Line data Source code
1 : /* SPDX-License-Identifier: GPL-2.0 */
2 : #ifndef _LINUX_RMAP_H
3 : #define _LINUX_RMAP_H
4 : /*
5 : * Declarations for Reverse Mapping functions in mm/rmap.c
6 : */
7 :
8 : #include <linux/list.h>
9 : #include <linux/slab.h>
10 : #include <linux/mm.h>
11 : #include <linux/rwsem.h>
12 : #include <linux/memcontrol.h>
13 : #include <linux/highmem.h>
14 : #include <linux/pagemap.h>
15 : #include <linux/memremap.h>
16 :
17 : /*
18 : * The anon_vma heads a list of private "related" vmas, to scan if
19 : * an anonymous page pointing to this anon_vma needs to be unmapped:
20 : * the vmas on the list will be related by forking, or by splitting.
21 : *
22 : * Since vmas come and go as they are split and merged (particularly
23 : * in mprotect), the mapping field of an anonymous page cannot point
24 : * directly to a vma: instead it points to an anon_vma, on whose list
25 : * the related vmas can be easily linked or unlinked.
26 : *
27 : * After unlinking the last vma on the list, we must garbage collect
28 : * the anon_vma object itself: we're guaranteed no page can be
29 : * pointing to this anon_vma once its vma list is empty.
30 : */
31 : struct anon_vma {
32 : struct anon_vma *root; /* Root of this anon_vma tree */
33 : struct rw_semaphore rwsem; /* W: modification, R: walking the list */
34 : /*
35 : * The refcount is taken on an anon_vma when there is no
36 : * guarantee that the vma of page tables will exist for
37 : * the duration of the operation. A caller that takes
38 : * the reference is responsible for clearing up the
39 : * anon_vma if they are the last user on release
40 : */
41 : atomic_t refcount;
42 :
43 : /*
44 : * Count of child anon_vmas. Equals to the count of all anon_vmas that
45 : * have ->parent pointing to this one, including itself.
46 : *
47 : * This counter is used for making decision about reusing anon_vma
48 : * instead of forking new one. See comments in function anon_vma_clone.
49 : */
50 : unsigned long num_children;
51 : /* Count of VMAs whose ->anon_vma pointer points to this object. */
52 : unsigned long num_active_vmas;
53 :
54 : struct anon_vma *parent; /* Parent of this anon_vma */
55 :
56 : /*
57 : * NOTE: the LSB of the rb_root.rb_node is set by
58 : * mm_take_all_locks() _after_ taking the above lock. So the
59 : * rb_root must only be read/written after taking the above lock
60 : * to be sure to see a valid next pointer. The LSB bit itself
61 : * is serialized by a system wide lock only visible to
62 : * mm_take_all_locks() (mm_all_locks_mutex).
63 : */
64 :
65 : /* Interval tree of private "related" vmas */
66 : struct rb_root_cached rb_root;
67 : };
68 :
69 : /*
70 : * The copy-on-write semantics of fork mean that an anon_vma
71 : * can become associated with multiple processes. Furthermore,
72 : * each child process will have its own anon_vma, where new
73 : * pages for that process are instantiated.
74 : *
75 : * This structure allows us to find the anon_vmas associated
76 : * with a VMA, or the VMAs associated with an anon_vma.
77 : * The "same_vma" list contains the anon_vma_chains linking
78 : * all the anon_vmas associated with this VMA.
79 : * The "rb" field indexes on an interval tree the anon_vma_chains
80 : * which link all the VMAs associated with this anon_vma.
81 : */
82 : struct anon_vma_chain {
83 : struct vm_area_struct *vma;
84 : struct anon_vma *anon_vma;
85 : struct list_head same_vma; /* locked by mmap_lock & page_table_lock */
86 : struct rb_node rb; /* locked by anon_vma->rwsem */
87 : unsigned long rb_subtree_last;
88 : #ifdef CONFIG_DEBUG_VM_RB
89 : unsigned long cached_vma_start, cached_vma_last;
90 : #endif
91 : };
92 :
93 : enum ttu_flags {
94 : TTU_SPLIT_HUGE_PMD = 0x4, /* split huge PMD if any */
95 : TTU_IGNORE_MLOCK = 0x8, /* ignore mlock */
96 : TTU_SYNC = 0x10, /* avoid racy checks with PVMW_SYNC */
97 : TTU_HWPOISON = 0x20, /* do convert pte to hwpoison entry */
98 : TTU_BATCH_FLUSH = 0x40, /* Batch TLB flushes where possible
99 : * and caller guarantees they will
100 : * do a final flush if necessary */
101 : TTU_RMAP_LOCKED = 0x80, /* do not grab rmap lock:
102 : * caller holds it */
103 : };
104 :
105 : #ifdef CONFIG_MMU
106 : static inline void get_anon_vma(struct anon_vma *anon_vma)
107 : {
108 0 : atomic_inc(&anon_vma->refcount);
109 : }
110 :
111 : void __put_anon_vma(struct anon_vma *anon_vma);
112 :
113 : static inline void put_anon_vma(struct anon_vma *anon_vma)
114 : {
115 0 : if (atomic_dec_and_test(&anon_vma->refcount))
116 0 : __put_anon_vma(anon_vma);
117 : }
118 :
119 : static inline void anon_vma_lock_write(struct anon_vma *anon_vma)
120 : {
121 0 : down_write(&anon_vma->root->rwsem);
122 : }
123 :
124 : static inline void anon_vma_unlock_write(struct anon_vma *anon_vma)
125 : {
126 0 : up_write(&anon_vma->root->rwsem);
127 : }
128 :
129 : static inline void anon_vma_lock_read(struct anon_vma *anon_vma)
130 : {
131 0 : down_read(&anon_vma->root->rwsem);
132 : }
133 :
134 : static inline int anon_vma_trylock_read(struct anon_vma *anon_vma)
135 : {
136 0 : return down_read_trylock(&anon_vma->root->rwsem);
137 : }
138 :
139 : static inline void anon_vma_unlock_read(struct anon_vma *anon_vma)
140 : {
141 0 : up_read(&anon_vma->root->rwsem);
142 : }
143 :
144 :
145 : /*
146 : * anon_vma helper functions.
147 : */
148 : void anon_vma_init(void); /* create anon_vma_cachep */
149 : int __anon_vma_prepare(struct vm_area_struct *);
150 : void unlink_anon_vmas(struct vm_area_struct *);
151 : int anon_vma_clone(struct vm_area_struct *, struct vm_area_struct *);
152 : int anon_vma_fork(struct vm_area_struct *, struct vm_area_struct *);
153 :
154 : static inline int anon_vma_prepare(struct vm_area_struct *vma)
155 : {
156 0 : if (likely(vma->anon_vma))
157 : return 0;
158 :
159 0 : return __anon_vma_prepare(vma);
160 : }
161 :
162 : static inline void anon_vma_merge(struct vm_area_struct *vma,
163 : struct vm_area_struct *next)
164 : {
165 : VM_BUG_ON_VMA(vma->anon_vma != next->anon_vma, vma);
166 0 : unlink_anon_vmas(next);
167 : }
168 :
169 : struct anon_vma *folio_get_anon_vma(struct folio *folio);
170 :
171 : /* RMAP flags, currently only relevant for some anon rmap operations. */
172 : typedef int __bitwise rmap_t;
173 :
174 : /*
175 : * No special request: if the page is a subpage of a compound page, it is
176 : * mapped via a PTE. The mapped (sub)page is possibly shared between processes.
177 : */
178 : #define RMAP_NONE ((__force rmap_t)0)
179 :
180 : /* The (sub)page is exclusive to a single process. */
181 : #define RMAP_EXCLUSIVE ((__force rmap_t)BIT(0))
182 :
183 : /*
184 : * The compound page is not mapped via PTEs, but instead via a single PMD and
185 : * should be accounted accordingly.
186 : */
187 : #define RMAP_COMPOUND ((__force rmap_t)BIT(1))
188 :
189 : /*
190 : * rmap interfaces called when adding or removing pte of page
191 : */
192 : void page_move_anon_rmap(struct page *, struct vm_area_struct *);
193 : void page_add_anon_rmap(struct page *, struct vm_area_struct *,
194 : unsigned long address, rmap_t flags);
195 : void page_add_new_anon_rmap(struct page *, struct vm_area_struct *,
196 : unsigned long address);
197 : void folio_add_new_anon_rmap(struct folio *, struct vm_area_struct *,
198 : unsigned long address);
199 : void page_add_file_rmap(struct page *, struct vm_area_struct *,
200 : bool compound);
201 : void page_remove_rmap(struct page *, struct vm_area_struct *,
202 : bool compound);
203 :
204 : void hugepage_add_anon_rmap(struct page *, struct vm_area_struct *,
205 : unsigned long address, rmap_t flags);
206 : void hugepage_add_new_anon_rmap(struct folio *, struct vm_area_struct *,
207 : unsigned long address);
208 :
209 : static inline void __page_dup_rmap(struct page *page, bool compound)
210 : {
211 0 : if (compound) {
212 0 : struct folio *folio = (struct folio *)page;
213 :
214 : VM_BUG_ON_PAGE(compound && !PageHead(page), page);
215 0 : atomic_inc(&folio->_entire_mapcount);
216 : } else {
217 0 : atomic_inc(&page->_mapcount);
218 : }
219 : }
220 :
221 : static inline void page_dup_file_rmap(struct page *page, bool compound)
222 : {
223 0 : __page_dup_rmap(page, compound);
224 : }
225 :
226 : /**
227 : * page_try_dup_anon_rmap - try duplicating a mapping of an already mapped
228 : * anonymous page
229 : * @page: the page to duplicate the mapping for
230 : * @compound: the page is mapped as compound or as a small page
231 : * @vma: the source vma
232 : *
233 : * The caller needs to hold the PT lock and the vma->vma_mm->write_protect_seq.
234 : *
235 : * Duplicating the mapping can only fail if the page may be pinned; device
236 : * private pages cannot get pinned and consequently this function cannot fail.
237 : *
238 : * If duplicating the mapping succeeds, the page has to be mapped R/O into
239 : * the parent and the child. It must *not* get mapped writable after this call.
240 : *
241 : * Returns 0 if duplicating the mapping succeeded. Returns -EBUSY otherwise.
242 : */
243 0 : static inline int page_try_dup_anon_rmap(struct page *page, bool compound,
244 : struct vm_area_struct *vma)
245 : {
246 : VM_BUG_ON_PAGE(!PageAnon(page), page);
247 :
248 : /*
249 : * No need to check+clear for already shared pages, including KSM
250 : * pages.
251 : */
252 0 : if (!PageAnonExclusive(page))
253 : goto dup;
254 :
255 : /*
256 : * If this page may have been pinned by the parent process,
257 : * don't allow to duplicate the mapping but instead require to e.g.,
258 : * copy the page immediately for the child so that we'll always
259 : * guarantee the pinned page won't be randomly replaced in the
260 : * future on write faults.
261 : */
262 0 : if (likely(!is_device_private_page(page) &&
263 : unlikely(page_needs_cow_for_dma(vma, page))))
264 : return -EBUSY;
265 :
266 : ClearPageAnonExclusive(page);
267 : /*
268 : * It's okay to share the anon page between both processes, mapping
269 : * the page R/O into both processes.
270 : */
271 : dup:
272 0 : __page_dup_rmap(page, compound);
273 : return 0;
274 : }
275 :
276 : /**
277 : * page_try_share_anon_rmap - try marking an exclusive anonymous page possibly
278 : * shared to prepare for KSM or temporary unmapping
279 : * @page: the exclusive anonymous page to try marking possibly shared
280 : *
281 : * The caller needs to hold the PT lock and has to have the page table entry
282 : * cleared/invalidated.
283 : *
284 : * This is similar to page_try_dup_anon_rmap(), however, not used during fork()
285 : * to duplicate a mapping, but instead to prepare for KSM or temporarily
286 : * unmapping a page (swap, migration) via page_remove_rmap().
287 : *
288 : * Marking the page shared can only fail if the page may be pinned; device
289 : * private pages cannot get pinned and consequently this function cannot fail.
290 : *
291 : * Returns 0 if marking the page possibly shared succeeded. Returns -EBUSY
292 : * otherwise.
293 : */
294 : static inline int page_try_share_anon_rmap(struct page *page)
295 : {
296 : VM_BUG_ON_PAGE(!PageAnon(page) || !PageAnonExclusive(page), page);
297 :
298 : /* device private pages cannot get pinned via GUP. */
299 0 : if (unlikely(is_device_private_page(page))) {
300 : ClearPageAnonExclusive(page);
301 : return 0;
302 : }
303 :
304 : /*
305 : * We have to make sure that when we clear PageAnonExclusive, that
306 : * the page is not pinned and that concurrent GUP-fast won't succeed in
307 : * concurrently pinning the page.
308 : *
309 : * Conceptually, PageAnonExclusive clearing consists of:
310 : * (A1) Clear PTE
311 : * (A2) Check if the page is pinned; back off if so.
312 : * (A3) Clear PageAnonExclusive
313 : * (A4) Restore PTE (optional, but certainly not writable)
314 : *
315 : * When clearing PageAnonExclusive, we cannot possibly map the page
316 : * writable again, because anon pages that may be shared must never
317 : * be writable. So in any case, if the PTE was writable it cannot
318 : * be writable anymore afterwards and there would be a PTE change. Only
319 : * if the PTE wasn't writable, there might not be a PTE change.
320 : *
321 : * Conceptually, GUP-fast pinning of an anon page consists of:
322 : * (B1) Read the PTE
323 : * (B2) FOLL_WRITE: check if the PTE is not writable; back off if so.
324 : * (B3) Pin the mapped page
325 : * (B4) Check if the PTE changed by re-reading it; back off if so.
326 : * (B5) If the original PTE is not writable, check if
327 : * PageAnonExclusive is not set; back off if so.
328 : *
329 : * If the PTE was writable, we only have to make sure that GUP-fast
330 : * observes a PTE change and properly backs off.
331 : *
332 : * If the PTE was not writable, we have to make sure that GUP-fast either
333 : * detects a (temporary) PTE change or that PageAnonExclusive is cleared
334 : * and properly backs off.
335 : *
336 : * Consequently, when clearing PageAnonExclusive(), we have to make
337 : * sure that (A1), (A2)/(A3) and (A4) happen in the right memory
338 : * order. In GUP-fast pinning code, we have to make sure that (B3),(B4)
339 : * and (B5) happen in the right memory order.
340 : *
341 : * We assume that there might not be a memory barrier after
342 : * clearing/invalidating the PTE (A1) and before restoring the PTE (A4),
343 : * so we use explicit ones here.
344 : */
345 :
346 : /* Paired with the memory barrier in try_grab_folio(). */
347 : if (IS_ENABLED(CONFIG_HAVE_FAST_GUP))
348 : smp_mb();
349 :
350 0 : if (unlikely(page_maybe_dma_pinned(page)))
351 : return -EBUSY;
352 0 : ClearPageAnonExclusive(page);
353 :
354 : /*
355 : * This is conceptually a smp_wmb() paired with the smp_rmb() in
356 : * gup_must_unshare().
357 : */
358 : if (IS_ENABLED(CONFIG_HAVE_FAST_GUP))
359 : smp_mb__after_atomic();
360 : return 0;
361 : }
362 :
363 : /*
364 : * Called from mm/vmscan.c to handle paging out
365 : */
366 : int folio_referenced(struct folio *, int is_locked,
367 : struct mem_cgroup *memcg, unsigned long *vm_flags);
368 :
369 : void try_to_migrate(struct folio *folio, enum ttu_flags flags);
370 : void try_to_unmap(struct folio *, enum ttu_flags flags);
371 :
372 : int make_device_exclusive_range(struct mm_struct *mm, unsigned long start,
373 : unsigned long end, struct page **pages,
374 : void *arg);
375 :
376 : /* Avoid racy checks */
377 : #define PVMW_SYNC (1 << 0)
378 : /* Look for migration entries rather than present PTEs */
379 : #define PVMW_MIGRATION (1 << 1)
380 :
381 : struct page_vma_mapped_walk {
382 : unsigned long pfn;
383 : unsigned long nr_pages;
384 : pgoff_t pgoff;
385 : struct vm_area_struct *vma;
386 : unsigned long address;
387 : pmd_t *pmd;
388 : pte_t *pte;
389 : spinlock_t *ptl;
390 : unsigned int flags;
391 : };
392 :
393 : #define DEFINE_PAGE_VMA_WALK(name, _page, _vma, _address, _flags) \
394 : struct page_vma_mapped_walk name = { \
395 : .pfn = page_to_pfn(_page), \
396 : .nr_pages = compound_nr(_page), \
397 : .pgoff = page_to_pgoff(_page), \
398 : .vma = _vma, \
399 : .address = _address, \
400 : .flags = _flags, \
401 : }
402 :
403 : #define DEFINE_FOLIO_VMA_WALK(name, _folio, _vma, _address, _flags) \
404 : struct page_vma_mapped_walk name = { \
405 : .pfn = folio_pfn(_folio), \
406 : .nr_pages = folio_nr_pages(_folio), \
407 : .pgoff = folio_pgoff(_folio), \
408 : .vma = _vma, \
409 : .address = _address, \
410 : .flags = _flags, \
411 : }
412 :
413 : static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw)
414 : {
415 : /* HugeTLB pte is set to the relevant page table entry without pte_mapped. */
416 0 : if (pvmw->pte && !is_vm_hugetlb_page(pvmw->vma))
417 : pte_unmap(pvmw->pte);
418 0 : if (pvmw->ptl)
419 0 : spin_unlock(pvmw->ptl);
420 : }
421 :
422 : bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw);
423 :
424 : /*
425 : * Used by swapoff to help locate where page is expected in vma.
426 : */
427 : unsigned long page_address_in_vma(struct page *, struct vm_area_struct *);
428 :
429 : /*
430 : * Cleans the PTEs of shared mappings.
431 : * (and since clean PTEs should also be readonly, write protects them too)
432 : *
433 : * returns the number of cleaned PTEs.
434 : */
435 : int folio_mkclean(struct folio *);
436 :
437 : int pfn_mkclean_range(unsigned long pfn, unsigned long nr_pages, pgoff_t pgoff,
438 : struct vm_area_struct *vma);
439 :
440 : void remove_migration_ptes(struct folio *src, struct folio *dst, bool locked);
441 :
442 : int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);
443 :
444 : /*
445 : * rmap_walk_control: To control rmap traversing for specific needs
446 : *
447 : * arg: passed to rmap_one() and invalid_vma()
448 : * try_lock: bail out if the rmap lock is contended
449 : * contended: indicate the rmap traversal bailed out due to lock contention
450 : * rmap_one: executed on each vma where page is mapped
451 : * done: for checking traversing termination condition
452 : * anon_lock: for getting anon_lock by optimized way rather than default
453 : * invalid_vma: for skipping uninterested vma
454 : */
455 : struct rmap_walk_control {
456 : void *arg;
457 : bool try_lock;
458 : bool contended;
459 : /*
460 : * Return false if page table scanning in rmap_walk should be stopped.
461 : * Otherwise, return true.
462 : */
463 : bool (*rmap_one)(struct folio *folio, struct vm_area_struct *vma,
464 : unsigned long addr, void *arg);
465 : int (*done)(struct folio *folio);
466 : struct anon_vma *(*anon_lock)(struct folio *folio,
467 : struct rmap_walk_control *rwc);
468 : bool (*invalid_vma)(struct vm_area_struct *vma, void *arg);
469 : };
470 :
471 : void rmap_walk(struct folio *folio, struct rmap_walk_control *rwc);
472 : void rmap_walk_locked(struct folio *folio, struct rmap_walk_control *rwc);
473 : struct anon_vma *folio_lock_anon_vma_read(struct folio *folio,
474 : struct rmap_walk_control *rwc);
475 :
476 : #else /* !CONFIG_MMU */
477 :
478 : #define anon_vma_init() do {} while (0)
479 : #define anon_vma_prepare(vma) (0)
480 : #define anon_vma_link(vma) do {} while (0)
481 :
482 : static inline int folio_referenced(struct folio *folio, int is_locked,
483 : struct mem_cgroup *memcg,
484 : unsigned long *vm_flags)
485 : {
486 : *vm_flags = 0;
487 : return 0;
488 : }
489 :
490 : static inline void try_to_unmap(struct folio *folio, enum ttu_flags flags)
491 : {
492 : }
493 :
494 : static inline int folio_mkclean(struct folio *folio)
495 : {
496 : return 0;
497 : }
498 : #endif /* CONFIG_MMU */
499 :
500 : static inline int page_mkclean(struct page *page)
501 : {
502 0 : return folio_mkclean(page_folio(page));
503 : }
504 : #endif /* _LINUX_RMAP_H */
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