230 lines
7.2 KiB
C
230 lines
7.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
/*
|
|
* include/linux/balloon_compaction.h
|
|
*
|
|
* Common interface definitions for making balloon pages movable by compaction.
|
|
*
|
|
* Despite being perfectly possible to perform ballooned pages migration, they
|
|
* make a special corner case to compaction scans because balloon pages are not
|
|
* enlisted at any LRU list like the other pages we do compact / migrate.
|
|
*
|
|
* 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 three 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. before isolating or dequeueing a balloon page from the balloon device
|
|
* pages list, the page reference counter must be raised by one and the
|
|
* extra refcount must be dropped when the page is enqueued back into
|
|
* the balloon device page list, thus a balloon page keeps its reference
|
|
* counter raised only while it is under our special handling;
|
|
*
|
|
* iii. after the lockless scan step have selected a potential balloon page for
|
|
* isolation, re-test the PageBalloon mark and the PagePrivate flag
|
|
* under the proper page lock, to ensure isolating a valid balloon page
|
|
* (not yet isolated, nor under release procedure)
|
|
*
|
|
* iv. isolation or dequeueing procedure must clear PagePrivate flag under
|
|
* page lock together with removing page from balloon device page list.
|
|
*
|
|
* 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);
|
|
struct inode *inode;
|
|
};
|
|
|
|
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);
|
|
|
|
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;
|
|
balloon->inode = NULL;
|
|
}
|
|
|
|
#ifdef CONFIG_BALLOON_COMPACTION
|
|
extern const struct address_space_operations balloon_aops;
|
|
extern bool balloon_page_isolate(struct page *page,
|
|
isolate_mode_t mode);
|
|
extern void balloon_page_putback(struct page *page);
|
|
extern int balloon_page_migrate(struct address_space *mapping,
|
|
struct page *newpage,
|
|
struct page *page, enum migrate_mode mode);
|
|
|
|
/*
|
|
* 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)
|
|
{
|
|
__SetPageBalloon(page);
|
|
__SetPageMovable(page, balloon->inode->i_mapping);
|
|
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)
|
|
{
|
|
__ClearPageBalloon(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)
|
|
{
|
|
__SetPageBalloon(page);
|
|
list_add(&page->lru, &balloon->pages);
|
|
}
|
|
|
|
static inline void balloon_page_delete(struct page *page)
|
|
{
|
|
__ClearPageBalloon(page);
|
|
list_del(&page->lru);
|
|
}
|
|
|
|
static inline bool __is_movable_balloon_page(struct page *page)
|
|
{
|
|
return false;
|
|
}
|
|
|
|
static inline bool balloon_page_movable(struct page *page)
|
|
{
|
|
return false;
|
|
}
|
|
|
|
static inline bool isolated_balloon_page(struct page *page)
|
|
{
|
|
return false;
|
|
}
|
|
|
|
static inline bool balloon_page_isolate(struct page *page)
|
|
{
|
|
return false;
|
|
}
|
|
|
|
static inline void balloon_page_putback(struct page *page)
|
|
{
|
|
return;
|
|
}
|
|
|
|
static inline int balloon_page_migrate(struct page *newpage,
|
|
struct page *page, enum migrate_mode mode)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
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 */
|