blob: da91df50ba31abfbe742afd9611682d5740a9afb
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_enqueue - allocates a new page and inserts it into the balloon |
15 | * page list. |
16 | * @b_dev_info: balloon device descriptor where we will insert a new page to |
17 | * |
18 | * Driver must call it to properly allocate a new enlisted balloon page |
19 | * before definitively removing it from the guest system. |
20 | * This function returns the page address for the recently enqueued page or |
21 | * NULL in the case we fail to allocate a new page this turn. |
22 | */ |
23 | struct page *balloon_page_enqueue(struct balloon_dev_info *b_dev_info) |
24 | { |
25 | unsigned long flags; |
26 | struct page *page = alloc_page(balloon_mapping_gfp_mask() | |
27 | __GFP_NOMEMALLOC | __GFP_NORETRY); |
28 | if (!page) |
29 | return NULL; |
30 | |
31 | /* |
32 | * Block others from accessing the 'page' when we get around to |
33 | * establishing additional references. We should be the only one |
34 | * holding a reference to the 'page' at this point. |
35 | */ |
36 | BUG_ON(!trylock_page(page)); |
37 | spin_lock_irqsave(&b_dev_info->pages_lock, flags); |
38 | balloon_page_insert(b_dev_info, page); |
39 | __count_vm_event(BALLOON_INFLATE); |
40 | spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); |
41 | unlock_page(page); |
42 | return page; |
43 | } |
44 | EXPORT_SYMBOL_GPL(balloon_page_enqueue); |
45 | |
46 | /* |
47 | * balloon_page_dequeue - removes a page from balloon's page list and returns |
48 | * the its address to allow the driver release the page. |
49 | * @b_dev_info: balloon device decriptor where we will grab a page from. |
50 | * |
51 | * Driver must call it to properly de-allocate a previous enlisted balloon page |
52 | * before definetively releasing it back to the guest system. |
53 | * This function returns the page address for the recently dequeued page or |
54 | * NULL in the case we find balloon's page list temporarily empty due to |
55 | * compaction isolated pages. |
56 | */ |
57 | struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info) |
58 | { |
59 | struct page *page, *tmp; |
60 | unsigned long flags; |
61 | bool dequeued_page; |
62 | |
63 | dequeued_page = false; |
64 | spin_lock_irqsave(&b_dev_info->pages_lock, flags); |
65 | list_for_each_entry_safe(page, tmp, &b_dev_info->pages, lru) { |
66 | /* |
67 | * Block others from accessing the 'page' while we get around |
68 | * establishing additional references and preparing the 'page' |
69 | * to be released by the balloon driver. |
70 | */ |
71 | if (trylock_page(page)) { |
72 | #ifdef CONFIG_BALLOON_COMPACTION |
73 | if (PageIsolated(page)) { |
74 | /* raced with isolation */ |
75 | unlock_page(page); |
76 | continue; |
77 | } |
78 | #endif |
79 | balloon_page_delete(page); |
80 | __count_vm_event(BALLOON_DEFLATE); |
81 | unlock_page(page); |
82 | dequeued_page = true; |
83 | break; |
84 | } |
85 | } |
86 | spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); |
87 | |
88 | if (!dequeued_page) { |
89 | /* |
90 | * If we are unable to dequeue a balloon page because the page |
91 | * list is empty and there is no isolated pages, then something |
92 | * went out of track and some balloon pages are lost. |
93 | * BUG() here, otherwise the balloon driver may get stuck into |
94 | * an infinite loop while attempting to release all its pages. |
95 | */ |
96 | spin_lock_irqsave(&b_dev_info->pages_lock, flags); |
97 | if (unlikely(list_empty(&b_dev_info->pages) && |
98 | !b_dev_info->isolated_pages)) |
99 | BUG(); |
100 | spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); |
101 | page = NULL; |
102 | } |
103 | return page; |
104 | } |
105 | EXPORT_SYMBOL_GPL(balloon_page_dequeue); |
106 | |
107 | #ifdef CONFIG_BALLOON_COMPACTION |
108 | |
109 | bool balloon_page_isolate(struct page *page, isolate_mode_t mode) |
110 | |
111 | { |
112 | struct balloon_dev_info *b_dev_info = balloon_page_device(page); |
113 | unsigned long flags; |
114 | |
115 | spin_lock_irqsave(&b_dev_info->pages_lock, flags); |
116 | list_del(&page->lru); |
117 | b_dev_info->isolated_pages++; |
118 | spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); |
119 | |
120 | return true; |
121 | } |
122 | |
123 | void balloon_page_putback(struct page *page) |
124 | { |
125 | struct balloon_dev_info *b_dev_info = balloon_page_device(page); |
126 | unsigned long flags; |
127 | |
128 | spin_lock_irqsave(&b_dev_info->pages_lock, flags); |
129 | list_add(&page->lru, &b_dev_info->pages); |
130 | b_dev_info->isolated_pages--; |
131 | spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); |
132 | } |
133 | |
134 | |
135 | /* move_to_new_page() counterpart for a ballooned page */ |
136 | int balloon_page_migrate(struct address_space *mapping, |
137 | struct page *newpage, struct page *page, |
138 | enum migrate_mode mode) |
139 | { |
140 | struct balloon_dev_info *balloon = balloon_page_device(page); |
141 | |
142 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
143 | VM_BUG_ON_PAGE(!PageLocked(newpage), newpage); |
144 | |
145 | return balloon->migratepage(balloon, newpage, page, mode); |
146 | } |
147 | |
148 | const struct address_space_operations balloon_aops = { |
149 | .migratepage = balloon_page_migrate, |
150 | .isolate_page = balloon_page_isolate, |
151 | .putback_page = balloon_page_putback, |
152 | }; |
153 | EXPORT_SYMBOL_GPL(balloon_aops); |
154 | |
155 | #endif /* CONFIG_BALLOON_COMPACTION */ |
156 |