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457c8996 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
18468d93 RA |
2 | /* |
3 | * mm/balloon_compaction.c | |
4 | * | |
5 | * Common interface for making balloon pages movable by compaction. | |
6 | * | |
7 | * Copyright (C) 2012, Red Hat, Inc. Rafael Aquini <aquini@redhat.com> | |
8 | */ | |
9 | #include <linux/mm.h> | |
10 | #include <linux/slab.h> | |
11 | #include <linux/export.h> | |
12 | #include <linux/balloon_compaction.h> | |
13 | ||
418a3ab1 NA |
14 | static void balloon_page_enqueue_one(struct balloon_dev_info *b_dev_info, |
15 | struct page *page) | |
16 | { | |
17 | /* | |
18 | * Block others from accessing the 'page' when we get around to | |
19 | * establishing additional references. We should be the only one | |
20 | * holding a reference to the 'page' at this point. If we are not, then | |
21 | * memory corruption is possible and we should stop execution. | |
22 | */ | |
23 | BUG_ON(!trylock_page(page)); | |
24 | list_del(&page->lru); | |
25 | balloon_page_insert(b_dev_info, page); | |
26 | unlock_page(page); | |
27 | __count_vm_event(BALLOON_INFLATE); | |
28 | } | |
29 | ||
30 | /** | |
31 | * balloon_page_list_enqueue() - inserts a list of pages into the balloon page | |
32 | * list. | |
33 | * @b_dev_info: balloon device descriptor where we will insert a new page to | |
34 | * @pages: pages to enqueue - allocated using balloon_page_alloc. | |
35 | * | |
36 | * Driver must call it to properly enqueue a balloon pages before definitively | |
37 | * removing it from the guest system. | |
38 | * | |
39 | * Return: number of pages that were enqueued. | |
40 | */ | |
41 | size_t balloon_page_list_enqueue(struct balloon_dev_info *b_dev_info, | |
42 | struct list_head *pages) | |
43 | { | |
44 | struct page *page, *tmp; | |
45 | unsigned long flags; | |
46 | size_t n_pages = 0; | |
47 | ||
48 | spin_lock_irqsave(&b_dev_info->pages_lock, flags); | |
49 | list_for_each_entry_safe(page, tmp, pages, lru) { | |
50 | balloon_page_enqueue_one(b_dev_info, page); | |
51 | n_pages++; | |
52 | } | |
53 | spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); | |
54 | return n_pages; | |
55 | } | |
56 | EXPORT_SYMBOL_GPL(balloon_page_list_enqueue); | |
57 | ||
58 | /** | |
59 | * balloon_page_list_dequeue() - removes pages from balloon's page list and | |
60 | * returns a list of the pages. | |
61 | * @b_dev_info: balloon device decriptor where we will grab a page from. | |
62 | * @pages: pointer to the list of pages that would be returned to the caller. | |
63 | * @n_req_pages: number of requested pages. | |
64 | * | |
65 | * Driver must call this function to properly de-allocate a previous enlisted | |
66 | * balloon pages before definetively releasing it back to the guest system. | |
67 | * This function tries to remove @n_req_pages from the ballooned pages and | |
68 | * return them to the caller in the @pages list. | |
69 | * | |
70 | * Note that this function may fail to dequeue some pages temporarily empty due | |
71 | * to compaction isolated pages. | |
72 | * | |
73 | * Return: number of pages that were added to the @pages list. | |
74 | */ | |
75 | size_t balloon_page_list_dequeue(struct balloon_dev_info *b_dev_info, | |
76 | struct list_head *pages, size_t n_req_pages) | |
77 | { | |
78 | struct page *page, *tmp; | |
79 | unsigned long flags; | |
80 | size_t n_pages = 0; | |
81 | ||
82 | spin_lock_irqsave(&b_dev_info->pages_lock, flags); | |
83 | list_for_each_entry_safe(page, tmp, &b_dev_info->pages, lru) { | |
84 | if (n_pages == n_req_pages) | |
85 | break; | |
86 | ||
87 | /* | |
88 | * Block others from accessing the 'page' while we get around to | |
89 | * establishing additional references and preparing the 'page' | |
90 | * to be released by the balloon driver. | |
91 | */ | |
92 | if (!trylock_page(page)) | |
93 | continue; | |
94 | ||
95 | if (IS_ENABLED(CONFIG_BALLOON_COMPACTION) && | |
96 | PageIsolated(page)) { | |
97 | /* raced with isolation */ | |
98 | unlock_page(page); | |
99 | continue; | |
100 | } | |
101 | balloon_page_delete(page); | |
102 | __count_vm_event(BALLOON_DEFLATE); | |
103 | list_add(&page->lru, pages); | |
104 | unlock_page(page); | |
105 | n_pages++; | |
106 | } | |
107 | spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); | |
108 | ||
109 | return n_pages; | |
110 | } | |
111 | EXPORT_SYMBOL_GPL(balloon_page_list_dequeue); | |
112 | ||
c7cdff0e MT |
113 | /* |
114 | * balloon_page_alloc - allocates a new page for insertion into the balloon | |
115 | * page list. | |
116 | * | |
117 | * Driver must call it to properly allocate a new enlisted balloon page. | |
118 | * Driver must call balloon_page_enqueue before definitively removing it from | |
119 | * the guest system. This function returns the page address for the recently | |
120 | * allocated page or NULL in the case we fail to allocate a new page this turn. | |
121 | */ | |
122 | struct page *balloon_page_alloc(void) | |
123 | { | |
124 | struct page *page = alloc_page(balloon_mapping_gfp_mask() | | |
125 | __GFP_NOMEMALLOC | __GFP_NORETRY); | |
126 | return page; | |
127 | } | |
128 | EXPORT_SYMBOL_GPL(balloon_page_alloc); | |
129 | ||
18468d93 RA |
130 | /* |
131 | * balloon_page_enqueue - allocates a new page and inserts it into the balloon | |
132 | * page list. | |
bdb428c8 | 133 | * @b_dev_info: balloon device descriptor where we will insert a new page to |
c7cdff0e | 134 | * @page: new page to enqueue - allocated using balloon_page_alloc. |
18468d93 | 135 | * |
c7cdff0e | 136 | * Driver must call it to properly enqueue a new allocated balloon page |
bdb428c8 | 137 | * before definitively removing it from the guest system. |
18468d93 RA |
138 | * This function returns the page address for the recently enqueued page or |
139 | * NULL in the case we fail to allocate a new page this turn. | |
140 | */ | |
c7cdff0e MT |
141 | void balloon_page_enqueue(struct balloon_dev_info *b_dev_info, |
142 | struct page *page) | |
18468d93 RA |
143 | { |
144 | unsigned long flags; | |
18468d93 | 145 | |
18468d93 | 146 | spin_lock_irqsave(&b_dev_info->pages_lock, flags); |
418a3ab1 | 147 | balloon_page_enqueue_one(b_dev_info, page); |
18468d93 | 148 | spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); |
18468d93 RA |
149 | } |
150 | EXPORT_SYMBOL_GPL(balloon_page_enqueue); | |
151 | ||
152 | /* | |
153 | * balloon_page_dequeue - removes a page from balloon's page list and returns | |
154 | * the its address to allow the driver release the page. | |
155 | * @b_dev_info: balloon device decriptor where we will grab a page from. | |
156 | * | |
157 | * Driver must call it to properly de-allocate a previous enlisted balloon page | |
158 | * before definetively releasing it back to the guest system. | |
159 | * This function returns the page address for the recently dequeued page or | |
160 | * NULL in the case we find balloon's page list temporarily empty due to | |
161 | * compaction isolated pages. | |
162 | */ | |
163 | struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info) | |
164 | { | |
18468d93 | 165 | unsigned long flags; |
418a3ab1 NA |
166 | LIST_HEAD(pages); |
167 | int n_pages; | |
18468d93 | 168 | |
418a3ab1 | 169 | n_pages = balloon_page_list_dequeue(b_dev_info, &pages, 1); |
18468d93 | 170 | |
418a3ab1 | 171 | if (n_pages != 1) { |
18468d93 RA |
172 | /* |
173 | * If we are unable to dequeue a balloon page because the page | |
174 | * list is empty and there is no isolated pages, then something | |
175 | * went out of track and some balloon pages are lost. | |
176 | * BUG() here, otherwise the balloon driver may get stuck into | |
177 | * an infinite loop while attempting to release all its pages. | |
178 | */ | |
179 | spin_lock_irqsave(&b_dev_info->pages_lock, flags); | |
180 | if (unlikely(list_empty(&b_dev_info->pages) && | |
181 | !b_dev_info->isolated_pages)) | |
182 | BUG(); | |
183 | spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); | |
418a3ab1 | 184 | return NULL; |
18468d93 | 185 | } |
418a3ab1 | 186 | return list_first_entry(&pages, struct page, lru); |
18468d93 RA |
187 | } |
188 | EXPORT_SYMBOL_GPL(balloon_page_dequeue); | |
189 | ||
190 | #ifdef CONFIG_BALLOON_COMPACTION | |
18468d93 | 191 | |
b1123ea6 MK |
192 | bool balloon_page_isolate(struct page *page, isolate_mode_t mode) |
193 | ||
18468d93 | 194 | { |
9d1ba805 | 195 | struct balloon_dev_info *b_dev_info = balloon_page_device(page); |
18468d93 | 196 | unsigned long flags; |
d6d86c0a | 197 | |
18468d93 RA |
198 | spin_lock_irqsave(&b_dev_info->pages_lock, flags); |
199 | list_del(&page->lru); | |
200 | b_dev_info->isolated_pages++; | |
201 | spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); | |
b1123ea6 MK |
202 | |
203 | return true; | |
18468d93 RA |
204 | } |
205 | ||
b1123ea6 | 206 | void balloon_page_putback(struct page *page) |
18468d93 | 207 | { |
9d1ba805 | 208 | struct balloon_dev_info *b_dev_info = balloon_page_device(page); |
18468d93 | 209 | unsigned long flags; |
d6d86c0a | 210 | |
18468d93 RA |
211 | spin_lock_irqsave(&b_dev_info->pages_lock, flags); |
212 | list_add(&page->lru, &b_dev_info->pages); | |
213 | b_dev_info->isolated_pages--; | |
214 | spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); | |
215 | } | |
216 | ||
18468d93 RA |
217 | |
218 | /* move_to_new_page() counterpart for a ballooned page */ | |
b1123ea6 MK |
219 | int balloon_page_migrate(struct address_space *mapping, |
220 | struct page *newpage, struct page *page, | |
221 | enum migrate_mode mode) | |
18468d93 | 222 | { |
9d1ba805 | 223 | struct balloon_dev_info *balloon = balloon_page_device(page); |
18468d93 | 224 | |
2916ecc0 JG |
225 | /* |
226 | * We can not easily support the no copy case here so ignore it as it | |
227 | * is unlikely to be use with ballon pages. See include/linux/hmm.h for | |
228 | * user of the MIGRATE_SYNC_NO_COPY mode. | |
229 | */ | |
230 | if (mode == MIGRATE_SYNC_NO_COPY) | |
231 | return -EINVAL; | |
232 | ||
7db7671f HD |
233 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
234 | VM_BUG_ON_PAGE(!PageLocked(newpage), newpage); | |
18468d93 | 235 | |
b1123ea6 MK |
236 | return balloon->migratepage(balloon, newpage, page, mode); |
237 | } | |
18468d93 | 238 | |
b1123ea6 MK |
239 | const struct address_space_operations balloon_aops = { |
240 | .migratepage = balloon_page_migrate, | |
241 | .isolate_page = balloon_page_isolate, | |
242 | .putback_page = balloon_page_putback, | |
243 | }; | |
244 | EXPORT_SYMBOL_GPL(balloon_aops); | |
18468d93 | 245 | |
18468d93 | 246 | #endif /* CONFIG_BALLOON_COMPACTION */ |