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
393#ifdef CONFIG_MEMORY_FAILURE
394
395/*
396 * Support for hardware poisoned pages
397 */
398static inline swp_entry_t make_hwpoison_entry(struct page *page)
399{
400 BUG_ON(!PageLocked(page));
401 return swp_entry(SWP_HWPOISON, page_to_pfn(page));
402}
403
404static inline int is_hwpoison_entry(swp_entry_t entry)
405{
406 return swp_type(entry) == SWP_HWPOISON;
407}
408
409#else
410
411static inline swp_entry_t make_hwpoison_entry(struct page *page)
412{
413 return swp_entry(0, 0);
414}
415
416static inline int is_hwpoison_entry(swp_entry_t swp)
417{
418 return 0;
419}
420#endif
421
422typedef unsigned long pte_marker;
423
424#define PTE_MARKER_UFFD_WP BIT(0)
425/*
426 * "Poisoned" here is meant in the very general sense of "future accesses are
427 * invalid", instead of referring very specifically to hardware memory errors.
428 * This marker is meant to represent any of various different causes of this.
429 */
430#define PTE_MARKER_POISONED BIT(1)
431#define PTE_MARKER_MASK (BIT(2) - 1)
432
433static inline swp_entry_t make_pte_marker_entry(pte_marker marker)
434{
435 return swp_entry(SWP_PTE_MARKER, offset: marker);
436}
437
438static inline bool is_pte_marker_entry(swp_entry_t entry)
439{
440 return swp_type(entry) == SWP_PTE_MARKER;
441}
442
443static inline pte_marker pte_marker_get(swp_entry_t entry)
444{
445 return swp_offset(entry) & PTE_MARKER_MASK;
446}
447
448static inline bool is_pte_marker(pte_t pte)
449{
450 return is_swap_pte(pte) && is_pte_marker_entry(entry: pte_to_swp_entry(pte));
451}
452
453static inline pte_t make_pte_marker(pte_marker marker)
454{
455 return swp_entry_to_pte(entry: make_pte_marker_entry(marker));
456}
457
458static inline swp_entry_t make_poisoned_swp_entry(void)
459{
460 return make_pte_marker_entry(PTE_MARKER_POISONED);
461}
462
463static inline int is_poisoned_swp_entry(swp_entry_t entry)
464{
465 return is_pte_marker_entry(entry) &&
466 (pte_marker_get(entry) & PTE_MARKER_POISONED);
467}
468
469/*
470 * This is a special version to check pte_none() just to cover the case when
471 * the pte is a pte marker. It existed because in many cases the pte marker
472 * should be seen as a none pte; it's just that we have stored some information
473 * onto the none pte so it becomes not-none any more.
474 *
475 * It should be used when the pte is file-backed, ram-based and backing
476 * userspace pages, like shmem. It is not needed upon pgtables that do not
477 * support pte markers at all. For example, it's not needed on anonymous
478 * memory, kernel-only memory (including when the system is during-boot),
479 * non-ram based generic file-system. It's fine to be used even there, but the
480 * extra pte marker check will be pure overhead.
481 */
482static inline int pte_none_mostly(pte_t pte)
483{
484 return pte_none(pte) || is_pte_marker(pte);
485}
486
487static inline struct page *pfn_swap_entry_to_page(swp_entry_t entry)
488{
489 struct page *p = pfn_to_page(swp_offset_pfn(entry));
490
491 /*
492 * Any use of migration entries may only occur while the
493 * corresponding page is locked
494 */
495 BUG_ON(is_migration_entry(entry) && !PageLocked(p));
496
497 return p;
498}
499
500static inline struct folio *pfn_swap_entry_folio(swp_entry_t entry)
501{
502 struct folio *folio = pfn_folio(pfn: swp_offset_pfn(entry));
503
504 /*
505 * Any use of migration entries may only occur while the
506 * corresponding folio is locked
507 */
508 BUG_ON(is_migration_entry(entry) && !folio_test_locked(folio));
509
510 return folio;
511}
512
513/*
514 * A pfn swap entry is a special type of swap entry that always has a pfn stored
515 * in the swap offset. They can either be used to represent unaddressable device
516 * memory, to restrict access to a page undergoing migration or to represent a
517 * pfn which has been hwpoisoned and unmapped.
518 */
519static inline bool is_pfn_swap_entry(swp_entry_t entry)
520{
521 /* Make sure the swp offset can always store the needed fields */
522 BUILD_BUG_ON(SWP_TYPE_SHIFT < SWP_PFN_BITS);
523
524 return is_migration_entry(entry) || is_device_private_entry(entry) ||
525 is_device_exclusive_entry(entry) || is_hwpoison_entry(entry);
526}
527
528struct page_vma_mapped_walk;
529
530#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
531extern int set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
532 struct page *page);
533
534extern void remove_migration_pmd(struct page_vma_mapped_walk *pvmw,
535 struct page *new);
536
537extern void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd);
538
539static inline swp_entry_t pmd_to_swp_entry(pmd_t pmd)
540{
541 swp_entry_t arch_entry;
542
543 if (pmd_swp_soft_dirty(pmd))
544 pmd = pmd_swp_clear_soft_dirty(pmd);
545 if (pmd_swp_uffd_wp(pmd))
546 pmd = pmd_swp_clear_uffd_wp(pmd);
547 arch_entry = __pmd_to_swp_entry(pmd);
548 return swp_entry(__swp_type(arch_entry), __swp_offset(arch_entry));
549}
550
551static inline pmd_t swp_entry_to_pmd(swp_entry_t entry)
552{
553 swp_entry_t arch_entry;
554
555 arch_entry = __swp_entry(swp_type(entry), swp_offset(entry));
556 return __swp_entry_to_pmd(arch_entry);
557}
558
559static inline int is_pmd_migration_entry(pmd_t pmd)
560{
561 return is_swap_pmd(pmd) && is_migration_entry(entry: pmd_to_swp_entry(pmd));
562}
563#else /* CONFIG_ARCH_ENABLE_THP_MIGRATION */
564static inline int set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
565 struct page *page)
566{
567 BUILD_BUG();
568}
569
570static inline void remove_migration_pmd(struct page_vma_mapped_walk *pvmw,
571 struct page *new)
572{
573 BUILD_BUG();
574}
575
576static inline void pmd_migration_entry_wait(struct mm_struct *m, pmd_t *p) { }
577
578static inline swp_entry_t pmd_to_swp_entry(pmd_t pmd)
579{
580 return swp_entry(0, 0);
581}
582
583static inline pmd_t swp_entry_to_pmd(swp_entry_t entry)
584{
585 return __pmd(0);
586}
587
588static inline int is_pmd_migration_entry(pmd_t pmd)
589{
590 return 0;
591}
592#endif /* CONFIG_ARCH_ENABLE_THP_MIGRATION */
593
594static inline int non_swap_entry(swp_entry_t entry)
595{
596 return swp_type(entry) >= MAX_SWAPFILES;
597}
598
599#endif /* CONFIG_MMU */
600#endif /* _LINUX_SWAPOPS_H */
601

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