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Rafael Aquini18468d92012-12-11 16:02:38 -08001/*
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/*
Rafael Aquini18468d92012-12-11 16:02:38 -080014 * balloon_page_enqueue - allocates a new page and inserts it into the balloon
15 * page list.
16 * @b_dev_info: balloon device decriptor where we will insert a new page to
17 *
18 * Driver must call it to properly allocate a new enlisted balloon page
19 * before definetively 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 */
23struct 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);
Konstantin Khlebnikov9d1ba802014-10-09 15:29:29 -070038 balloon_page_insert(b_dev_info, page);
Konstantin Khlebnikov09316c02014-10-09 15:29:32 -070039 __count_vm_event(BALLOON_INFLATE);
Rafael Aquini18468d92012-12-11 16:02:38 -080040 spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
41 unlock_page(page);
42 return page;
43}
44EXPORT_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 */
57struct 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 list_for_each_entry_safe(page, tmp, &b_dev_info->pages, lru) {
65 /*
66 * Block others from accessing the 'page' while we get around
67 * establishing additional references and preparing the 'page'
68 * to be released by the balloon driver.
69 */
70 if (trylock_page(page)) {
Konstantin Khlebnikov4d88e6f2014-10-29 14:51:02 -070071#ifdef CONFIG_BALLOON_COMPACTION
Konstantin Khlebnikovd6d86c02014-10-09 15:29:27 -070072 if (!PagePrivate(page)) {
73 /* raced with isolation */
74 unlock_page(page);
75 continue;
76 }
Konstantin Khlebnikov4d88e6f2014-10-29 14:51:02 -070077#endif
Rafael Aquini18468d92012-12-11 16:02:38 -080078 spin_lock_irqsave(&b_dev_info->pages_lock, flags);
Rafael Aquini18468d92012-12-11 16:02:38 -080079 balloon_page_delete(page);
Konstantin Khlebnikov09316c02014-10-09 15:29:32 -070080 __count_vm_event(BALLOON_DEFLATE);
Rafael Aquini18468d92012-12-11 16:02:38 -080081 spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
82 unlock_page(page);
83 dequeued_page = true;
84 break;
85 }
86 }
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}
105EXPORT_SYMBOL_GPL(balloon_page_dequeue);
106
107#ifdef CONFIG_BALLOON_COMPACTION
Rafael Aquini18468d92012-12-11 16:02:38 -0800108
109static inline void __isolate_balloon_page(struct page *page)
110{
Konstantin Khlebnikov9d1ba802014-10-09 15:29:29 -0700111 struct balloon_dev_info *b_dev_info = balloon_page_device(page);
Rafael Aquini18468d92012-12-11 16:02:38 -0800112 unsigned long flags;
Konstantin Khlebnikovd6d86c02014-10-09 15:29:27 -0700113
Rafael Aquini18468d92012-12-11 16:02:38 -0800114 spin_lock_irqsave(&b_dev_info->pages_lock, flags);
Konstantin Khlebnikovd6d86c02014-10-09 15:29:27 -0700115 ClearPagePrivate(page);
Rafael Aquini18468d92012-12-11 16:02:38 -0800116 list_del(&page->lru);
117 b_dev_info->isolated_pages++;
118 spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
119}
120
121static inline void __putback_balloon_page(struct page *page)
122{
Konstantin Khlebnikov9d1ba802014-10-09 15:29:29 -0700123 struct balloon_dev_info *b_dev_info = balloon_page_device(page);
Rafael Aquini18468d92012-12-11 16:02:38 -0800124 unsigned long flags;
Konstantin Khlebnikovd6d86c02014-10-09 15:29:27 -0700125
Rafael Aquini18468d92012-12-11 16:02:38 -0800126 spin_lock_irqsave(&b_dev_info->pages_lock, flags);
Konstantin Khlebnikovd6d86c02014-10-09 15:29:27 -0700127 SetPagePrivate(page);
Rafael Aquini18468d92012-12-11 16:02:38 -0800128 list_add(&page->lru, &b_dev_info->pages);
129 b_dev_info->isolated_pages--;
130 spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
131}
132
Rafael Aquini18468d92012-12-11 16:02:38 -0800133/* __isolate_lru_page() counterpart for a ballooned page */
134bool balloon_page_isolate(struct page *page)
135{
136 /*
137 * Avoid burning cycles with pages that are yet under __free_pages(),
138 * or just got freed under us.
139 *
140 * In case we 'win' a race for a balloon page being freed under us and
141 * raise its refcount preventing __free_pages() from doing its job
142 * the put_page() at the end of this block will take care of
143 * release this page, thus avoiding a nasty leakage.
144 */
145 if (likely(get_page_unless_zero(page))) {
146 /*
147 * As balloon pages are not isolated from LRU lists, concurrent
148 * compaction threads can race against page migration functions
149 * as well as race against the balloon driver releasing a page.
150 *
151 * In order to avoid having an already isolated balloon page
152 * being (wrongly) re-isolated while it is under migration,
153 * or to avoid attempting to isolate pages being released by
154 * the balloon driver, lets be sure we have the page lock
155 * before proceeding with the balloon page isolation steps.
156 */
157 if (likely(trylock_page(page))) {
158 /*
Konstantin Khlebnikovd6d86c02014-10-09 15:29:27 -0700159 * A ballooned page, by default, has PagePrivate set.
Rafael Aquini18468d92012-12-11 16:02:38 -0800160 * Prevent concurrent compaction threads from isolating
Konstantin Khlebnikovd6d86c02014-10-09 15:29:27 -0700161 * an already isolated balloon page by clearing it.
Rafael Aquini18468d92012-12-11 16:02:38 -0800162 */
Konstantin Khlebnikovd6d86c02014-10-09 15:29:27 -0700163 if (balloon_page_movable(page)) {
Rafael Aquini18468d92012-12-11 16:02:38 -0800164 __isolate_balloon_page(page);
165 unlock_page(page);
166 return true;
167 }
168 unlock_page(page);
169 }
170 put_page(page);
171 }
172 return false;
173}
174
175/* putback_lru_page() counterpart for a ballooned page */
176void balloon_page_putback(struct page *page)
177{
178 /*
179 * 'lock_page()' stabilizes the page and prevents races against
180 * concurrent isolation threads attempting to re-isolate it.
181 */
182 lock_page(page);
183
184 if (__is_movable_balloon_page(page)) {
185 __putback_balloon_page(page);
186 /* drop the extra ref count taken for page isolation */
187 put_page(page);
188 } else {
189 WARN_ON(1);
Dave Hansenf0b791a2014-01-23 15:52:49 -0800190 dump_page(page, "not movable balloon page");
Rafael Aquini18468d92012-12-11 16:02:38 -0800191 }
192 unlock_page(page);
193}
194
195/* move_to_new_page() counterpart for a ballooned page */
196int balloon_page_migrate(struct page *newpage,
197 struct page *page, enum migrate_mode mode)
198{
Konstantin Khlebnikov9d1ba802014-10-09 15:29:29 -0700199 struct balloon_dev_info *balloon = balloon_page_device(page);
Rafael Aquini18468d92012-12-11 16:02:38 -0800200 int rc = -EAGAIN;
201
Hugh Dickins7db76712015-11-05 18:49:49 -0800202 VM_BUG_ON_PAGE(!PageLocked(page), page);
203 VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
Rafael Aquini18468d92012-12-11 16:02:38 -0800204
205 if (WARN_ON(!__is_movable_balloon_page(page))) {
Dave Hansenf0b791a2014-01-23 15:52:49 -0800206 dump_page(page, "not movable balloon page");
Rafael Aquini18468d92012-12-11 16:02:38 -0800207 return rc;
208 }
209
Konstantin Khlebnikov9d1ba802014-10-09 15:29:29 -0700210 if (balloon && balloon->migratepage)
211 rc = balloon->migratepage(balloon, newpage, page, mode);
Rafael Aquini18468d92012-12-11 16:02:38 -0800212
Rafael Aquini18468d92012-12-11 16:02:38 -0800213 return rc;
214}
215#endif /* CONFIG_BALLOON_COMPACTION */