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Release 4.12 include/linux/balloon_compaction.h

Directory: include/linux
/*
 * 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>

/*
 * 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_enqueue(struct balloon_dev_info *b_dev_info);
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; }

Contributors

PersonTokensPropCommitsCommitProp
Konstantin Khlebnikov2758.70%133.33%
Rafael Aquini1328.26%133.33%
MinChan Kim613.04%133.33%
Total46100.00%3100.00%

#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); }

Contributors

PersonTokensPropCommitsCommitProp
Konstantin Khlebnikov2645.61%250.00%
Rafael Aquini2442.11%125.00%
MinChan Kim712.28%125.00%
Total57100.00%4100.00%

/* * 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); }

Contributors

PersonTokensPropCommitsCommitProp
Rafael Aquini2247.83%125.00%
Konstantin Khlebnikov1634.78%250.00%
MinChan Kim817.39%125.00%
Total46100.00%4100.00%

/* * 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); }

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PersonTokensPropCommitsCommitProp
Rafael Aquini1768.00%150.00%
Konstantin Khlebnikov832.00%150.00%
Total25100.00%2100.00%


static inline gfp_t balloon_mapping_gfp_mask(void) { return GFP_HIGHUSER_MOVABLE; }

Contributors

PersonTokensPropCommitsCommitProp
Rafael Aquini12100.00%1100.00%
Total12100.00%1100.00%

#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); }

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PersonTokensPropCommitsCommitProp
Rafael Aquini2262.86%133.33%
Konstantin Khlebnikov1337.14%266.67%
Total35100.00%3100.00%


static inline void balloon_page_delete(struct page *page) { __ClearPageBalloon(page); list_del(&page->lru); }

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PersonTokensPropCommitsCommitProp
Rafael Aquini2080.00%150.00%
Konstantin Khlebnikov520.00%150.00%
Total25100.00%2100.00%


static inline bool __is_movable_balloon_page(struct page *page) { return false; }

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PersonTokensPropCommitsCommitProp
Konstantin Khlebnikov15100.00%1100.00%
Total15100.00%1100.00%


static inline bool balloon_page_movable(struct page *page) { return false; }

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PersonTokensPropCommitsCommitProp
Rafael Aquini15100.00%1100.00%
Total15100.00%1100.00%


static inline bool isolated_balloon_page(struct page *page) { return false; }

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PersonTokensPropCommitsCommitProp
Rafael Aquini15100.00%1100.00%
Total15100.00%1100.00%


static inline bool balloon_page_isolate(struct page *page) { return false; }

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PersonTokensPropCommitsCommitProp
Rafael Aquini15100.00%1100.00%
Total15100.00%1100.00%


static inline void balloon_page_putback(struct page *page) { return; }

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PersonTokensPropCommitsCommitProp
Rafael Aquini13100.00%1100.00%
Total13100.00%1100.00%


static inline int balloon_page_migrate(struct page *newpage, struct page *page, enum migrate_mode mode) { return 0; }

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PersonTokensPropCommitsCommitProp
Rafael Aquini24100.00%1100.00%
Total24100.00%1100.00%


static inline gfp_t balloon_mapping_gfp_mask(void) { return GFP_HIGHUSER; }

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PersonTokensPropCommitsCommitProp
Rafael Aquini12100.00%1100.00%
Total12100.00%1100.00%

#endif /* CONFIG_BALLOON_COMPACTION */ #endif /* _LINUX_BALLOON_COMPACTION_H */

Overall Contributors

PersonTokensPropCommitsCommitProp
Rafael Aquini34065.13%228.57%
Konstantin Khlebnikov13826.44%342.86%
MinChan Kim448.43%228.57%
Total522100.00%7100.00%
Directory: include/linux
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