1 | /* |
2 | * mm/balloon_compaction.c |
3 | * |
4 | * Common interface for making balloon pages movable by compaction. |
5 | * |
6 | * Copyright (C) 2012, Red Hat, Inc. Rafael Aquini <aquini@redhat.com> |
7 | */ |
8 | #include <linux/mm.h> |
9 | #include <linux/slab.h> |
10 | #include <linux/export.h> |
11 | #include <linux/balloon_compaction.h> |
12 | |
13 | /* |
14 | * balloon_page_alloc - allocates a new page for insertion into the balloon |
15 | * page list. |
16 | * |
17 | * Driver must call it to properly allocate a new enlisted balloon page. |
18 | * Driver must call balloon_page_enqueue before definitively removing it from |
19 | * the guest system. This function returns the page address for the recently |
20 | * allocated page or NULL in the case we fail to allocate a new page this turn. |
21 | */ |
22 | struct page *balloon_page_alloc(void) |
23 | { |
24 | struct page *page = alloc_page(balloon_mapping_gfp_mask() | |
25 | __GFP_NOMEMALLOC | __GFP_NORETRY); |
26 | return page; |
27 | } |
28 | EXPORT_SYMBOL_GPL(balloon_page_alloc); |
29 | |
30 | /* |
31 | * balloon_page_enqueue - allocates a new page and inserts it into the balloon |
32 | * page list. |
33 | * @b_dev_info: balloon device descriptor where we will insert a new page to |
34 | * @page: new page to enqueue - allocated using balloon_page_alloc. |
35 | * |
36 | * Driver must call it to properly enqueue a new allocated balloon page |
37 | * before definitively removing it from the guest system. |
38 | * This function returns the page address for the recently enqueued page or |
39 | * NULL in the case we fail to allocate a new page this turn. |
40 | */ |
41 | void balloon_page_enqueue(struct balloon_dev_info *b_dev_info, |
42 | struct page *page) |
43 | { |
44 | unsigned long flags; |
45 | |
46 | /* |
47 | * Block others from accessing the 'page' when we get around to |
48 | * establishing additional references. We should be the only one |
49 | * holding a reference to the 'page' at this point. |
50 | */ |
51 | BUG_ON(!trylock_page(page)); |
52 | spin_lock_irqsave(&b_dev_info->pages_lock, flags); |
53 | balloon_page_insert(b_dev_info, page); |
54 | __count_vm_event(BALLOON_INFLATE); |
55 | spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); |
56 | unlock_page(page); |
57 | } |
58 | EXPORT_SYMBOL_GPL(balloon_page_enqueue); |
59 | |
60 | /* |
61 | * balloon_page_dequeue - removes a page from balloon's page list and returns |
62 | * the its address to allow the driver release the page. |
63 | * @b_dev_info: balloon device decriptor where we will grab a page from. |
64 | * |
65 | * Driver must call it to properly de-allocate a previous enlisted balloon page |
66 | * before definetively releasing it back to the guest system. |
67 | * This function returns the page address for the recently dequeued page or |
68 | * NULL in the case we find balloon's page list temporarily empty due to |
69 | * compaction isolated pages. |
70 | */ |
71 | struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info) |
72 | { |
73 | struct page *page, *tmp; |
74 | unsigned long flags; |
75 | bool dequeued_page; |
76 | |
77 | dequeued_page = false; |
78 | spin_lock_irqsave(&b_dev_info->pages_lock, flags); |
79 | list_for_each_entry_safe(page, tmp, &b_dev_info->pages, lru) { |
80 | /* |
81 | * Block others from accessing the 'page' while we get around |
82 | * establishing additional references and preparing the 'page' |
83 | * to be released by the balloon driver. |
84 | */ |
85 | if (trylock_page(page)) { |
86 | #ifdef CONFIG_BALLOON_COMPACTION |
87 | if (PageIsolated(page)) { |
88 | /* raced with isolation */ |
89 | unlock_page(page); |
90 | continue; |
91 | } |
92 | #endif |
93 | balloon_page_delete(page); |
94 | __count_vm_event(BALLOON_DEFLATE); |
95 | unlock_page(page); |
96 | dequeued_page = true; |
97 | break; |
98 | } |
99 | } |
100 | spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); |
101 | |
102 | if (!dequeued_page) { |
103 | /* |
104 | * If we are unable to dequeue a balloon page because the page |
105 | * list is empty and there is no isolated pages, then something |
106 | * went out of track and some balloon pages are lost. |
107 | * BUG() here, otherwise the balloon driver may get stuck into |
108 | * an infinite loop while attempting to release all its pages. |
109 | */ |
110 | spin_lock_irqsave(&b_dev_info->pages_lock, flags); |
111 | if (unlikely(list_empty(&b_dev_info->pages) && |
112 | !b_dev_info->isolated_pages)) |
113 | BUG(); |
114 | spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); |
115 | page = NULL; |
116 | } |
117 | return page; |
118 | } |
119 | EXPORT_SYMBOL_GPL(balloon_page_dequeue); |
120 | |
121 | #ifdef CONFIG_BALLOON_COMPACTION |
122 | |
123 | bool balloon_page_isolate(struct page *page, isolate_mode_t mode) |
124 | |
125 | { |
126 | struct balloon_dev_info *b_dev_info = balloon_page_device(page); |
127 | unsigned long flags; |
128 | |
129 | spin_lock_irqsave(&b_dev_info->pages_lock, flags); |
130 | list_del(&page->lru); |
131 | b_dev_info->isolated_pages++; |
132 | spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); |
133 | |
134 | return true; |
135 | } |
136 | |
137 | void balloon_page_putback(struct page *page) |
138 | { |
139 | struct balloon_dev_info *b_dev_info = balloon_page_device(page); |
140 | unsigned long flags; |
141 | |
142 | spin_lock_irqsave(&b_dev_info->pages_lock, flags); |
143 | list_add(&page->lru, &b_dev_info->pages); |
144 | b_dev_info->isolated_pages--; |
145 | spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); |
146 | } |
147 | |
148 | |
149 | /* move_to_new_page() counterpart for a ballooned page */ |
150 | int balloon_page_migrate(struct address_space *mapping, |
151 | struct page *newpage, struct page *page, |
152 | enum migrate_mode mode) |
153 | { |
154 | struct balloon_dev_info *balloon = balloon_page_device(page); |
155 | |
156 | /* |
157 | * We can not easily support the no copy case here so ignore it as it |
158 | * is unlikely to be use with ballon pages. See include/linux/hmm.h for |
159 | * user of the MIGRATE_SYNC_NO_COPY mode. |
160 | */ |
161 | if (mode == MIGRATE_SYNC_NO_COPY) |
162 | return -EINVAL; |
163 | |
164 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
165 | VM_BUG_ON_PAGE(!PageLocked(newpage), newpage); |
166 | |
167 | return balloon->migratepage(balloon, newpage, page, mode); |
168 | } |
169 | |
170 | const struct address_space_operations balloon_aops = { |
171 | .migratepage = balloon_page_migrate, |
172 | .isolate_page = balloon_page_isolate, |
173 | .putback_page = balloon_page_putback, |
174 | }; |
175 | EXPORT_SYMBOL_GPL(balloon_aops); |
176 | |
177 | #endif /* CONFIG_BALLOON_COMPACTION */ |
178 | |