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![Ingo Molnar](/assets/img/avatar_default.png)
Fix ~94 single-word typos in locking code comments, plus a few very obvious grammar mistakes. Link: https://lkml.kernel.org/r/20210322212624.GA1963421@gmail.com Link: https://lore.kernel.org/r/20210322205203.GB1959563@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org> Reviewed-by: Randy Dunlap <rdunlap@infradead.org> Cc: Bhaskar Chowdhury <unixbhaskar@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
260 lines
8.2 KiB
C
260 lines
8.2 KiB
C
// 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 <aquini@redhat.com>
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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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