1	// SPDX-License-Identifier: GPL-2.0-only
2	#include <linux/kernel.h>
3	#include <linux/errno.h>
4	#include <linux/err.h>
5	#include <linux/spinlock.h>
6
7	#include <linux/mm.h>
8	#include <linux/memremap.h>
9	#include <linux/pagemap.h>
10	#include <linux/rmap.h>
11	#include <linux/swap.h>
12	#include <linux/swapops.h>
13	#include <linux/secretmem.h>
14
15	#include <linux/sched/signal.h>
16	#include <linux/rwsem.h>
17	#include <linux/hugetlb.h>
18	#include <linux/migrate.h>
19	#include <linux/mm_inline.h>
20	#include <linux/sched/mm.h>
21	#include <linux/shmem_fs.h>
22
23	#include <asm/mmu_context.h>
24	#include <asm/tlbflush.h>
25
26	#include "internal.h"
27
28	struct follow_page_context {
29	struct dev_pagemap *pgmap;
30	unsigned int page_mask;
31	};
32
33	static inline void sanity_check_pinned_pages(struct page **pages,
34	unsigned long npages)
35	{
36	if (!IS_ENABLED(CONFIG_DEBUG_VM))
37	return;
38
39	/*
40	* We only pin anonymous pages if they are exclusive. Once pinned, we
41	* can no longer turn them possibly shared and PageAnonExclusive() will
42	* stick around until the page is freed.
43	*
44	* We'd like to verify that our pinned anonymous pages are still mapped
45	* exclusively. The issue with anon THP is that we don't know how
46	* they are/were mapped when pinning them. However, for anon
47	* THP we can assume that either the given page (PTE-mapped THP) or
48	* the head page (PMD-mapped THP) should be PageAnonExclusive(). If
49	* neither is the case, there is certainly something wrong.
50	*/
51	for (; npages; npages--, pages++) {
52	struct page *page = *pages;
53	struct folio *folio = page_folio(page);
54
55	if (is_zero_page(page) ||
56	!folio_test_anon(folio))
57	continue;
58	if (!folio_test_large(folio) || folio_test_hugetlb(folio))
59	VM_BUG_ON_PAGE(!PageAnonExclusive(&folio->page), page);
60	else
61	/* Either a PTE-mapped or a PMD-mapped THP. */
62	VM_BUG_ON_PAGE(!PageAnonExclusive(&folio->page) &&
63	!PageAnonExclusive(page), page);
64	}
65	}
66
67	/*
68	* Return the folio with ref appropriately incremented,
69	* or NULL if that failed.
70	*/
71	static inline struct folio *try_get_folio(struct page *page, int refs)
72	{
73	struct folio *folio;
74
75	retry:
76	folio = page_folio(page);
77	if (WARN_ON_ONCE(folio_ref_count(folio) < 0))
78	return NULL;
79	if (unlikely(!folio_ref_try_add_rcu(folio, refs)))
80	return NULL;
81
82	/*
83	* At this point we have a stable reference to the folio; but it
84	* could be that between calling page_folio() and the refcount
85	* increment, the folio was split, in which case we'd end up
86	* holding a reference on a folio that has nothing to do with the page
87	* we were given anymore.
88	* So now that the folio is stable, recheck that the page still
89	* belongs to this folio.
90	*/
91	if (unlikely(page_folio(page) != folio)) {
92	if (!put_devmap_managed_page_refs(page: &folio->page, refs))
93	folio_put_refs(folio, refs);
94	goto retry;
95	}
96
97	return folio;
98	}
99
100	/**
101	* try_grab_folio() - Attempt to get or pin a folio.
102	* @page: pointer to page to be grabbed
103	* @refs: the value to (effectively) add to the folio's refcount
104	* @flags: gup flags: these are the FOLL_* flag values.
105	*
106	* "grab" names in this file mean, "look at flags to decide whether to use
107	* FOLL_PIN or FOLL_GET behavior, when incrementing the folio's refcount.
108	*
109	* Either FOLL_PIN or FOLL_GET (or neither) must be set, but not both at the
110	* same time. (That's true throughout the get_user_pages*() and
111	* pin_user_pages*() APIs.) Cases:
112	*
113	* FOLL_GET: folio's refcount will be incremented by @refs.
114	*
115	* FOLL_PIN on large folios: folio's refcount will be incremented by
116	* @refs, and its pincount will be incremented by @refs.
117	*
118	* FOLL_PIN on single-page folios: folio's refcount will be incremented by
119	* @refs * GUP_PIN_COUNTING_BIAS.
120	*
121	* Return: The folio containing @page (with refcount appropriately
122	* incremented) for success, or NULL upon failure. If neither FOLL_GET
123	* nor FOLL_PIN was set, that's considered failure, and furthermore,
124	* a likely bug in the caller, so a warning is also emitted.
125	*/
126	struct folio *try_grab_folio(struct page *page, int refs, unsigned int flags)
127	{
128	struct folio *folio;
129
130	if (WARN_ON_ONCE((flags & (FOLL_GET | FOLL_PIN)) == 0))
131	return NULL;
132
133	if (unlikely(!(flags & FOLL_PCI_P2PDMA) && is_pci_p2pdma_page(page)))
134	return NULL;
135
136	if (flags & FOLL_GET)
137	return try_get_folio(page, refs);
138
139	/* FOLL_PIN is set */
140
141	/*
142	* Don't take a pin on the zero page - it's not going anywhere
143	* and it is used in a *lot* of places.
144	*/
145	if (is_zero_page(page))
146	return page_folio(page);
147
148	folio = try_get_folio(page, refs);
149	if (!folio)
150	return NULL;
151
152	/*
153	* Can't do FOLL_LONGTERM + FOLL_PIN gup fast path if not in a
154	* right zone, so fail and let the caller fall back to the slow
155	* path.
156	*/
157	if (unlikely((flags & FOLL_LONGTERM) &&
158	!folio_is_longterm_pinnable(folio))) {
159	if (!put_devmap_managed_page_refs(page: &folio->page, refs))
160	folio_put_refs(folio, refs);
161	return NULL;
162	}
163
164	/*
165	* When pinning a large folio, use an exact count to track it.
166	*
167	* However, be sure to *also* increment the normal folio
168	* refcount field at least once, so that the folio really
169	* is pinned. That's why the refcount from the earlier
170	* try_get_folio() is left intact.
171	*/
172	if (folio_test_large(folio))
173	atomic_add(i: refs, v: &folio->_pincount);
174	else
175	folio_ref_add(folio,
176	nr: refs * (GUP_PIN_COUNTING_BIAS - 1));
177	/*
178	* Adjust the pincount before re-checking the PTE for changes.
179	* This is essentially a smp_mb() and is paired with a memory
180	* barrier in folio_try_share_anon_rmap_*().
181	*/
182	smp_mb__after_atomic();
183
184	node_stat_mod_folio(folio, item: NR_FOLL_PIN_ACQUIRED, nr: refs);
185
186	return folio;
187	}
188
189	static void gup_put_folio(struct folio *folio, int refs, unsigned int flags)
190	{
191	if (flags & FOLL_PIN) {
192	if (is_zero_folio(folio))
193	return;
194	node_stat_mod_folio(folio, item: NR_FOLL_PIN_RELEASED, nr: refs);
195	if (folio_test_large(folio))
196	atomic_sub(i: refs, v: &folio->_pincount);
197	else
198	refs *= GUP_PIN_COUNTING_BIAS;
199	}
200
201	if (!put_devmap_managed_page_refs(page: &folio->page, refs))
202	folio_put_refs(folio, refs);
203	}
204
205	/**
206	* try_grab_page() - elevate a page's refcount by a flag-dependent amount
207	* @page: pointer to page to be grabbed
208	* @flags: gup flags: these are the FOLL_* flag values.
209	*
210	* This might not do anything at all, depending on the flags argument.
211	*
212	* "grab" names in this file mean, "look at flags to decide whether to use
213	* FOLL_PIN or FOLL_GET behavior, when incrementing the page's refcount.
214	*
215	* Either FOLL_PIN or FOLL_GET (or neither) may be set, but not both at the same
216	* time. Cases: please see the try_grab_folio() documentation, with
217	* "refs=1".
218	*
219	* Return: 0 for success, or if no action was required (if neither FOLL_PIN
220	* nor FOLL_GET was set, nothing is done). A negative error code for failure:
221	*
222	* -ENOMEM FOLL_GET or FOLL_PIN was set, but the page could not
223	* be grabbed.
224	*/
225	int __must_check try_grab_page(struct page *page, unsigned int flags)
226	{
227	struct folio *folio = page_folio(page);
228
229	if (WARN_ON_ONCE(folio_ref_count(folio) <= 0))
230	return -ENOMEM;
231
232	if (unlikely(!(flags & FOLL_PCI_P2PDMA) && is_pci_p2pdma_page(page)))
233	return -EREMOTEIO;
234
235	if (flags & FOLL_GET)
236	folio_ref_inc(folio);
237	else if (flags & FOLL_PIN) {
238	/*
239	* Don't take a pin on the zero page - it's not going anywhere
240	* and it is used in a *lot* of places.
241	*/
242	if (is_zero_page(page))
243	return 0;
244
245	/*
246	* Similar to try_grab_folio(): be sure to *also*
247	* increment the normal page refcount field at least once,
248	* so that the page really is pinned.
249	*/
250	if (folio_test_large(folio)) {
251	folio_ref_add(folio, nr: 1);
252	atomic_add(i: 1, v: &folio->_pincount);
253	} else {
254	folio_ref_add(folio, GUP_PIN_COUNTING_BIAS);
255	}
256
257	node_stat_mod_folio(folio, item: NR_FOLL_PIN_ACQUIRED, nr: 1);
258	}
259
260	return 0;
261	}
262
263	/**
264	* unpin_user_page() - release a dma-pinned page
265	* @page: pointer to page to be released
266	*
267	* Pages that were pinned via pin_user_pages*() must be released via either
268	* unpin_user_page(), or one of the unpin_user_pages*() routines. This is so
269	* that such pages can be separately tracked and uniquely handled. In
270	* particular, interactions with RDMA and filesystems need special handling.
271	*/
272	void unpin_user_page(struct page *page)
273	{
274	sanity_check_pinned_pages(pages: &page, npages: 1);
275	gup_put_folio(page_folio(page), refs: 1, flags: FOLL_PIN);
276	}
277	EXPORT_SYMBOL(unpin_user_page);
278
279	/**
280	* folio_add_pin - Try to get an additional pin on a pinned folio
281	* @folio: The folio to be pinned
282	*
283	* Get an additional pin on a folio we already have a pin on. Makes no change
284	* if the folio is a zero_page.
285	*/
286	void folio_add_pin(struct folio *folio)
287	{
288	if (is_zero_folio(folio))
289	return;
290
291	/*
292	* Similar to try_grab_folio(): be sure to *also* increment the normal
293	* page refcount field at least once, so that the page really is
294	* pinned.
295	*/
296	if (folio_test_large(folio)) {
297	WARN_ON_ONCE(atomic_read(&folio->_pincount) < 1);
298	folio_ref_inc(folio);
299	atomic_inc(v: &folio->_pincount);
300	} else {
301	WARN_ON_ONCE(folio_ref_count(folio) < GUP_PIN_COUNTING_BIAS);
302	folio_ref_add(folio, GUP_PIN_COUNTING_BIAS);
303	}
304	}
305
306	static inline struct folio *gup_folio_range_next(struct page *start,
307	unsigned long npages, unsigned long i, unsigned int *ntails)
308	{
309	struct page *next = nth_page(start, i);
310	struct folio *folio = page_folio(next);
311	unsigned int nr = 1;
312
313	if (folio_test_large(folio))
314	nr = min_t(unsigned int, npages - i,
315	folio_nr_pages(folio) - folio_page_idx(folio, next));
316
317	*ntails = nr;
318	return folio;
319	}
320
321	static inline struct folio *gup_folio_next(struct page **list,
322	unsigned long npages, unsigned long i, unsigned int *ntails)
323	{
324	struct folio *folio = page_folio(list[i]);
325	unsigned int nr;
326
327	for (nr = i + 1; nr < npages; nr++) {
328	if (page_folio(list[nr]) != folio)
329	break;
330	}
331
332	*ntails = nr - i;
333	return folio;
334	}
335
336	/**
337	* unpin_user_pages_dirty_lock() - release and optionally dirty gup-pinned pages
338	* @pages: array of pages to be maybe marked dirty, and definitely released.
339	* @npages: number of pages in the @pages array.
340	* @make_dirty: whether to mark the pages dirty
341	*
342	* "gup-pinned page" refers to a page that has had one of the get_user_pages()
343	* variants called on that page.
344	*
345	* For each page in the @pages array, make that page (or its head page, if a
346	* compound page) dirty, if @make_dirty is true, and if the page was previously
347	* listed as clean. In any case, releases all pages using unpin_user_page(),
348	* possibly via unpin_user_pages(), for the non-dirty case.
349	*
350	* Please see the unpin_user_page() documentation for details.
351	*
352	* set_page_dirty_lock() is used internally. If instead, set_page_dirty() is
353	* required, then the caller should a) verify that this is really correct,
354	* because _lock() is usually required, and b) hand code it:
355	* set_page_dirty_lock(), unpin_user_page().
356	*
357	*/
358	void unpin_user_pages_dirty_lock(struct page **pages, unsigned long npages,
359	bool make_dirty)
360	{
361	unsigned long i;
362	struct folio *folio;
363	unsigned int nr;
364
365	if (!make_dirty) {
366	unpin_user_pages(pages, npages);
367	return;
368	}
369
370	sanity_check_pinned_pages(pages, npages);
371	for (i = 0; i < npages; i += nr) {
372	folio = gup_folio_next(list: pages, npages, i, ntails: &nr);
373	/*
374	* Checking PageDirty at this point may race with
375	* clear_page_dirty_for_io(), but that's OK. Two key
376	* cases:
377	*
378	* 1) This code sees the page as already dirty, so it
379	* skips the call to set_page_dirty(). That could happen
380	* because clear_page_dirty_for_io() called
381	* page_mkclean(), followed by set_page_dirty().
382	* However, now the page is going to get written back,
383	* which meets the original intention of setting it
384	* dirty, so all is well: clear_page_dirty_for_io() goes
385	* on to call TestClearPageDirty(), and write the page
386	* back.
387	*
388	* 2) This code sees the page as clean, so it calls
389	* set_page_dirty(). The page stays dirty, despite being
390	* written back, so it gets written back again in the
391	* next writeback cycle. This is harmless.
392	*/
393	if (!folio_test_dirty(folio)) {
394	folio_lock(folio);
395	folio_mark_dirty(folio);
396	folio_unlock(folio);
397	}
398	gup_put_folio(folio, refs: nr, flags: FOLL_PIN);
399	}
400	}
401	EXPORT_SYMBOL(unpin_user_pages_dirty_lock);
402
403	/**
404	* unpin_user_page_range_dirty_lock() - release and optionally dirty
405	* gup-pinned page range
406	*
407	* @page: the starting page of a range maybe marked dirty, and definitely released.
408	* @npages: number of consecutive pages to release.
409	* @make_dirty: whether to mark the pages dirty
410	*
411	* "gup-pinned page range" refers to a range of pages that has had one of the
412	* pin_user_pages() variants called on that page.
413	*
414	* For the page ranges defined by [page .. page+npages], make that range (or
415	* its head pages, if a compound page) dirty, if @make_dirty is true, and if the
416	* page range was previously listed as clean.
417	*
418	* set_page_dirty_lock() is used internally. If instead, set_page_dirty() is
419	* required, then the caller should a) verify that this is really correct,
420	* because _lock() is usually required, and b) hand code it:
421	* set_page_dirty_lock(), unpin_user_page().
422	*
423	*/
424	void unpin_user_page_range_dirty_lock(struct page *page, unsigned long npages,
425	bool make_dirty)
426	{
427	unsigned long i;
428	struct folio *folio;
429	unsigned int nr;
430
431	for (i = 0; i < npages; i += nr) {
432	folio = gup_folio_range_next(start: page, npages, i, ntails: &nr);
433	if (make_dirty && !folio_test_dirty(folio)) {
434	folio_lock(folio);
435	folio_mark_dirty(folio);
436	folio_unlock(folio);
437	}
438	gup_put_folio(folio, refs: nr, flags: FOLL_PIN);
439	}
440	}
441	EXPORT_SYMBOL(unpin_user_page_range_dirty_lock);
442
443	static void unpin_user_pages_lockless(struct page **pages, unsigned long npages)
444	{
445	unsigned long i;
446	struct folio *folio;
447	unsigned int nr;
448
449	/*
450	* Don't perform any sanity checks because we might have raced with
451	* fork() and some anonymous pages might now actually be shared --
452	* which is why we're unpinning after all.
453	*/
454	for (i = 0; i < npages; i += nr) {
455	folio = gup_folio_next(list: pages, npages, i, ntails: &nr);
456	gup_put_folio(folio, refs: nr, flags: FOLL_PIN);
457	}
458	}
459
460	/**
461	* unpin_user_pages() - release an array of gup-pinned pages.
462	* @pages: array of pages to be marked dirty and released.
463	* @npages: number of pages in the @pages array.
464	*
465	* For each page in the @pages array, release the page using unpin_user_page().
466	*
467	* Please see the unpin_user_page() documentation for details.
468	*/
469	void unpin_user_pages(struct page **pages, unsigned long npages)
470	{
471	unsigned long i;
472	struct folio *folio;
473	unsigned int nr;
474
475	/*
476	* If this WARN_ON() fires, then the system *might* be leaking pages (by
477	* leaving them pinned), but probably not. More likely, gup/pup returned
478	* a hard -ERRNO error to the caller, who erroneously passed it here.
479	*/
480	if (WARN_ON(IS_ERR_VALUE(npages)))
481	return;
482
483	sanity_check_pinned_pages(pages, npages);
484	for (i = 0; i < npages; i += nr) {
485	folio = gup_folio_next(list: pages, npages, i, ntails: &nr);
486	gup_put_folio(folio, refs: nr, flags: FOLL_PIN);
487	}
488	}
489	EXPORT_SYMBOL(unpin_user_pages);
490
491	/*
492	* Set the MMF_HAS_PINNED if not set yet; after set it'll be there for the mm's
493	* lifecycle. Avoid setting the bit unless necessary, or it might cause write
494	* cache bouncing on large SMP machines for concurrent pinned gups.
495	*/
496	static inline void mm_set_has_pinned_flag(unsigned long *mm_flags)
497	{
498	if (!test_bit(MMF_HAS_PINNED, mm_flags))
499	set_bit(MMF_HAS_PINNED, addr: mm_flags);
500	}
501
502	#ifdef CONFIG_MMU
503	static struct page *no_page_table(struct vm_area_struct *vma,
504	unsigned int flags)
505	{
506	/*
507	* When core dumping an enormous anonymous area that nobody
508	* has touched so far, we don't want to allocate unnecessary pages or
509	* page tables. Return error instead of NULL to skip handle_mm_fault,
510	* then get_dump_page() will return NULL to leave a hole in the dump.
511	* But we can only make this optimization where a hole would surely
512	* be zero-filled if handle_mm_fault() actually did handle it.
513	*/
514	if ((flags & FOLL_DUMP) &&
515	(vma_is_anonymous(vma) || !vma->vm_ops->fault))
516	return ERR_PTR(error: -EFAULT);
517	return NULL;
518	}
519
520	static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address,
521	pte_t *pte, unsigned int flags)
522	{
523	if (flags & FOLL_TOUCH) {
524	pte_t orig_entry = ptep_get(ptep: pte);
525	pte_t entry = orig_entry;
526
527	if (flags & FOLL_WRITE)
528	entry = pte_mkdirty(pte: entry);
529	entry = pte_mkyoung(pte: entry);
530
531	if (!pte_same(a: orig_entry, b: entry)) {
532	set_pte_at(vma->vm_mm, address, pte, entry);
533	update_mmu_cache(vma, addr: address, ptep: pte);
534	}
535	}
536
537	/* Proper page table entry exists, but no corresponding struct page */
538	return -EEXIST;
539	}
540
541	/* FOLL_FORCE can write to even unwritable PTEs in COW mappings. */
542	static inline bool can_follow_write_pte(pte_t pte, struct page *page,
543	struct vm_area_struct *vma,
544	unsigned int flags)
545	{
546	/* If the pte is writable, we can write to the page. */
547	if (pte_write(pte))
548	return true;
549
550	/* Maybe FOLL_FORCE is set to override it? */
551	if (!(flags & FOLL_FORCE))
552	return false;
553
554	/* But FOLL_FORCE has no effect on shared mappings */
555	if (vma->vm_flags & (VM_MAYSHARE | VM_SHARED))
556	return false;
557
558	/* ... or read-only private ones */
559	if (!(vma->vm_flags & VM_MAYWRITE))
560	return false;
561
562	/* ... or already writable ones that just need to take a write fault */
563	if (vma->vm_flags & VM_WRITE)
564	return false;
565
566	/*
567	* See can_change_pte_writable(): we broke COW and could map the page
568	* writable if we have an exclusive anonymous page ...
569	*/
570	if (!page || !PageAnon(page) || !PageAnonExclusive(page))
571	return false;
572
573	/* ... and a write-fault isn't required for other reasons. */
574	if (vma_soft_dirty_enabled(vma) && !pte_soft_dirty(pte))
575	return false;
576	return !userfaultfd_pte_wp(vma, pte);
577	}
578
579	static struct page *follow_page_pte(struct vm_area_struct *vma,
580	unsigned long address, pmd_t *pmd, unsigned int flags,
581	struct dev_pagemap **pgmap)
582	{
583	struct mm_struct *mm = vma->vm_mm;
584	struct page *page;
585	spinlock_t *ptl;
586	pte_t *ptep, pte;
587	int ret;
588
589	/* FOLL_GET and FOLL_PIN are mutually exclusive. */
590	if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) ==
591	(FOLL_PIN | FOLL_GET)))
592	return ERR_PTR(error: -EINVAL);
593
594	ptep = pte_offset_map_lock(mm, pmd, addr: address, ptlp: &ptl);
595	if (!ptep)
596	return no_page_table(vma, flags);
597	pte = ptep_get(ptep);
598	if (!pte_present(a: pte))
599	goto no_page;
600	if (pte_protnone(pte) && !gup_can_follow_protnone(vma, flags))
601	goto no_page;
602
603	page = vm_normal_page(vma, addr: address, pte);
604
605	/*
606	* We only care about anon pages in can_follow_write_pte() and don't
607	* have to worry about pte_devmap() because they are never anon.
608	*/
609	if ((flags & FOLL_WRITE) &&
610	!can_follow_write_pte(pte, page, vma, flags)) {
611	page = NULL;
612	goto out;
613	}
614
615	if (!page && pte_devmap(a: pte) && (flags & (FOLL_GET | FOLL_PIN))) {
616	/*
617	* Only return device mapping pages in the FOLL_GET or FOLL_PIN
618	* case since they are only valid while holding the pgmap
619	* reference.
620	*/
621	*pgmap = get_dev_pagemap(pfn: pte_pfn(pte), pgmap: *pgmap);
622	if (*pgmap)
623	page = pte_page(pte);
624	else
625	goto no_page;
626	} else if (unlikely(!page)) {
627	if (flags & FOLL_DUMP) {
628	/* Avoid special (like zero) pages in core dumps */
629	page = ERR_PTR(error: -EFAULT);
630	goto out;
631	}
632
633	if (is_zero_pfn(pfn: pte_pfn(pte))) {
634	page = pte_page(pte);
635	} else {
636	ret = follow_pfn_pte(vma, address, pte: ptep, flags);
637	page = ERR_PTR(error: ret);
638	goto out;
639	}
640	}
641
642	if (!pte_write(pte) && gup_must_unshare(vma, flags, page)) {
643	page = ERR_PTR(error: -EMLINK);
644	goto out;
645	}
646
647	VM_BUG_ON_PAGE((flags & FOLL_PIN) && PageAnon(page) &&
648	!PageAnonExclusive(page), page);
649
650	/* try_grab_page() does nothing unless FOLL_GET or FOLL_PIN is set. */
651	ret = try_grab_page(page, flags);
652	if (unlikely(ret)) {
653	page = ERR_PTR(error: ret);
654	goto out;
655	}
656
657	/*
658	* We need to make the page accessible if and only if we are going
659	* to access its content (the FOLL_PIN case). Please see
660	* Documentation/core-api/pin_user_pages.rst for details.
661	*/
662	if (flags & FOLL_PIN) {
663	ret = arch_make_page_accessible(page);
664	if (ret) {
665	unpin_user_page(page);
666	page = ERR_PTR(error: ret);
667	goto out;
668	}
669	}
670	if (flags & FOLL_TOUCH) {
671	if ((flags & FOLL_WRITE) &&
672	!pte_dirty(pte) && !PageDirty(page))
673	set_page_dirty(page);
674	/*
675	* pte_mkyoung() would be more correct here, but atomic care
676	* is needed to avoid losing the dirty bit: it is easier to use
677	* mark_page_accessed().
678	*/
679	mark_page_accessed(page);
680	}
681	out:
682	pte_unmap_unlock(ptep, ptl);
683	return page;
684	no_page:
685	pte_unmap_unlock(ptep, ptl);
686	if (!pte_none(pte))
687	return NULL;
688	return no_page_table(vma, flags);
689	}
690
691	static struct page *follow_pmd_mask(struct vm_area_struct *vma,
692	unsigned long address, pud_t *pudp,
693	unsigned int flags,
694	struct follow_page_context *ctx)
695	{
696	pmd_t *pmd, pmdval;
697	spinlock_t *ptl;
698	struct page *page;
699	struct mm_struct *mm = vma->vm_mm;
700
701	pmd = pmd_offset(pud: pudp, address);
702	pmdval = pmdp_get_lockless(pmdp: pmd);
703	if (pmd_none(pmd: pmdval))
704	return no_page_table(vma, flags);
705	if (!pmd_present(pmd: pmdval))
706	return no_page_table(vma, flags);
707	if (pmd_devmap(pmd: pmdval)) {
708	ptl = pmd_lock(mm, pmd);
709	page = follow_devmap_pmd(vma, addr: address, pmd, flags, pgmap: &ctx->pgmap);
710	spin_unlock(lock: ptl);
711	if (page)
712	return page;
713	return no_page_table(vma, flags);
714	}
715	if (likely(!pmd_trans_huge(pmdval)))
716	return follow_page_pte(vma, address, pmd, flags, pgmap: &ctx->pgmap);
717
718	if (pmd_protnone(pmd: pmdval) && !gup_can_follow_protnone(vma, flags))
719	return no_page_table(vma, flags);
720
721	ptl = pmd_lock(mm, pmd);
722	if (unlikely(!pmd_present(*pmd))) {
723	spin_unlock(lock: ptl);
724	return no_page_table(vma, flags);
725	}
726	if (unlikely(!pmd_trans_huge(*pmd))) {
727	spin_unlock(lock: ptl);
728	return follow_page_pte(vma, address, pmd, flags, pgmap: &ctx->pgmap);
729	}
730	if (flags & FOLL_SPLIT_PMD) {
731	spin_unlock(lock: ptl);
732	split_huge_pmd(vma, pmd, address);
733	/* If pmd was left empty, stuff a page table in there quickly */
734	return pte_alloc(mm, pmd) ? ERR_PTR(error: -ENOMEM) :
735	follow_page_pte(vma, address, pmd, flags, pgmap: &ctx->pgmap);
736	}
737	page = follow_trans_huge_pmd(vma, addr: address, pmd, flags);
738	spin_unlock(lock: ptl);
739	ctx->page_mask = HPAGE_PMD_NR - 1;
740	return page;
741	}
742
743	static struct page *follow_pud_mask(struct vm_area_struct *vma,
744	unsigned long address, p4d_t *p4dp,
745	unsigned int flags,
746	struct follow_page_context *ctx)
747	{
748	pud_t *pud;
749	spinlock_t *ptl;
750	struct page *page;
751	struct mm_struct *mm = vma->vm_mm;
752
753	pud = pud_offset(p4d: p4dp, address);
754	if (pud_none(pud: *pud))
755	return no_page_table(vma, flags);
756	if (pud_devmap(pud: *pud)) {
757	ptl = pud_lock(mm, pud);
758	page = follow_devmap_pud(vma, addr: address, pud, flags, pgmap: &ctx->pgmap);
759	spin_unlock(lock: ptl);
760	if (page)
761	return page;
762	return no_page_table(vma, flags);
763	}
764	if (unlikely(pud_bad(*pud)))
765	return no_page_table(vma, flags);
766
767	return follow_pmd_mask(vma, address, pudp: pud, flags, ctx);
768	}
769
770	static struct page *follow_p4d_mask(struct vm_area_struct *vma,
771	unsigned long address, pgd_t *pgdp,
772	unsigned int flags,
773	struct follow_page_context *ctx)
774	{
775	p4d_t *p4d;
776
777	p4d = p4d_offset(pgd: pgdp, address);
778	if (p4d_none(p4d: *p4d))
779	return no_page_table(vma, flags);
780	BUILD_BUG_ON(p4d_huge(*p4d));
781	if (unlikely(p4d_bad(*p4d)))
782	return no_page_table(vma, flags);
783
784	return follow_pud_mask(vma, address, p4dp: p4d, flags, ctx);
785	}
786
787	/**
788	* follow_page_mask - look up a page descriptor from a user-virtual address
789	* @vma: vm_area_struct mapping @address
790	* @address: virtual address to look up
791	* @flags: flags modifying lookup behaviour
792	* @ctx: contains dev_pagemap for %ZONE_DEVICE memory pinning and a
793	* pointer to output page_mask
794	*
795	* @flags can have FOLL_ flags set, defined in <linux/mm.h>
796	*
797	* When getting pages from ZONE_DEVICE memory, the @ctx->pgmap caches
798	* the device's dev_pagemap metadata to avoid repeating expensive lookups.
799	*
800	* When getting an anonymous page and the caller has to trigger unsharing
801	* of a shared anonymous page first, -EMLINK is returned. The caller should
802	* trigger a fault with FAULT_FLAG_UNSHARE set. Note that unsharing is only
803	* relevant with FOLL_PIN and !FOLL_WRITE.
804	*
805	* On output, the @ctx->page_mask is set according to the size of the page.
806	*
807	* Return: the mapped (struct page *), %NULL if no mapping exists, or
808	* an error pointer if there is a mapping to something not represented
809	* by a page descriptor (see also vm_normal_page()).
810	*/
811	static struct page *follow_page_mask(struct vm_area_struct *vma,
812	unsigned long address, unsigned int flags,
813	struct follow_page_context *ctx)
814	{
815	pgd_t *pgd;
816	struct mm_struct *mm = vma->vm_mm;
817
818	ctx->page_mask = 0;
819
820	/*
821	* Call hugetlb_follow_page_mask for hugetlb vmas as it will use
822	* special hugetlb page table walking code. This eliminates the
823	* need to check for hugetlb entries in the general walking code.
824	*/
825	if (is_vm_hugetlb_page(vma))
826	return hugetlb_follow_page_mask(vma, address, flags,
827	page_mask: &ctx->page_mask);
828
829	pgd = pgd_offset(mm, address);
830
831	if (pgd_none(pgd: *pgd) || unlikely(pgd_bad(*pgd)))
832	return no_page_table(vma, flags);
833
834	return follow_p4d_mask(vma, address, pgdp: pgd, flags, ctx);
835	}
836
837	struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
838	unsigned int foll_flags)
839	{
840	struct follow_page_context ctx = { NULL };
841	struct page *page;
842
843	if (vma_is_secretmem(vma))
844	return NULL;
845
846	if (WARN_ON_ONCE(foll_flags & FOLL_PIN))
847	return NULL;
848
849	/*
850	* We never set FOLL_HONOR_NUMA_FAULT because callers don't expect
851	* to fail on PROT_NONE-mapped pages.
852	*/
853	page = follow_page_mask(vma, address, flags: foll_flags, ctx: &ctx);
854	if (ctx.pgmap)
855	put_dev_pagemap(pgmap: ctx.pgmap);
856	return page;
857	}
858
859	static int get_gate_page(struct mm_struct *mm, unsigned long address,
860	unsigned int gup_flags, struct vm_area_struct **vma,
861	struct page **page)
862	{
863	pgd_t *pgd;
864	p4d_t *p4d;
865	pud_t *pud;
866	pmd_t *pmd;
867	pte_t *pte;
868	pte_t entry;
869	int ret = -EFAULT;
870
871	/* user gate pages are read-only */
872	if (gup_flags & FOLL_WRITE)
873	return -EFAULT;
874	if (address > TASK_SIZE)
875	pgd = pgd_offset_k(address);
876	else
877	pgd = pgd_offset_gate(mm, address);
878	if (pgd_none(pgd: *pgd))
879	return -EFAULT;
880	p4d = p4d_offset(pgd, address);
881	if (p4d_none(p4d: *p4d))
882	return -EFAULT;
883	pud = pud_offset(p4d, address);
884	if (pud_none(pud: *pud))
885	return -EFAULT;
886	pmd = pmd_offset(pud, address);
887	if (!pmd_present(pmd: *pmd))
888	return -EFAULT;
889	pte = pte_offset_map(pmd, addr: address);
890	if (!pte)
891	return -EFAULT;
892	entry = ptep_get(ptep: pte);
893	if (pte_none(pte: entry))
894	goto unmap;
895	*vma = get_gate_vma(mm);
896	if (!page)
897	goto out;
898	*page = vm_normal_page(vma: *vma, addr: address, pte: entry);
899	if (!*page) {
900	if ((gup_flags & FOLL_DUMP) || !is_zero_pfn(pfn: pte_pfn(pte: entry)))
901	goto unmap;
902	*page = pte_page(entry);
903	}
904	ret = try_grab_page(page: *page, flags: gup_flags);
905	if (unlikely(ret))
906	goto unmap;
907	out:
908	ret = 0;
909	unmap:
910	pte_unmap(pte);
911	return ret;
912	}
913
914	/*
915	* mmap_lock must be held on entry. If @flags has FOLL_UNLOCKABLE but not
916	* FOLL_NOWAIT, the mmap_lock may be released. If it is, *@locked will be set
917	* to 0 and -EBUSY returned.
918	*/
919	static int faultin_page(struct vm_area_struct *vma,
920	unsigned long address, unsigned int *flags, bool unshare,
921	int *locked)
922	{
923	unsigned int fault_flags = 0;
924	vm_fault_t ret;
925
926	if (*flags & FOLL_NOFAULT)
927	return -EFAULT;
928	if (*flags & FOLL_WRITE)
929	fault_flags |= FAULT_FLAG_WRITE;
930	if (*flags & FOLL_REMOTE)
931	fault_flags |= FAULT_FLAG_REMOTE;
932	if (*flags & FOLL_UNLOCKABLE) {
933	fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
934	/*
935	* FAULT_FLAG_INTERRUPTIBLE is opt-in. GUP callers must set
936	* FOLL_INTERRUPTIBLE to enable FAULT_FLAG_INTERRUPTIBLE.
937	* That's because some callers may not be prepared to
938	* handle early exits caused by non-fatal signals.
939	*/
940	if (*flags & FOLL_INTERRUPTIBLE)
941	fault_flags |= FAULT_FLAG_INTERRUPTIBLE;
942	}
943	if (*flags & FOLL_NOWAIT)
944	fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT;
945	if (*flags & FOLL_TRIED) {
946	/*
947	* Note: FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_TRIED
948	* can co-exist
949	*/
950	fault_flags |= FAULT_FLAG_TRIED;
951	}
952	if (unshare) {
953	fault_flags |= FAULT_FLAG_UNSHARE;
954	/* FAULT_FLAG_WRITE and FAULT_FLAG_UNSHARE are incompatible */
955	VM_BUG_ON(fault_flags & FAULT_FLAG_WRITE);
956	}
957
958	ret = handle_mm_fault(vma, address, flags: fault_flags, NULL);
959
960	if (ret & VM_FAULT_COMPLETED) {
961	/*
962	* With FAULT_FLAG_RETRY_NOWAIT we'll never release the
963	* mmap lock in the page fault handler. Sanity check this.
964	*/
965	WARN_ON_ONCE(fault_flags & FAULT_FLAG_RETRY_NOWAIT);
966	*locked = 0;
967
968	/*
969	* We should do the same as VM_FAULT_RETRY, but let's not
970	* return -EBUSY since that's not reflecting the reality of
971	* what has happened - we've just fully completed a page
972	* fault, with the mmap lock released. Use -EAGAIN to show
973	* that we want to take the mmap lock _again_.
974	*/
975	return -EAGAIN;
976	}
977
978	if (ret & VM_FAULT_ERROR) {
979	int err = vm_fault_to_errno(vm_fault: ret, foll_flags: *flags);
980
981	if (err)
982	return err;
983	BUG();
984	}
985
986	if (ret & VM_FAULT_RETRY) {
987	if (!(fault_flags & FAULT_FLAG_RETRY_NOWAIT))
988	*locked = 0;
989	return -EBUSY;
990	}
991
992	return 0;
993	}
994
995	/*
996	* Writing to file-backed mappings which require folio dirty tracking using GUP
997	* is a fundamentally broken operation, as kernel write access to GUP mappings
998	* do not adhere to the semantics expected by a file system.
999	*
1000	* Consider the following scenario:-
1001	*
1002	* 1. A folio is written to via GUP which write-faults the memory, notifying
1003	* the file system and dirtying the folio.
1004	* 2. Later, writeback is triggered, resulting in the folio being cleaned and
1005	* the PTE being marked read-only.
1006	* 3. The GUP caller writes to the folio, as it is mapped read/write via the
1007	* direct mapping.
1008	* 4. The GUP caller, now done with the page, unpins it and sets it dirty
1009	* (though it does not have to).
1010	*
1011	* This results in both data being written to a folio without writenotify, and
1012	* the folio being dirtied unexpectedly (if the caller decides to do so).
1013	*/
1014	static bool writable_file_mapping_allowed(struct vm_area_struct *vma,
1015	unsigned long gup_flags)
1016	{
1017	/*
1018	* If we aren't pinning then no problematic write can occur. A long term
1019	* pin is the most egregious case so this is the case we disallow.
1020	*/
1021	if ((gup_flags & (FOLL_PIN | FOLL_LONGTERM)) !=
1022	(FOLL_PIN | FOLL_LONGTERM))
1023	return true;
1024
1025	/*
1026	* If the VMA does not require dirty tracking then no problematic write
1027	* can occur either.
1028	*/
1029	return !vma_needs_dirty_tracking(vma);
1030	}
1031
1032	static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)
1033	{
1034	vm_flags_t vm_flags = vma->vm_flags;
1035	int write = (gup_flags & FOLL_WRITE);
1036	int foreign = (gup_flags & FOLL_REMOTE);
1037	bool vma_anon = vma_is_anonymous(vma);
1038
1039	if (vm_flags & (VM_IO | VM_PFNMAP))
1040	return -EFAULT;
1041
1042	if ((gup_flags & FOLL_ANON) && !vma_anon)
1043	return -EFAULT;
1044
1045	if ((gup_flags & FOLL_LONGTERM) && vma_is_fsdax(vma))
1046	return -EOPNOTSUPP;
1047
1048	if (vma_is_secretmem(vma))
1049	return -EFAULT;
1050
1051	if (write) {
1052	if (!vma_anon &&
1053	!writable_file_mapping_allowed(vma, gup_flags))
1054	return -EFAULT;
1055
1056	if (!(vm_flags & VM_WRITE) || (vm_flags & VM_SHADOW_STACK)) {
1057	if (!(gup_flags & FOLL_FORCE))
1058	return -EFAULT;
1059	/* hugetlb does not support FOLL_FORCE|FOLL_WRITE. */
1060	if (is_vm_hugetlb_page(vma))
1061	return -EFAULT;
1062	/*
1063	* We used to let the write,force case do COW in a
1064	* VM_MAYWRITE VM_SHARED !VM_WRITE vma, so ptrace could
1065	* set a breakpoint in a read-only mapping of an
1066	* executable, without corrupting the file (yet only
1067	* when that file had been opened for writing!).
1068	* Anon pages in shared mappings are surprising: now
1069	* just reject it.
1070	*/
1071	if (!is_cow_mapping(flags: vm_flags))
1072	return -EFAULT;
1073	}
1074	} else if (!(vm_flags & VM_READ)) {
1075	if (!(gup_flags & FOLL_FORCE))
1076	return -EFAULT;
1077	/*
1078	* Is there actually any vma we can reach here which does not
1079	* have VM_MAYREAD set?
1080	*/
1081	if (!(vm_flags & VM_MAYREAD))
1082	return -EFAULT;
1083	}
1084	/*
1085	* gups are always data accesses, not instruction
1086	* fetches, so execute=false here
1087	*/
1088	if (!arch_vma_access_permitted(vma, write, execute: false, foreign))
1089	return -EFAULT;
1090	return 0;
1091	}
1092
1093	/*
1094	* This is "vma_lookup()", but with a warning if we would have
1095	* historically expanded the stack in the GUP code.
1096	*/
1097	static struct vm_area_struct *gup_vma_lookup(struct mm_struct *mm,
1098	unsigned long addr)
1099	{
1100	#ifdef CONFIG_STACK_GROWSUP
1101	return vma_lookup(mm, addr);
1102	#else
1103	static volatile unsigned long next_warn;
1104	struct vm_area_struct *vma;
1105	unsigned long now, next;
1106
1107	vma = find_vma(mm, addr);
1108	if (!vma || (addr >= vma->vm_start))
1109	return vma;
1110
1111	/* Only warn for half-way relevant accesses */
1112	if (!(vma->vm_flags & VM_GROWSDOWN))
1113	return NULL;
1114	if (vma->vm_start - addr > 65536)
1115	return NULL;
1116
1117	/* Let's not warn more than once an hour.. */
1118	now = jiffies; next = next_warn;
1119	if (next && time_before(now, next))
1120	return NULL;
1121	next_warn = now + 60*60*HZ;
1122
1123	/* Let people know things may have changed. */
1124	pr_warn("GUP no longer grows the stack in %s (%d): %lx-%lx (%lx)\n",
1125	current->comm, task_pid_nr(current),
1126	vma->vm_start, vma->vm_end, addr);
1127	dump_stack();
1128	return NULL;
1129	#endif
1130	}
1131
1132	/**
1133	* __get_user_pages() - pin user pages in memory
1134	* @mm: mm_struct of target mm
1135	* @start: starting user address
1136	* @nr_pages: number of pages from start to pin
1137	* @gup_flags: flags modifying pin behaviour
1138	* @pages: array that receives pointers to the pages pinned.
1139	* Should be at least nr_pages long. Or NULL, if caller
1140	* only intends to ensure the pages are faulted in.
1141	* @locked: whether we're still with the mmap_lock held
1142	*
1143	* Returns either number of pages pinned (which may be less than the
1144	* number requested), or an error. Details about the return value:
1145	*
1146	* -- If nr_pages is 0, returns 0.
1147	* -- If nr_pages is >0, but no pages were pinned, returns -errno.
1148	* -- If nr_pages is >0, and some pages were pinned, returns the number of
1149	* pages pinned. Again, this may be less than nr_pages.
1150	* -- 0 return value is possible when the fault would need to be retried.
1151	*
1152	* The caller is responsible for releasing returned @pages, via put_page().
1153	*
1154	* Must be called with mmap_lock held. It may be released. See below.
1155	*
1156	* __get_user_pages walks a process's page tables and takes a reference to
1157	* each struct page that each user address corresponds to at a given
1158	* instant. That is, it takes the page that would be accessed if a user
1159	* thread accesses the given user virtual address at that instant.
1160	*
1161	* This does not guarantee that the page exists in the user mappings when
1162	* __get_user_pages returns, and there may even be a completely different
1163	* page there in some cases (eg. if mmapped pagecache has been invalidated
1164	* and subsequently re-faulted). However it does guarantee that the page
1165	* won't be freed completely. And mostly callers simply care that the page
1166	* contains data that was valid *at some point in time*. Typically, an IO
1167	* or similar operation cannot guarantee anything stronger anyway because
1168	* locks can't be held over the syscall boundary.
1169	*
1170	* If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If
1171	* the page is written to, set_page_dirty (or set_page_dirty_lock, as
1172	* appropriate) must be called after the page is finished with, and
1173	* before put_page is called.
1174	*
1175	* If FOLL_UNLOCKABLE is set without FOLL_NOWAIT then the mmap_lock may
1176	* be released. If this happens *@locked will be set to 0 on return.
1177	*
1178	* A caller using such a combination of @gup_flags must therefore hold the
1179	* mmap_lock for reading only, and recognize when it's been released. Otherwise,
1180	* it must be held for either reading or writing and will not be released.
1181	*
1182	* In most cases, get_user_pages or get_user_pages_fast should be used
1183	* instead of __get_user_pages. __get_user_pages should be used only if
1184	* you need some special @gup_flags.
1185	*/
1186	static long __get_user_pages(struct mm_struct *mm,
1187	unsigned long start, unsigned long nr_pages,
1188	unsigned int gup_flags, struct page **pages,
1189	int *locked)
1190	{
1191	long ret = 0, i = 0;
1192	struct vm_area_struct *vma = NULL;
1193	struct follow_page_context ctx = { NULL };
1194
1195	if (!nr_pages)
1196	return 0;
1197
1198	start = untagged_addr_remote(mm, start);
1199
1200	VM_BUG_ON(!!pages != !!(gup_flags & (FOLL_GET | FOLL_PIN)));
1201
1202	do {
1203	struct page *page;
1204	unsigned int foll_flags = gup_flags;
1205	unsigned int page_increm;
1206
1207	/* first iteration or cross vma bound */
1208	if (!vma || start >= vma->vm_end) {
1209	/*
1210	* MADV_POPULATE_(READ|WRITE) wants to handle VMA
1211	* lookups+error reporting differently.
1212	*/
1213	if (gup_flags & FOLL_MADV_POPULATE) {
1214	vma = vma_lookup(mm, addr: start);
1215	if (!vma) {
1216	ret = -ENOMEM;
1217	goto out;
1218	}
1219	if (check_vma_flags(vma, gup_flags)) {
1220	ret = -EINVAL;
1221	goto out;
1222	}
1223	goto retry;
1224	}
1225	vma = gup_vma_lookup(mm, addr: start);
1226	if (!vma && in_gate_area(mm, addr: start)) {
1227	ret = get_gate_page(mm, address: start & PAGE_MASK,
1228	gup_flags, vma: &vma,
1229	page: pages ? &page : NULL);
1230	if (ret)
1231	goto out;
1232	ctx.page_mask = 0;
1233	goto next_page;
1234	}
1235
1236	if (!vma) {
1237	ret = -EFAULT;
1238	goto out;
1239	}
1240	ret = check_vma_flags(vma, gup_flags);
1241	if (ret)
1242	goto out;
1243	}
1244	retry:
1245	/*
1246	* If we have a pending SIGKILL, don't keep faulting pages and
1247	* potentially allocating memory.
1248	*/
1249	if (fatal_signal_pending(current)) {
1250	ret = -EINTR;
1251	goto out;
1252	}
1253	cond_resched();
1254
1255	page = follow_page_mask(vma, address: start, flags: foll_flags, ctx: &ctx);
1256	if (!page || PTR_ERR(ptr: page) == -EMLINK) {
1257	ret = faultin_page(vma, address: start, flags: &foll_flags,
1258	unshare: PTR_ERR(ptr: page) == -EMLINK, locked);
1259	switch (ret) {
1260	case 0:
1261	goto retry;
1262	case -EBUSY:
1263	case -EAGAIN:
1264	ret = 0;
1265	fallthrough;
1266	case -EFAULT:
1267	case -ENOMEM:
1268	case -EHWPOISON:
1269	goto out;
1270	}
1271	BUG();
1272	} else if (PTR_ERR(ptr: page) == -EEXIST) {
1273	/*
1274	* Proper page table entry exists, but no corresponding
1275	* struct page. If the caller expects **pages to be
1276	* filled in, bail out now, because that can't be done
1277	* for this page.
1278	*/
1279	if (pages) {
1280	ret = PTR_ERR(ptr: page);
1281	goto out;
1282	}
1283	} else if (IS_ERR(ptr: page)) {
1284	ret = PTR_ERR(ptr: page);
1285	goto out;
1286	}
1287	next_page:
1288	page_increm = 1 + (~(start >> PAGE_SHIFT) & ctx.page_mask);
1289	if (page_increm > nr_pages)
1290	page_increm = nr_pages;
1291
1292	if (pages) {
1293	struct page *subpage;
1294	unsigned int j;
1295
1296	/*
1297	* This must be a large folio (and doesn't need to
1298	* be the whole folio; it can be part of it), do
1299	* the refcount work for all the subpages too.
1300	*
1301	* NOTE: here the page may not be the head page
1302	* e.g. when start addr is not thp-size aligned.
1303	* try_grab_folio() should have taken care of tail
1304	* pages.
1305	*/
1306	if (page_increm > 1) {
1307	struct folio *folio;
1308
1309	/*
1310	* Since we already hold refcount on the
1311	* large folio, this should never fail.
1312	*/
1313	folio = try_grab_folio(page, refs: page_increm - 1,
1314	flags: foll_flags);
1315	if (WARN_ON_ONCE(!folio)) {
1316	/*
1317	* Release the 1st page ref if the
1318	* folio is problematic, fail hard.
1319	*/
1320	gup_put_folio(page_folio(page), refs: 1,
1321	flags: foll_flags);
1322	ret = -EFAULT;
1323	goto out;
1324	}
1325	}
1326
1327	for (j = 0; j < page_increm; j++) {
1328	subpage = nth_page(page, j);
1329	pages[i + j] = subpage;
1330	flush_anon_page(vma, page: subpage, vmaddr: start + j * PAGE_SIZE);
1331	flush_dcache_page(page: subpage);
1332	}
1333	}
1334
1335	i += page_increm;
1336	start += page_increm * PAGE_SIZE;
1337	nr_pages -= page_increm;
1338	} while (nr_pages);
1339	out:
1340	if (ctx.pgmap)
1341	put_dev_pagemap(pgmap: ctx.pgmap);
1342	return i ? i : ret;
1343	}
1344
1345	static bool vma_permits_fault(struct vm_area_struct *vma,
1346	unsigned int fault_flags)
1347	{
1348	bool write = !!(fault_flags & FAULT_FLAG_WRITE);
1349	bool foreign = !!(fault_flags & FAULT_FLAG_REMOTE);
1350	vm_flags_t vm_flags = write ? VM_WRITE : VM_READ;
1351
1352	if (!(vm_flags & vma->vm_flags))
1353	return false;
1354
1355	/*
1356	* The architecture might have a hardware protection
1357	* mechanism other than read/write that can deny access.
1358	*
1359	* gup always represents data access, not instruction
1360	* fetches, so execute=false here:
1361	*/
1362	if (!arch_vma_access_permitted(vma, write, execute: false, foreign))
1363	return false;
1364
1365	return true;
1366	}
1367
1368	/**
1369	* fixup_user_fault() - manually resolve a user page fault
1370	* @mm: mm_struct of target mm
1371	* @address: user address
1372	* @fault_flags:flags to pass down to handle_mm_fault()
1373	* @unlocked: did we unlock the mmap_lock while retrying, maybe NULL if caller
1374	* does not allow retry. If NULL, the caller must guarantee
1375	* that fault_flags does not contain FAULT_FLAG_ALLOW_RETRY.
1376	*
1377	* This is meant to be called in the specific scenario where for locking reasons
1378	* we try to access user memory in atomic context (within a pagefault_disable()
1379	* section), this returns -EFAULT, and we want to resolve the user fault before
1380	* trying again.
1381	*
1382	* Typically this is meant to be used by the futex code.
1383	*
1384	* The main difference with get_user_pages() is that this function will
1385	* unconditionally call handle_mm_fault() which will in turn perform all the
1386	* necessary SW fixup of the dirty and young bits in the PTE, while
1387	* get_user_pages() only guarantees to update these in the struct page.
1388	*
1389	* This is important for some architectures where those bits also gate the
1390	* access permission to the page because they are maintained in software. On
1391	* such architectures, gup() will not be enough to make a subsequent access
1392	* succeed.
1393	*
1394	* This function will not return with an unlocked mmap_lock. So it has not the
1395	* same semantics wrt the @mm->mmap_lock as does filemap_fault().
1396	*/
1397	int fixup_user_fault(struct mm_struct *mm,
1398	unsigned long address, unsigned int fault_flags,
1399	bool *unlocked)
1400	{
1401	struct vm_area_struct *vma;
1402	vm_fault_t ret;
1403
1404	address = untagged_addr_remote(mm, address);
1405
1406	if (unlocked)
1407	fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
1408
1409	retry:
1410	vma = gup_vma_lookup(mm, addr: address);
1411	if (!vma)
1412	return -EFAULT;
1413
1414	if (!vma_permits_fault(vma, fault_flags))
1415	return -EFAULT;
1416
1417	if ((fault_flags & FAULT_FLAG_KILLABLE) &&
1418	fatal_signal_pending(current))
1419	return -EINTR;
1420
1421	ret = handle_mm_fault(vma, address, flags: fault_flags, NULL);
1422
1423	if (ret & VM_FAULT_COMPLETED) {
1424	/*
1425	* NOTE: it's a pity that we need to retake the lock here
1426	* to pair with the unlock() in the callers. Ideally we
1427	* could tell the callers so they do not need to unlock.
1428	*/
1429	mmap_read_lock(mm);
1430	*unlocked = true;
1431	return 0;
1432	}
1433
1434	if (ret & VM_FAULT_ERROR) {
1435	int err = vm_fault_to_errno(vm_fault: ret, foll_flags: 0);
1436
1437	if (err)
1438	return err;
1439	BUG();
1440	}
1441
1442	if (ret & VM_FAULT_RETRY) {
1443	mmap_read_lock(mm);
1444	*unlocked = true;
1445	fault_flags |= FAULT_FLAG_TRIED;
1446	goto retry;
1447	}
1448
1449	return 0;
1450	}
1451	EXPORT_SYMBOL_GPL(fixup_user_fault);
1452
1453	/*
1454	* GUP always responds to fatal signals. When FOLL_INTERRUPTIBLE is
1455	* specified, it'll also respond to generic signals. The caller of GUP
1456	* that has FOLL_INTERRUPTIBLE should take care of the GUP interruption.
1457	*/
1458	static bool gup_signal_pending(unsigned int flags)
1459	{
1460	if (fatal_signal_pending(current))
1461	return true;
1462
1463	if (!(flags & FOLL_INTERRUPTIBLE))
1464	return false;
1465
1466	return signal_pending(current);
1467	}
1468
1469	/*
1470	* Locking: (*locked == 1) means that the mmap_lock has already been acquired by
1471	* the caller. This function may drop the mmap_lock. If it does so, then it will
1472	* set (*locked = 0).
1473	*
1474	* (*locked == 0) means that the caller expects this function to acquire and
1475	* drop the mmap_lock. Therefore, the value of *locked will still be zero when
1476	* the function returns, even though it may have changed temporarily during
1477	* function execution.
1478	*
1479	* Please note that this function, unlike __get_user_pages(), will not return 0
1480	* for nr_pages > 0, unless FOLL_NOWAIT is used.
1481	*/
1482	static __always_inline long __get_user_pages_locked(struct mm_struct *mm,
1483	unsigned long start,
1484	unsigned long nr_pages,
1485	struct page **pages,
1486	int *locked,
1487	unsigned int flags)
1488	{
1489	long ret, pages_done;
1490	bool must_unlock = false;
1491
1492	if (!nr_pages)
1493	return 0;
1494
1495	/*
1496	* The internal caller expects GUP to manage the lock internally and the
1497	* lock must be released when this returns.
1498	*/
1499	if (!*locked) {
1500	if (mmap_read_lock_killable(mm))
1501	return -EAGAIN;
1502	must_unlock = true;
1503	*locked = 1;
1504	}
1505	else
1506	mmap_assert_locked(mm);
1507
1508	if (flags & FOLL_PIN)
1509	mm_set_has_pinned_flag(mm_flags: &mm->flags);
1510
1511	/*
1512	* FOLL_PIN and FOLL_GET are mutually exclusive. Traditional behavior
1513	* is to set FOLL_GET if the caller wants pages[] filled in (but has
1514	* carelessly failed to specify FOLL_GET), so keep doing that, but only
1515	* for FOLL_GET, not for the newer FOLL_PIN.
1516	*
1517	* FOLL_PIN always expects pages to be non-null, but no need to assert
1518	* that here, as any failures will be obvious enough.
1519	*/
1520	if (pages && !(flags & FOLL_PIN))
1521	flags |= FOLL_GET;
1522
1523	pages_done = 0;
1524	for (;;) {
1525	ret = __get_user_pages(mm, start, nr_pages, gup_flags: flags, pages,
1526	locked);
1527	if (!(flags & FOLL_UNLOCKABLE)) {
1528	/* VM_FAULT_RETRY couldn't trigger, bypass */
1529	pages_done = ret;
1530	break;
1531	}
1532
1533	/* VM_FAULT_RETRY or VM_FAULT_COMPLETED cannot return errors */
1534	if (!*locked) {
1535	BUG_ON(ret < 0);
1536	BUG_ON(ret >= nr_pages);
1537	}
1538
1539	if (ret > 0) {
1540	nr_pages -= ret;
1541	pages_done += ret;
1542	if (!nr_pages)
1543	break;
1544	}
1545	if (*locked) {
1546	/*
1547	* VM_FAULT_RETRY didn't trigger or it was a
1548	* FOLL_NOWAIT.
1549	*/
1550	if (!pages_done)
1551	pages_done = ret;
1552	break;
1553	}
1554	/*
1555	* VM_FAULT_RETRY triggered, so seek to the faulting offset.
1556	* For the prefault case (!pages) we only update counts.
1557	*/
1558	if (likely(pages))
1559	pages += ret;
1560	start += ret << PAGE_SHIFT;
1561
1562	/* The lock was temporarily dropped, so we must unlock later */
1563	must_unlock = true;
1564
1565	retry:
1566	/*
1567	* Repeat on the address that fired VM_FAULT_RETRY
1568	* with both FAULT_FLAG_ALLOW_RETRY and
1569	* FAULT_FLAG_TRIED. Note that GUP can be interrupted
1570	* by fatal signals of even common signals, depending on
1571	* the caller's request. So we need to check it before we
1572	* start trying again otherwise it can loop forever.
1573	*/
1574	if (gup_signal_pending(flags)) {
1575	if (!pages_done)
1576	pages_done = -EINTR;
1577	break;
1578	}
1579
1580	ret = mmap_read_lock_killable(mm);
1581	if (ret) {
1582	BUG_ON(ret > 0);
1583	if (!pages_done)
1584	pages_done = ret;
1585	break;
1586	}
1587
1588	*locked = 1;
1589	ret = __get_user_pages(mm, start, nr_pages: 1, gup_flags: flags | FOLL_TRIED,
1590	pages, locked);
1591	if (!*locked) {
1592	/* Continue to retry until we succeeded */
1593	BUG_ON(ret != 0);
1594	goto retry;
1595	}
1596	if (ret != 1) {
1597	BUG_ON(ret > 1);
1598	if (!pages_done)
1599	pages_done = ret;
1600	break;
1601	}
1602	nr_pages--;
1603	pages_done++;
1604	if (!nr_pages)
1605	break;
1606	if (likely(pages))
1607	pages++;
1608	start += PAGE_SIZE;
1609	}
1610	if (must_unlock && *locked) {
1611	/*
1612	* We either temporarily dropped the lock, or the caller
1613	* requested that we both acquire and drop the lock. Either way,
1614	* we must now unlock, and notify the caller of that state.
1615	*/
1616	mmap_read_unlock(mm);
1617	*locked = 0;
1618	}
1619
1620	/*
1621	* Failing to pin anything implies something has gone wrong (except when
1622	* FOLL_NOWAIT is specified).
1623	*/
1624	if (WARN_ON_ONCE(pages_done == 0 && !(flags & FOLL_NOWAIT)))
1625	return -EFAULT;
1626
1627	return pages_done;
1628	}
1629
1630	/**
1631	* populate_vma_page_range() - populate a range of pages in the vma.
1632	* @vma: target vma
1633	* @start: start address
1634	* @end: end address
1635	* @locked: whether the mmap_lock is still held
1636	*
1637	* This takes care of mlocking the pages too if VM_LOCKED is set.
1638	*
1639	* Return either number of pages pinned in the vma, or a negative error
1640	* code on error.
1641	*
1642	* vma->vm_mm->mmap_lock must be held.
1643	*
1644	* If @locked is NULL, it may be held for read or write and will
1645	* be unperturbed.
1646	*
1647	* If @locked is non-NULL, it must held for read only and may be
1648	* released. If it's released, *@locked will be set to 0.
1649	*/
1650	long populate_vma_page_range(struct vm_area_struct *vma,
1651	unsigned long start, unsigned long end, int *locked)
1652	{
1653	struct mm_struct *mm = vma->vm_mm;
1654	unsigned long nr_pages = (end - start) / PAGE_SIZE;
1655	int local_locked = 1;
1656	int gup_flags;
1657	long ret;
1658
1659	VM_BUG_ON(!PAGE_ALIGNED(start));
1660	VM_BUG_ON(!PAGE_ALIGNED(end));
1661	VM_BUG_ON_VMA(start < vma->vm_start, vma);
1662	VM_BUG_ON_VMA(end > vma->vm_end, vma);
1663	mmap_assert_locked(mm);
1664
1665	/*
1666	* Rightly or wrongly, the VM_LOCKONFAULT case has never used
1667	* faultin_page() to break COW, so it has no work to do here.
1668	*/
1669	if (vma->vm_flags & VM_LOCKONFAULT)
1670	return nr_pages;
1671
1672	/* ... similarly, we've never faulted in PROT_NONE pages */
1673	if (!vma_is_accessible(vma))
1674	return -EFAULT;
1675
1676	gup_flags = FOLL_TOUCH;
1677	/*
1678	* We want to touch writable mappings with a write fault in order
1679	* to break COW, except for shared mappings because these don't COW
1680	* and we would not want to dirty them for nothing.
1681	*
1682	* Otherwise, do a read fault, and use FOLL_FORCE in case it's not
1683	* readable (ie write-only or executable).
1684	*/
1685	if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
1686	gup_flags |= FOLL_WRITE;
1687	else
1688	gup_flags |= FOLL_FORCE;
1689
1690	if (locked)
1691	gup_flags |= FOLL_UNLOCKABLE;
1692
1693	/*
1694	* We made sure addr is within a VMA, so the following will
1695	* not result in a stack expansion that recurses back here.
1696	*/
1697	ret = __get_user_pages(mm, start, nr_pages, gup_flags,
1698	NULL, locked: locked ? locked : &local_locked);
1699	lru_add_drain();
1700	return ret;
1701	}
1702
1703	/*
1704	* faultin_page_range() - populate (prefault) page tables inside the
1705	* given range readable/writable
1706	*
1707	* This takes care of mlocking the pages, too, if VM_LOCKED is set.
1708	*
1709	* @mm: the mm to populate page tables in
1710	* @start: start address
1711	* @end: end address
1712	* @write: whether to prefault readable or writable
1713	* @locked: whether the mmap_lock is still held
1714	*
1715	* Returns either number of processed pages in the MM, or a negative error
1716	* code on error (see __get_user_pages()). Note that this function reports
1717	* errors related to VMAs, such as incompatible mappings, as expected by
1718	* MADV_POPULATE_(READ|WRITE).
1719	*
1720	* The range must be page-aligned.
1721	*
1722	* mm->mmap_lock must be held. If it's released, *@locked will be set to 0.
1723	*/
1724	long faultin_page_range(struct mm_struct *mm, unsigned long start,
1725	unsigned long end, bool write, int *locked)
1726	{
1727	unsigned long nr_pages = (end - start) / PAGE_SIZE;
1728	int gup_flags;
1729	long ret;
1730
1731	VM_BUG_ON(!PAGE_ALIGNED(start));
1732	VM_BUG_ON(!PAGE_ALIGNED(end));
1733	mmap_assert_locked(mm);
1734
1735	/*
1736	* FOLL_TOUCH: Mark page accessed and thereby young; will also mark
1737	* the page dirty with FOLL_WRITE -- which doesn't make a
1738	* difference with !FOLL_FORCE, because the page is writable
1739	* in the page table.
1740	* FOLL_HWPOISON: Return -EHWPOISON instead of -EFAULT when we hit
1741	* a poisoned page.
1742	* !FOLL_FORCE: Require proper access permissions.
1743	*/
1744	gup_flags = FOLL_TOUCH | FOLL_HWPOISON | FOLL_UNLOCKABLE |
1745	FOLL_MADV_POPULATE;
1746	if (write)
1747	gup_flags |= FOLL_WRITE;
1748
1749	ret = __get_user_pages_locked(mm, start, nr_pages, NULL, locked,
1750	flags: gup_flags);
1751	lru_add_drain();
1752	return ret;
1753	}
1754
1755	/*
1756	* __mm_populate - populate and/or mlock pages within a range of address space.
1757	*
1758	* This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
1759	* flags. VMAs must be already marked with the desired vm_flags, and
1760	* mmap_lock must not be held.
1761	*/
1762	int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
1763	{
1764	struct mm_struct *mm = current->mm;
1765	unsigned long end, nstart, nend;
1766	struct vm_area_struct *vma = NULL;
1767	int locked = 0;
1768	long ret = 0;
1769
1770	end = start + len;
1771
1772	for (nstart = start; nstart < end; nstart = nend) {
1773	/*
1774	* We want to fault in pages for [nstart; end) address range.
1775	* Find first corresponding VMA.
1776	*/
1777	if (!locked) {
1778	locked = 1;
1779	mmap_read_lock(mm);
1780	vma = find_vma_intersection(mm, start_addr: nstart, end_addr: end);
1781	} else if (nstart >= vma->vm_end)
1782	vma = find_vma_intersection(mm, start_addr: vma->vm_end, end_addr: end);
1783
1784	if (!vma)
1785	break;
1786	/*
1787	* Set [nstart; nend) to intersection of desired address
1788	* range with the first VMA. Also, skip undesirable VMA types.
1789	*/
1790	nend = min(end, vma->vm_end);
1791	if (vma->vm_flags & (VM_IO | VM_PFNMAP))
1792	continue;
1793	if (nstart < vma->vm_start)
1794	nstart = vma->vm_start;
1795	/*
1796	* Now fault in a range of pages. populate_vma_page_range()
1797	* double checks the vma flags, so that it won't mlock pages
1798	* if the vma was already munlocked.
1799	*/
1800	ret = populate_vma_page_range(vma, start: nstart, end: nend, locked: &locked);
1801	if (ret < 0) {
1802	if (ignore_errors) {
1803	ret = 0;
1804	continue; /* continue at next VMA */
1805	}
1806	break;
1807	}
1808	nend = nstart + ret * PAGE_SIZE;
1809	ret = 0;
1810	}
1811	if (locked)
1812	mmap_read_unlock(mm);
1813	return ret; /* 0 or negative error code */
1814	}
1815	#else /* CONFIG_MMU */
1816	static long __get_user_pages_locked(struct mm_struct *mm, unsigned long start,
1817	unsigned long nr_pages, struct page **pages,
1818	int *locked, unsigned int foll_flags)
1819	{
1820	struct vm_area_struct *vma;
1821	bool must_unlock = false;
1822	unsigned long vm_flags;
1823	long i;
1824
1825	if (!nr_pages)
1826	return 0;
1827
1828	/*
1829	* The internal caller expects GUP to manage the lock internally and the
1830	* lock must be released when this returns.
1831	*/
1832	if (!*locked) {
1833	if (mmap_read_lock_killable(mm))
1834	return -EAGAIN;
1835	must_unlock = true;
1836	*locked = 1;
1837	}
1838
1839	/* calculate required read or write permissions.
1840	* If FOLL_FORCE is set, we only require the "MAY" flags.
1841	*/
1842	vm_flags = (foll_flags & FOLL_WRITE) ?
1843	(VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
1844	vm_flags &= (foll_flags & FOLL_FORCE) ?
1845	(VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
1846
1847	for (i = 0; i < nr_pages; i++) {
1848	vma = find_vma(mm, start);
1849	if (!vma)
1850	break;
1851
1852	/* protect what we can, including chardevs */
1853	if ((vma->vm_flags & (VM_IO | VM_PFNMAP)) ||
1854	!(vm_flags & vma->vm_flags))
1855	break;
1856
1857	if (pages) {
1858	pages[i] = virt_to_page((void *)start);
1859	if (pages[i])
1860	get_page(pages[i]);
1861	}
1862
1863	start = (start + PAGE_SIZE) & PAGE_MASK;
1864	}
1865
1866	if (must_unlock && *locked) {
1867	mmap_read_unlock(mm);
1868	*locked = 0;
1869	}
1870
1871	return i ? : -EFAULT;
1872	}
1873	#endif /* !CONFIG_MMU */
1874
1875	/**
1876	* fault_in_writeable - fault in userspace address range for writing
1877	* @uaddr: start of address range
1878	* @size: size of address range
1879	*
1880	* Returns the number of bytes not faulted in (like copy_to_user() and
1881	* copy_from_user()).
1882	*/
1883	size_t fault_in_writeable(char __user *uaddr, size_t size)
1884	{
1885	char __user *start = uaddr, *end;
1886
1887	if (unlikely(size == 0))
1888	return 0;
1889	if (!user_write_access_begin(uaddr, size))
1890	return size;
1891	if (!PAGE_ALIGNED(uaddr)) {
1892	unsafe_put_user(0, uaddr, out);
1893	uaddr = (char __user *)PAGE_ALIGN((unsigned long)uaddr);
1894	}
1895	end = (char __user *)PAGE_ALIGN((unsigned long)start + size);
1896	if (unlikely(end < start))
1897	end = NULL;
1898	while (uaddr != end) {
1899	unsafe_put_user(0, uaddr, out);
1900	uaddr += PAGE_SIZE;
1901	}
1902
1903	out:
1904	user_write_access_end();
1905	if (size > uaddr - start)
1906	return size - (uaddr - start);
1907	return 0;
1908	}
1909	EXPORT_SYMBOL(fault_in_writeable);
1910
1911	/**
1912	* fault_in_subpage_writeable - fault in an address range for writing
1913	* @uaddr: start of address range
1914	* @size: size of address range
1915	*
1916	* Fault in a user address range for writing while checking for permissions at
1917	* sub-page granularity (e.g. arm64 MTE). This function should be used when
1918	* the caller cannot guarantee forward progress of a copy_to_user() loop.
1919	*
1920	* Returns the number of bytes not faulted in (like copy_to_user() and
1921	* copy_from_user()).
1922	*/
1923	size_t fault_in_subpage_writeable(char __user *uaddr, size_t size)
1924	{
1925	size_t faulted_in;
1926
1927	/*
1928	* Attempt faulting in at page granularity first for page table
1929	* permission checking. The arch-specific probe_subpage_writeable()
1930	* functions may not check for this.
1931	*/
1932	faulted_in = size - fault_in_writeable(uaddr, size);
1933	if (faulted_in)
1934	faulted_in -= probe_subpage_writeable(uaddr, size: faulted_in);
1935
1936	return size - faulted_in;
1937	}
1938	EXPORT_SYMBOL(fault_in_subpage_writeable);
1939
1940	/*
1941	* fault_in_safe_writeable - fault in an address range for writing
1942	* @uaddr: start of address range
1943	* @size: length of address range
1944	*
1945	* Faults in an address range for writing. This is primarily useful when we
1946	* already know that some or all of the pages in the address range aren't in
1947	* memory.
1948	*
1949	* Unlike fault_in_writeable(), this function is non-destructive.
1950	*
1951	* Note that we don't pin or otherwise hold the pages referenced that we fault
1952	* in. There's no guarantee that they'll stay in memory for any duration of
1953	* time.
1954	*
1955	* Returns the number of bytes not faulted in, like copy_to_user() and
1956	* copy_from_user().
1957	*/
1958	size_t fault_in_safe_writeable(const char __user *uaddr, size_t size)
1959	{
1960	unsigned long start = (unsigned long)uaddr, end;
1961	struct mm_struct *mm = current->mm;
1962	bool unlocked = false;
1963
1964	if (unlikely(size == 0))
1965	return 0;
1966	end = PAGE_ALIGN(start + size);
1967	if (end < start)
1968	end = 0;
1969
1970	mmap_read_lock(mm);
1971	do {
1972	if (fixup_user_fault(mm, start, FAULT_FLAG_WRITE, &unlocked))
1973	break;
1974	start = (start + PAGE_SIZE) & PAGE_MASK;
1975	} while (start != end);
1976	mmap_read_unlock(mm);
1977
1978	if (size > (unsigned long)uaddr - start)
1979	return size - ((unsigned long)uaddr - start);
1980	return 0;
1981	}
1982	EXPORT_SYMBOL(fault_in_safe_writeable);
1983
1984	/**
1985	* fault_in_readable - fault in userspace address range for reading
1986	* @uaddr: start of user address range
1987	* @size: size of user address range
1988	*
1989	* Returns the number of bytes not faulted in (like copy_to_user() and
1990	* copy_from_user()).
1991	*/
1992	size_t fault_in_readable(const char __user *uaddr, size_t size)
1993	{
1994	const char __user *start = uaddr, *end;
1995	volatile char c;
1996
1997	if (unlikely(size == 0))
1998	return 0;
1999	if (!user_read_access_begin(uaddr, size))
2000	return size;
2001	if (!PAGE_ALIGNED(uaddr)) {
2002	unsafe_get_user(c, uaddr, out);
2003	uaddr = (const char __user *)PAGE_ALIGN((unsigned long)uaddr);
2004	}
2005	end = (const char __user *)PAGE_ALIGN((unsigned long)start + size);
2006	if (unlikely(end < start))
2007	end = NULL;
2008	while (uaddr != end) {
2009	unsafe_get_user(c, uaddr, out);
2010	uaddr += PAGE_SIZE;
2011	}
2012
2013	out:
2014	user_read_access_end();
2015	(void)c;
2016	if (size > uaddr - start)
2017	return size - (uaddr - start);
2018	return 0;
2019	}
2020	EXPORT_SYMBOL(fault_in_readable);
2021
2022	/**
2023	* get_dump_page() - pin user page in memory while writing it to core dump
2024	* @addr: user address
2025	*
2026	* Returns struct page pointer of user page pinned for dump,
2027	* to be freed afterwards by put_page().
2028	*
2029	* Returns NULL on any kind of failure - a hole must then be inserted into
2030	* the corefile, to preserve alignment with its headers; and also returns
2031	* NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
2032	* allowing a hole to be left in the corefile to save disk space.
2033	*
2034	* Called without mmap_lock (takes and releases the mmap_lock by itself).
2035	*/
2036	#ifdef CONFIG_ELF_CORE
2037	struct page *get_dump_page(unsigned long addr)
2038	{
2039	struct page *page;
2040	int locked = 0;
2041	int ret;
2042
2043	ret = __get_user_pages_locked(current->mm, start: addr, nr_pages: 1, pages: &page, locked: &locked,
2044	flags: FOLL_FORCE | FOLL_DUMP | FOLL_GET);
2045	return (ret == 1) ? page : NULL;
2046	}
2047	#endif /* CONFIG_ELF_CORE */
2048
2049	#ifdef CONFIG_MIGRATION
2050	/*
2051	* Returns the number of collected pages. Return value is always >= 0.
2052	*/
2053	static unsigned long collect_longterm_unpinnable_pages(
2054	struct list_head *movable_page_list,
2055	unsigned long nr_pages,
2056	struct page **pages)
2057	{
2058	unsigned long i, collected = 0;
2059	struct folio *prev_folio = NULL;
2060	bool drain_allow = true;
2061
2062	for (i = 0; i < nr_pages; i++) {
2063	struct folio *folio = page_folio(pages[i]);
2064
2065	if (folio == prev_folio)
2066	continue;
2067	prev_folio = folio;
2068
2069	if (folio_is_longterm_pinnable(folio))
2070	continue;
2071
2072	collected++;
2073
2074	if (folio_is_device_coherent(folio))
2075	continue;
2076
2077	if (folio_test_hugetlb(folio)) {
2078	isolate_hugetlb(folio, list: movable_page_list);
2079	continue;
2080	}
2081
2082	if (!folio_test_lru(folio) && drain_allow) {
2083	lru_add_drain_all();
2084	drain_allow = false;
2085	}
2086
2087	if (!folio_isolate_lru(folio))
2088	continue;
2089
2090	list_add_tail(new: &folio->lru, head: movable_page_list);
2091	node_stat_mod_folio(folio,
2092	item: NR_ISOLATED_ANON + folio_is_file_lru(folio),
2093	nr: folio_nr_pages(folio));
2094	}
2095
2096	return collected;
2097	}
2098
2099	/*
2100	* Unpins all pages and migrates device coherent pages and movable_page_list.
2101	* Returns -EAGAIN if all pages were successfully migrated or -errno for failure
2102	* (or partial success).
2103	*/
2104	static int migrate_longterm_unpinnable_pages(
2105	struct list_head *movable_page_list,
2106	unsigned long nr_pages,
2107	struct page **pages)
2108	{
2109	int ret;
2110	unsigned long i;
2111
2112	for (i = 0; i < nr_pages; i++) {
2113	struct folio *folio = page_folio(pages[i]);
2114
2115	if (folio_is_device_coherent(folio)) {
2116	/*
2117	* Migration will fail if the page is pinned, so convert
2118	* the pin on the source page to a normal reference.
2119	*/
2120	pages[i] = NULL;
2121	folio_get(folio);
2122	gup_put_folio(folio, refs: 1, flags: FOLL_PIN);
2123
2124	if (migrate_device_coherent_page(page: &folio->page)) {
2125	ret = -EBUSY;
2126	goto err;
2127	}
2128
2129	continue;
2130	}
2131
2132	/*
2133	* We can't migrate pages with unexpected references, so drop
2134	* the reference obtained by __get_user_pages_locked().
2135	* Migrating pages have been added to movable_page_list after
2136	* calling folio_isolate_lru() which takes a reference so the
2137	* page won't be freed if it's migrating.
2138	*/
2139	unpin_user_page(pages[i]);
2140	pages[i] = NULL;
2141	}
2142
2143	if (!list_empty(head: movable_page_list)) {
2144	struct migration_target_control mtc = {
2145	.nid = NUMA_NO_NODE,
2146	.gfp_mask = GFP_USER | __GFP_NOWARN,
2147	};
2148
2149	if (migrate_pages(l: movable_page_list, new: alloc_migration_target,
2150	NULL, private: (unsigned long)&mtc, mode: MIGRATE_SYNC,
2151	reason: MR_LONGTERM_PIN, NULL)) {
2152	ret = -ENOMEM;
2153	goto err;
2154	}
2155	}
2156
2157	putback_movable_pages(l: movable_page_list);
2158
2159	return -EAGAIN;
2160
2161	err:
2162	for (i = 0; i < nr_pages; i++)
2163	if (pages[i])
2164	unpin_user_page(pages[i]);
2165	putback_movable_pages(l: movable_page_list);
2166
2167	return ret;
2168	}
2169
2170	/*
2171	* Check whether all pages are *allowed* to be pinned. Rather confusingly, all
2172	* pages in the range are required to be pinned via FOLL_PIN, before calling
2173	* this routine.
2174	*
2175	* If any pages in the range are not allowed to be pinned, then this routine
2176	* will migrate those pages away, unpin all the pages in the range and return
2177	* -EAGAIN. The caller should re-pin the entire range with FOLL_PIN and then
2178	* call this routine again.
2179	*
2180	* If an error other than -EAGAIN occurs, this indicates a migration failure.
2181	* The caller should give up, and propagate the error back up the call stack.
2182	*
2183	* If everything is OK and all pages in the range are allowed to be pinned, then
2184	* this routine leaves all pages pinned and returns zero for success.
2185	*/
2186	static long check_and_migrate_movable_pages(unsigned long nr_pages,
2187	struct page **pages)
2188	{
2189	unsigned long collected;
2190	LIST_HEAD(movable_page_list);
2191
2192	collected = collect_longterm_unpinnable_pages(movable_page_list: &movable_page_list,
2193	nr_pages, pages);
2194	if (!collected)
2195	return 0;
2196
2197	return migrate_longterm_unpinnable_pages(movable_page_list: &movable_page_list, nr_pages,
2198	pages);
2199	}
2200	#else
2201	static long check_and_migrate_movable_pages(unsigned long nr_pages,
2202	struct page **pages)
2203	{
2204	return 0;
2205	}
2206	#endif /* CONFIG_MIGRATION */
2207
2208	/*
2209	* __gup_longterm_locked() is a wrapper for __get_user_pages_locked which
2210	* allows us to process the FOLL_LONGTERM flag.
2211	*/
2212	static long __gup_longterm_locked(struct mm_struct *mm,
2213	unsigned long start,
2214	unsigned long nr_pages,
2215	struct page **pages,
2216	int *locked,
2217	unsigned int gup_flags)
2218	{
2219	unsigned int flags;
2220	long rc, nr_pinned_pages;
2221
2222	if (!(gup_flags & FOLL_LONGTERM))
2223	return __get_user_pages_locked(mm, start, nr_pages, pages,
2224	locked, flags: gup_flags);
2225
2226	flags = memalloc_pin_save();
2227	do {
2228	nr_pinned_pages = __get_user_pages_locked(mm, start, nr_pages,
2229	pages, locked,
2230	flags: gup_flags);
2231	if (nr_pinned_pages <= 0) {
2232	rc = nr_pinned_pages;
2233	break;
2234	}
2235
2236	/* FOLL_LONGTERM implies FOLL_PIN */
2237	rc = check_and_migrate_movable_pages(nr_pages: nr_pinned_pages, pages);
2238	} while (rc == -EAGAIN);
2239	memalloc_pin_restore(flags);
2240	return rc ? rc : nr_pinned_pages;
2241	}
2242
2243	/*
2244	* Check that the given flags are valid for the exported gup/pup interface, and
2245	* update them with the required flags that the caller must have set.
2246	*/
2247	static bool is_valid_gup_args(struct page **pages, int *locked,
2248	unsigned int *gup_flags_p, unsigned int to_set)
2249	{
2250	unsigned int gup_flags = *gup_flags_p;
2251
2252	/*
2253	* These flags not allowed to be specified externally to the gup
2254	* interfaces:
2255	* - FOLL_TOUCH/FOLL_PIN/FOLL_TRIED/FOLL_FAST_ONLY are internal only
2256	* - FOLL_REMOTE is internal only and used on follow_page()
2257	* - FOLL_UNLOCKABLE is internal only and used if locked is !NULL
2258	*/
2259	if (WARN_ON_ONCE(gup_flags & INTERNAL_GUP_FLAGS))
2260	return false;
2261
2262	gup_flags |= to_set;
2263	if (locked) {
2264	/* At the external interface locked must be set */
2265	if (WARN_ON_ONCE(*locked != 1))
2266	return false;
2267
2268	gup_flags |= FOLL_UNLOCKABLE;
2269	}
2270
2271	/* FOLL_GET and FOLL_PIN are mutually exclusive. */
2272	if (WARN_ON_ONCE((gup_flags & (FOLL_PIN | FOLL_GET)) ==
2273	(FOLL_PIN | FOLL_GET)))
2274	return false;
2275
2276	/* LONGTERM can only be specified when pinning */
2277	if (WARN_ON_ONCE(!(gup_flags & FOLL_PIN) && (gup_flags & FOLL_LONGTERM)))
2278	return false;
2279
2280	/* Pages input must be given if using GET/PIN */
2281	if (WARN_ON_ONCE((gup_flags & (FOLL_GET | FOLL_PIN)) && !pages))
2282	return false;
2283
2284	/* We want to allow the pgmap to be hot-unplugged at all times */
2285	if (WARN_ON_ONCE((gup_flags & FOLL_LONGTERM) &&
2286	(gup_flags & FOLL_PCI_P2PDMA)))
2287	return false;
2288
2289	*gup_flags_p = gup_flags;
2290	return true;
2291	}
2292
2293	#ifdef CONFIG_MMU
2294	/**
2295	* get_user_pages_remote() - pin user pages in memory
2296	* @mm: mm_struct of target mm
2297	* @start: starting user address
2298	* @nr_pages: number of pages from start to pin
2299	* @gup_flags: flags modifying lookup behaviour
2300	* @pages: array that receives pointers to the pages pinned.
2301	* Should be at least nr_pages long. Or NULL, if caller
2302	* only intends to ensure the pages are faulted in.
2303	* @locked: pointer to lock flag indicating whether lock is held and
2304	* subsequently whether VM_FAULT_RETRY functionality can be
2305	* utilised. Lock must initially be held.
2306	*
2307	* Returns either number of pages pinned (which may be less than the
2308	* number requested), or an error. Details about the return value:
2309	*
2310	* -- If nr_pages is 0, returns 0.
2311	* -- If nr_pages is >0, but no pages were pinned, returns -errno.
2312	* -- If nr_pages is >0, and some pages were pinned, returns the number of
2313	* pages pinned. Again, this may be less than nr_pages.
2314	*
2315	* The caller is responsible for releasing returned @pages, via put_page().
2316	*
2317	* Must be called with mmap_lock held for read or write.
2318	*
2319	* get_user_pages_remote walks a process's page tables and takes a reference
2320	* to each struct page that each user address corresponds to at a given
2321	* instant. That is, it takes the page that would be accessed if a user
2322	* thread accesses the given user virtual address at that instant.
2323	*
2324	* This does not guarantee that the page exists in the user mappings when
2325	* get_user_pages_remote returns, and there may even be a completely different
2326	* page there in some cases (eg. if mmapped pagecache has been invalidated
2327	* and subsequently re-faulted). However it does guarantee that the page
2328	* won't be freed completely. And mostly callers simply care that the page
2329	* contains data that was valid *at some point in time*. Typically, an IO
2330	* or similar operation cannot guarantee anything stronger anyway because
2331	* locks can't be held over the syscall boundary.
2332	*
2333	* If gup_flags & FOLL_WRITE == 0, the page must not be written to. If the page
2334	* is written to, set_page_dirty (or set_page_dirty_lock, as appropriate) must
2335	* be called after the page is finished with, and before put_page is called.
2336	*
2337	* get_user_pages_remote is typically used for fewer-copy IO operations,
2338	* to get a handle on the memory by some means other than accesses
2339	* via the user virtual addresses. The pages may be submitted for
2340	* DMA to devices or accessed via their kernel linear mapping (via the
2341	* kmap APIs). Care should be taken to use the correct cache flushing APIs.
2342	*
2343	* See also get_user_pages_fast, for performance critical applications.
2344	*
2345	* get_user_pages_remote should be phased out in favor of
2346	* get_user_pages_locked|unlocked or get_user_pages_fast. Nothing
2347	* should use get_user_pages_remote because it cannot pass
2348	* FAULT_FLAG_ALLOW_RETRY to handle_mm_fault.
2349	*/
2350	long get_user_pages_remote(struct mm_struct *mm,
2351	unsigned long start, unsigned long nr_pages,
2352	unsigned int gup_flags, struct page **pages,
2353	int *locked)
2354	{
2355	int local_locked = 1;
2356
2357	if (!is_valid_gup_args(pages, locked, gup_flags_p: &gup_flags,
2358	to_set: FOLL_TOUCH | FOLL_REMOTE))
2359	return -EINVAL;
2360
2361	return __get_user_pages_locked(mm, start, nr_pages, pages,
2362	locked: locked ? locked : &local_locked,
2363	flags: gup_flags);
2364	}
2365	EXPORT_SYMBOL(get_user_pages_remote);
2366
2367	#else /* CONFIG_MMU */
2368	long get_user_pages_remote(struct mm_struct *mm,
2369	unsigned long start, unsigned long nr_pages,
2370	unsigned int gup_flags, struct page **pages,
2371	int *locked)
2372	{
2373	return 0;
2374	}
2375	#endif /* !CONFIG_MMU */
2376
2377	/**
2378	* get_user_pages() - pin user pages in memory
2379	* @start: starting user address
2380	* @nr_pages: number of pages from start to pin
2381	* @gup_flags: flags modifying lookup behaviour
2382	* @pages: array that receives pointers to the pages pinned.
2383	* Should be at least nr_pages long. Or NULL, if caller
2384	* only intends to ensure the pages are faulted in.
2385	*
2386	* This is the same as get_user_pages_remote(), just with a less-flexible
2387	* calling convention where we assume that the mm being operated on belongs to
2388	* the current task, and doesn't allow passing of a locked parameter. We also
2389	* obviously don't pass FOLL_REMOTE in here.
2390	*/
2391	long get_user_pages(unsigned long start, unsigned long nr_pages,
2392	unsigned int gup_flags, struct page **pages)
2393	{
2394	int locked = 1;
2395
2396	if (!is_valid_gup_args(pages, NULL, gup_flags_p: &gup_flags, to_set: FOLL_TOUCH))
2397	return -EINVAL;
2398
2399	return __get_user_pages_locked(current->mm, start, nr_pages, pages,
2400	locked: &locked, flags: gup_flags);
2401	}
2402	EXPORT_SYMBOL(get_user_pages);
2403
2404	/*
2405	* get_user_pages_unlocked() is suitable to replace the form:
2406	*
2407	* mmap_read_lock(mm);
2408	* get_user_pages(mm, ..., pages, NULL);
2409	* mmap_read_unlock(mm);
2410	*
2411	* with:
2412	*
2413	* get_user_pages_unlocked(mm, ..., pages);
2414	*
2415	* It is functionally equivalent to get_user_pages_fast so
2416	* get_user_pages_fast should be used instead if specific gup_flags
2417	* (e.g. FOLL_FORCE) are not required.
2418	*/
2419	long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
2420	struct page **pages, unsigned int gup_flags)
2421	{
2422	int locked = 0;
2423
2424	if (!is_valid_gup_args(pages, NULL, gup_flags_p: &gup_flags,
2425	to_set: FOLL_TOUCH | FOLL_UNLOCKABLE))
2426	return -EINVAL;
2427
2428	return __get_user_pages_locked(current->mm, start, nr_pages, pages,
2429	locked: &locked, flags: gup_flags);
2430	}
2431	EXPORT_SYMBOL(get_user_pages_unlocked);
2432
2433	/*
2434	* Fast GUP
2435	*
2436	* get_user_pages_fast attempts to pin user pages by walking the page
2437	* tables directly and avoids taking locks. Thus the walker needs to be
2438	* protected from page table pages being freed from under it, and should
2439	* block any THP splits.
2440	*
2441	* One way to achieve this is to have the walker disable interrupts, and
2442	* rely on IPIs from the TLB flushing code blocking before the page table
2443	* pages are freed. This is unsuitable for architectures that do not need
2444	* to broadcast an IPI when invalidating TLBs.
2445	*
2446	* Another way to achieve this is to batch up page table containing pages
2447	* belonging to more than one mm_user, then rcu_sched a callback to free those
2448	* pages. Disabling interrupts will allow the fast_gup walker to both block
2449	* the rcu_sched callback, and an IPI that we broadcast for splitting THPs
2450	* (which is a relatively rare event). The code below adopts this strategy.
2451	*
2452	* Before activating this code, please be aware that the following assumptions
2453	* are currently made:
2454	*
2455	* *) Either MMU_GATHER_RCU_TABLE_FREE is enabled, and tlb_remove_table() is used to
2456	* free pages containing page tables or TLB flushing requires IPI broadcast.
2457	*
2458	* *) ptes can be read atomically by the architecture.
2459	*
2460	* *) access_ok is sufficient to validate userspace address ranges.
2461	*
2462	* The last two assumptions can be relaxed by the addition of helper functions.
2463	*
2464	* This code is based heavily on the PowerPC implementation by Nick Piggin.
2465	*/
2466	#ifdef CONFIG_HAVE_FAST_GUP
2467
2468	/*
2469	* Used in the GUP-fast path to determine whether a pin is permitted for a
2470	* specific folio.
2471	*
2472	* This call assumes the caller has pinned the folio, that the lowest page table
2473	* level still points to this folio, and that interrupts have been disabled.
2474	*
2475	* Writing to pinned file-backed dirty tracked folios is inherently problematic
2476	* (see comment describing the writable_file_mapping_allowed() function). We
2477	* therefore try to avoid the most egregious case of a long-term mapping doing
2478	* so.
2479	*
2480	* This function cannot be as thorough as that one as the VMA is not available
2481	* in the fast path, so instead we whitelist known good cases and if in doubt,
2482	* fall back to the slow path.
2483	*/
2484	static bool folio_fast_pin_allowed(struct folio *folio, unsigned int flags)
2485	{
2486	struct address_space *mapping;
2487	unsigned long mapping_flags;
2488
2489	/*
2490	* If we aren't pinning then no problematic write can occur. A long term
2491	* pin is the most egregious case so this is the one we disallow.
2492	*/
2493	if ((flags & (FOLL_PIN | FOLL_LONGTERM | FOLL_WRITE)) !=
2494	(FOLL_PIN | FOLL_LONGTERM | FOLL_WRITE))
2495	return true;
2496
2497	/* The folio is pinned, so we can safely access folio fields. */
2498
2499	if (WARN_ON_ONCE(folio_test_slab(folio)))
2500	return false;
2501
2502	/* hugetlb mappings do not require dirty-tracking. */
2503	if (folio_test_hugetlb(folio))
2504	return true;
2505
2506	/*
2507	* GUP-fast disables IRQs. When IRQS are disabled, RCU grace periods
2508	* cannot proceed, which means no actions performed under RCU can
2509	* proceed either.
2510	*
2511	* inodes and thus their mappings are freed under RCU, which means the
2512	* mapping cannot be freed beneath us and thus we can safely dereference
2513	* it.
2514	*/
2515	lockdep_assert_irqs_disabled();
2516
2517	/*
2518	* However, there may be operations which _alter_ the mapping, so ensure
2519	* we read it once and only once.
2520	*/
2521	mapping = READ_ONCE(folio->mapping);
2522
2523	/*
2524	* The mapping may have been truncated, in any case we cannot determine
2525	* if this mapping is safe - fall back to slow path to determine how to
2526	* proceed.
2527	*/
2528	if (!mapping)
2529	return false;
2530
2531	/* Anonymous folios pose no problem. */
2532	mapping_flags = (unsigned long)mapping & PAGE_MAPPING_FLAGS;
2533	if (mapping_flags)
2534	return mapping_flags & PAGE_MAPPING_ANON;
2535
2536	/*
2537	* At this point, we know the mapping is non-null and points to an
2538	* address_space object. The only remaining whitelisted file system is
2539	* shmem.
2540	*/
2541	return shmem_mapping(mapping);
2542	}
2543
2544	static void __maybe_unused undo_dev_pagemap(int *nr, int nr_start,
2545	unsigned int flags,
2546	struct page **pages)
2547	{
2548	while ((*nr) - nr_start) {
2549	struct page *page = pages[--(*nr)];
2550
2551	ClearPageReferenced(page);
2552	if (flags & FOLL_PIN)
2553	unpin_user_page(page);
2554	else
2555	put_page(page);
2556	}
2557	}
2558
2559	#ifdef CONFIG_ARCH_HAS_PTE_SPECIAL
2560	/*
2561	* Fast-gup relies on pte change detection to avoid concurrent pgtable
2562	* operations.
2563	*
2564	* To pin the page, fast-gup needs to do below in order:
2565	* (1) pin the page (by prefetching pte), then (2) check pte not changed.
2566	*
2567	* For the rest of pgtable operations where pgtable updates can be racy
2568	* with fast-gup, we need to do (1) clear pte, then (2) check whether page
2569	* is pinned.
2570	*
2571	* Above will work for all pte-level operations, including THP split.
2572	*
2573	* For THP collapse, it's a bit more complicated because fast-gup may be
2574	* walking a pgtable page that is being freed (pte is still valid but pmd
2575	* can be cleared already). To avoid race in such condition, we need to
2576	* also check pmd here to make sure pmd doesn't change (corresponds to
2577	* pmdp_collapse_flush() in the THP collapse code path).
2578	*/
2579	static int gup_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr,
2580	unsigned long end, unsigned int flags,
2581	struct page **pages, int *nr)
2582	{
2583	struct dev_pagemap *pgmap = NULL;
2584	int nr_start = *nr, ret = 0;
2585	pte_t *ptep, *ptem;
2586
2587	ptem = ptep = pte_offset_map(pmd: &pmd, addr);
2588	if (!ptep)
2589	return 0;
2590	do {
2591	pte_t pte = ptep_get_lockless(ptep);
2592	struct page *page;
2593	struct folio *folio;
2594
2595	/*
2596	* Always fallback to ordinary GUP on PROT_NONE-mapped pages:
2597	* pte_access_permitted() better should reject these pages
2598	* either way: otherwise, GUP-fast might succeed in
2599	* cases where ordinary GUP would fail due to VMA access
2600	* permissions.
2601	*/
2602	if (pte_protnone(pte))
2603	goto pte_unmap;
2604
2605	if (!pte_access_permitted(pte, write: flags & FOLL_WRITE))
2606	goto pte_unmap;
2607
2608	if (pte_devmap(a: pte)) {
2609	if (unlikely(flags & FOLL_LONGTERM))
2610	goto pte_unmap;
2611
2612	pgmap = get_dev_pagemap(pfn: pte_pfn(pte), pgmap);
2613	if (unlikely(!pgmap)) {
2614	undo_dev_pagemap(nr, nr_start, flags, pages);
2615	goto pte_unmap;
2616	}
2617	} else if (pte_special(pte))
2618	goto pte_unmap;
2619
2620	VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
2621	page = pte_page(pte);
2622
2623	folio = try_grab_folio(page, refs: 1, flags);
2624	if (!folio)
2625	goto pte_unmap;
2626
2627	if (unlikely(folio_is_secretmem(folio))) {
2628	gup_put_folio(folio, refs: 1, flags);
2629	goto pte_unmap;
2630	}
2631
2632	if (unlikely(pmd_val(pmd) != pmd_val(*pmdp)) ||
2633	unlikely(pte_val(pte) != pte_val(ptep_get(ptep)))) {
2634	gup_put_folio(folio, refs: 1, flags);
2635	goto pte_unmap;
2636	}
2637
2638	if (!folio_fast_pin_allowed(folio, flags)) {
2639	gup_put_folio(folio, refs: 1, flags);
2640	goto pte_unmap;
2641	}
2642
2643	if (!pte_write(pte) && gup_must_unshare(NULL, flags, page)) {
2644	gup_put_folio(folio, refs: 1, flags);
2645	goto pte_unmap;
2646	}
2647
2648	/*
2649	* We need to make the page accessible if and only if we are
2650	* going to access its content (the FOLL_PIN case). Please
2651	* see Documentation/core-api/pin_user_pages.rst for
2652	* details.
2653	*/
2654	if (flags & FOLL_PIN) {
2655	ret = arch_make_page_accessible(page);
2656	if (ret) {
2657	gup_put_folio(folio, refs: 1, flags);
2658	goto pte_unmap;
2659	}
2660	}
2661	folio_set_referenced(folio);
2662	pages[*nr] = page;
2663	(*nr)++;
2664	} while (ptep++, addr += PAGE_SIZE, addr != end);
2665
2666	ret = 1;
2667
2668	pte_unmap:
2669	if (pgmap)
2670	put_dev_pagemap(pgmap);
2671	pte_unmap(pte: ptem);
2672	return ret;
2673	}
2674	#else
2675
2676	/*
2677	* If we can't determine whether or not a pte is special, then fail immediately
2678	* for ptes. Note, we can still pin HugeTLB and THP as these are guaranteed not
2679	* to be special.
2680	*
2681	* For a futex to be placed on a THP tail page, get_futex_key requires a
2682	* get_user_pages_fast_only implementation that can pin pages. Thus it's still
2683	* useful to have gup_huge_pmd even if we can't operate on ptes.
2684	*/
2685	static int gup_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr,
2686	unsigned long end, unsigned int flags,
2687	struct page **pages, int *nr)
2688	{
2689	return 0;
2690	}
2691	#endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */
2692
2693	#if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
2694	static int __gup_device_huge(unsigned long pfn, unsigned long addr,
2695	unsigned long end, unsigned int flags,
2696	struct page **pages, int *nr)
2697	{
2698	int nr_start = *nr;
2699	struct dev_pagemap *pgmap = NULL;
2700
2701	do {
2702	struct page *page = pfn_to_page(pfn);
2703
2704	pgmap = get_dev_pagemap(pfn, pgmap);
2705	if (unlikely(!pgmap)) {
2706	undo_dev_pagemap(nr, nr_start, flags, pages);
2707	break;
2708	}
2709
2710	if (!(flags & FOLL_PCI_P2PDMA) && is_pci_p2pdma_page(page)) {
2711	undo_dev_pagemap(nr, nr_start, flags, pages);
2712	break;
2713	}
2714
2715	SetPageReferenced(page);
2716	pages[*nr] = page;
2717	if (unlikely(try_grab_page(page, flags))) {
2718	undo_dev_pagemap(nr, nr_start, flags, pages);
2719	break;
2720	}
2721	(*nr)++;
2722	pfn++;
2723	} while (addr += PAGE_SIZE, addr != end);
2724
2725	put_dev_pagemap(pgmap);
2726	return addr == end;
2727	}
2728
2729	static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
2730	unsigned long end, unsigned int flags,
2731	struct page **pages, int *nr)
2732	{
2733	unsigned long fault_pfn;
2734	int nr_start = *nr;
2735
2736	fault_pfn = pmd_pfn(pmd: orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
2737	if (!__gup_device_huge(pfn: fault_pfn, addr, end, flags, pages, nr))
2738	return 0;
2739
2740	if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
2741	undo_dev_pagemap(nr, nr_start, flags, pages);
2742	return 0;
2743	}
2744	return 1;
2745	}
2746
2747	static int __gup_device_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
2748	unsigned long end, unsigned int flags,
2749	struct page **pages, int *nr)
2750	{
2751	unsigned long fault_pfn;
2752	int nr_start = *nr;
2753
2754	fault_pfn = pud_pfn(pud: orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
2755	if (!__gup_device_huge(pfn: fault_pfn, addr, end, flags, pages, nr))
2756	return 0;
2757
2758	if (unlikely(pud_val(orig) != pud_val(*pudp))) {
2759	undo_dev_pagemap(nr, nr_start, flags, pages);
2760	return 0;
2761	}
2762	return 1;
2763	}
2764	#else
2765	static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
2766	unsigned long end, unsigned int flags,
2767	struct page **pages, int *nr)
2768	{
2769	BUILD_BUG();
2770	return 0;
2771	}
2772
2773	static int __gup_device_huge_pud(pud_t pud, pud_t *pudp, unsigned long addr,
2774	unsigned long end, unsigned int flags,
2775	struct page **pages, int *nr)
2776	{
2777	BUILD_BUG();
2778	return 0;
2779	}
2780	#endif
2781
2782	static int record_subpages(struct page *page, unsigned long addr,
2783	unsigned long end, struct page **pages)
2784	{
2785	int nr;
2786
2787	for (nr = 0; addr != end; nr++, addr += PAGE_SIZE)
2788	pages[nr] = nth_page(page, nr);
2789
2790	return nr;
2791	}
2792
2793	#ifdef CONFIG_ARCH_HAS_HUGEPD
2794	static unsigned long hugepte_addr_end(unsigned long addr, unsigned long end,
2795	unsigned long sz)
2796	{
2797	unsigned long __boundary = (addr + sz) & ~(sz-1);
2798	return (__boundary - 1 < end - 1) ? __boundary : end;
2799	}
2800
2801	static int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr,
2802	unsigned long end, unsigned int flags,
2803	struct page **pages, int *nr)
2804	{
2805	unsigned long pte_end;
2806	struct page *page;
2807	struct folio *folio;
2808	pte_t pte;
2809	int refs;
2810
2811	pte_end = (addr + sz) & ~(sz-1);
2812	if (pte_end < end)
2813	end = pte_end;
2814
2815	pte = huge_ptep_get(ptep);
2816
2817	if (!pte_access_permitted(pte, flags & FOLL_WRITE))
2818	return 0;
2819
2820	/* hugepages are never "special" */
2821	VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
2822
2823	page = nth_page(pte_page(pte), (addr & (sz - 1)) >> PAGE_SHIFT);
2824	refs = record_subpages(page, addr, end, pages + *nr);
2825
2826	folio = try_grab_folio(page, refs, flags);
2827	if (!folio)
2828	return 0;
2829
2830	if (unlikely(pte_val(pte) != pte_val(ptep_get(ptep)))) {
2831	gup_put_folio(folio, refs, flags);
2832	return 0;
2833	}
2834
2835	if (!folio_fast_pin_allowed(folio, flags)) {
2836	gup_put_folio(folio, refs, flags);
2837	return 0;
2838	}
2839
2840	if (!pte_write(pte) && gup_must_unshare(NULL, flags, &folio->page)) {
2841	gup_put_folio(folio, refs, flags);
2842	return 0;
2843	}
2844
2845	*nr += refs;
2846	folio_set_referenced(folio);
2847	return 1;
2848	}
2849
2850	static int gup_huge_pd(hugepd_t hugepd, unsigned long addr,
2851	unsigned int pdshift, unsigned long end, unsigned int flags,
2852	struct page **pages, int *nr)
2853	{
2854	pte_t *ptep;
2855	unsigned long sz = 1UL << hugepd_shift(hugepd);
2856	unsigned long next;
2857
2858	ptep = hugepte_offset(hugepd, addr, pdshift);
2859	do {
2860	next = hugepte_addr_end(addr, end, sz);
2861	if (!gup_hugepte(ptep, sz, addr, end, flags, pages, nr))
2862	return 0;
2863	} while (ptep++, addr = next, addr != end);
2864
2865	return 1;
2866	}
2867	#else
2868	static inline int gup_huge_pd(hugepd_t hugepd, unsigned long addr,
2869	unsigned int pdshift, unsigned long end, unsigned int flags,
2870	struct page **pages, int *nr)
2871	{
2872	return 0;
2873	}
2874	#endif /* CONFIG_ARCH_HAS_HUGEPD */
2875
2876	static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
2877	unsigned long end, unsigned int flags,
2878	struct page **pages, int *nr)
2879	{
2880	struct page *page;
2881	struct folio *folio;
2882	int refs;
2883
2884	if (!pmd_access_permitted(pmd: orig, write: flags & FOLL_WRITE))
2885	return 0;
2886
2887	if (pmd_devmap(pmd: orig)) {
2888	if (unlikely(flags & FOLL_LONGTERM))
2889	return 0;
2890	return __gup_device_huge_pmd(orig, pmdp, addr, end, flags,
2891	pages, nr);
2892	}
2893
2894	page = nth_page(pmd_page(orig), (addr & ~PMD_MASK) >> PAGE_SHIFT);
2895	refs = record_subpages(page, addr, end, pages: pages + *nr);
2896
2897	folio = try_grab_folio(page, refs, flags);
2898	if (!folio)
2899	return 0;
2900
2901	if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
2902	gup_put_folio(folio, refs, flags);
2903	return 0;
2904	}
2905
2906	if (!folio_fast_pin_allowed(folio, flags)) {
2907	gup_put_folio(folio, refs, flags);
2908	return 0;
2909	}
2910	if (!pmd_write(pmd: orig) && gup_must_unshare(NULL, flags, page: &folio->page)) {
2911	gup_put_folio(folio, refs, flags);
2912	return 0;
2913	}
2914
2915	*nr += refs;
2916	folio_set_referenced(folio);
2917	return 1;
2918	}
2919
2920	static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
2921	unsigned long end, unsigned int flags,
2922	struct page **pages, int *nr)
2923	{
2924	struct page *page;
2925	struct folio *folio;
2926	int refs;
2927
2928	if (!pud_access_permitted(pud: orig, write: flags & FOLL_WRITE))
2929	return 0;
2930
2931	if (pud_devmap(pud: orig)) {
2932	if (unlikely(flags & FOLL_LONGTERM))
2933	return 0;
2934	return __gup_device_huge_pud(orig, pudp, addr, end, flags,
2935	pages, nr);
2936	}
2937
2938	page = nth_page(pud_page(orig), (addr & ~PUD_MASK) >> PAGE_SHIFT);
2939	refs = record_subpages(page, addr, end, pages: pages + *nr);
2940
2941	folio = try_grab_folio(page, refs, flags);
2942	if (!folio)
2943	return 0;
2944
2945	if (unlikely(pud_val(orig) != pud_val(*pudp))) {
2946	gup_put_folio(folio, refs, flags);
2947	return 0;
2948	}
2949
2950	if (!folio_fast_pin_allowed(folio, flags)) {
2951	gup_put_folio(folio, refs, flags);
2952	return 0;
2953	}
2954
2955	if (!pud_write(pud: orig) && gup_must_unshare(NULL, flags, page: &folio->page)) {
2956	gup_put_folio(folio, refs, flags);
2957	return 0;
2958	}
2959
2960	*nr += refs;
2961	folio_set_referenced(folio);
2962	return 1;
2963	}
2964
2965	static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
2966	unsigned long end, unsigned int flags,
2967	struct page **pages, int *nr)
2968	{
2969	int refs;
2970	struct page *page;
2971	struct folio *folio;
2972
2973	if (!pgd_access_permitted(orig, flags & FOLL_WRITE))
2974	return 0;
2975
2976	BUILD_BUG_ON(pgd_devmap(orig));
2977
2978	page = nth_page(pgd_page(orig), (addr & ~PGDIR_MASK) >> PAGE_SHIFT);
2979	refs = record_subpages(page, addr, end, pages: pages + *nr);
2980
2981	folio = try_grab_folio(page, refs, flags);
2982	if (!folio)
2983	return 0;
2984
2985	if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) {
2986	gup_put_folio(folio, refs, flags);
2987	return 0;
2988	}
2989
2990	if (!pgd_write(pgd: orig) && gup_must_unshare(NULL, flags, page: &folio->page)) {
2991	gup_put_folio(folio, refs, flags);
2992	return 0;
2993	}
2994
2995	if (!folio_fast_pin_allowed(folio, flags)) {
2996	gup_put_folio(folio, refs, flags);
2997	return 0;
2998	}
2999
3000	*nr += refs;
3001	folio_set_referenced(folio);
3002	return 1;
3003	}
3004
3005	static int gup_pmd_range(pud_t *pudp, pud_t pud, unsigned long addr, unsigned long end,
3006	unsigned int flags, struct page **pages, int *nr)
3007	{
3008	unsigned long next;
3009	pmd_t *pmdp;
3010
3011	pmdp = pmd_offset_lockless(pudp, pud, addr);
3012	do {
3013	pmd_t pmd = pmdp_get_lockless(pmdp);
3014
3015	next = pmd_addr_end(addr, end);
3016	if (!pmd_present(pmd))
3017	return 0;
3018
3019	if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd) ||
3020	pmd_devmap(pmd))) {
3021	/* See gup_pte_range() */
3022	if (pmd_protnone(pmd))
3023	return 0;
3024
3025	if (!gup_huge_pmd(orig: pmd, pmdp, addr, end: next, flags,
3026	pages, nr))
3027	return 0;
3028
3029	} else if (unlikely(is_hugepd(__hugepd(pmd_val(pmd))))) {
3030	/*
3031	* architecture have different format for hugetlbfs
3032	* pmd format and THP pmd format
3033	*/
3034	if (!gup_huge_pd(__hugepd(pmd_val(pmd)), addr,
3035	PMD_SHIFT, end: next, flags, pages, nr))
3036	return 0;
3037	} else if (!gup_pte_range(pmd, pmdp, addr, end: next, flags, pages, nr))
3038	return 0;
3039	} while (pmdp++, addr = next, addr != end);
3040
3041	return 1;
3042	}
3043
3044	static int gup_pud_range(p4d_t *p4dp, p4d_t p4d, unsigned long addr, unsigned long end,
3045	unsigned int flags, struct page **pages, int *nr)
3046	{
3047	unsigned long next;
3048	pud_t *pudp;
3049
3050	pudp = pud_offset_lockless(p4dp, p4d, addr);
3051	do {
3052	pud_t pud = READ_ONCE(*pudp);
3053
3054	next = pud_addr_end(addr, end);
3055	if (unlikely(!pud_present(pud)))
3056	return 0;
3057	if (unlikely(pud_huge(pud) || pud_devmap(pud))) {
3058	if (!gup_huge_pud(orig: pud, pudp, addr, end: next, flags,
3059	pages, nr))
3060	return 0;
3061	} else if (unlikely(is_hugepd(__hugepd(pud_val(pud))))) {
3062	if (!gup_huge_pd(__hugepd(pud_val(pud)), addr,
3063	PUD_SHIFT, end: next, flags, pages, nr))
3064	return 0;
3065	} else if (!gup_pmd_range(pudp, pud, addr, end: next, flags, pages, nr))
3066	return 0;
3067	} while (pudp++, addr = next, addr != end);
3068
3069	return 1;
3070	}
3071
3072	static int gup_p4d_range(pgd_t *pgdp, pgd_t pgd, unsigned long addr, unsigned long end,
3073	unsigned int flags, struct page **pages, int *nr)
3074	{
3075	unsigned long next;
3076	p4d_t *p4dp;
3077
3078	p4dp = p4d_offset_lockless(pgdp, pgd, addr);
3079	do {
3080	p4d_t p4d = READ_ONCE(*p4dp);
3081
3082	next = p4d_addr_end(addr, end);
3083	if (p4d_none(p4d))
3084	return 0;
3085	BUILD_BUG_ON(p4d_huge(p4d));
3086	if (unlikely(is_hugepd(__hugepd(p4d_val(p4d))))) {
3087	if (!gup_huge_pd(__hugepd(p4d_val(p4d)), addr,
3088	P4D_SHIFT, end: next, flags, pages, nr))
3089	return 0;
3090	} else if (!gup_pud_range(p4dp, p4d, addr, end: next, flags, pages, nr))
3091	return 0;
3092	} while (p4dp++, addr = next, addr != end);
3093
3094	return 1;
3095	}
3096
3097	static void gup_pgd_range(unsigned long addr, unsigned long end,
3098	unsigned int flags, struct page **pages, int *nr)
3099	{
3100	unsigned long next;
3101	pgd_t *pgdp;
3102
3103	pgdp = pgd_offset(current->mm, addr);
3104	do {
3105	pgd_t pgd = READ_ONCE(*pgdp);
3106
3107	next = pgd_addr_end(addr, end);
3108	if (pgd_none(pgd))
3109	return;
3110	if (unlikely(pgd_huge(pgd))) {
3111	if (!gup_huge_pgd(orig: pgd, pgdp, addr, end: next, flags,
3112	pages, nr))
3113	return;
3114	} else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd))))) {
3115	if (!gup_huge_pd(__hugepd(pgd_val(pgd)), addr,
3116	PGDIR_SHIFT, end: next, flags, pages, nr))
3117	return;
3118	} else if (!gup_p4d_range(pgdp, pgd, addr, end: next, flags, pages, nr))
3119	return;
3120	} while (pgdp++, addr = next, addr != end);
3121	}
3122	#else
3123	static inline void gup_pgd_range(unsigned long addr, unsigned long end,
3124	unsigned int flags, struct page **pages, int *nr)
3125	{
3126	}
3127	#endif /* CONFIG_HAVE_FAST_GUP */
3128
3129	#ifndef gup_fast_permitted
3130	/*
3131	* Check if it's allowed to use get_user_pages_fast_only() for the range, or
3132	* we need to fall back to the slow version:
3133	*/
3134	static bool gup_fast_permitted(unsigned long start, unsigned long end)
3135	{
3136	return true;
3137	}
3138	#endif
3139
3140	static unsigned long lockless_pages_from_mm(unsigned long start,
3141	unsigned long end,
3142	unsigned int gup_flags,
3143	struct page **pages)
3144	{
3145	unsigned long flags;
3146	int nr_pinned = 0;
3147	unsigned seq;
3148
3149	if (!IS_ENABLED(CONFIG_HAVE_FAST_GUP) ||
3150	!gup_fast_permitted(start, end))
3151	return 0;
3152
3153	if (gup_flags & FOLL_PIN) {
3154	seq = raw_read_seqcount(&current->mm->write_protect_seq);
3155	if (seq & 1)
3156	return 0;
3157	}
3158
3159	/*
3160	* Disable interrupts. The nested form is used, in order to allow full,
3161	* general purpose use of this routine.
3162	*
3163	* With interrupts disabled, we block page table pages from being freed
3164	* from under us. See struct mmu_table_batch comments in
3165	* include/asm-generic/tlb.h for more details.
3166	*
3167	* We do not adopt an rcu_read_lock() here as we also want to block IPIs
3168	* that come from THPs splitting.
3169	*/
3170	local_irq_save(flags);
3171	gup_pgd_range(addr: start, end, flags: gup_flags, pages, nr: &nr_pinned);
3172	local_irq_restore(flags);
3173
3174	/*
3175	* When pinning pages for DMA there could be a concurrent write protect
3176	* from fork() via copy_page_range(), in this case always fail fast GUP.
3177	*/
3178	if (gup_flags & FOLL_PIN) {
3179	if (read_seqcount_retry(&current->mm->write_protect_seq, seq)) {
3180	unpin_user_pages_lockless(pages, npages: nr_pinned);
3181	return 0;
3182	} else {
3183	sanity_check_pinned_pages(pages, npages: nr_pinned);
3184	}
3185	}
3186	return nr_pinned;
3187	}
3188
3189	static int internal_get_user_pages_fast(unsigned long start,
3190	unsigned long nr_pages,
3191	unsigned int gup_flags,
3192	struct page **pages)
3193	{
3194	unsigned long len, end;
3195	unsigned long nr_pinned;
3196	int locked = 0;
3197	int ret;
3198
3199	if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM |
3200	FOLL_FORCE | FOLL_PIN | FOLL_GET |
3201	FOLL_FAST_ONLY | FOLL_NOFAULT |
3202	FOLL_PCI_P2PDMA | FOLL_HONOR_NUMA_FAULT)))
3203	return -EINVAL;
3204
3205	if (gup_flags & FOLL_PIN)
3206	mm_set_has_pinned_flag(mm_flags: &current->mm->flags);
3207
3208	if (!(gup_flags & FOLL_FAST_ONLY))
3209	might_lock_read(&current->mm->mmap_lock);
3210
3211	start = untagged_addr(start) & PAGE_MASK;
3212	len = nr_pages << PAGE_SHIFT;
3213	if (check_add_overflow(start, len, &end))
3214	return -EOVERFLOW;
3215	if (end > TASK_SIZE_MAX)
3216	return -EFAULT;
3217	if (unlikely(!access_ok((void __user *)start, len)))
3218	return -EFAULT;
3219
3220	nr_pinned = lockless_pages_from_mm(start, end, gup_flags, pages);
3221	if (nr_pinned == nr_pages || gup_flags & FOLL_FAST_ONLY)
3222	return nr_pinned;
3223
3224	/* Slow path: try to get the remaining pages with get_user_pages */
3225	start += nr_pinned << PAGE_SHIFT;
3226	pages += nr_pinned;
3227	ret = __gup_longterm_locked(current->mm, start, nr_pages: nr_pages - nr_pinned,
3228	pages, locked: &locked,
3229	gup_flags: gup_flags | FOLL_TOUCH | FOLL_UNLOCKABLE);
3230	if (ret < 0) {
3231	/*
3232	* The caller has to unpin the pages we already pinned so
3233	* returning -errno is not an option
3234	*/
3235	if (nr_pinned)
3236	return nr_pinned;
3237	return ret;
3238	}
3239	return ret + nr_pinned;
3240	}
3241
3242	/**
3243	* get_user_pages_fast_only() - pin user pages in memory
3244	* @start: starting user address
3245	* @nr_pages: number of pages from start to pin
3246	* @gup_flags: flags modifying pin behaviour
3247	* @pages: array that receives pointers to the pages pinned.
3248	* Should be at least nr_pages long.
3249	*
3250	* Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to
3251	* the regular GUP.
3252	*
3253	* If the architecture does not support this function, simply return with no
3254	* pages pinned.
3255	*
3256	* Careful, careful! COW breaking can go either way, so a non-write
3257	* access can get ambiguous page results. If you call this function without
3258	* 'write' set, you'd better be sure that you're ok with that ambiguity.
3259	*/
3260	int get_user_pages_fast_only(unsigned long start, int nr_pages,
3261	unsigned int gup_flags, struct page **pages)
3262	{
3263	/*
3264	* Internally (within mm/gup.c), gup fast variants must set FOLL_GET,
3265	* because gup fast is always a "pin with a +1 page refcount" request.
3266	*
3267	* FOLL_FAST_ONLY is required in order to match the API description of
3268	* this routine: no fall back to regular ("slow") GUP.
3269	*/
3270	if (!is_valid_gup_args(pages, NULL, gup_flags_p: &gup_flags,
3271	to_set: FOLL_GET | FOLL_FAST_ONLY))
3272	return -EINVAL;
3273
3274	return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages);
3275	}
3276	EXPORT_SYMBOL_GPL(get_user_pages_fast_only);
3277
3278	/**
3279	* get_user_pages_fast() - pin user pages in memory
3280	* @start: starting user address
3281	* @nr_pages: number of pages from start to pin
3282	* @gup_flags: flags modifying pin behaviour
3283	* @pages: array that receives pointers to the pages pinned.
3284	* Should be at least nr_pages long.
3285	*
3286	* Attempt to pin user pages in memory without taking mm->mmap_lock.
3287	* If not successful, it will fall back to taking the lock and
3288	* calling get_user_pages().
3289	*
3290	* Returns number of pages pinned. This may be fewer than the number requested.
3291	* If nr_pages is 0 or negative, returns 0. If no pages were pinned, returns
3292	* -errno.
3293	*/
3294	int get_user_pages_fast(unsigned long start, int nr_pages,
3295	unsigned int gup_flags, struct page **pages)
3296	{
3297	/*
3298	* The caller may or may not have explicitly set FOLL_GET; either way is
3299	* OK. However, internally (within mm/gup.c), gup fast variants must set
3300	* FOLL_GET, because gup fast is always a "pin with a +1 page refcount"
3301	* request.
3302	*/
3303	if (!is_valid_gup_args(pages, NULL, gup_flags_p: &gup_flags, to_set: FOLL_GET))
3304	return -EINVAL;
3305	return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages);
3306	}
3307	EXPORT_SYMBOL_GPL(get_user_pages_fast);
3308
3309	/**
3310	* pin_user_pages_fast() - pin user pages in memory without taking locks
3311	*
3312	* @start: starting user address
3313	* @nr_pages: number of pages from start to pin
3314	* @gup_flags: flags modifying pin behaviour
3315	* @pages: array that receives pointers to the pages pinned.
3316	* Should be at least nr_pages long.
3317	*
3318	* Nearly the same as get_user_pages_fast(), except that FOLL_PIN is set. See
3319	* get_user_pages_fast() for documentation on the function arguments, because
3320	* the arguments here are identical.
3321	*
3322	* FOLL_PIN means that the pages must be released via unpin_user_page(). Please
3323	* see Documentation/core-api/pin_user_pages.rst for further details.
3324	*
3325	* Note that if a zero_page is amongst the returned pages, it will not have
3326	* pins in it and unpin_user_page() will not remove pins from it.
3327	*/
3328	int pin_user_pages_fast(unsigned long start, int nr_pages,
3329	unsigned int gup_flags, struct page **pages)
3330	{
3331	if (!is_valid_gup_args(pages, NULL, gup_flags_p: &gup_flags, to_set: FOLL_PIN))
3332	return -EINVAL;
3333	return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages);
3334	}
3335	EXPORT_SYMBOL_GPL(pin_user_pages_fast);
3336
3337	/**
3338	* pin_user_pages_remote() - pin pages of a remote process
3339	*
3340	* @mm: mm_struct of target mm
3341	* @start: starting user address
3342	* @nr_pages: number of pages from start to pin
3343	* @gup_flags: flags modifying lookup behaviour
3344	* @pages: array that receives pointers to the pages pinned.
3345	* Should be at least nr_pages long.
3346	* @locked: pointer to lock flag indicating whether lock is held and
3347	* subsequently whether VM_FAULT_RETRY functionality can be
3348	* utilised. Lock must initially be held.
3349	*
3350	* Nearly the same as get_user_pages_remote(), except that FOLL_PIN is set. See
3351	* get_user_pages_remote() for documentation on the function arguments, because
3352	* the arguments here are identical.
3353	*
3354	* FOLL_PIN means that the pages must be released via unpin_user_page(). Please
3355	* see Documentation/core-api/pin_user_pages.rst for details.
3356	*
3357	* Note that if a zero_page is amongst the returned pages, it will not have
3358	* pins in it and unpin_user_page*() will not remove pins from it.
3359	*/
3360	long pin_user_pages_remote(struct mm_struct *mm,
3361	unsigned long start, unsigned long nr_pages,
3362	unsigned int gup_flags, struct page **pages,
3363	int *locked)
3364	{
3365	int local_locked = 1;
3366
3367	if (!is_valid_gup_args(pages, locked, gup_flags_p: &gup_flags,
3368	to_set: FOLL_PIN | FOLL_TOUCH | FOLL_REMOTE))
3369	return 0;
3370	return __gup_longterm_locked(mm, start, nr_pages, pages,
3371	locked: locked ? locked : &local_locked,
3372	gup_flags);
3373	}
3374	EXPORT_SYMBOL(pin_user_pages_remote);
3375
3376	/**
3377	* pin_user_pages() - pin user pages in memory for use by other devices
3378	*
3379	* @start: starting user address
3380	* @nr_pages: number of pages from start to pin
3381	* @gup_flags: flags modifying lookup behaviour
3382	* @pages: array that receives pointers to the pages pinned.
3383	* Should be at least nr_pages long.
3384	*
3385	* Nearly the same as get_user_pages(), except that FOLL_TOUCH is not set, and
3386	* FOLL_PIN is set.
3387	*
3388	* FOLL_PIN means that the pages must be released via unpin_user_page(). Please
3389	* see Documentation/core-api/pin_user_pages.rst for details.
3390	*
3391	* Note that if a zero_page is amongst the returned pages, it will not have
3392	* pins in it and unpin_user_page*() will not remove pins from it.
3393	*/
3394	long pin_user_pages(unsigned long start, unsigned long nr_pages,
3395	unsigned int gup_flags, struct page **pages)
3396	{
3397	int locked = 1;
3398
3399	if (!is_valid_gup_args(pages, NULL, gup_flags_p: &gup_flags, to_set: FOLL_PIN))
3400	return 0;
3401	return __gup_longterm_locked(current->mm, start, nr_pages,
3402	pages, locked: &locked, gup_flags);
3403	}
3404	EXPORT_SYMBOL(pin_user_pages);
3405
3406	/*
3407	* pin_user_pages_unlocked() is the FOLL_PIN variant of
3408	* get_user_pages_unlocked(). Behavior is the same, except that this one sets
3409	* FOLL_PIN and rejects FOLL_GET.
3410	*
3411	* Note that if a zero_page is amongst the returned pages, it will not have
3412	* pins in it and unpin_user_page*() will not remove pins from it.
3413	*/
3414	long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
3415	struct page **pages, unsigned int gup_flags)
3416	{
3417	int locked = 0;
3418
3419	if (!is_valid_gup_args(pages, NULL, gup_flags_p: &gup_flags,
3420	to_set: FOLL_PIN | FOLL_TOUCH | FOLL_UNLOCKABLE))
3421	return 0;
3422
3423	return __gup_longterm_locked(current->mm, start, nr_pages, pages,
3424	locked: &locked, gup_flags);
3425	}
3426	EXPORT_SYMBOL(pin_user_pages_unlocked);
3427