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- // 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)
- {
- /*
- * Block others from accessing the 'page' when we get around to
- * establishing additional references. We should be the only one
- * holding a reference to the 'page' at this point. If we are not, then
- * memory corruption is possible and we should stop execution.
- */
- BUG_ON(!trylock_page(page));
- balloon_page_insert(b_dev_info, page);
- unlock_page(page);
- __count_vm_event(BALLOON_INFLATE);
- }
- /**
- * 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)
- {
- struct page *page, *tmp;
- unsigned long flags;
- size_t n_pages = 0;
- spin_lock_irqsave(&b_dev_info->pages_lock, flags);
- list_for_each_entry_safe(page, tmp, pages, lru) {
- list_del(&page->lru);
- balloon_page_enqueue_one(b_dev_info, page);
- n_pages++;
- }
- spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
- return n_pages;
- }
- EXPORT_SYMBOL_GPL(balloon_page_list_enqueue);
- /**
- * 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)
- {
- struct page *page, *tmp;
- unsigned long flags;
- size_t n_pages = 0;
- spin_lock_irqsave(&b_dev_info->pages_lock, flags);
- list_for_each_entry_safe(page, tmp, &b_dev_info->pages, lru) {
- if (n_pages == n_req_pages)
- break;
- /*
- * Block others from accessing the 'page' while we get around to
- * establishing additional references and preparing the 'page'
- * to be released by the balloon driver.
- */
- if (!trylock_page(page))
- continue;
- if (IS_ENABLED(CONFIG_BALLOON_COMPACTION) &&
- PageIsolated(page)) {
- /* raced with isolation */
- unlock_page(page);
- continue;
- }
- balloon_page_delete(page);
- __count_vm_event(BALLOON_DEFLATE);
- list_add(&page->lru, pages);
- unlock_page(page);
- n_pages++;
- }
- spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
- return n_pages;
- }
- EXPORT_SYMBOL_GPL(balloon_page_list_dequeue);
- /*
- * 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)
- {
- struct page *page = alloc_page(balloon_mapping_gfp_mask() |
- __GFP_NOMEMALLOC | __GFP_NORETRY |
- __GFP_NOWARN);
- return page;
- }
- EXPORT_SYMBOL_GPL(balloon_page_alloc);
- /*
- * 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)
- {
- unsigned long flags;
- spin_lock_irqsave(&b_dev_info->pages_lock, flags);
- balloon_page_enqueue_one(b_dev_info, page);
- spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
- }
- EXPORT_SYMBOL_GPL(balloon_page_enqueue);
- /*
- * 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)
- {
- unsigned long flags;
- LIST_HEAD(pages);
- int n_pages;
- n_pages = balloon_page_list_dequeue(b_dev_info, &pages, 1);
- if (n_pages != 1) {
- /*
- * If we are unable to dequeue a balloon page because the page
- * list is empty and there are no isolated pages, then something
- * went out of track and some balloon pages are lost.
- * BUG() here, otherwise the balloon driver may get stuck in
- * an infinite loop while attempting to release all its pages.
- */
- spin_lock_irqsave(&b_dev_info->pages_lock, flags);
- if (unlikely(list_empty(&b_dev_info->pages) &&
- !b_dev_info->isolated_pages))
- BUG();
- spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
- return NULL;
- }
- return list_first_entry(&pages, struct page, lru);
- }
- EXPORT_SYMBOL_GPL(balloon_page_dequeue);
- #ifdef CONFIG_BALLOON_COMPACTION
- static bool balloon_page_isolate(struct page *page, isolate_mode_t mode)
- {
- struct balloon_dev_info *b_dev_info = balloon_page_device(page);
- unsigned long flags;
- spin_lock_irqsave(&b_dev_info->pages_lock, flags);
- list_del(&page->lru);
- b_dev_info->isolated_pages++;
- spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
- return true;
- }
- static void balloon_page_putback(struct page *page)
- {
- struct balloon_dev_info *b_dev_info = balloon_page_device(page);
- unsigned long flags;
- spin_lock_irqsave(&b_dev_info->pages_lock, flags);
- list_add(&page->lru, &b_dev_info->pages);
- b_dev_info->isolated_pages--;
- spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
- }
- /* move_to_new_page() counterpart for a ballooned page */
- static int balloon_page_migrate(struct page *newpage, struct page *page,
- enum migrate_mode mode)
- {
- struct balloon_dev_info *balloon = balloon_page_device(page);
- /*
- * We can not easily support the no copy case here so ignore it as it
- * is unlikely to be used with balloon pages. See include/linux/hmm.h
- * for a user of the MIGRATE_SYNC_NO_COPY mode.
- */
- if (mode == MIGRATE_SYNC_NO_COPY)
- return -EINVAL;
- VM_BUG_ON_PAGE(!PageLocked(page), page);
- VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
- return balloon->migratepage(balloon, newpage, page, mode);
- }
- const struct movable_operations balloon_mops = {
- .migrate_page = balloon_page_migrate,
- .isolate_page = balloon_page_isolate,
- .putback_page = balloon_page_putback,
- };
- EXPORT_SYMBOL_GPL(balloon_mops);
- #endif /* CONFIG_BALLOON_COMPACTION */
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