]>
git.proxmox.com Git - mirror_ubuntu-jammy-kernel.git/blob - mm/balloon_compaction.c
2 * mm/balloon_compaction.c
4 * Common interface for making balloon pages movable by compaction.
6 * Copyright (C) 2012, Red Hat, Inc. Rafael Aquini <aquini@redhat.com>
9 #include <linux/slab.h>
10 #include <linux/export.h>
11 #include <linux/balloon_compaction.h>
14 * balloon_devinfo_alloc - allocates a balloon device information descriptor.
15 * @balloon_dev_descriptor: pointer to reference the balloon device which
16 * this struct balloon_dev_info will be servicing.
18 * Driver must call it to properly allocate and initialize an instance of
19 * struct balloon_dev_info which will be used to reference a balloon device
20 * as well as to keep track of the balloon device page list.
22 struct balloon_dev_info
*balloon_devinfo_alloc(void *balloon_dev_descriptor
)
24 struct balloon_dev_info
*b_dev_info
;
25 b_dev_info
= kmalloc(sizeof(*b_dev_info
), GFP_KERNEL
);
27 return ERR_PTR(-ENOMEM
);
29 b_dev_info
->balloon_device
= balloon_dev_descriptor
;
30 b_dev_info
->mapping
= NULL
;
31 b_dev_info
->isolated_pages
= 0;
32 spin_lock_init(&b_dev_info
->pages_lock
);
33 INIT_LIST_HEAD(&b_dev_info
->pages
);
37 EXPORT_SYMBOL_GPL(balloon_devinfo_alloc
);
40 * balloon_page_enqueue - allocates a new page and inserts it into the balloon
42 * @b_dev_info: balloon device decriptor where we will insert a new page to
44 * Driver must call it to properly allocate a new enlisted balloon page
45 * before definetively removing it from the guest system.
46 * This function returns the page address for the recently enqueued page or
47 * NULL in the case we fail to allocate a new page this turn.
49 struct page
*balloon_page_enqueue(struct balloon_dev_info
*b_dev_info
)
52 struct page
*page
= alloc_page(balloon_mapping_gfp_mask() |
53 __GFP_NOMEMALLOC
| __GFP_NORETRY
);
58 * Block others from accessing the 'page' when we get around to
59 * establishing additional references. We should be the only one
60 * holding a reference to the 'page' at this point.
62 BUG_ON(!trylock_page(page
));
63 spin_lock_irqsave(&b_dev_info
->pages_lock
, flags
);
64 balloon_page_insert(page
, b_dev_info
->mapping
, &b_dev_info
->pages
);
65 spin_unlock_irqrestore(&b_dev_info
->pages_lock
, flags
);
69 EXPORT_SYMBOL_GPL(balloon_page_enqueue
);
72 * balloon_page_dequeue - removes a page from balloon's page list and returns
73 * the its address to allow the driver release the page.
74 * @b_dev_info: balloon device decriptor where we will grab a page from.
76 * Driver must call it to properly de-allocate a previous enlisted balloon page
77 * before definetively releasing it back to the guest system.
78 * This function returns the page address for the recently dequeued page or
79 * NULL in the case we find balloon's page list temporarily empty due to
80 * compaction isolated pages.
82 struct page
*balloon_page_dequeue(struct balloon_dev_info
*b_dev_info
)
84 struct page
*page
, *tmp
;
88 dequeued_page
= false;
89 list_for_each_entry_safe(page
, tmp
, &b_dev_info
->pages
, lru
) {
91 * Block others from accessing the 'page' while we get around
92 * establishing additional references and preparing the 'page'
93 * to be released by the balloon driver.
95 if (trylock_page(page
)) {
96 spin_lock_irqsave(&b_dev_info
->pages_lock
, flags
);
98 * Raise the page refcount here to prevent any wrong
99 * attempt to isolate this page, in case of coliding
100 * with balloon_page_isolate() just after we release
103 * balloon_page_free() will take care of dropping
104 * this extra refcount later.
107 balloon_page_delete(page
);
108 spin_unlock_irqrestore(&b_dev_info
->pages_lock
, flags
);
110 dequeued_page
= true;
115 if (!dequeued_page
) {
117 * If we are unable to dequeue a balloon page because the page
118 * list is empty and there is no isolated pages, then something
119 * went out of track and some balloon pages are lost.
120 * BUG() here, otherwise the balloon driver may get stuck into
121 * an infinite loop while attempting to release all its pages.
123 spin_lock_irqsave(&b_dev_info
->pages_lock
, flags
);
124 if (unlikely(list_empty(&b_dev_info
->pages
) &&
125 !b_dev_info
->isolated_pages
))
127 spin_unlock_irqrestore(&b_dev_info
->pages_lock
, flags
);
132 EXPORT_SYMBOL_GPL(balloon_page_dequeue
);
134 #ifdef CONFIG_BALLOON_COMPACTION
136 * balloon_mapping_alloc - allocates a special ->mapping for ballooned pages.
137 * @b_dev_info: holds the balloon device information descriptor.
138 * @a_ops: balloon_mapping address_space_operations descriptor.
140 * Driver must call it to properly allocate and initialize an instance of
141 * struct address_space which will be used as the special page->mapping for
142 * balloon device enlisted page instances.
144 struct address_space
*balloon_mapping_alloc(struct balloon_dev_info
*b_dev_info
,
145 const struct address_space_operations
*a_ops
)
147 struct address_space
*mapping
;
149 mapping
= kmalloc(sizeof(*mapping
), GFP_KERNEL
);
151 return ERR_PTR(-ENOMEM
);
154 * Give a clean 'zeroed' status to all elements of this special
155 * balloon page->mapping struct address_space instance.
157 address_space_init_once(mapping
);
160 * Set mapping->flags appropriately, to allow balloon pages
161 * ->mapping identification.
163 mapping_set_balloon(mapping
);
164 mapping_set_gfp_mask(mapping
, balloon_mapping_gfp_mask());
166 /* balloon's page->mapping->a_ops callback descriptor */
167 mapping
->a_ops
= a_ops
;
170 * Establish a pointer reference back to the balloon device descriptor
171 * this particular page->mapping will be servicing.
172 * This is used by compaction / migration procedures to identify and
173 * access the balloon device pageset while isolating / migrating pages.
175 * As some balloon drivers can register multiple balloon devices
176 * for a single guest, this also helps compaction / migration to
177 * properly deal with multiple balloon pagesets, when required.
179 mapping
->private_data
= b_dev_info
;
180 b_dev_info
->mapping
= mapping
;
184 EXPORT_SYMBOL_GPL(balloon_mapping_alloc
);
186 static inline void __isolate_balloon_page(struct page
*page
)
188 struct balloon_dev_info
*b_dev_info
= page
->mapping
->private_data
;
190 spin_lock_irqsave(&b_dev_info
->pages_lock
, flags
);
191 list_del(&page
->lru
);
192 b_dev_info
->isolated_pages
++;
193 spin_unlock_irqrestore(&b_dev_info
->pages_lock
, flags
);
196 static inline void __putback_balloon_page(struct page
*page
)
198 struct balloon_dev_info
*b_dev_info
= page
->mapping
->private_data
;
200 spin_lock_irqsave(&b_dev_info
->pages_lock
, flags
);
201 list_add(&page
->lru
, &b_dev_info
->pages
);
202 b_dev_info
->isolated_pages
--;
203 spin_unlock_irqrestore(&b_dev_info
->pages_lock
, flags
);
206 static inline int __migrate_balloon_page(struct address_space
*mapping
,
207 struct page
*newpage
, struct page
*page
, enum migrate_mode mode
)
209 return page
->mapping
->a_ops
->migratepage(mapping
, newpage
, page
, mode
);
212 /* __isolate_lru_page() counterpart for a ballooned page */
213 bool balloon_page_isolate(struct page
*page
)
216 * Avoid burning cycles with pages that are yet under __free_pages(),
217 * or just got freed under us.
219 * In case we 'win' a race for a balloon page being freed under us and
220 * raise its refcount preventing __free_pages() from doing its job
221 * the put_page() at the end of this block will take care of
222 * release this page, thus avoiding a nasty leakage.
224 if (likely(get_page_unless_zero(page
))) {
226 * As balloon pages are not isolated from LRU lists, concurrent
227 * compaction threads can race against page migration functions
228 * as well as race against the balloon driver releasing a page.
230 * In order to avoid having an already isolated balloon page
231 * being (wrongly) re-isolated while it is under migration,
232 * or to avoid attempting to isolate pages being released by
233 * the balloon driver, lets be sure we have the page lock
234 * before proceeding with the balloon page isolation steps.
236 if (likely(trylock_page(page
))) {
238 * A ballooned page, by default, has just one refcount.
239 * Prevent concurrent compaction threads from isolating
240 * an already isolated balloon page by refcount check.
242 if (__is_movable_balloon_page(page
) &&
243 page_count(page
) == 2) {
244 __isolate_balloon_page(page
);
255 /* putback_lru_page() counterpart for a ballooned page */
256 void balloon_page_putback(struct page
*page
)
259 * 'lock_page()' stabilizes the page and prevents races against
260 * concurrent isolation threads attempting to re-isolate it.
264 if (__is_movable_balloon_page(page
)) {
265 __putback_balloon_page(page
);
266 /* drop the extra ref count taken for page isolation */
275 /* move_to_new_page() counterpart for a ballooned page */
276 int balloon_page_migrate(struct page
*newpage
,
277 struct page
*page
, enum migrate_mode mode
)
279 struct address_space
*mapping
;
283 * Block others from accessing the 'newpage' when we get around to
284 * establishing additional references. We should be the only one
285 * holding a reference to the 'newpage' at this point.
287 BUG_ON(!trylock_page(newpage
));
289 if (WARN_ON(!__is_movable_balloon_page(page
))) {
291 unlock_page(newpage
);
295 mapping
= page
->mapping
;
297 rc
= __migrate_balloon_page(mapping
, newpage
, page
, mode
);
299 unlock_page(newpage
);
302 #endif /* CONFIG_BALLOON_COMPACTION */