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mm/balloon_compaction.c
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// SPDX-License-Identifier: GPL-2.0-only |
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/* * mm/balloon_compaction.c * * Common interface for making balloon pages movable by compaction. * * Copyright (C) 2012, Red Hat, Inc. Rafael Aquini <aquini@redhat.com> */ #include <linux/mm.h> #include <linux/slab.h> #include <linux/export.h> #include <linux/balloon_compaction.h> |
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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)); |
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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. * |
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* Driver must call this function to properly enqueue balloon pages before * definitively removing them from the guest system. |
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* * 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) { |
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list_del(&page->lru); |
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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 decriptor 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 |
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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 * return them to the caller in the @pages list. * |
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* 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. |
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* * 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); |
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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. * 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. |
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*/ struct page *balloon_page_alloc(void) { struct page *page = alloc_page(balloon_mapping_gfp_mask() | |
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__GFP_NOMEMALLOC | __GFP_NORETRY | __GFP_NOWARN); |
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return page; } EXPORT_SYMBOL_GPL(balloon_page_alloc); /* |
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* balloon_page_enqueue - inserts a new page into the balloon page list. * |
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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 * 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 * 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. |
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*/ |
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void balloon_page_enqueue(struct balloon_dev_info *b_dev_info, struct page *page) |
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{ unsigned long flags; |
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|
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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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} EXPORT_SYMBOL_GPL(balloon_page_enqueue); /* * 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 decriptor where we will grab a page from. * |
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* 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. |
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*/ struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info) { |
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unsigned long flags; |
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LIST_HEAD(pages); int n_pages; |
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|
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n_pages = balloon_page_list_dequeue(b_dev_info, &pages, 1); |
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|
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if (n_pages != 1) { |
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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. */ 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); |
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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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} EXPORT_SYMBOL_GPL(balloon_page_dequeue); #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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|
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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); |
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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); list_add(&page->lru, &b_dev_info->pages); b_dev_info->isolated_pages--; spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); } |
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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, struct page *newpage, struct page *page, 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 * for a user of the MIGRATE_SYNC_NO_COPY mode. |
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*/ if (mode == MIGRATE_SYNC_NO_COPY) return -EINVAL; |
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VM_BUG_ON_PAGE(!PageLocked(page), page); VM_BUG_ON_PAGE(!PageLocked(newpage), newpage); |
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return balloon->migratepage(balloon, newpage, page, mode); } |
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const struct address_space_operations balloon_aops = { .migratepage = balloon_page_migrate, .isolate_page = balloon_page_isolate, .putback_page = balloon_page_putback, }; EXPORT_SYMBOL_GPL(balloon_aops); |
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#endif /* CONFIG_BALLOON_COMPACTION */ |