon(page); |
b1123ea6 | 107 | __SetPageMovable(page, balloon->inode->i_mapping); |
9d1ba805 KK |
108 | set_page_private(page, (unsigned long)balloon); |
109 | list_add(&page->lru, &balloon->pages); | |
18468d93 RA |
110 | } |
111 | ||
112 | /* | |
113 | * balloon_page_delete - delete a page from balloon's page list and clear | |
9d1ba805 | 114 | * the page->private assignement accordingly. |
18468d93 RA |
115 | * @page : page to be released from balloon's page list |
116 | * | |
117 | * Caller must ensure the page is locked and the spin_lock protecting balloon | |
118 | * pages list is held before deleting a page from the balloon device. | |
119 | */ | |
120 | static inline void balloon_page_delete(struct page *page) | |
121 | { | |
d6d86c0a | 122 | __ClearPageBalloon(page); |
b1123ea6 | 123 | __ClearPageMovable(page); |
9d1ba805 | 124 | set_page_private(page, 0); |
b1123ea6 MK |
125 | /* |
126 | * No touch page.lru field once @page has been isolated | |
127 | * because VM is using the field. | |
128 | */ | |
129 | if (!PageIsolated(page)) | |
d6d86c0a | 130 | list_del(&page->lru); |
18468d93 RA |
131 | } |
132 | ||
133 | /* | |
134 | * balloon_page_device - get the b_dev_info descriptor for the balloon device | |
135 | * that enqueues the given page. | |
136 | */ | |
137 | static inline struct balloon_dev_info *balloon_page_device(struct page *page) | |
138 | { | |
9d1ba805 | 139 | return (struct balloon_dev_info *)page_private(page); |
18468d93 RA |
140 | } |
141 | ||
142 | static inline gfp_t balloon_mapping_gfp_mask(void) | |
143 | { | |
144 | return GFP_HIGHUSER_MOVABLE; | |
145 | } | |
146 | ||
18468d93 RA |
147 | #else /* !CONFIG_BALLOON_COMPACTION */ |
148 | ||
9d1ba805 KK |
149 | static inline void balloon_page_insert(struct balloon_dev_info *balloon, |
150 | struct page *page) | |
18468d93 | 151 | { |
09316c09 | 152 | __SetPageBalloon(page); |
9d1ba805 | 153 | list_add(&page->lru, &balloon->pages); |
18468d93 RA |
154 | } |
155 | ||
156 | static inline void balloon_page_delete(struct page *page) | |
157 | { | |
09316c09 | 158 | __ClearPageBalloon(page); |
18468d93 RA |
159 | list_del(&page->lru); |
160 | } | |
161 | ||
d6d86c0a KK |
162 | static inline bool __is_movable_balloon_page(struct page *page) |
163 | { | |
164 | return false; | |
165 | } | |
166 | ||
18468d93 RA |
167 | static inline bool balloon_page_movable(struct page *page) |
168 | { | |
169 | return false; | |
170 | } | |
171 | ||
117aad1e RA |
172 | static inline bool isolated_balloon_page(struct page *page) |
173 | { | |
174 | return false; | |
175 | } | |
176 | ||
18468d93 RA |
177 | static inline bool balloon_page_isolate(struct page *page) |
178 | { | |
179 | return false; | |
180 | } | |
181 | ||
182 | static inline void balloon_page_putback(struct page *page) | |
183 | { | |
184 | return; | |
185 | } | |
186 | ||
187 | static inline int balloon_page_migrate(struct page *newpage, | |
188 | struct page *page, enum migrate_mode mode) | |
189 | { | |
190 | return 0; | |
191 | } | |
192 | ||
193 | static inline gfp_t balloon_mapping_gfp_mask(void) | |
194 | { | |
195 | return GFP_HIGHUSER; | |
196 | } | |
197 | ||
18468d93 | 198 | #endif /* CONFIG_BALLOON_COMPACTION */ |
c7cdff0e MT |
199 | |
200 | /* | |
201 | * balloon_page_push - insert a page into a page list. | |
202 | * @head : pointer to list | |
203 | * @page : page to be added | |
204 | * | |
205 | * Caller must ensure the page is private and protect the list. | |
206 | */ | |
207 | static inline void balloon_page_push(struct list_head *pages, struct page *page) | |
208 | { | |
209 | list_add(&page->lru, pages); | |
210 | } | |
211 | ||
212 | /* | |
213 | * balloon_page_pop - remove a page from a page list. | |
214 | * @head : pointer to list | |
215 | * @page : page to be added | |
216 | * | |
217 | * Caller must ensure the page is private and protect the list. | |
218 | */ | |
219 | static inline struct page *balloon_page_pop(struct list_head *pages) | |
220 | { | |
221 | struct page *page = list_first_entry_or_null(pages, struct page, lru); | |
222 | ||
223 | if (!page) | |
224 | return NULL; | |
225 | ||
226 | list_del(&page->lru); | |
227 | return page; | |
228 | } | |
18468d93 | 229 | #endif /* _LINUX_BALLOON_COMPACTION_H */ |