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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/20260119230133.3551867-23-david@kernel.org Signed-off-by: David Hildenbrand (Red Hat) <david@kernel.org> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Christophe Leroy <christophe.leroy@csgroup.eu> Cc: Eugenio Pérez <eperezma@redhat.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Jason Wang <jasowang@redhat.com> Cc: Jerrin Shaji George <jerrin.shaji-george@broadcom.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Madhavan Srinivasan <maddy@linux.ibm.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: SeongJae Park <sj@kernel.org> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Xuan Zhuo <xuanzhuo@linux.alibaba.com> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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 <aquini@redhat.com>
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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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