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1/* SPDX-License-Identifier: GPL-2.0 */2/*3 * include/linux/balloon_compaction.h4 *5 * Common interface definitions for making balloon pages movable by compaction.6 *7 * Balloon page migration makes use of the general non-lru movable page8 * 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 reference12 * the address space operations for page isolation/migration/compaction.13 *14 * As the page isolation scanning step a compaction thread does is a lockless15 * procedure (from a page standpoint), it might bring some racy situations while16 * performing balloon page compaction. In order to sort out these racy scenarios17 * 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 under21 * the following lock order, independently of the far superior22 * 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 balloon28 * device page list under b_dev_info->pages_lock.29 *30 * The functions provided by this interface are placed to help on coping with31 * the aforementioned balloon page corner case, as well as to ensure the simple32 * set of exposed rules are satisfied while we are dealing with balloon pages33 * compaction / migration.34 *35 * Copyright (C) 2012, Red Hat, Inc. Rafael Aquini <aquini@redhat.com>36 */37#ifndef _LINUX_BALLOON_COMPACTION_H38#define _LINUX_BALLOON_COMPACTION_H39#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 interface50 * procedures to find the proper balloon device holding memory pages they'll51 * have to cope for page compaction / migration, as well as it serves the52 * 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_COMPACTION80extern const struct movable_operations balloon_mops;81 82/*83 * balloon_page_insert - insert a page into the balloon's page list and make84 * the page->private assignment accordingly.85 * @balloon : pointer to balloon device86 * @page : page to be assigned as a 'balloon page'87 *88 * Caller must ensure the page is locked and the spin_lock protecting balloon89 * 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 clear102 * the page->private assignement accordingly.103 * @page : page to be released from balloon's page list104 *105 * Caller must ensure the page is locked and the spin_lock protecting balloon106 * 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 isolated115 * 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 device123 * 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 list160 * @page : page to be added161 *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 list172 * @page : page to be added173 *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