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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 | * | |
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35 | * iv. isolation or dequeueing procedure must clear PagePrivate flag under |
36 | * page lock together with removing page from balloon device page list. | |
37 | * | |
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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> |
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53 | |
54 | /* | |
55 | * Balloon device information descriptor. | |
56 | * This struct is used to allow the common balloon compaction interface | |
57 | * procedures to find the proper balloon device holding memory pages they'll | |
58 | * have to cope for page compaction / migration, as well as it serves the | |
59 | * balloon driver as a page book-keeper for its registered balloon devices. | |
60 | */ | |
61 | struct balloon_dev_info { | |
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62 | unsigned long isolated_pages; /* # of isolated pages for migration */ |
63 | spinlock_t pages_lock; /* Protection to pages list */ | |
64 | struct list_head pages; /* Pages enqueued & handled to Host */ | |
9d1ba805 KK |
65 | int (*migratepage)(struct balloon_dev_info *, struct page *newpage, |
66 | struct page *page, enum migrate_mode mode); | |
b1123ea6 | 67 | struct inode *inode; |
18468d93 RA |
68 | }; |
69 | ||
70 | extern struct page *balloon_page_enqueue(struct balloon_dev_info *b_dev_info); | |
71 | extern struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info); | |
18468d93 | 72 | |
9d1ba805 | 73 | static inline void balloon_devinfo_init(struct balloon_dev_info *balloon) |
18468d93 | 74 | { |
9d1ba805 KK |
75 | balloon->isolated_pages = 0; |
76 | spin_lock_init(&balloon->pages_lock); | |
77 | INIT_LIST_HEAD(&balloon->pages); | |
78 | balloon->migratepage = NULL; | |
b1123ea6 | 79 | balloon->inode = NULL; |
18468d93 RA |
80 | } |
81 | ||
18468d93 | 82 | #ifdef CONFIG_BALLOON_COMPACTION |
b1123ea6 MK |
83 | extern const struct address_space_operations balloon_aops; |
84 | extern bool balloon_page_isolate(struct page *page, | |
85 | isolate_mode_t mode); | |
18468d93 | 86 | extern void balloon_page_putback(struct page *page); |
b1123ea6 MK |
87 | extern int balloon_page_migrate(struct address_space *mapping, |
88 | struct page *newpage, | |
18468d93 | 89 | struct page *page, enum migrate_mode mode); |
18468d93 | 90 | |
18468d93 RA |
91 | /* |
92 | * balloon_page_insert - insert a page into the balloon's page list and make | |
9d1ba805 KK |
93 | * the page->private assignment accordingly. |
94 | * @balloon : pointer to balloon device | |
18468d93 | 95 | * @page : page to be assigned as a 'balloon page' |
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96 | * |
97 | * Caller must ensure the page is locked and the spin_lock protecting balloon | |
98 | * pages list is held before inserting a page into the balloon device. | |
99 | */ | |
9d1ba805 KK |
100 | static inline void balloon_page_insert(struct balloon_dev_info *balloon, |
101 | struct page *page) | |
18468d93 | 102 | { |
d6d86c0a | 103 | __SetPageBalloon(page); |
b1123ea6 | 104 | __SetPageMovable(page, balloon->inode->i_mapping); |
9d1ba805 KK |
105 | set_page_private(page, (unsigned long)balloon); |
106 | list_add(&page->lru, &balloon->pages); | |
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107 | } |
108 | ||
109 | /* | |
110 | * balloon_page_delete - delete a page from balloon's page list and clear | |
9d1ba805 | 111 | * the page->private assignement accordingly. |
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112 | * @page : page to be released from balloon's page list |
113 | * | |
114 | * Caller must ensure the page is locked and the spin_lock protecting balloon | |
115 | * pages list is held before deleting a page from the balloon device. | |
116 | */ | |
117 | static inline void balloon_page_delete(struct page *page) | |
118 | { | |
d6d86c0a | 119 | __ClearPageBalloon(page); |
b1123ea6 | 120 | __ClearPageMovable(page); |
9d1ba805 | 121 | set_page_private(page, 0); |
b1123ea6 MK |
122 | /* |
123 | * No touch page.lru field once @page has been isolated | |
124 | * because VM is using the field. | |
125 | */ | |
126 | if (!PageIsolated(page)) | |
d6d86c0a | 127 | list_del(&page->lru); |
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128 | } |
129 | ||
130 | /* | |
131 | * balloon_page_device - get the b_dev_info descriptor for the balloon device | |
132 | * that enqueues the given page. | |
133 | */ | |
134 | static inline struct balloon_dev_info *balloon_page_device(struct page *page) | |
135 | { | |
9d1ba805 | 136 | return (struct balloon_dev_info *)page_private(page); |
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137 | } |
138 | ||
139 | static inline gfp_t balloon_mapping_gfp_mask(void) | |
140 | { | |
141 | return GFP_HIGHUSER_MOVABLE; | |
142 | } | |
143 | ||
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144 | #else /* !CONFIG_BALLOON_COMPACTION */ |
145 | ||
9d1ba805 KK |
146 | static inline void balloon_page_insert(struct balloon_dev_info *balloon, |
147 | struct page *page) | |
18468d93 | 148 | { |
09316c09 | 149 | __SetPageBalloon(page); |
9d1ba805 | 150 | list_add(&page->lru, &balloon->pages); |
18468d93 RA |
151 | } |
152 | ||
153 | static inline void balloon_page_delete(struct page *page) | |
154 | { | |
09316c09 | 155 | __ClearPageBalloon(page); |
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156 | list_del(&page->lru); |
157 | } | |
158 | ||
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159 | static inline bool __is_movable_balloon_page(struct page *page) |
160 | { | |
161 | return false; | |
162 | } | |
163 | ||
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164 | static inline bool balloon_page_movable(struct page *page) |
165 | { | |
166 | return false; | |
167 | } | |
168 | ||
117aad1e RA |
169 | static inline bool isolated_balloon_page(struct page *page) |
170 | { | |
171 | return false; | |
172 | } | |
173 | ||
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174 | static inline bool balloon_page_isolate(struct page *page) |
175 | { | |
176 | return false; | |
177 | } | |
178 | ||
179 | static inline void balloon_page_putback(struct page *page) | |
180 | { | |
181 | return; | |
182 | } | |
183 | ||
184 | static inline int balloon_page_migrate(struct page *newpage, | |
185 | struct page *page, enum migrate_mode mode) | |
186 | { | |
187 | return 0; | |
188 | } | |
189 | ||
190 | static inline gfp_t balloon_mapping_gfp_mask(void) | |
191 | { | |
192 | return GFP_HIGHUSER; | |
193 | } | |
194 | ||
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195 | #endif /* CONFIG_BALLOON_COMPACTION */ |
196 | #endif /* _LINUX_BALLOON_COMPACTION_H */ |