/* 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_COMPACTIONextern 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 */