1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 * include/linux/balloon_compaction.h
4 *
5 * Common interface definitions for making balloon pages movable by compaction.
6 *
7 * Balloon page migration makes use of the general non-lru movable page
8 * feature.
9 *
10 * page->private is used to reference the responsible balloon device.
11 * page->mapping is used in context of non-lru page migration to reference
12 * the address space operations for page isolation/migration/compaction.
13 *
14 * As the page isolation scanning step a compaction thread does is a lockless
15 * procedure (from a page standpoint), it might bring some racy situations while
16 * performing balloon page compaction. In order to sort out these racy scenarios
17 * and safely perform balloon's page compaction and migration we must, always,
18 * ensure following these simple rules:
19 *
20 * i. when updating a balloon's page ->mapping element, strictly do it under
21 * the following lock order, independently of the far superior
22 * locking scheme (lru_lock, balloon_lock):
23 * +-page_lock(page);
24 * +--spin_lock_irq(&b_dev_info->pages_lock);
25 * ... page->mapping updates here ...
26 *
27 * ii. isolation or dequeueing procedure must remove the page from balloon
28 * device page list under b_dev_info->pages_lock.
29 *
30 * The functions provided by this interface are placed to help on coping with
31 * the aforementioned balloon page corner case, as well as to ensure the simple
32 * set of exposed rules are satisfied while we are dealing with balloon pages
33 * compaction / migration.
34 *
35 * Copyright (C) 2012, Red Hat, Inc. Rafael Aquini <aquini@redhat.com>
36 */
37#ifndef _LINUX_BALLOON_COMPACTION_H
38#define _LINUX_BALLOON_COMPACTION_H
39#include <linux/pagemap.h>
40#include <linux/page-flags.h>
41#include <linux/migrate.h>
42#include <linux/gfp.h>
43#include <linux/err.h>
44#include <linux/fs.h>
45#include <linux/list.h>
46
47/*
48 * Balloon device information descriptor.
49 * This struct is used to allow the common balloon compaction interface
50 * procedures to find the proper balloon device holding memory pages they'll
51 * have to cope for page compaction / migration, as well as it serves the
52 * balloon driver as a page book-keeper for its registered balloon devices.
53 */
54struct balloon_dev_info {
55 unsigned long isolated_pages; /* # of isolated pages for migration */
56 spinlock_t pages_lock; /* Protection to pages list */
57 struct list_head pages; /* Pages enqueued & handled to Host */
58 int (*migratepage)(struct balloon_dev_info *, struct page *newpage,
59 struct page *page, enum migrate_mode mode);
60};
61
62extern struct page *balloon_page_alloc(void);
63extern void balloon_page_enqueue(struct balloon_dev_info *b_dev_info,
64 struct page *page);
65extern struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info);
66extern size_t balloon_page_list_enqueue(struct balloon_dev_info *b_dev_info,
67 struct list_head *pages);
68extern size_t balloon_page_list_dequeue(struct balloon_dev_info *b_dev_info,
69 struct list_head *pages, size_t n_req_pages);
70
71static inline void balloon_devinfo_init(struct balloon_dev_info *balloon)
72{
73 balloon->isolated_pages = 0;
74 spin_lock_init(&balloon->pages_lock);
75 INIT_LIST_HEAD(list: &balloon->pages);
76 balloon->migratepage = NULL;
77}
78
79#ifdef CONFIG_BALLOON_COMPACTION
80extern const struct movable_operations balloon_mops;
81
82/*
83 * balloon_page_insert - insert a page into the balloon's page list and make
84 * the page->private assignment accordingly.
85 * @balloon : pointer to balloon device
86 * @page : page to be assigned as a 'balloon page'
87 *
88 * Caller must ensure the page is locked and the spin_lock protecting balloon
89 * pages list is held before inserting a page into the balloon device.
90 */
91static inline void balloon_page_insert(struct balloon_dev_info *balloon,
92 struct page *page)
93{
94 __SetPageOffline(page);
95 __SetPageMovable(page, ops: &balloon_mops);
96 set_page_private(page, private: (unsigned long)balloon);
97 list_add(new: &page->lru, head: &balloon->pages);
98}
99
100/*
101 * balloon_page_delete - delete a page from balloon's page list and clear
102 * the page->private assignement accordingly.
103 * @page : page to be released from balloon's page list
104 *
105 * Caller must ensure the page is locked and the spin_lock protecting balloon
106 * pages list is held before deleting a page from the balloon device.
107 */
108static inline void balloon_page_delete(struct page *page)
109{
110 __ClearPageOffline(page);
111 __ClearPageMovable(page);
112 set_page_private(page, private: 0);
113 /*
114 * No touch page.lru field once @page has been isolated
115 * because VM is using the field.
116 */
117 if (!PageIsolated(page))
118 list_del(entry: &page->lru);
119}
120
121/*
122 * balloon_page_device - get the b_dev_info descriptor for the balloon device
123 * that enqueues the given page.
124 */
125static inline struct balloon_dev_info *balloon_page_device(struct page *page)
126{
127 return (struct balloon_dev_info *)page_private(page);
128}
129
130static inline gfp_t balloon_mapping_gfp_mask(void)
131{
132 return GFP_HIGHUSER_MOVABLE;
133}
134
135#else /* !CONFIG_BALLOON_COMPACTION */
136
137static inline void balloon_page_insert(struct balloon_dev_info *balloon,
138 struct page *page)
139{
140 __SetPageOffline(page);
141 list_add(&page->lru, &balloon->pages);
142}
143
144static inline void balloon_page_delete(struct page *page)
145{
146 __ClearPageOffline(page);
147 list_del(&page->lru);
148}
149
150static inline gfp_t balloon_mapping_gfp_mask(void)
151{
152 return GFP_HIGHUSER;
153}
154
155#endif /* CONFIG_BALLOON_COMPACTION */
156
157/*
158 * balloon_page_push - insert a page into a page list.
159 * @head : pointer to list
160 * @page : page to be added
161 *
162 * Caller must ensure the page is private and protect the list.
163 */
164static inline void balloon_page_push(struct list_head *pages, struct page *page)
165{
166 list_add(new: &page->lru, head: pages);
167}
168
169/*
170 * balloon_page_pop - remove a page from a page list.
171 * @head : pointer to list
172 * @page : page to be added
173 *
174 * Caller must ensure the page is private and protect the list.
175 */
176static inline struct page *balloon_page_pop(struct list_head *pages)
177{
178 struct page *page = list_first_entry_or_null(pages, struct page, lru);
179
180 if (!page)
181 return NULL;
182
183 list_del(entry: &page->lru);
184 return page;
185}
186#endif /* _LINUX_BALLOON_COMPACTION_H */
187

source code of linux/include/linux/balloon_compaction.h

Morty Proxy This is a proxified and sanitized view of the page, visit original site.