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260 lines
8.2 KiB
260 lines
8.2 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* mm/balloon_compaction.c |
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* |
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* Common interface for making balloon pages movable by compaction. |
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* |
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* Copyright (C) 2012, Red Hat, Inc. Rafael Aquini <[email protected]> |
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*/ |
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#include <linux/mm.h> |
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#include <linux/slab.h> |
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#include <linux/export.h> |
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#include <linux/balloon_compaction.h> |
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static void balloon_page_enqueue_one(struct balloon_dev_info *b_dev_info, |
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struct page *page) |
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{ |
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/* |
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* Block others from accessing the 'page' when we get around to |
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* establishing additional references. We should be the only one |
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* holding a reference to the 'page' at this point. If we are not, then |
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* memory corruption is possible and we should stop execution. |
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*/ |
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BUG_ON(!trylock_page(page)); |
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balloon_page_insert(b_dev_info, page); |
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unlock_page(page); |
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__count_vm_event(BALLOON_INFLATE); |
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} |
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/** |
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* balloon_page_list_enqueue() - inserts a list of pages into the balloon page |
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* list. |
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* @b_dev_info: balloon device descriptor where we will insert a new page to |
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* @pages: pages to enqueue - allocated using balloon_page_alloc. |
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* |
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* Driver must call this function to properly enqueue balloon pages before |
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* definitively removing them from the guest system. |
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* |
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* Return: number of pages that were enqueued. |
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*/ |
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size_t balloon_page_list_enqueue(struct balloon_dev_info *b_dev_info, |
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struct list_head *pages) |
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{ |
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struct page *page, *tmp; |
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unsigned long flags; |
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size_t n_pages = 0; |
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spin_lock_irqsave(&b_dev_info->pages_lock, flags); |
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list_for_each_entry_safe(page, tmp, pages, lru) { |
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list_del(&page->lru); |
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balloon_page_enqueue_one(b_dev_info, page); |
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n_pages++; |
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} |
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spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); |
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return n_pages; |
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} |
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EXPORT_SYMBOL_GPL(balloon_page_list_enqueue); |
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/** |
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* balloon_page_list_dequeue() - removes pages from balloon's page list and |
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* returns a list of the pages. |
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* @b_dev_info: balloon device descriptor where we will grab a page from. |
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* @pages: pointer to the list of pages that would be returned to the caller. |
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* @n_req_pages: number of requested pages. |
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* |
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* Driver must call this function to properly de-allocate a previous enlisted |
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* balloon pages before definitively releasing it back to the guest system. |
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* This function tries to remove @n_req_pages from the ballooned pages and |
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* return them to the caller in the @pages list. |
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* |
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* Note that this function may fail to dequeue some pages even if the balloon |
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* isn't empty - since the page list can be temporarily empty due to compaction |
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* of isolated pages. |
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* |
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* Return: number of pages that were added to the @pages list. |
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*/ |
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size_t balloon_page_list_dequeue(struct balloon_dev_info *b_dev_info, |
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struct list_head *pages, size_t n_req_pages) |
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{ |
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struct page *page, *tmp; |
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unsigned long flags; |
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size_t n_pages = 0; |
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spin_lock_irqsave(&b_dev_info->pages_lock, flags); |
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list_for_each_entry_safe(page, tmp, &b_dev_info->pages, lru) { |
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if (n_pages == n_req_pages) |
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break; |
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/* |
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* Block others from accessing the 'page' while we get around to |
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* establishing additional references and preparing the 'page' |
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* to be released by the balloon driver. |
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*/ |
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if (!trylock_page(page)) |
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continue; |
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if (IS_ENABLED(CONFIG_BALLOON_COMPACTION) && |
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PageIsolated(page)) { |
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/* raced with isolation */ |
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unlock_page(page); |
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continue; |
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} |
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balloon_page_delete(page); |
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__count_vm_event(BALLOON_DEFLATE); |
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list_add(&page->lru, pages); |
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unlock_page(page); |
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n_pages++; |
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} |
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spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); |
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return n_pages; |
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} |
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EXPORT_SYMBOL_GPL(balloon_page_list_dequeue); |
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/* |
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* balloon_page_alloc - allocates a new page for insertion into the balloon |
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* page list. |
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* |
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* Driver must call this function to properly allocate a new balloon page. |
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* Driver must call balloon_page_enqueue before definitively removing the page |
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* from the guest system. |
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* |
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* Return: struct page for the allocated page or NULL on allocation failure. |
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*/ |
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struct page *balloon_page_alloc(void) |
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{ |
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struct page *page = alloc_page(balloon_mapping_gfp_mask() | |
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__GFP_NOMEMALLOC | __GFP_NORETRY | |
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__GFP_NOWARN); |
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return page; |
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} |
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EXPORT_SYMBOL_GPL(balloon_page_alloc); |
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/* |
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* balloon_page_enqueue - inserts a new page into the balloon page list. |
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* |
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* @b_dev_info: balloon device descriptor where we will insert a new page |
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* @page: new page to enqueue - allocated using balloon_page_alloc. |
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* |
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* Drivers must call this function to properly enqueue a new allocated balloon |
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* page before definitively removing the page from the guest system. |
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* |
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* Drivers must not call balloon_page_enqueue on pages that have been pushed to |
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* a list with balloon_page_push before removing them with balloon_page_pop. To |
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* enqueue a list of pages, use balloon_page_list_enqueue instead. |
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*/ |
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void balloon_page_enqueue(struct balloon_dev_info *b_dev_info, |
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struct page *page) |
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{ |
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unsigned long flags; |
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spin_lock_irqsave(&b_dev_info->pages_lock, flags); |
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balloon_page_enqueue_one(b_dev_info, page); |
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spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); |
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} |
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EXPORT_SYMBOL_GPL(balloon_page_enqueue); |
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/* |
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* balloon_page_dequeue - removes a page from balloon's page list and returns |
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* its address to allow the driver to release the page. |
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* @b_dev_info: balloon device descriptor where we will grab a page from. |
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* |
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* Driver must call this function to properly dequeue a previously enqueued page |
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* before definitively releasing it back to the guest system. |
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* |
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* Caller must perform its own accounting to ensure that this |
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* function is called only if some pages are actually enqueued. |
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* |
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* Note that this function may fail to dequeue some pages even if there are |
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* some enqueued pages - since the page list can be temporarily empty due to |
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* the compaction of isolated pages. |
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* |
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* TODO: remove the caller accounting requirements, and allow caller to wait |
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* until all pages can be dequeued. |
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* |
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* Return: struct page for the dequeued page, or NULL if no page was dequeued. |
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*/ |
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struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info) |
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{ |
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unsigned long flags; |
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LIST_HEAD(pages); |
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int n_pages; |
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n_pages = balloon_page_list_dequeue(b_dev_info, &pages, 1); |
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if (n_pages != 1) { |
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/* |
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* If we are unable to dequeue a balloon page because the page |
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* list is empty and there are no isolated pages, then something |
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* went out of track and some balloon pages are lost. |
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* BUG() here, otherwise the balloon driver may get stuck in |
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* an infinite loop while attempting to release all its pages. |
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*/ |
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spin_lock_irqsave(&b_dev_info->pages_lock, flags); |
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if (unlikely(list_empty(&b_dev_info->pages) && |
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!b_dev_info->isolated_pages)) |
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BUG(); |
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spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); |
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return NULL; |
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} |
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return list_first_entry(&pages, struct page, lru); |
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} |
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EXPORT_SYMBOL_GPL(balloon_page_dequeue); |
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#ifdef CONFIG_BALLOON_COMPACTION |
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bool balloon_page_isolate(struct page *page, isolate_mode_t mode) |
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{ |
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struct balloon_dev_info *b_dev_info = balloon_page_device(page); |
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unsigned long flags; |
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spin_lock_irqsave(&b_dev_info->pages_lock, flags); |
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list_del(&page->lru); |
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b_dev_info->isolated_pages++; |
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spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); |
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return true; |
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} |
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void balloon_page_putback(struct page *page) |
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{ |
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struct balloon_dev_info *b_dev_info = balloon_page_device(page); |
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unsigned long flags; |
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spin_lock_irqsave(&b_dev_info->pages_lock, flags); |
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list_add(&page->lru, &b_dev_info->pages); |
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b_dev_info->isolated_pages--; |
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spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); |
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} |
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/* move_to_new_page() counterpart for a ballooned page */ |
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int balloon_page_migrate(struct address_space *mapping, |
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struct page *newpage, struct page *page, |
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enum migrate_mode mode) |
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{ |
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struct balloon_dev_info *balloon = balloon_page_device(page); |
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/* |
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* We can not easily support the no copy case here so ignore it as it |
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* is unlikely to be used with balloon pages. See include/linux/hmm.h |
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* for a user of the MIGRATE_SYNC_NO_COPY mode. |
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*/ |
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if (mode == MIGRATE_SYNC_NO_COPY) |
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return -EINVAL; |
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VM_BUG_ON_PAGE(!PageLocked(page), page); |
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VM_BUG_ON_PAGE(!PageLocked(newpage), newpage); |
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return balloon->migratepage(balloon, newpage, page, mode); |
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} |
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const struct address_space_operations balloon_aops = { |
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.migratepage = balloon_page_migrate, |
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.isolate_page = balloon_page_isolate, |
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.putback_page = balloon_page_putback, |
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}; |
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EXPORT_SYMBOL_GPL(balloon_aops); |
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#endif /* CONFIG_BALLOON_COMPACTION */
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