mirror of
git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs.git
synced 2026-10-28 21:02:43 +01:00
David Hildenbrand (Red Hat)
cd8e95d80b
While compaction depends on migration, the other direction is not the case. So let's make it clearer that this is all about migration of balloon pages. Adjust all comments/docs in the core to talk about "migration" instead of "compaction". While at it add some "/* CONFIG_BALLOON_MIGRATION */". Link: https://lkml.kernel.org/r/[email protected] Signed-off-by: David Hildenbrand (Red Hat) <[email protected]> Reviewed-by: Lorenzo Stoakes <[email protected]> Acked-by: Michael S. Tsirkin <[email protected]> Cc: Arnd Bergmann <[email protected]> Cc: Christophe Leroy <[email protected]> Cc: Eugenio Pérez <[email protected]> Cc: Greg Kroah-Hartman <[email protected]> Cc: Jason Wang <[email protected]> Cc: Jerrin Shaji George <[email protected]> Cc: Jonathan Corbet <[email protected]> Cc: Liam Howlett <[email protected]> Cc: Madhavan Srinivasan <[email protected]> Cc: Michael Ellerman <[email protected]> Cc: Michal Hocko <[email protected]> Cc: Mike Rapoport <[email protected]> Cc: Nicholas Piggin <[email protected]> Cc: Oscar Salvador <[email protected]> Cc: SeongJae Park <[email protected]> Cc: Suren Baghdasaryan <[email protected]> Cc: Vlastimil Babka <[email protected]> Cc: Xuan Zhuo <[email protected]> Cc: Zi Yan <[email protected]> Signed-off-by: Andrew Morton <[email protected]>
78 lines
3.1 KiB
C
78 lines
3.1 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Common interface for implementing a memory balloon, including support
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* for migration of pages inflated in a memory balloon.
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*
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* Balloon page migration makes use of the general "movable_ops page migration"
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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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* That these pages have movable_ops, and which movable_ops apply,
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* is derived from the page type (PageOffline()) combined with the
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* PG_movable_ops flag (PageMovableOps()).
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*
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* Once the page type and the PG_movable_ops are set, migration code
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* can initiate page isolation by invoking the
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* movable_operations()->isolate_page() callback
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*
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* As long as page->private is set, the page is either on the balloon list
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* or isolated for migration. If page->private is not set, the page is
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* either still getting inflated, or was deflated to be freed by the balloon
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* driver soon. Isolation is impossible in both cases.
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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 migration. In order to sort out these racy scenarios
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* and safely perform balloon's page migration we must, always, ensure following
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* these simple rules:
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*
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* i. Inflation/deflation must set/clear page->private under the
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* balloon_pages_lock
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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 balloon_pages_lock
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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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#ifndef _LINUX_BALLOON_H
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#define _LINUX_BALLOON_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/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 page migration 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 migration, as well as it serves the balloon driver as
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* 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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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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bool adjust_managed_page_count;
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};
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struct page *balloon_page_alloc(void);
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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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struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info);
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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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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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INIT_LIST_HEAD(&balloon->pages);
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balloon->migratepage = NULL;
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balloon->adjust_managed_page_count = false;
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}
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#endif /* _LINUX_BALLOON_H */
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