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![Nadav Amit](/assets/img/avatar_default.png)
Introduce interfaces for ballooning enqueueing and dequeueing of a list of pages. These interfaces reduce the overhead of storing and restoring IRQs by batching the operations. In addition they do not panic if the list of pages is empty. Cc: Jason Wang <jasowang@redhat.com> Cc: linux-mm@kvack.org Cc: virtualization@lists.linux-foundation.org Acked-by: Michael S. Tsirkin <mst@redhat.com> Reviewed-by: Xavier Deguillard <xdeguillard@vmware.com> Signed-off-by: Nadav Amit <namit@vmware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
210 lines
6.6 KiB
C
210 lines
6.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* include/linux/balloon_compaction.h
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*
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* Common interface definitions for making balloon pages movable by compaction.
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*
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* Balloon page migration makes use of the general non-lru movable page
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* feature.
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*
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* page->private is used to reference the responsible balloon device.
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* page->mapping is used in context of non-lru page migration to reference
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* the address space operations for page isolation/migration/compaction.
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*
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* As the page isolation scanning step a compaction thread does is a lockless
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* procedure (from a page standpoint), it might bring some racy situations while
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* performing balloon page compaction. In order to sort out these racy scenarios
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* and safely perform balloon's page compaction and migration we must, always,
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* ensure following these simple rules:
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*
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* i. when updating a balloon's page ->mapping element, strictly do it under
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* the following lock order, independently of the far superior
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* locking scheme (lru_lock, balloon_lock):
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* +-page_lock(page);
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* +--spin_lock_irq(&b_dev_info->pages_lock);
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* ... page->mapping updates here ...
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*
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* ii. isolation or dequeueing procedure must remove the page from balloon
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* device page list under b_dev_info->pages_lock.
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*
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* The functions provided by this interface are placed to help on coping with
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* the aforementioned balloon page corner case, as well as to ensure the simple
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* set of exposed rules are satisfied while we are dealing with balloon pages
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* compaction / migration.
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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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#ifndef _LINUX_BALLOON_COMPACTION_H
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#define _LINUX_BALLOON_COMPACTION_H
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#include <linux/pagemap.h>
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#include <linux/page-flags.h>
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#include <linux/migrate.h>
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#include <linux/gfp.h>
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#include <linux/err.h>
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#include <linux/fs.h>
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#include <linux/list.h>
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/*
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* Balloon device information descriptor.
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* This struct is used to allow the common balloon compaction interface
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* procedures to find the proper balloon device holding memory pages they'll
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* have to cope for page compaction / migration, as well as it serves the
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* balloon driver as a page book-keeper for its registered balloon devices.
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*/
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struct balloon_dev_info {
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unsigned long isolated_pages; /* # of isolated pages for migration */
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spinlock_t pages_lock; /* Protection to pages list */
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struct list_head pages; /* Pages enqueued & handled to Host */
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int (*migratepage)(struct balloon_dev_info *, struct page *newpage,
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struct page *page, enum migrate_mode mode);
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struct inode *inode;
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};
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extern struct page *balloon_page_alloc(void);
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extern void balloon_page_enqueue(struct balloon_dev_info *b_dev_info,
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struct page *page);
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extern struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info);
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extern 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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extern 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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static inline void balloon_devinfo_init(struct balloon_dev_info *balloon)
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{
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balloon->isolated_pages = 0;
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spin_lock_init(&balloon->pages_lock);
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INIT_LIST_HEAD(&balloon->pages);
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balloon->migratepage = NULL;
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balloon->inode = NULL;
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}
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#ifdef CONFIG_BALLOON_COMPACTION
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extern const struct address_space_operations balloon_aops;
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extern bool balloon_page_isolate(struct page *page,
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isolate_mode_t mode);
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extern void balloon_page_putback(struct page *page);
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extern int balloon_page_migrate(struct address_space *mapping,
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struct page *newpage,
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struct page *page, enum migrate_mode mode);
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/*
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* balloon_page_insert - insert a page into the balloon's page list and make
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* the page->private assignment accordingly.
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* @balloon : pointer to balloon device
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* @page : page to be assigned as a 'balloon page'
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*
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* Caller must ensure the page is locked and the spin_lock protecting balloon
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* pages list is held before inserting a page into the balloon device.
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*/
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static inline void balloon_page_insert(struct balloon_dev_info *balloon,
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struct page *page)
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{
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__SetPageOffline(page);
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__SetPageMovable(page, balloon->inode->i_mapping);
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set_page_private(page, (unsigned long)balloon);
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list_add(&page->lru, &balloon->pages);
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}
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/*
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* balloon_page_delete - delete a page from balloon's page list and clear
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* the page->private assignement accordingly.
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* @page : page to be released from balloon's page list
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*
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* Caller must ensure the page is locked and the spin_lock protecting balloon
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* pages list is held before deleting a page from the balloon device.
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*/
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static inline void balloon_page_delete(struct page *page)
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{
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__ClearPageOffline(page);
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__ClearPageMovable(page);
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set_page_private(page, 0);
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/*
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* No touch page.lru field once @page has been isolated
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* because VM is using the field.
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*/
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if (!PageIsolated(page))
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list_del(&page->lru);
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}
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/*
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* balloon_page_device - get the b_dev_info descriptor for the balloon device
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* that enqueues the given page.
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*/
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static inline struct balloon_dev_info *balloon_page_device(struct page *page)
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{
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return (struct balloon_dev_info *)page_private(page);
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}
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static inline gfp_t balloon_mapping_gfp_mask(void)
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{
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return GFP_HIGHUSER_MOVABLE;
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}
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#else /* !CONFIG_BALLOON_COMPACTION */
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static inline void balloon_page_insert(struct balloon_dev_info *balloon,
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struct page *page)
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{
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__SetPageOffline(page);
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list_add(&page->lru, &balloon->pages);
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}
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static inline void balloon_page_delete(struct page *page)
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{
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__ClearPageOffline(page);
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list_del(&page->lru);
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}
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static inline bool balloon_page_isolate(struct page *page)
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{
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return false;
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}
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static inline void balloon_page_putback(struct page *page)
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{
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return;
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}
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static inline int balloon_page_migrate(struct page *newpage,
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struct page *page, enum migrate_mode mode)
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{
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return 0;
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}
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static inline gfp_t balloon_mapping_gfp_mask(void)
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{
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return GFP_HIGHUSER;
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}
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#endif /* CONFIG_BALLOON_COMPACTION */
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/*
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* balloon_page_push - insert a page into a page list.
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* @head : pointer to list
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* @page : page to be added
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*
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* Caller must ensure the page is private and protect the list.
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*/
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static inline void balloon_page_push(struct list_head *pages, struct page *page)
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{
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list_add(&page->lru, pages);
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}
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/*
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* balloon_page_pop - remove a page from a page list.
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* @head : pointer to list
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* @page : page to be added
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*
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* Caller must ensure the page is private and protect the list.
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*/
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static inline struct page *balloon_page_pop(struct list_head *pages)
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{
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struct page *page = list_first_entry_or_null(pages, struct page, lru);
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if (!page)
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return NULL;
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list_del(&page->lru);
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return page;
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}
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#endif /* _LINUX_BALLOON_COMPACTION_H */
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