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1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _LINUX_MIGRATE_H
3#define _LINUX_MIGRATE_H
4
5#include <linux/mm.h>
6#include <linux/mempolicy.h>
7#include <linux/migrate_mode.h>
8#include <linux/hugetlb.h>
9
10typedef struct folio *new_folio_t(struct folio *folio, unsigned long private);
11typedef void free_folio_t(struct folio *folio, unsigned long private);
12
13struct migration_target_control;
14
15/*
16 * Return values from addresss_space_operations.migratepage():
17 * - negative errno on page migration failure;
18 * - zero on page migration success;
19 */
20#define MIGRATEPAGE_SUCCESS 0
21#define MIGRATEPAGE_UNMAP 1
22
23/**
24 * struct movable_operations - Driver page migration
25 * @isolate_page:
26 * The VM calls this function to prepare the page to be moved. The page
27 * is locked and the driver should not unlock it. The driver should
28 * return ``true`` if the page is movable and ``false`` if it is not
29 * currently movable. After this function returns, the VM uses the
30 * page->lru field, so the driver must preserve any information which
31 * is usually stored here.
32 *
33 * @migrate_page:
34 * After isolation, the VM calls this function with the isolated
35 * @src page. The driver should copy the contents of the
36 * @src page to the @dst page and set up the fields of @dst page.
37 * Both pages are locked.
38 * If page migration is successful, the driver should
39 * return MIGRATEPAGE_SUCCESS.
40 * If the driver cannot migrate the page at the moment, it can return
41 * -EAGAIN. The VM interprets this as a temporary migration failure and
42 * will retry it later. Any other error value is a permanent migration
43 * failure and migration will not be retried.
44 * The driver shouldn't touch the @src->lru field while in the
45 * migrate_page() function. It may write to @dst->lru.
46 *
47 * @putback_page:
48 * If migration fails on the isolated page, the VM informs the driver
49 * that the page is no longer a candidate for migration by calling
50 * this function. The driver should put the isolated page back into
51 * its own data structure.
52 */
53struct movable_operations {
54 bool (*isolate_page)(struct page *, isolate_mode_t);
55 int (*migrate_page)(struct page *dst, struct page *src,
56 enum migrate_mode);
57 void (*putback_page)(struct page *);
58};
59
60/* Defined in mm/debug.c: */
61extern const char *migrate_reason_names[MR_TYPES];
62
63#ifdef CONFIG_MIGRATION
64
65void putback_movable_pages(struct list_head *l);
66int migrate_folio(struct address_space *mapping, struct folio *dst,
67 struct folio *src, enum migrate_mode mode);
68int migrate_pages(struct list_head *l, new_folio_t new, free_folio_t free,
69 unsigned long private, enum migrate_mode mode, int reason,
70 unsigned int *ret_succeeded);
71struct folio *alloc_migration_target(struct folio *src, unsigned long private);
72bool isolate_movable_ops_page(struct page *page, isolate_mode_t mode);
73bool isolate_folio_to_list(struct folio *folio, struct list_head *list);
74
75int migrate_huge_page_move_mapping(struct address_space *mapping,
76 struct folio *dst, struct folio *src);
77void migration_entry_wait_on_locked(swp_entry_t entry, spinlock_t *ptl)
78 __releases(ptl);
79void folio_migrate_flags(struct folio *newfolio, struct folio *folio);
80int folio_migrate_mapping(struct address_space *mapping,
81 struct folio *newfolio, struct folio *folio, int extra_count);
82
83#else
84
85static inline void putback_movable_pages(struct list_head *l) {}
86static inline int migrate_pages(struct list_head *l, new_folio_t new,
87 free_folio_t free, unsigned long private,
88 enum migrate_mode mode, int reason, unsigned int *ret_succeeded)
89 { return -ENOSYS; }
90static inline struct folio *alloc_migration_target(struct folio *src,
91 unsigned long private)
92 { return NULL; }
93static inline bool isolate_movable_ops_page(struct page *page, isolate_mode_t mode)
94 { return false; }
95static inline bool isolate_folio_to_list(struct folio *folio, struct list_head *list)
96 { return false; }
97
98static inline int migrate_huge_page_move_mapping(struct address_space *mapping,
99 struct folio *dst, struct folio *src)
100{
101 return -ENOSYS;
102}
103
104#endif /* CONFIG_MIGRATION */
105
106#ifdef CONFIG_NUMA_BALANCING
107int migrate_misplaced_folio_prepare(struct folio *folio,
108 struct vm_area_struct *vma, int node);
109int migrate_misplaced_folio(struct folio *folio, int node);
110#else
111static inline int migrate_misplaced_folio_prepare(struct folio *folio,
112 struct vm_area_struct *vma, int node)
113{
114 return -EAGAIN; /* can't migrate now */
115}
116static inline int migrate_misplaced_folio(struct folio *folio, int node)
117{
118 return -EAGAIN; /* can't migrate now */
119}
120#endif /* CONFIG_NUMA_BALANCING */
121
122#ifdef CONFIG_MIGRATION
123
124/*
125 * Watch out for PAE architecture, which has an unsigned long, and might not
126 * have enough bits to store all physical address and flags. So far we have
127 * enough room for all our flags.
128 */
129#define MIGRATE_PFN_VALID (1UL << 0)
130#define MIGRATE_PFN_MIGRATE (1UL << 1)
131#define MIGRATE_PFN_WRITE (1UL << 3)
132#define MIGRATE_PFN_SHIFT 6
133
134static inline struct page *migrate_pfn_to_page(unsigned long mpfn)
135{
136 if (!(mpfn & MIGRATE_PFN_VALID))
137 return NULL;
138 return pfn_to_page(mpfn >> MIGRATE_PFN_SHIFT);
139}
140
141static inline unsigned long migrate_pfn(unsigned long pfn)
142{
143 return (pfn << MIGRATE_PFN_SHIFT) | MIGRATE_PFN_VALID;
144}
145
146enum migrate_vma_direction {
147 MIGRATE_VMA_SELECT_SYSTEM = 1 << 0,
148 MIGRATE_VMA_SELECT_DEVICE_PRIVATE = 1 << 1,
149 MIGRATE_VMA_SELECT_DEVICE_COHERENT = 1 << 2,
150};
151
152struct migrate_vma {
153 struct vm_area_struct *vma;
154 /*
155 * Both src and dst array must be big enough for
156 * (end - start) >> PAGE_SHIFT entries.
157 *
158 * The src array must not be modified by the caller after
159 * migrate_vma_setup(), and must not change the dst array after
160 * migrate_vma_pages() returns.
161 */
162 unsigned long *dst;
163 unsigned long *src;
164 unsigned long cpages;
165 unsigned long npages;
166 unsigned long start;
167 unsigned long end;
168
169 /*
170 * Set to the owner value also stored in page_pgmap(page)->owner
171 * for migrating out of device private memory. The flags also need to
172 * be set to MIGRATE_VMA_SELECT_DEVICE_PRIVATE.
173 * The caller should always set this field when using mmu notifier
174 * callbacks to avoid device MMU invalidations for device private
175 * pages that are not being migrated.
176 */
177 void *pgmap_owner;
178 unsigned long flags;
179
180 /*
181 * Set to vmf->page if this is being called to migrate a page as part of
182 * a migrate_to_ram() callback.
183 */
184 struct page *fault_page;
185};
186
187int migrate_vma_setup(struct migrate_vma *args);
188void migrate_vma_pages(struct migrate_vma *migrate);
189void migrate_vma_finalize(struct migrate_vma *migrate);
190int migrate_device_range(unsigned long *src_pfns, unsigned long start,
191 unsigned long npages);
192int migrate_device_pfns(unsigned long *src_pfns, unsigned long npages);
193void migrate_device_pages(unsigned long *src_pfns, unsigned long *dst_pfns,
194 unsigned long npages);
195void migrate_device_finalize(unsigned long *src_pfns,
196 unsigned long *dst_pfns, unsigned long npages);
197
198#endif /* CONFIG_MIGRATION */
199
200#endif /* _LINUX_MIGRATE_H */