Rafael Aquini | 18468d9 | 2012-12-11 16:02:38 -0800 | [diff] [blame] | 1 | /* |
| 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 Khlebnikov | d6d86c0 | 2014-10-09 15:29:27 -0700 | [diff] [blame^] | 30 | * isolation, re-test the PageBalloon mark and the PagePrivate flag |
Rafael Aquini | 18468d9 | 2012-12-11 16:02:38 -0800 | [diff] [blame] | 31 | * under the proper page lock, to ensure isolating a valid balloon page |
| 32 | * (not yet isolated, nor under release procedure) |
| 33 | * |
Konstantin Khlebnikov | d6d86c0 | 2014-10-09 15:29:27 -0700 | [diff] [blame^] | 34 | * iv. isolation or dequeueing procedure must clear PagePrivate flag under |
| 35 | * page lock together with removing page from balloon device page list. |
| 36 | * |
Rafael Aquini | 18468d9 | 2012-12-11 16:02:38 -0800 | [diff] [blame] | 37 | * 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 | */ |
| 59 | struct balloon_dev_info { |
| 60 | void *balloon_device; /* balloon device descriptor */ |
| 61 | struct address_space *mapping; /* balloon special page->mapping */ |
| 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 */ |
| 65 | }; |
| 66 | |
| 67 | extern struct page *balloon_page_enqueue(struct balloon_dev_info *b_dev_info); |
| 68 | extern struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info); |
| 69 | extern struct balloon_dev_info *balloon_devinfo_alloc( |
| 70 | void *balloon_dev_descriptor); |
| 71 | |
| 72 | static inline void balloon_devinfo_free(struct balloon_dev_info *b_dev_info) |
| 73 | { |
| 74 | kfree(b_dev_info); |
| 75 | } |
| 76 | |
Rafael Aquini | 18468d9 | 2012-12-11 16:02:38 -0800 | [diff] [blame] | 77 | #ifdef CONFIG_BALLOON_COMPACTION |
| 78 | extern bool balloon_page_isolate(struct page *page); |
| 79 | extern void balloon_page_putback(struct page *page); |
| 80 | extern int balloon_page_migrate(struct page *newpage, |
| 81 | struct page *page, enum migrate_mode mode); |
| 82 | extern struct address_space |
| 83 | *balloon_mapping_alloc(struct balloon_dev_info *b_dev_info, |
| 84 | const struct address_space_operations *a_ops); |
| 85 | |
| 86 | static inline void balloon_mapping_free(struct address_space *balloon_mapping) |
| 87 | { |
| 88 | kfree(balloon_mapping); |
| 89 | } |
| 90 | |
| 91 | /* |
Konstantin Khlebnikov | d6d86c0 | 2014-10-09 15:29:27 -0700 | [diff] [blame^] | 92 | * __is_movable_balloon_page - helper to perform @page PageBalloon tests |
Rafael Aquini | 18468d9 | 2012-12-11 16:02:38 -0800 | [diff] [blame] | 93 | */ |
| 94 | static inline bool __is_movable_balloon_page(struct page *page) |
| 95 | { |
Konstantin Khlebnikov | d6d86c0 | 2014-10-09 15:29:27 -0700 | [diff] [blame^] | 96 | return PageBalloon(page); |
Rafael Aquini | 18468d9 | 2012-12-11 16:02:38 -0800 | [diff] [blame] | 97 | } |
| 98 | |
| 99 | /* |
Konstantin Khlebnikov | d6d86c0 | 2014-10-09 15:29:27 -0700 | [diff] [blame^] | 100 | * balloon_page_movable - test PageBalloon to identify balloon pages |
| 101 | * and PagePrivate to check that the page is not |
| 102 | * isolated and can be moved by compaction/migration. |
Rafael Aquini | 18468d9 | 2012-12-11 16:02:38 -0800 | [diff] [blame] | 103 | * |
| 104 | * As we might return false positives in the case of a balloon page being just |
Konstantin Khlebnikov | d6d86c0 | 2014-10-09 15:29:27 -0700 | [diff] [blame^] | 105 | * released under us, this need to be re-tested later, under the page lock. |
Rafael Aquini | 18468d9 | 2012-12-11 16:02:38 -0800 | [diff] [blame] | 106 | */ |
| 107 | static inline bool balloon_page_movable(struct page *page) |
| 108 | { |
Konstantin Khlebnikov | d6d86c0 | 2014-10-09 15:29:27 -0700 | [diff] [blame^] | 109 | return PageBalloon(page) && PagePrivate(page); |
Rafael Aquini | 18468d9 | 2012-12-11 16:02:38 -0800 | [diff] [blame] | 110 | } |
| 111 | |
| 112 | /* |
Rafael Aquini | 117aad1 | 2013-09-30 13:45:16 -0700 | [diff] [blame] | 113 | * isolated_balloon_page - identify an isolated balloon page on private |
| 114 | * compaction/migration page lists. |
Rafael Aquini | 117aad1 | 2013-09-30 13:45:16 -0700 | [diff] [blame] | 115 | */ |
| 116 | static inline bool isolated_balloon_page(struct page *page) |
| 117 | { |
Konstantin Khlebnikov | d6d86c0 | 2014-10-09 15:29:27 -0700 | [diff] [blame^] | 118 | return PageBalloon(page); |
Rafael Aquini | 117aad1 | 2013-09-30 13:45:16 -0700 | [diff] [blame] | 119 | } |
| 120 | |
| 121 | /* |
Rafael Aquini | 18468d9 | 2012-12-11 16:02:38 -0800 | [diff] [blame] | 122 | * balloon_page_insert - insert a page into the balloon's page list and make |
| 123 | * the page->mapping assignment accordingly. |
| 124 | * @page : page to be assigned as a 'balloon page' |
| 125 | * @mapping : allocated special 'balloon_mapping' |
| 126 | * @head : balloon's device page list head |
| 127 | * |
| 128 | * Caller must ensure the page is locked and the spin_lock protecting balloon |
| 129 | * pages list is held before inserting a page into the balloon device. |
| 130 | */ |
| 131 | static inline void balloon_page_insert(struct page *page, |
| 132 | struct address_space *mapping, |
| 133 | struct list_head *head) |
| 134 | { |
Konstantin Khlebnikov | d6d86c0 | 2014-10-09 15:29:27 -0700 | [diff] [blame^] | 135 | __SetPageBalloon(page); |
| 136 | SetPagePrivate(page); |
Rafael Aquini | 18468d9 | 2012-12-11 16:02:38 -0800 | [diff] [blame] | 137 | page->mapping = mapping; |
| 138 | list_add(&page->lru, head); |
| 139 | } |
| 140 | |
| 141 | /* |
| 142 | * balloon_page_delete - delete a page from balloon's page list and clear |
| 143 | * the page->mapping assignement accordingly. |
| 144 | * @page : page to be released from balloon's page list |
| 145 | * |
| 146 | * Caller must ensure the page is locked and the spin_lock protecting balloon |
| 147 | * pages list is held before deleting a page from the balloon device. |
| 148 | */ |
| 149 | static inline void balloon_page_delete(struct page *page) |
| 150 | { |
Konstantin Khlebnikov | d6d86c0 | 2014-10-09 15:29:27 -0700 | [diff] [blame^] | 151 | __ClearPageBalloon(page); |
Rafael Aquini | 18468d9 | 2012-12-11 16:02:38 -0800 | [diff] [blame] | 152 | page->mapping = NULL; |
Konstantin Khlebnikov | d6d86c0 | 2014-10-09 15:29:27 -0700 | [diff] [blame^] | 153 | if (PagePrivate(page)) { |
| 154 | ClearPagePrivate(page); |
| 155 | list_del(&page->lru); |
| 156 | } |
Rafael Aquini | 18468d9 | 2012-12-11 16:02:38 -0800 | [diff] [blame] | 157 | } |
| 158 | |
| 159 | /* |
| 160 | * balloon_page_device - get the b_dev_info descriptor for the balloon device |
| 161 | * that enqueues the given page. |
| 162 | */ |
| 163 | static inline struct balloon_dev_info *balloon_page_device(struct page *page) |
| 164 | { |
| 165 | struct address_space *mapping = page->mapping; |
| 166 | if (likely(mapping)) |
| 167 | return mapping->private_data; |
| 168 | |
| 169 | return NULL; |
| 170 | } |
| 171 | |
| 172 | static inline gfp_t balloon_mapping_gfp_mask(void) |
| 173 | { |
| 174 | return GFP_HIGHUSER_MOVABLE; |
| 175 | } |
| 176 | |
| 177 | static inline bool balloon_compaction_check(void) |
| 178 | { |
| 179 | return true; |
| 180 | } |
| 181 | |
| 182 | #else /* !CONFIG_BALLOON_COMPACTION */ |
| 183 | |
| 184 | static inline void *balloon_mapping_alloc(void *balloon_device, |
| 185 | const struct address_space_operations *a_ops) |
| 186 | { |
| 187 | return ERR_PTR(-EOPNOTSUPP); |
| 188 | } |
| 189 | |
| 190 | static inline void balloon_mapping_free(struct address_space *balloon_mapping) |
| 191 | { |
| 192 | return; |
| 193 | } |
| 194 | |
| 195 | static inline void balloon_page_insert(struct page *page, |
| 196 | struct address_space *mapping, |
| 197 | struct list_head *head) |
| 198 | { |
| 199 | list_add(&page->lru, head); |
| 200 | } |
| 201 | |
| 202 | static inline void balloon_page_delete(struct page *page) |
| 203 | { |
| 204 | list_del(&page->lru); |
| 205 | } |
| 206 | |
Konstantin Khlebnikov | d6d86c0 | 2014-10-09 15:29:27 -0700 | [diff] [blame^] | 207 | static inline bool __is_movable_balloon_page(struct page *page) |
| 208 | { |
| 209 | return false; |
| 210 | } |
| 211 | |
Rafael Aquini | 18468d9 | 2012-12-11 16:02:38 -0800 | [diff] [blame] | 212 | static inline bool balloon_page_movable(struct page *page) |
| 213 | { |
| 214 | return false; |
| 215 | } |
| 216 | |
Rafael Aquini | 117aad1 | 2013-09-30 13:45:16 -0700 | [diff] [blame] | 217 | static inline bool isolated_balloon_page(struct page *page) |
| 218 | { |
| 219 | return false; |
| 220 | } |
| 221 | |
Rafael Aquini | 18468d9 | 2012-12-11 16:02:38 -0800 | [diff] [blame] | 222 | static inline bool balloon_page_isolate(struct page *page) |
| 223 | { |
| 224 | return false; |
| 225 | } |
| 226 | |
| 227 | static inline void balloon_page_putback(struct page *page) |
| 228 | { |
| 229 | return; |
| 230 | } |
| 231 | |
| 232 | static inline int balloon_page_migrate(struct page *newpage, |
| 233 | struct page *page, enum migrate_mode mode) |
| 234 | { |
| 235 | return 0; |
| 236 | } |
| 237 | |
| 238 | static inline gfp_t balloon_mapping_gfp_mask(void) |
| 239 | { |
| 240 | return GFP_HIGHUSER; |
| 241 | } |
| 242 | |
| 243 | static inline bool balloon_compaction_check(void) |
| 244 | { |
| 245 | return false; |
| 246 | } |
| 247 | #endif /* CONFIG_BALLOON_COMPACTION */ |
| 248 | #endif /* _LINUX_BALLOON_COMPACTION_H */ |