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(&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, &balloon_mops); 96 set_page_private(page, (unsigned long)balloon); 97 list_add(&page->lru, &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, 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(&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(&page->lru, 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(&page->lru); 184 return page; 185} 186#endif /* _LINUX_BALLOON_COMPACTION_H */ 187