name : balloon_compaction.h /* SPDX-License-Identifier: GPL-2.0 */ /* * include/linux/balloon_compaction.h * * Common interface definitions for making balloon pages movable by compaction. * * Balloon page migration makes use of the general non-lru movable page * feature. * * page->private is used to reference the responsible balloon device. * page->mapping is used in context of non-lru page migration to reference * the address space operations for page isolation/migration/compaction. * * As the page isolation scanning step a compaction thread does is a lockless * procedure (from a page standpoint), it might bring some racy situations while * performing balloon page compaction. In order to sort out these racy scenarios * and safely perform balloon's page compaction and migration we must, always, * ensure following these simple rules: * * i. when updating a balloon's page ->mapping element, strictly do it under * the following lock order, independently of the far superior * locking scheme (lru_lock, balloon_lock): * +-page_lock(page); * +--spin_lock_irq(&b_dev_info->pages_lock); * ... page->mapping updates here ... * * ii. isolation or dequeueing procedure must remove the page from balloon * device page list under b_dev_info->pages_lock. * * The functions provided by this interface are placed to help on coping with * the aforementioned balloon page corner case, as well as to ensure the simple * set of exposed rules are satisfied while we are dealing with balloon pages * compaction / migration. * * Copyright (C) 2012, Red Hat, Inc. Rafael Aquini <aquini@redhat.com> */ #ifndef _LINUX_BALLOON_COMPACTION_H #define _LINUX_BALLOON_COMPACTION_H #include <linux/pagemap.h> #include <linux/page-flags.h> #include <linux/migrate.h> #include <linux/gfp.h> #include <linux/err.h> #include <linux/fs.h> #include <linux/list.h> /* * Balloon device information descriptor. * This struct is used to allow the common balloon compaction interface * procedures to find the proper balloon device holding memory pages they'll * have to cope for page compaction / migration, as well as it serves the * balloon driver as a page book-keeper for its registered balloon devices. */ struct balloon_dev_info { unsigned long isolated_pages; /* # of isolated pages for migration */ spinlock_t pages_lock; /* Protection to pages list */ struct list_head pages; /* Pages enqueued & handled to Host */ int (*migratepage)(struct balloon_dev_info *, struct page *newpage, struct page *page, enum migrate_mode mode); }; extern struct page *balloon_page_alloc(void); extern void balloon_page_enqueue(struct balloon_dev_info *b_dev_info, struct page *page); extern struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info); extern size_t balloon_page_list_enqueue(struct balloon_dev_info *b_dev_info, struct list_head *pages); extern size_t balloon_page_list_dequeue(struct balloon_dev_info *b_dev_info, struct list_head *pages, size_t n_req_pages); static inline void balloon_devinfo_init(struct balloon_dev_info *balloon) { balloon->isolated_pages = 0; spin_lock_init(&balloon->pages_lock); INIT_LIST_HEAD(&balloon->pages); balloon->migratepage = NULL; } #ifdef CONFIG_BALLOON_COMPACTION extern const struct movable_operations balloon_mops; /* * balloon_page_insert - insert a page into the balloon's page list and make * the page->private assignment accordingly. * @balloon : pointer to balloon device * @page : page to be assigned as a 'balloon page' * * Caller must ensure the page is locked and the spin_lock protecting balloon * pages list is held before inserting a page into the balloon device. */ static inline void balloon_page_insert(struct balloon_dev_info *balloon, struct page *page) { __SetPageOffline(page); __SetPageMovable(page, &balloon_mops); set_page_private(page, (unsigned long)balloon); list_add(&page->lru, &balloon->pages); } /* * balloon_page_delete - delete a page from balloon's page list and clear * the page->private assignement accordingly. * @page : page to be released from balloon's page list * * Caller must ensure the page is locked and the spin_lock protecting balloon * pages list is held before deleting a page from the balloon device. */ static inline void balloon_page_delete(struct page *page) { __ClearPageOffline(page); __ClearPageMovable(page); set_page_private(page, 0); /* * No touch page.lru field once @page has been isolated * because VM is using the field. */ if (!PageIsolated(page)) list_del(&page->lru); } /* * balloon_page_device - get the b_dev_info descriptor for the balloon device * that enqueues the given page. */ static inline struct balloon_dev_info *balloon_page_device(struct page *page) { return (struct balloon_dev_info *)page_private(page); } static inline gfp_t balloon_mapping_gfp_mask(void) { return GFP_HIGHUSER_MOVABLE; } #else /* !CONFIG_BALLOON_COMPACTION */ static inline void balloon_page_insert(struct balloon_dev_info *balloon, struct page *page) { __SetPageOffline(page); list_add(&page->lru, &balloon->pages); } static inline void balloon_page_delete(struct page *page) { __ClearPageOffline(page); list_del(&page->lru); } static inline gfp_t balloon_mapping_gfp_mask(void) { return GFP_HIGHUSER; } #endif /* CONFIG_BALLOON_COMPACTION */ /* * balloon_page_push - insert a page into a page list. * @head : pointer to list * @page : page to be added * * Caller must ensure the page is private and protect the list. */ static inline void balloon_page_push(struct list_head *pages, struct page *page) { list_add(&page->lru, pages); } /* * balloon_page_pop - remove a page from a page list. * @head : pointer to list * @page : page to be added * * Caller must ensure the page is private and protect the list. */ static inline struct page *balloon_page_pop(struct list_head *pages) { struct page *page = list_first_entry_or_null(pages, struct page, lru); if (!page) return NULL; list_del(&page->lru); return page; } #endif /* _LINUX_BALLOON_COMPACTION_H */