tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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 */
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);
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}
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 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}
105EXPORT_SYMBOL_GPL(balloon_page_dequeue);
106
107#ifdef CONFIG_BALLOON_COMPACTION
108
109bool 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
123void 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 */
136int 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
148const struct address_space_operations balloon_aops = {
149 .migratepage = balloon_page_migrate,
150 .isolate_page = balloon_page_isolate,
151 .putback_page = balloon_page_putback,
152};
153EXPORT_SYMBOL_GPL(balloon_aops);
154
155#endif /* CONFIG_BALLOON_COMPACTION */