1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _LINUX_SWAPOPS_H
3#define _LINUX_SWAPOPS_H
4
5#include <linux/radix-tree.h>
6#include <linux/bug.h>
7#include <linux/mm_types.h>
8
9#ifdef CONFIG_MMU
10
11#ifdef CONFIG_SWAP
12#include <linux/swapfile.h>
13#endif /* CONFIG_SWAP */
14
15/*
16 * swapcache pages are stored in the swapper_space radix tree. We want to
17 * get good packing density in that tree, so the index should be dense in
18 * the low-order bits.
19 *
20 * We arrange the `type' and `offset' fields so that `type' is at the six
21 * high-order bits of the swp_entry_t and `offset' is right-aligned in the
22 * remaining bits. Although `type' itself needs only five bits, we allow for
23 * shmem/tmpfs to shift it all up a further one bit: see swp_to_radix_entry().
24 *
25 * swp_entry_t's are *never* stored anywhere in their arch-dependent format.
26 */
27#define SWP_TYPE_SHIFT (BITS_PER_XA_VALUE - MAX_SWAPFILES_SHIFT)
28#define SWP_OFFSET_MASK ((1UL << SWP_TYPE_SHIFT) - 1)
29
30/*
31 * Definitions only for PFN swap entries (see is_pfn_swap_entry()). To
32 * store PFN, we only need SWP_PFN_BITS bits. Each of the pfn swap entries
33 * can use the extra bits to store other information besides PFN.
34 */
35#ifdef MAX_PHYSMEM_BITS
36#define SWP_PFN_BITS (MAX_PHYSMEM_BITS - PAGE_SHIFT)
37#else /* MAX_PHYSMEM_BITS */
38#define SWP_PFN_BITS min_t(int, \
39 sizeof(phys_addr_t) * 8 - PAGE_SHIFT, \
40 SWP_TYPE_SHIFT)
41#endif /* MAX_PHYSMEM_BITS */
42#define SWP_PFN_MASK (BIT(SWP_PFN_BITS) - 1)
43
44/**
45 * Migration swap entry specific bitfield definitions. Layout:
46 *
47 * |----------+--------------------|
48 * | swp_type | swp_offset |
49 * |----------+--------+-+-+-------|
50 * | | resv |D|A| PFN |
51 * |----------+--------+-+-+-------|
52 *
53 * @SWP_MIG_YOUNG_BIT: Whether the page used to have young bit set (bit A)
54 * @SWP_MIG_DIRTY_BIT: Whether the page used to have dirty bit set (bit D)
55 *
56 * Note: A/D bits will be stored in migration entries iff there're enough
57 * free bits in arch specific swp offset. By default we'll ignore A/D bits
58 * when migrating a page. Please refer to migration_entry_supports_ad()
59 * for more information. If there're more bits besides PFN and A/D bits,
60 * they should be reserved and always be zeros.
61 */
62#define SWP_MIG_YOUNG_BIT (SWP_PFN_BITS)
63#define SWP_MIG_DIRTY_BIT (SWP_PFN_BITS + 1)
64#define SWP_MIG_TOTAL_BITS (SWP_PFN_BITS + 2)
65
66#define SWP_MIG_YOUNG BIT(SWP_MIG_YOUNG_BIT)
67#define SWP_MIG_DIRTY BIT(SWP_MIG_DIRTY_BIT)
68
69static inline bool is_pfn_swap_entry(swp_entry_t entry);
70
71/* Clear all flags but only keep swp_entry_t related information */
72static inline pte_t pte_swp_clear_flags(pte_t pte)
73{
74 if (pte_swp_exclusive(pte))
75 pte = pte_swp_clear_exclusive(pte);
76 if (pte_swp_soft_dirty(pte))
77 pte = pte_swp_clear_soft_dirty(pte);
78 if (pte_swp_uffd_wp(pte))
79 pte = pte_swp_clear_uffd_wp(pte);
80 return pte;
81}
82
83/*
84 * Store a type+offset into a swp_entry_t in an arch-independent format
85 */
86static inline swp_entry_t swp_entry(unsigned long type, pgoff_t offset)
87{
88 swp_entry_t ret;
89
90 ret.val = (type << SWP_TYPE_SHIFT) | (offset & SWP_OFFSET_MASK);
91 return ret;
92}
93
94/*
95 * Extract the `type' field from a swp_entry_t. The swp_entry_t is in
96 * arch-independent format
97 */
98static inline unsigned swp_type(swp_entry_t entry)
99{
100 return (entry.val >> SWP_TYPE_SHIFT);
101}
102
103/*
104 * Extract the `offset' field from a swp_entry_t. The swp_entry_t is in
105 * arch-independent format
106 */
107static inline pgoff_t swp_offset(swp_entry_t entry)
108{
109 return entry.val & SWP_OFFSET_MASK;
110}
111
112/*
113 * This should only be called upon a pfn swap entry to get the PFN stored
114 * in the swap entry. Please refers to is_pfn_swap_entry() for definition
115 * of pfn swap entry.
116 */
117static inline unsigned long swp_offset_pfn(swp_entry_t entry)
118{
119 VM_BUG_ON(!is_pfn_swap_entry(entry));
120 return swp_offset(entry) & SWP_PFN_MASK;
121}
122
123/* check whether a pte points to a swap entry */
124static inline int is_swap_pte(pte_t pte)
125{
126 return !pte_none(pte) && !pte_present(a: pte);
127}
128
129/*
130 * Convert the arch-dependent pte representation of a swp_entry_t into an
131 * arch-independent swp_entry_t.
132 */
133static inline swp_entry_t pte_to_swp_entry(pte_t pte)
134{
135 swp_entry_t arch_entry;
136
137 pte = pte_swp_clear_flags(pte);
138 arch_entry = __pte_to_swp_entry(pte);
139 return swp_entry(__swp_type(arch_entry), __swp_offset(arch_entry));
140}
141
142/*
143 * Convert the arch-independent representation of a swp_entry_t into the
144 * arch-dependent pte representation.
145 */
146static inline pte_t swp_entry_to_pte(swp_entry_t entry)
147{
148 swp_entry_t arch_entry;
149
150 arch_entry = __swp_entry(swp_type(entry), swp_offset(entry));
151 return __swp_entry_to_pte(arch_entry);
152}
153
154static inline swp_entry_t radix_to_swp_entry(void *arg)
155{
156 swp_entry_t entry;
157
158 entry.val = xa_to_value(entry: arg);
159 return entry;
160}
161
162static inline void *swp_to_radix_entry(swp_entry_t entry)
163{
164 return xa_mk_value(v: entry.val);
165}
166
167#if IS_ENABLED(CONFIG_DEVICE_PRIVATE)
168static inline swp_entry_t make_readable_device_private_entry(pgoff_t offset)
169{
170 return swp_entry(SWP_DEVICE_READ, offset);
171}
172
173static inline swp_entry_t make_writable_device_private_entry(pgoff_t offset)
174{
175 return swp_entry(SWP_DEVICE_WRITE, offset);
176}
177
178static inline bool is_device_private_entry(swp_entry_t entry)
179{
180 int type = swp_type(entry);
181 return type == SWP_DEVICE_READ || type == SWP_DEVICE_WRITE;
182}
183
184static inline bool is_writable_device_private_entry(swp_entry_t entry)
185{
186 return unlikely(swp_type(entry) == SWP_DEVICE_WRITE);
187}
188
189static inline swp_entry_t make_readable_device_exclusive_entry(pgoff_t offset)
190{
191 return swp_entry(SWP_DEVICE_EXCLUSIVE_READ, offset);
192}
193
194static inline swp_entry_t make_writable_device_exclusive_entry(pgoff_t offset)
195{
196 return swp_entry(SWP_DEVICE_EXCLUSIVE_WRITE, offset);
197}
198
199static inline bool is_device_exclusive_entry(swp_entry_t entry)
200{
201 return swp_type(entry) == SWP_DEVICE_EXCLUSIVE_READ ||
202 swp_type(entry) == SWP_DEVICE_EXCLUSIVE_WRITE;
203}
204
205static inline bool is_writable_device_exclusive_entry(swp_entry_t entry)
206{
207 return unlikely(swp_type(entry) == SWP_DEVICE_EXCLUSIVE_WRITE);
208}
209#else /* CONFIG_DEVICE_PRIVATE */
210static inline swp_entry_t make_readable_device_private_entry(pgoff_t offset)
211{
212 return swp_entry(0, 0);
213}
214
215static inline swp_entry_t make_writable_device_private_entry(pgoff_t offset)
216{
217 return swp_entry(0, 0);
218}
219
220static inline bool is_device_private_entry(swp_entry_t entry)
221{
222 return false;
223}
224
225static inline bool is_writable_device_private_entry(swp_entry_t entry)
226{
227 return false;
228}
229
230static inline swp_entry_t make_readable_device_exclusive_entry(pgoff_t offset)
231{
232 return swp_entry(0, 0);
233}
234
235static inline swp_entry_t make_writable_device_exclusive_entry(pgoff_t offset)
236{
237 return swp_entry(0, 0);
238}
239
240static inline bool is_device_exclusive_entry(swp_entry_t entry)
241{
242 return false;
243}
244
245static inline bool is_writable_device_exclusive_entry(swp_entry_t entry)
246{
247 return false;
248}
249#endif /* CONFIG_DEVICE_PRIVATE */
250
251#ifdef CONFIG_MIGRATION
252static inline int is_migration_entry(swp_entry_t entry)
253{
254 return unlikely(swp_type(entry) == SWP_MIGRATION_READ ||
255 swp_type(entry) == SWP_MIGRATION_READ_EXCLUSIVE ||
256 swp_type(entry) == SWP_MIGRATION_WRITE);
257}
258
259static inline int is_writable_migration_entry(swp_entry_t entry)
260{
261 return unlikely(swp_type(entry) == SWP_MIGRATION_WRITE);
262}
263
264static inline int is_readable_migration_entry(swp_entry_t entry)
265{
266 return unlikely(swp_type(entry) == SWP_MIGRATION_READ);
267}
268
269static inline int is_readable_exclusive_migration_entry(swp_entry_t entry)
270{
271 return unlikely(swp_type(entry) == SWP_MIGRATION_READ_EXCLUSIVE);
272}
273
274static inline swp_entry_t make_readable_migration_entry(pgoff_t offset)
275{
276 return swp_entry(SWP_MIGRATION_READ, offset);
277}
278
279static inline swp_entry_t make_readable_exclusive_migration_entry(pgoff_t offset)
280{
281 return swp_entry(SWP_MIGRATION_READ_EXCLUSIVE, offset);
282}
283
284static inline swp_entry_t make_writable_migration_entry(pgoff_t offset)
285{
286 return swp_entry(SWP_MIGRATION_WRITE, offset);
287}
288
289/*
290 * Returns whether the host has large enough swap offset field to support
291 * carrying over pgtable A/D bits for page migrations. The result is
292 * pretty much arch specific.
293 */
294static inline bool migration_entry_supports_ad(void)
295{
296#ifdef CONFIG_SWAP
297 return swap_migration_ad_supported;
298#else /* CONFIG_SWAP */
299 return false;
300#endif /* CONFIG_SWAP */
301}
302
303static inline swp_entry_t make_migration_entry_young(swp_entry_t entry)
304{
305 if (migration_entry_supports_ad())
306 return swp_entry(type: swp_type(entry),
307 offset: swp_offset(entry) | SWP_MIG_YOUNG);
308 return entry;
309}
310
311static inline bool is_migration_entry_young(swp_entry_t entry)
312{
313 if (migration_entry_supports_ad())
314 return swp_offset(entry) & SWP_MIG_YOUNG;
315 /* Keep the old behavior of aging page after migration */
316 return false;
317}
318
319static inline swp_entry_t make_migration_entry_dirty(swp_entry_t entry)
320{
321 if (migration_entry_supports_ad())
322 return swp_entry(type: swp_type(entry),
323 offset: swp_offset(entry) | SWP_MIG_DIRTY);
324 return entry;
325}
326
327static inline bool is_migration_entry_dirty(swp_entry_t entry)
328{
329 if (migration_entry_supports_ad())
330 return swp_offset(entry) & SWP_MIG_DIRTY;
331 /* Keep the old behavior of clean page after migration */
332 return false;
333}
334
335extern void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
336 unsigned long address);
337extern void migration_entry_wait_huge(struct vm_area_struct *vma, pte_t *pte);
338#else /* CONFIG_MIGRATION */
339static inline swp_entry_t make_readable_migration_entry(pgoff_t offset)
340{
341 return swp_entry(0, 0);
342}
343
344static inline swp_entry_t make_readable_exclusive_migration_entry(pgoff_t offset)
345{
346 return swp_entry(0, 0);
347}
348
349static inline swp_entry_t make_writable_migration_entry(pgoff_t offset)
350{
351 return swp_entry(0, 0);
352}
353
354static inline int is_migration_entry(swp_entry_t swp)
355{
356 return 0;
357}
358
359static inline void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
360 unsigned long address) { }
361static inline void migration_entry_wait_huge(struct vm_area_struct *vma,
362 pte_t *pte) { }
363static inline int is_writable_migration_entry(swp_entry_t entry)
364{
365 return 0;
366}
367static inline int is_readable_migration_entry(swp_entry_t entry)
368{
369 return 0;
370}
371
372static inline swp_entry_t make_migration_entry_young(swp_entry_t entry)
373{
374 return entry;
375}
376
377static inline bool is_migration_entry_young(swp_entry_t entry)
378{
379 return false;
380}
381
382static inline swp_entry_t make_migration_entry_dirty(swp_entry_t entry)
383{
384 return entry;
385}
386
387static inline bool is_migration_entry_dirty(swp_entry_t entry)
388{
389 return false;
390}
391#endif /* CONFIG_MIGRATION */
392
393typedef unsigned long pte_marker;
394
395#define PTE_MARKER_UFFD_WP BIT(0)
396/*
397 * "Poisoned" here is meant in the very general sense of "future accesses are
398 * invalid", instead of referring very specifically to hardware memory errors.
399 * This marker is meant to represent any of various different causes of this.
400 */
401#define PTE_MARKER_POISONED BIT(1)
402#define PTE_MARKER_MASK (BIT(2) - 1)
403
404static inline swp_entry_t make_pte_marker_entry(pte_marker marker)
405{
406 return swp_entry(SWP_PTE_MARKER, offset: marker);
407}
408
409static inline bool is_pte_marker_entry(swp_entry_t entry)
410{
411 return swp_type(entry) == SWP_PTE_MARKER;
412}
413
414static inline pte_marker pte_marker_get(swp_entry_t entry)
415{
416 return swp_offset(entry) & PTE_MARKER_MASK;
417}
418
419static inline bool is_pte_marker(pte_t pte)
420{
421 return is_swap_pte(pte) && is_pte_marker_entry(entry: pte_to_swp_entry(pte));
422}
423
424static inline pte_t make_pte_marker(pte_marker marker)
425{
426 return swp_entry_to_pte(entry: make_pte_marker_entry(marker));
427}
428
429static inline swp_entry_t make_poisoned_swp_entry(void)
430{
431 return make_pte_marker_entry(PTE_MARKER_POISONED);
432}
433
434static inline int is_poisoned_swp_entry(swp_entry_t entry)
435{
436 return is_pte_marker_entry(entry) &&
437 (pte_marker_get(entry) & PTE_MARKER_POISONED);
438}
439
440/*
441 * This is a special version to check pte_none() just to cover the case when
442 * the pte is a pte marker. It existed because in many cases the pte marker
443 * should be seen as a none pte; it's just that we have stored some information
444 * onto the none pte so it becomes not-none any more.
445 *
446 * It should be used when the pte is file-backed, ram-based and backing
447 * userspace pages, like shmem. It is not needed upon pgtables that do not
448 * support pte markers at all. For example, it's not needed on anonymous
449 * memory, kernel-only memory (including when the system is during-boot),
450 * non-ram based generic file-system. It's fine to be used even there, but the
451 * extra pte marker check will be pure overhead.
452 */
453static inline int pte_none_mostly(pte_t pte)
454{
455 return pte_none(pte) || is_pte_marker(pte);
456}
457
458static inline struct page *pfn_swap_entry_to_page(swp_entry_t entry)
459{
460 struct page *p = pfn_to_page(swp_offset_pfn(entry));
461
462 /*
463 * Any use of migration entries may only occur while the
464 * corresponding page is locked
465 */
466 BUG_ON(is_migration_entry(entry) && !PageLocked(p));
467
468 return p;
469}
470
471/*
472 * A pfn swap entry is a special type of swap entry that always has a pfn stored
473 * in the swap offset. They are used to represent unaddressable device memory
474 * and to restrict access to a page undergoing migration.
475 */
476static inline bool is_pfn_swap_entry(swp_entry_t entry)
477{
478 /* Make sure the swp offset can always store the needed fields */
479 BUILD_BUG_ON(SWP_TYPE_SHIFT < SWP_PFN_BITS);
480
481 return is_migration_entry(entry) || is_device_private_entry(entry) ||
482 is_device_exclusive_entry(entry);
483}
484
485struct page_vma_mapped_walk;
486
487#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
488extern int set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
489 struct page *page);
490
491extern void remove_migration_pmd(struct page_vma_mapped_walk *pvmw,
492 struct page *new);
493
494extern void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd);
495
496static inline swp_entry_t pmd_to_swp_entry(pmd_t pmd)
497{
498 swp_entry_t arch_entry;
499
500 if (pmd_swp_soft_dirty(pmd))
501 pmd = pmd_swp_clear_soft_dirty(pmd);
502 if (pmd_swp_uffd_wp(pmd))
503 pmd = pmd_swp_clear_uffd_wp(pmd);
504 arch_entry = __pmd_to_swp_entry(pmd);
505 return swp_entry(__swp_type(arch_entry), __swp_offset(arch_entry));
506}
507
508static inline pmd_t swp_entry_to_pmd(swp_entry_t entry)
509{
510 swp_entry_t arch_entry;
511
512 arch_entry = __swp_entry(swp_type(entry), swp_offset(entry));
513 return __swp_entry_to_pmd(arch_entry);
514}
515
516static inline int is_pmd_migration_entry(pmd_t pmd)
517{
518 return is_swap_pmd(pmd) && is_migration_entry(entry: pmd_to_swp_entry(pmd));
519}
520#else /* CONFIG_ARCH_ENABLE_THP_MIGRATION */
521static inline int set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
522 struct page *page)
523{
524 BUILD_BUG();
525}
526
527static inline void remove_migration_pmd(struct page_vma_mapped_walk *pvmw,
528 struct page *new)
529{
530 BUILD_BUG();
531}
532
533static inline void pmd_migration_entry_wait(struct mm_struct *m, pmd_t *p) { }
534
535static inline swp_entry_t pmd_to_swp_entry(pmd_t pmd)
536{
537 return swp_entry(0, 0);
538}
539
540static inline pmd_t swp_entry_to_pmd(swp_entry_t entry)
541{
542 return __pmd(0);
543}
544
545static inline int is_pmd_migration_entry(pmd_t pmd)
546{
547 return 0;
548}
549#endif /* CONFIG_ARCH_ENABLE_THP_MIGRATION */
550
551#ifdef CONFIG_MEMORY_FAILURE
552
553/*
554 * Support for hardware poisoned pages
555 */
556static inline swp_entry_t make_hwpoison_entry(struct page *page)
557{
558 BUG_ON(!PageLocked(page));
559 return swp_entry(SWP_HWPOISON, page_to_pfn(page));
560}
561
562static inline int is_hwpoison_entry(swp_entry_t entry)
563{
564 return swp_type(entry) == SWP_HWPOISON;
565}
566
567#else
568
569static inline swp_entry_t make_hwpoison_entry(struct page *page)
570{
571 return swp_entry(0, 0);
572}
573
574static inline int is_hwpoison_entry(swp_entry_t swp)
575{
576 return 0;
577}
578#endif
579
580static inline int non_swap_entry(swp_entry_t entry)
581{
582 return swp_type(entry) >= MAX_SWAPFILES;
583}
584
585#endif /* CONFIG_MMU */
586#endif /* _LINUX_SWAPOPS_H */
587

source code of linux/include/linux/swapops.h