linux/mm/balloon_compaction.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * mm/balloon_compaction.c
 *
 * Common interface for making balloon pages movable by compaction.
 *
 * Copyright (C) 2012, Red Hat, Inc.  Rafael Aquini <[email protected]>
 */
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/export.h>
#include <linux/balloon_compaction.h>

static void balloon_page_enqueue_one(struct balloon_dev_info *b_dev_info,
				     struct page *page)
{ … }

/**
 * balloon_page_list_enqueue() - inserts a list of pages into the balloon page
 *				 list.
 * @b_dev_info: balloon device descriptor where we will insert a new page to
 * @pages: pages to enqueue - allocated using balloon_page_alloc.
 *
 * Driver must call this function to properly enqueue balloon pages before
 * definitively removing them from the guest system.
 *
 * Return: number of pages that were enqueued.
 */
size_t balloon_page_list_enqueue(struct balloon_dev_info *b_dev_info,
				 struct list_head *pages)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * balloon_page_list_dequeue() - removes pages from balloon's page list and
 *				 returns a list of the pages.
 * @b_dev_info: balloon device descriptor where we will grab a page from.
 * @pages: pointer to the list of pages that would be returned to the caller.
 * @n_req_pages: number of requested pages.
 *
 * Driver must call this function to properly de-allocate a previous enlisted
 * balloon pages before definitively releasing it back to the guest system.
 * This function tries to remove @n_req_pages from the ballooned pages and
 * return them to the caller in the @pages list.
 *
 * Note that this function may fail to dequeue some pages even if the balloon
 * isn't empty - since the page list can be temporarily empty due to compaction
 * of isolated pages.
 *
 * Return: number of pages that were added to the @pages list.
 */
size_t balloon_page_list_dequeue(struct balloon_dev_info *b_dev_info,
				 struct list_head *pages, size_t n_req_pages)
{ … }
EXPORT_SYMBOL_GPL(…);

/*
 * balloon_page_alloc - allocates a new page for insertion into the balloon
 *			page list.
 *
 * Driver must call this function to properly allocate a new balloon page.
 * Driver must call balloon_page_enqueue before definitively removing the page
 * from the guest system.
 *
 * Return: struct page for the allocated page or NULL on allocation failure.
 */
struct page *balloon_page_alloc(void)
{ … }
EXPORT_SYMBOL_GPL(…);

/*
 * balloon_page_enqueue - inserts a new page into the balloon page list.
 *
 * @b_dev_info: balloon device descriptor where we will insert a new page
 * @page: new page to enqueue - allocated using balloon_page_alloc.
 *
 * Drivers must call this function to properly enqueue a new allocated balloon
 * page before definitively removing the page from the guest system.
 *
 * Drivers must not call balloon_page_enqueue on pages that have been pushed to
 * a list with balloon_page_push before removing them with balloon_page_pop. To
 * enqueue a list of pages, use balloon_page_list_enqueue instead.
 */
void balloon_page_enqueue(struct balloon_dev_info *b_dev_info,
			  struct page *page)
{ … }
EXPORT_SYMBOL_GPL(…);

/*
 * balloon_page_dequeue - removes a page from balloon's page list and returns
 *			  its address to allow the driver to release the page.
 * @b_dev_info: balloon device descriptor where we will grab a page from.
 *
 * Driver must call this function to properly dequeue a previously enqueued page
 * before definitively releasing it back to the guest system.
 *
 * Caller must perform its own accounting to ensure that this
 * function is called only if some pages are actually enqueued.
 *
 * Note that this function may fail to dequeue some pages even if there are
 * some enqueued pages - since the page list can be temporarily empty due to
 * the compaction of isolated pages.
 *
 * TODO: remove the caller accounting requirements, and allow caller to wait
 * until all pages can be dequeued.
 *
 * Return: struct page for the dequeued page, or NULL if no page was dequeued.
 */
struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info)
{ … }
EXPORT_SYMBOL_GPL(…);

#ifdef CONFIG_BALLOON_COMPACTION

static bool balloon_page_isolate(struct page *page, isolate_mode_t mode)

{ … }

static void balloon_page_putback(struct page *page)
{ … }

/* move_to_new_page() counterpart for a ballooned page */
static int balloon_page_migrate(struct page *newpage, struct page *page,
		enum migrate_mode mode)
{ … }

const struct movable_operations balloon_mops = …;
EXPORT_SYMBOL_GPL(…);

#endif /* CONFIG_BALLOON_COMPACTION */