1 // SPDX-License-Identifier: GPL-2.0-only
2 #include <linux/kernel.h>
3 #include <linux/errno.h>
5 #include <linux/spinlock.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>
14 #include <linux/sched/signal.h>
15 #include <linux/rwsem.h>
16 #include <linux/hugetlb.h>
17 #include <linux/migrate.h>
18 #include <linux/mm_inline.h>
19 #include <linux/sched/mm.h>
21 #include <asm/mmu_context.h>
22 #include <asm/pgtable.h>
23 #include <asm/tlbflush.h>
27 struct follow_page_context {
28 struct dev_pagemap *pgmap;
29 unsigned int page_mask;
32 static void hpage_pincount_add(struct page *page, int refs)
34 VM_BUG_ON_PAGE(!hpage_pincount_available(page), page);
35 VM_BUG_ON_PAGE(page != compound_head(page), page);
37 atomic_add(refs, compound_pincount_ptr(page));
40 static void hpage_pincount_sub(struct page *page, int refs)
42 VM_BUG_ON_PAGE(!hpage_pincount_available(page), page);
43 VM_BUG_ON_PAGE(page != compound_head(page), page);
45 atomic_sub(refs, compound_pincount_ptr(page));
49 * Return the compound head page with ref appropriately incremented,
50 * or NULL if that failed.
52 static inline struct page *try_get_compound_head(struct page *page, int refs)
54 struct page *head = compound_head(page);
56 if (WARN_ON_ONCE(page_ref_count(head) < 0))
58 if (unlikely(!page_cache_add_speculative(head, refs)))
64 * try_grab_compound_head() - attempt to elevate a page's refcount, by a
65 * flags-dependent amount.
67 * "grab" names in this file mean, "look at flags to decide whether to use
68 * FOLL_PIN or FOLL_GET behavior, when incrementing the page's refcount.
70 * Either FOLL_PIN or FOLL_GET (or neither) must be set, but not both at the
71 * same time. (That's true throughout the get_user_pages*() and
72 * pin_user_pages*() APIs.) Cases:
74 * FOLL_GET: page's refcount will be incremented by 1.
75 * FOLL_PIN: page's refcount will be incremented by GUP_PIN_COUNTING_BIAS.
77 * Return: head page (with refcount appropriately incremented) for success, or
78 * NULL upon failure. If neither FOLL_GET nor FOLL_PIN was set, that's
79 * considered failure, and furthermore, a likely bug in the caller, so a warning
82 static __maybe_unused struct page *try_grab_compound_head(struct page *page,
87 return try_get_compound_head(page, refs);
88 else if (flags & FOLL_PIN) {
92 * Can't do FOLL_LONGTERM + FOLL_PIN with CMA in the gup fast
93 * path, so fail and let the caller fall back to the slow path.
95 if (unlikely(flags & FOLL_LONGTERM) &&
96 is_migrate_cma_page(page))
100 * When pinning a compound page of order > 1 (which is what
101 * hpage_pincount_available() checks for), use an exact count to
102 * track it, via hpage_pincount_add/_sub().
104 * However, be sure to *also* increment the normal page refcount
105 * field at least once, so that the page really is pinned.
107 if (!hpage_pincount_available(page))
108 refs *= GUP_PIN_COUNTING_BIAS;
110 page = try_get_compound_head(page, refs);
114 if (hpage_pincount_available(page))
115 hpage_pincount_add(page, refs);
117 mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_ACQUIRED,
128 * try_grab_page() - elevate a page's refcount by a flag-dependent amount
130 * This might not do anything at all, depending on the flags argument.
132 * "grab" names in this file mean, "look at flags to decide whether to use
133 * FOLL_PIN or FOLL_GET behavior, when incrementing the page's refcount.
135 * @page: pointer to page to be grabbed
136 * @flags: gup flags: these are the FOLL_* flag values.
138 * Either FOLL_PIN or FOLL_GET (or neither) may be set, but not both at the same
141 * FOLL_GET: page's refcount will be incremented by 1.
142 * FOLL_PIN: page's refcount will be incremented by GUP_PIN_COUNTING_BIAS.
144 * Return: true for success, or if no action was required (if neither FOLL_PIN
145 * nor FOLL_GET was set, nothing is done). False for failure: FOLL_GET or
146 * FOLL_PIN was set, but the page could not be grabbed.
148 bool __must_check try_grab_page(struct page *page, unsigned int flags)
150 WARN_ON_ONCE((flags & (FOLL_GET | FOLL_PIN)) == (FOLL_GET | FOLL_PIN));
152 if (flags & FOLL_GET)
153 return try_get_page(page);
154 else if (flags & FOLL_PIN) {
157 page = compound_head(page);
159 if (WARN_ON_ONCE(page_ref_count(page) <= 0))
162 if (hpage_pincount_available(page))
163 hpage_pincount_add(page, 1);
165 refs = GUP_PIN_COUNTING_BIAS;
168 * Similar to try_grab_compound_head(): even if using the
169 * hpage_pincount_add/_sub() routines, be sure to
170 * *also* increment the normal page refcount field at least
171 * once, so that the page really is pinned.
173 page_ref_add(page, refs);
175 mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_ACQUIRED, 1);
181 #ifdef CONFIG_DEV_PAGEMAP_OPS
182 static bool __unpin_devmap_managed_user_page(struct page *page)
186 if (!page_is_devmap_managed(page))
189 if (hpage_pincount_available(page))
190 hpage_pincount_sub(page, 1);
192 refs = GUP_PIN_COUNTING_BIAS;
194 count = page_ref_sub_return(page, refs);
196 mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_RELEASED, 1);
198 * devmap page refcounts are 1-based, rather than 0-based: if
199 * refcount is 1, then the page is free and the refcount is
200 * stable because nobody holds a reference on the page.
203 free_devmap_managed_page(page);
210 static bool __unpin_devmap_managed_user_page(struct page *page)
214 #endif /* CONFIG_DEV_PAGEMAP_OPS */
217 * unpin_user_page() - release a dma-pinned page
218 * @page: pointer to page to be released
220 * Pages that were pinned via pin_user_pages*() must be released via either
221 * unpin_user_page(), or one of the unpin_user_pages*() routines. This is so
222 * that such pages can be separately tracked and uniquely handled. In
223 * particular, interactions with RDMA and filesystems need special handling.
225 void unpin_user_page(struct page *page)
229 page = compound_head(page);
232 * For devmap managed pages we need to catch refcount transition from
233 * GUP_PIN_COUNTING_BIAS to 1, when refcount reach one it means the
234 * page is free and we need to inform the device driver through
235 * callback. See include/linux/memremap.h and HMM for details.
237 if (__unpin_devmap_managed_user_page(page))
240 if (hpage_pincount_available(page))
241 hpage_pincount_sub(page, 1);
243 refs = GUP_PIN_COUNTING_BIAS;
245 if (page_ref_sub_and_test(page, refs))
248 mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_RELEASED, 1);
250 EXPORT_SYMBOL(unpin_user_page);
253 * unpin_user_pages_dirty_lock() - release and optionally dirty gup-pinned pages
254 * @pages: array of pages to be maybe marked dirty, and definitely released.
255 * @npages: number of pages in the @pages array.
256 * @make_dirty: whether to mark the pages dirty
258 * "gup-pinned page" refers to a page that has had one of the get_user_pages()
259 * variants called on that page.
261 * For each page in the @pages array, make that page (or its head page, if a
262 * compound page) dirty, if @make_dirty is true, and if the page was previously
263 * listed as clean. In any case, releases all pages using unpin_user_page(),
264 * possibly via unpin_user_pages(), for the non-dirty case.
266 * Please see the unpin_user_page() documentation for details.
268 * set_page_dirty_lock() is used internally. If instead, set_page_dirty() is
269 * required, then the caller should a) verify that this is really correct,
270 * because _lock() is usually required, and b) hand code it:
271 * set_page_dirty_lock(), unpin_user_page().
274 void unpin_user_pages_dirty_lock(struct page **pages, unsigned long npages,
280 * TODO: this can be optimized for huge pages: if a series of pages is
281 * physically contiguous and part of the same compound page, then a
282 * single operation to the head page should suffice.
286 unpin_user_pages(pages, npages);
290 for (index = 0; index < npages; index++) {
291 struct page *page = compound_head(pages[index]);
293 * Checking PageDirty at this point may race with
294 * clear_page_dirty_for_io(), but that's OK. Two key
297 * 1) This code sees the page as already dirty, so it
298 * skips the call to set_page_dirty(). That could happen
299 * because clear_page_dirty_for_io() called
300 * page_mkclean(), followed by set_page_dirty().
301 * However, now the page is going to get written back,
302 * which meets the original intention of setting it
303 * dirty, so all is well: clear_page_dirty_for_io() goes
304 * on to call TestClearPageDirty(), and write the page
307 * 2) This code sees the page as clean, so it calls
308 * set_page_dirty(). The page stays dirty, despite being
309 * written back, so it gets written back again in the
310 * next writeback cycle. This is harmless.
312 if (!PageDirty(page))
313 set_page_dirty_lock(page);
314 unpin_user_page(page);
317 EXPORT_SYMBOL(unpin_user_pages_dirty_lock);
320 * unpin_user_pages() - release an array of gup-pinned pages.
321 * @pages: array of pages to be marked dirty and released.
322 * @npages: number of pages in the @pages array.
324 * For each page in the @pages array, release the page using unpin_user_page().
326 * Please see the unpin_user_page() documentation for details.
328 void unpin_user_pages(struct page **pages, unsigned long npages)
333 * TODO: this can be optimized for huge pages: if a series of pages is
334 * physically contiguous and part of the same compound page, then a
335 * single operation to the head page should suffice.
337 for (index = 0; index < npages; index++)
338 unpin_user_page(pages[index]);
340 EXPORT_SYMBOL(unpin_user_pages);
343 static struct page *no_page_table(struct vm_area_struct *vma,
347 * When core dumping an enormous anonymous area that nobody
348 * has touched so far, we don't want to allocate unnecessary pages or
349 * page tables. Return error instead of NULL to skip handle_mm_fault,
350 * then get_dump_page() will return NULL to leave a hole in the dump.
351 * But we can only make this optimization where a hole would surely
352 * be zero-filled if handle_mm_fault() actually did handle it.
354 if ((flags & FOLL_DUMP) && (!vma->vm_ops || !vma->vm_ops->fault))
355 return ERR_PTR(-EFAULT);
359 static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address,
360 pte_t *pte, unsigned int flags)
362 /* No page to get reference */
363 if (flags & FOLL_GET)
366 if (flags & FOLL_TOUCH) {
369 if (flags & FOLL_WRITE)
370 entry = pte_mkdirty(entry);
371 entry = pte_mkyoung(entry);
373 if (!pte_same(*pte, entry)) {
374 set_pte_at(vma->vm_mm, address, pte, entry);
375 update_mmu_cache(vma, address, pte);
379 /* Proper page table entry exists, but no corresponding struct page */
384 * FOLL_FORCE can write to even unwritable pte's, but only
385 * after we've gone through a COW cycle and they are dirty.
387 static inline bool can_follow_write_pte(pte_t pte, unsigned int flags)
389 return pte_write(pte) ||
390 ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pte_dirty(pte));
393 static struct page *follow_page_pte(struct vm_area_struct *vma,
394 unsigned long address, pmd_t *pmd, unsigned int flags,
395 struct dev_pagemap **pgmap)
397 struct mm_struct *mm = vma->vm_mm;
403 /* FOLL_GET and FOLL_PIN are mutually exclusive. */
404 if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) ==
405 (FOLL_PIN | FOLL_GET)))
406 return ERR_PTR(-EINVAL);
408 if (unlikely(pmd_bad(*pmd)))
409 return no_page_table(vma, flags);
411 ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
413 if (!pte_present(pte)) {
416 * KSM's break_ksm() relies upon recognizing a ksm page
417 * even while it is being migrated, so for that case we
418 * need migration_entry_wait().
420 if (likely(!(flags & FOLL_MIGRATION)))
424 entry = pte_to_swp_entry(pte);
425 if (!is_migration_entry(entry))
427 pte_unmap_unlock(ptep, ptl);
428 migration_entry_wait(mm, pmd, address);
431 if ((flags & FOLL_NUMA) && pte_protnone(pte))
433 if ((flags & FOLL_WRITE) && !can_follow_write_pte(pte, flags)) {
434 pte_unmap_unlock(ptep, ptl);
438 page = vm_normal_page(vma, address, pte);
439 if (!page && pte_devmap(pte) && (flags & (FOLL_GET | FOLL_PIN))) {
441 * Only return device mapping pages in the FOLL_GET or FOLL_PIN
442 * case since they are only valid while holding the pgmap
445 *pgmap = get_dev_pagemap(pte_pfn(pte), *pgmap);
447 page = pte_page(pte);
450 } else if (unlikely(!page)) {
451 if (flags & FOLL_DUMP) {
452 /* Avoid special (like zero) pages in core dumps */
453 page = ERR_PTR(-EFAULT);
457 if (is_zero_pfn(pte_pfn(pte))) {
458 page = pte_page(pte);
460 ret = follow_pfn_pte(vma, address, ptep, flags);
466 if (flags & FOLL_SPLIT && PageTransCompound(page)) {
468 pte_unmap_unlock(ptep, ptl);
470 ret = split_huge_page(page);
478 /* try_grab_page() does nothing unless FOLL_GET or FOLL_PIN is set. */
479 if (unlikely(!try_grab_page(page, flags))) {
480 page = ERR_PTR(-ENOMEM);
484 * We need to make the page accessible if and only if we are going
485 * to access its content (the FOLL_PIN case). Please see
486 * Documentation/core-api/pin_user_pages.rst for details.
488 if (flags & FOLL_PIN) {
489 ret = arch_make_page_accessible(page);
491 unpin_user_page(page);
496 if (flags & FOLL_TOUCH) {
497 if ((flags & FOLL_WRITE) &&
498 !pte_dirty(pte) && !PageDirty(page))
499 set_page_dirty(page);
501 * pte_mkyoung() would be more correct here, but atomic care
502 * is needed to avoid losing the dirty bit: it is easier to use
503 * mark_page_accessed().
505 mark_page_accessed(page);
507 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
508 /* Do not mlock pte-mapped THP */
509 if (PageTransCompound(page))
513 * The preliminary mapping check is mainly to avoid the
514 * pointless overhead of lock_page on the ZERO_PAGE
515 * which might bounce very badly if there is contention.
517 * If the page is already locked, we don't need to
518 * handle it now - vmscan will handle it later if and
519 * when it attempts to reclaim the page.
521 if (page->mapping && trylock_page(page)) {
522 lru_add_drain(); /* push cached pages to LRU */
524 * Because we lock page here, and migration is
525 * blocked by the pte's page reference, and we
526 * know the page is still mapped, we don't even
527 * need to check for file-cache page truncation.
529 mlock_vma_page(page);
534 pte_unmap_unlock(ptep, ptl);
537 pte_unmap_unlock(ptep, ptl);
540 return no_page_table(vma, flags);
543 static struct page *follow_pmd_mask(struct vm_area_struct *vma,
544 unsigned long address, pud_t *pudp,
546 struct follow_page_context *ctx)
551 struct mm_struct *mm = vma->vm_mm;
553 pmd = pmd_offset(pudp, address);
555 * The READ_ONCE() will stabilize the pmdval in a register or
556 * on the stack so that it will stop changing under the code.
558 pmdval = READ_ONCE(*pmd);
559 if (pmd_none(pmdval))
560 return no_page_table(vma, flags);
561 if (pmd_huge(pmdval) && is_vm_hugetlb_page(vma)) {
562 page = follow_huge_pmd(mm, address, pmd, flags);
565 return no_page_table(vma, flags);
567 if (is_hugepd(__hugepd(pmd_val(pmdval)))) {
568 page = follow_huge_pd(vma, address,
569 __hugepd(pmd_val(pmdval)), flags,
573 return no_page_table(vma, flags);
576 if (!pmd_present(pmdval)) {
577 if (likely(!(flags & FOLL_MIGRATION)))
578 return no_page_table(vma, flags);
579 VM_BUG_ON(thp_migration_supported() &&
580 !is_pmd_migration_entry(pmdval));
581 if (is_pmd_migration_entry(pmdval))
582 pmd_migration_entry_wait(mm, pmd);
583 pmdval = READ_ONCE(*pmd);
585 * MADV_DONTNEED may convert the pmd to null because
586 * mmap_sem is held in read mode
588 if (pmd_none(pmdval))
589 return no_page_table(vma, flags);
592 if (pmd_devmap(pmdval)) {
593 ptl = pmd_lock(mm, pmd);
594 page = follow_devmap_pmd(vma, address, pmd, flags, &ctx->pgmap);
599 if (likely(!pmd_trans_huge(pmdval)))
600 return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
602 if ((flags & FOLL_NUMA) && pmd_protnone(pmdval))
603 return no_page_table(vma, flags);
606 ptl = pmd_lock(mm, pmd);
607 if (unlikely(pmd_none(*pmd))) {
609 return no_page_table(vma, flags);
611 if (unlikely(!pmd_present(*pmd))) {
613 if (likely(!(flags & FOLL_MIGRATION)))
614 return no_page_table(vma, flags);
615 pmd_migration_entry_wait(mm, pmd);
618 if (unlikely(!pmd_trans_huge(*pmd))) {
620 return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
622 if (flags & (FOLL_SPLIT | FOLL_SPLIT_PMD)) {
624 page = pmd_page(*pmd);
625 if (is_huge_zero_page(page)) {
628 split_huge_pmd(vma, pmd, address);
629 if (pmd_trans_unstable(pmd))
631 } else if (flags & FOLL_SPLIT) {
632 if (unlikely(!try_get_page(page))) {
634 return ERR_PTR(-ENOMEM);
638 ret = split_huge_page(page);
642 return no_page_table(vma, flags);
643 } else { /* flags & FOLL_SPLIT_PMD */
645 split_huge_pmd(vma, pmd, address);
646 ret = pte_alloc(mm, pmd) ? -ENOMEM : 0;
649 return ret ? ERR_PTR(ret) :
650 follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
652 page = follow_trans_huge_pmd(vma, address, pmd, flags);
654 ctx->page_mask = HPAGE_PMD_NR - 1;
658 static struct page *follow_pud_mask(struct vm_area_struct *vma,
659 unsigned long address, p4d_t *p4dp,
661 struct follow_page_context *ctx)
666 struct mm_struct *mm = vma->vm_mm;
668 pud = pud_offset(p4dp, address);
670 return no_page_table(vma, flags);
671 if (pud_huge(*pud) && is_vm_hugetlb_page(vma)) {
672 page = follow_huge_pud(mm, address, pud, flags);
675 return no_page_table(vma, flags);
677 if (is_hugepd(__hugepd(pud_val(*pud)))) {
678 page = follow_huge_pd(vma, address,
679 __hugepd(pud_val(*pud)), flags,
683 return no_page_table(vma, flags);
685 if (pud_devmap(*pud)) {
686 ptl = pud_lock(mm, pud);
687 page = follow_devmap_pud(vma, address, pud, flags, &ctx->pgmap);
692 if (unlikely(pud_bad(*pud)))
693 return no_page_table(vma, flags);
695 return follow_pmd_mask(vma, address, pud, flags, ctx);
698 static struct page *follow_p4d_mask(struct vm_area_struct *vma,
699 unsigned long address, pgd_t *pgdp,
701 struct follow_page_context *ctx)
706 p4d = p4d_offset(pgdp, address);
708 return no_page_table(vma, flags);
709 BUILD_BUG_ON(p4d_huge(*p4d));
710 if (unlikely(p4d_bad(*p4d)))
711 return no_page_table(vma, flags);
713 if (is_hugepd(__hugepd(p4d_val(*p4d)))) {
714 page = follow_huge_pd(vma, address,
715 __hugepd(p4d_val(*p4d)), flags,
719 return no_page_table(vma, flags);
721 return follow_pud_mask(vma, address, p4d, flags, ctx);
725 * follow_page_mask - look up a page descriptor from a user-virtual address
726 * @vma: vm_area_struct mapping @address
727 * @address: virtual address to look up
728 * @flags: flags modifying lookup behaviour
729 * @ctx: contains dev_pagemap for %ZONE_DEVICE memory pinning and a
730 * pointer to output page_mask
732 * @flags can have FOLL_ flags set, defined in <linux/mm.h>
734 * When getting pages from ZONE_DEVICE memory, the @ctx->pgmap caches
735 * the device's dev_pagemap metadata to avoid repeating expensive lookups.
737 * On output, the @ctx->page_mask is set according to the size of the page.
739 * Return: the mapped (struct page *), %NULL if no mapping exists, or
740 * an error pointer if there is a mapping to something not represented
741 * by a page descriptor (see also vm_normal_page()).
743 static struct page *follow_page_mask(struct vm_area_struct *vma,
744 unsigned long address, unsigned int flags,
745 struct follow_page_context *ctx)
749 struct mm_struct *mm = vma->vm_mm;
753 /* make this handle hugepd */
754 page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
756 WARN_ON_ONCE(flags & (FOLL_GET | FOLL_PIN));
760 pgd = pgd_offset(mm, address);
762 if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
763 return no_page_table(vma, flags);
765 if (pgd_huge(*pgd)) {
766 page = follow_huge_pgd(mm, address, pgd, flags);
769 return no_page_table(vma, flags);
771 if (is_hugepd(__hugepd(pgd_val(*pgd)))) {
772 page = follow_huge_pd(vma, address,
773 __hugepd(pgd_val(*pgd)), flags,
777 return no_page_table(vma, flags);
780 return follow_p4d_mask(vma, address, pgd, flags, ctx);
783 struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
784 unsigned int foll_flags)
786 struct follow_page_context ctx = { NULL };
789 page = follow_page_mask(vma, address, foll_flags, &ctx);
791 put_dev_pagemap(ctx.pgmap);
795 static int get_gate_page(struct mm_struct *mm, unsigned long address,
796 unsigned int gup_flags, struct vm_area_struct **vma,
806 /* user gate pages are read-only */
807 if (gup_flags & FOLL_WRITE)
809 if (address > TASK_SIZE)
810 pgd = pgd_offset_k(address);
812 pgd = pgd_offset_gate(mm, address);
815 p4d = p4d_offset(pgd, address);
818 pud = pud_offset(p4d, address);
821 pmd = pmd_offset(pud, address);
822 if (!pmd_present(*pmd))
824 VM_BUG_ON(pmd_trans_huge(*pmd));
825 pte = pte_offset_map(pmd, address);
828 *vma = get_gate_vma(mm);
831 *page = vm_normal_page(*vma, address, *pte);
833 if ((gup_flags & FOLL_DUMP) || !is_zero_pfn(pte_pfn(*pte)))
835 *page = pte_page(*pte);
837 if (unlikely(!try_get_page(*page))) {
849 * mmap_sem must be held on entry. If @locked != NULL and *@flags
850 * does not include FOLL_NOWAIT, the mmap_sem may be released. If it
851 * is, *@locked will be set to 0 and -EBUSY returned.
853 static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma,
854 unsigned long address, unsigned int *flags, int *locked)
856 unsigned int fault_flags = 0;
859 /* mlock all present pages, but do not fault in new pages */
860 if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK)
862 if (*flags & FOLL_WRITE)
863 fault_flags |= FAULT_FLAG_WRITE;
864 if (*flags & FOLL_REMOTE)
865 fault_flags |= FAULT_FLAG_REMOTE;
867 fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
868 if (*flags & FOLL_NOWAIT)
869 fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT;
870 if (*flags & FOLL_TRIED) {
872 * Note: FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_TRIED
875 fault_flags |= FAULT_FLAG_TRIED;
878 ret = handle_mm_fault(vma, address, fault_flags);
879 if (ret & VM_FAULT_ERROR) {
880 int err = vm_fault_to_errno(ret, *flags);
888 if (ret & VM_FAULT_MAJOR)
894 if (ret & VM_FAULT_RETRY) {
895 if (locked && !(fault_flags & FAULT_FLAG_RETRY_NOWAIT))
901 * The VM_FAULT_WRITE bit tells us that do_wp_page has broken COW when
902 * necessary, even if maybe_mkwrite decided not to set pte_write. We
903 * can thus safely do subsequent page lookups as if they were reads.
904 * But only do so when looping for pte_write is futile: in some cases
905 * userspace may also be wanting to write to the gotten user page,
906 * which a read fault here might prevent (a readonly page might get
907 * reCOWed by userspace write).
909 if ((ret & VM_FAULT_WRITE) && !(vma->vm_flags & VM_WRITE))
914 static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)
916 vm_flags_t vm_flags = vma->vm_flags;
917 int write = (gup_flags & FOLL_WRITE);
918 int foreign = (gup_flags & FOLL_REMOTE);
920 if (vm_flags & (VM_IO | VM_PFNMAP))
923 if (gup_flags & FOLL_ANON && !vma_is_anonymous(vma))
927 if (!(vm_flags & VM_WRITE)) {
928 if (!(gup_flags & FOLL_FORCE))
931 * We used to let the write,force case do COW in a
932 * VM_MAYWRITE VM_SHARED !VM_WRITE vma, so ptrace could
933 * set a breakpoint in a read-only mapping of an
934 * executable, without corrupting the file (yet only
935 * when that file had been opened for writing!).
936 * Anon pages in shared mappings are surprising: now
939 if (!is_cow_mapping(vm_flags))
942 } else if (!(vm_flags & VM_READ)) {
943 if (!(gup_flags & FOLL_FORCE))
946 * Is there actually any vma we can reach here which does not
947 * have VM_MAYREAD set?
949 if (!(vm_flags & VM_MAYREAD))
953 * gups are always data accesses, not instruction
954 * fetches, so execute=false here
956 if (!arch_vma_access_permitted(vma, write, false, foreign))
962 * __get_user_pages() - pin user pages in memory
963 * @tsk: task_struct of target task
964 * @mm: mm_struct of target mm
965 * @start: starting user address
966 * @nr_pages: number of pages from start to pin
967 * @gup_flags: flags modifying pin behaviour
968 * @pages: array that receives pointers to the pages pinned.
969 * Should be at least nr_pages long. Or NULL, if caller
970 * only intends to ensure the pages are faulted in.
971 * @vmas: array of pointers to vmas corresponding to each page.
972 * Or NULL if the caller does not require them.
973 * @locked: whether we're still with the mmap_sem held
975 * Returns either number of pages pinned (which may be less than the
976 * number requested), or an error. Details about the return value:
978 * -- If nr_pages is 0, returns 0.
979 * -- If nr_pages is >0, but no pages were pinned, returns -errno.
980 * -- If nr_pages is >0, and some pages were pinned, returns the number of
981 * pages pinned. Again, this may be less than nr_pages.
983 * The caller is responsible for releasing returned @pages, via put_page().
985 * @vmas are valid only as long as mmap_sem is held.
987 * Must be called with mmap_sem held. It may be released. See below.
989 * __get_user_pages walks a process's page tables and takes a reference to
990 * each struct page that each user address corresponds to at a given
991 * instant. That is, it takes the page that would be accessed if a user
992 * thread accesses the given user virtual address at that instant.
994 * This does not guarantee that the page exists in the user mappings when
995 * __get_user_pages returns, and there may even be a completely different
996 * page there in some cases (eg. if mmapped pagecache has been invalidated
997 * and subsequently re faulted). However it does guarantee that the page
998 * won't be freed completely. And mostly callers simply care that the page
999 * contains data that was valid *at some point in time*. Typically, an IO
1000 * or similar operation cannot guarantee anything stronger anyway because
1001 * locks can't be held over the syscall boundary.
1003 * If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If
1004 * the page is written to, set_page_dirty (or set_page_dirty_lock, as
1005 * appropriate) must be called after the page is finished with, and
1006 * before put_page is called.
1008 * If @locked != NULL, *@locked will be set to 0 when mmap_sem is
1009 * released by an up_read(). That can happen if @gup_flags does not
1012 * A caller using such a combination of @locked and @gup_flags
1013 * must therefore hold the mmap_sem for reading only, and recognize
1014 * when it's been released. Otherwise, it must be held for either
1015 * reading or writing and will not be released.
1017 * In most cases, get_user_pages or get_user_pages_fast should be used
1018 * instead of __get_user_pages. __get_user_pages should be used only if
1019 * you need some special @gup_flags.
1021 static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
1022 unsigned long start, unsigned long nr_pages,
1023 unsigned int gup_flags, struct page **pages,
1024 struct vm_area_struct **vmas, int *locked)
1026 long ret = 0, i = 0;
1027 struct vm_area_struct *vma = NULL;
1028 struct follow_page_context ctx = { NULL };
1033 start = untagged_addr(start);
1035 VM_BUG_ON(!!pages != !!(gup_flags & (FOLL_GET | FOLL_PIN)));
1038 * If FOLL_FORCE is set then do not force a full fault as the hinting
1039 * fault information is unrelated to the reference behaviour of a task
1040 * using the address space
1042 if (!(gup_flags & FOLL_FORCE))
1043 gup_flags |= FOLL_NUMA;
1047 unsigned int foll_flags = gup_flags;
1048 unsigned int page_increm;
1050 /* first iteration or cross vma bound */
1051 if (!vma || start >= vma->vm_end) {
1052 vma = find_extend_vma(mm, start);
1053 if (!vma && in_gate_area(mm, start)) {
1054 ret = get_gate_page(mm, start & PAGE_MASK,
1056 pages ? &pages[i] : NULL);
1063 if (!vma || check_vma_flags(vma, gup_flags)) {
1067 if (is_vm_hugetlb_page(vma)) {
1068 i = follow_hugetlb_page(mm, vma, pages, vmas,
1069 &start, &nr_pages, i,
1071 if (locked && *locked == 0) {
1073 * We've got a VM_FAULT_RETRY
1074 * and we've lost mmap_sem.
1075 * We must stop here.
1077 BUG_ON(gup_flags & FOLL_NOWAIT);
1086 * If we have a pending SIGKILL, don't keep faulting pages and
1087 * potentially allocating memory.
1089 if (fatal_signal_pending(current)) {
1095 page = follow_page_mask(vma, start, foll_flags, &ctx);
1097 ret = faultin_page(tsk, vma, start, &foll_flags,
1113 } else if (PTR_ERR(page) == -EEXIST) {
1115 * Proper page table entry exists, but no corresponding
1119 } else if (IS_ERR(page)) {
1120 ret = PTR_ERR(page);
1125 flush_anon_page(vma, page, start);
1126 flush_dcache_page(page);
1134 page_increm = 1 + (~(start >> PAGE_SHIFT) & ctx.page_mask);
1135 if (page_increm > nr_pages)
1136 page_increm = nr_pages;
1138 start += page_increm * PAGE_SIZE;
1139 nr_pages -= page_increm;
1143 put_dev_pagemap(ctx.pgmap);
1147 static bool vma_permits_fault(struct vm_area_struct *vma,
1148 unsigned int fault_flags)
1150 bool write = !!(fault_flags & FAULT_FLAG_WRITE);
1151 bool foreign = !!(fault_flags & FAULT_FLAG_REMOTE);
1152 vm_flags_t vm_flags = write ? VM_WRITE : VM_READ;
1154 if (!(vm_flags & vma->vm_flags))
1158 * The architecture might have a hardware protection
1159 * mechanism other than read/write that can deny access.
1161 * gup always represents data access, not instruction
1162 * fetches, so execute=false here:
1164 if (!arch_vma_access_permitted(vma, write, false, foreign))
1171 * fixup_user_fault() - manually resolve a user page fault
1172 * @tsk: the task_struct to use for page fault accounting, or
1173 * NULL if faults are not to be recorded.
1174 * @mm: mm_struct of target mm
1175 * @address: user address
1176 * @fault_flags:flags to pass down to handle_mm_fault()
1177 * @unlocked: did we unlock the mmap_sem while retrying, maybe NULL if caller
1178 * does not allow retry
1180 * This is meant to be called in the specific scenario where for locking reasons
1181 * we try to access user memory in atomic context (within a pagefault_disable()
1182 * section), this returns -EFAULT, and we want to resolve the user fault before
1185 * Typically this is meant to be used by the futex code.
1187 * The main difference with get_user_pages() is that this function will
1188 * unconditionally call handle_mm_fault() which will in turn perform all the
1189 * necessary SW fixup of the dirty and young bits in the PTE, while
1190 * get_user_pages() only guarantees to update these in the struct page.
1192 * This is important for some architectures where those bits also gate the
1193 * access permission to the page because they are maintained in software. On
1194 * such architectures, gup() will not be enough to make a subsequent access
1197 * This function will not return with an unlocked mmap_sem. So it has not the
1198 * same semantics wrt the @mm->mmap_sem as does filemap_fault().
1200 int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
1201 unsigned long address, unsigned int fault_flags,
1204 struct vm_area_struct *vma;
1205 vm_fault_t ret, major = 0;
1207 address = untagged_addr(address);
1210 fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
1213 vma = find_extend_vma(mm, address);
1214 if (!vma || address < vma->vm_start)
1217 if (!vma_permits_fault(vma, fault_flags))
1220 ret = handle_mm_fault(vma, address, fault_flags);
1221 major |= ret & VM_FAULT_MAJOR;
1222 if (ret & VM_FAULT_ERROR) {
1223 int err = vm_fault_to_errno(ret, 0);
1230 if (ret & VM_FAULT_RETRY) {
1231 down_read(&mm->mmap_sem);
1232 if (!(fault_flags & FAULT_FLAG_TRIED)) {
1234 fault_flags |= FAULT_FLAG_TRIED;
1247 EXPORT_SYMBOL_GPL(fixup_user_fault);
1249 static __always_inline long __get_user_pages_locked(struct task_struct *tsk,
1250 struct mm_struct *mm,
1251 unsigned long start,
1252 unsigned long nr_pages,
1253 struct page **pages,
1254 struct vm_area_struct **vmas,
1258 long ret, pages_done;
1262 /* if VM_FAULT_RETRY can be returned, vmas become invalid */
1264 /* check caller initialized locked */
1265 BUG_ON(*locked != 1);
1269 * FOLL_PIN and FOLL_GET are mutually exclusive. Traditional behavior
1270 * is to set FOLL_GET if the caller wants pages[] filled in (but has
1271 * carelessly failed to specify FOLL_GET), so keep doing that, but only
1272 * for FOLL_GET, not for the newer FOLL_PIN.
1274 * FOLL_PIN always expects pages to be non-null, but no need to assert
1275 * that here, as any failures will be obvious enough.
1277 if (pages && !(flags & FOLL_PIN))
1281 lock_dropped = false;
1283 ret = __get_user_pages(tsk, mm, start, nr_pages, flags, pages,
1286 /* VM_FAULT_RETRY couldn't trigger, bypass */
1289 /* VM_FAULT_RETRY cannot return errors */
1292 BUG_ON(ret >= nr_pages);
1303 * VM_FAULT_RETRY didn't trigger or it was a
1311 * VM_FAULT_RETRY triggered, so seek to the faulting offset.
1312 * For the prefault case (!pages) we only update counts.
1316 start += ret << PAGE_SHIFT;
1317 lock_dropped = true;
1321 * Repeat on the address that fired VM_FAULT_RETRY
1322 * with both FAULT_FLAG_ALLOW_RETRY and
1323 * FAULT_FLAG_TRIED. Note that GUP can be interrupted
1324 * by fatal signals, so we need to check it before we
1325 * start trying again otherwise it can loop forever.
1328 if (fatal_signal_pending(current))
1332 ret = down_read_killable(&mm->mmap_sem);
1340 ret = __get_user_pages(tsk, mm, start, 1, flags | FOLL_TRIED,
1341 pages, NULL, locked);
1343 /* Continue to retry until we succeeded */
1361 if (lock_dropped && *locked) {
1363 * We must let the caller know we temporarily dropped the lock
1364 * and so the critical section protected by it was lost.
1366 up_read(&mm->mmap_sem);
1373 * populate_vma_page_range() - populate a range of pages in the vma.
1375 * @start: start address
1377 * @locked: whether the mmap_sem is still held
1379 * This takes care of mlocking the pages too if VM_LOCKED is set.
1381 * return 0 on success, negative error code on error.
1383 * vma->vm_mm->mmap_sem must be held.
1385 * If @locked is NULL, it may be held for read or write and will
1388 * If @locked is non-NULL, it must held for read only and may be
1389 * released. If it's released, *@locked will be set to 0.
1391 long populate_vma_page_range(struct vm_area_struct *vma,
1392 unsigned long start, unsigned long end, int *locked)
1394 struct mm_struct *mm = vma->vm_mm;
1395 unsigned long nr_pages = (end - start) / PAGE_SIZE;
1398 VM_BUG_ON(start & ~PAGE_MASK);
1399 VM_BUG_ON(end & ~PAGE_MASK);
1400 VM_BUG_ON_VMA(start < vma->vm_start, vma);
1401 VM_BUG_ON_VMA(end > vma->vm_end, vma);
1402 VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm);
1404 gup_flags = FOLL_TOUCH | FOLL_POPULATE | FOLL_MLOCK;
1405 if (vma->vm_flags & VM_LOCKONFAULT)
1406 gup_flags &= ~FOLL_POPULATE;
1408 * We want to touch writable mappings with a write fault in order
1409 * to break COW, except for shared mappings because these don't COW
1410 * and we would not want to dirty them for nothing.
1412 if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
1413 gup_flags |= FOLL_WRITE;
1416 * We want mlock to succeed for regions that have any permissions
1417 * other than PROT_NONE.
1419 if (vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))
1420 gup_flags |= FOLL_FORCE;
1423 * We made sure addr is within a VMA, so the following will
1424 * not result in a stack expansion that recurses back here.
1426 return __get_user_pages(current, mm, start, nr_pages, gup_flags,
1427 NULL, NULL, locked);
1431 * __mm_populate - populate and/or mlock pages within a range of address space.
1433 * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
1434 * flags. VMAs must be already marked with the desired vm_flags, and
1435 * mmap_sem must not be held.
1437 int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
1439 struct mm_struct *mm = current->mm;
1440 unsigned long end, nstart, nend;
1441 struct vm_area_struct *vma = NULL;
1447 for (nstart = start; nstart < end; nstart = nend) {
1449 * We want to fault in pages for [nstart; end) address range.
1450 * Find first corresponding VMA.
1454 down_read(&mm->mmap_sem);
1455 vma = find_vma(mm, nstart);
1456 } else if (nstart >= vma->vm_end)
1458 if (!vma || vma->vm_start >= end)
1461 * Set [nstart; nend) to intersection of desired address
1462 * range with the first VMA. Also, skip undesirable VMA types.
1464 nend = min(end, vma->vm_end);
1465 if (vma->vm_flags & (VM_IO | VM_PFNMAP))
1467 if (nstart < vma->vm_start)
1468 nstart = vma->vm_start;
1470 * Now fault in a range of pages. populate_vma_page_range()
1471 * double checks the vma flags, so that it won't mlock pages
1472 * if the vma was already munlocked.
1474 ret = populate_vma_page_range(vma, nstart, nend, &locked);
1476 if (ignore_errors) {
1478 continue; /* continue at next VMA */
1482 nend = nstart + ret * PAGE_SIZE;
1486 up_read(&mm->mmap_sem);
1487 return ret; /* 0 or negative error code */
1491 * get_dump_page() - pin user page in memory while writing it to core dump
1492 * @addr: user address
1494 * Returns struct page pointer of user page pinned for dump,
1495 * to be freed afterwards by put_page().
1497 * Returns NULL on any kind of failure - a hole must then be inserted into
1498 * the corefile, to preserve alignment with its headers; and also returns
1499 * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
1500 * allowing a hole to be left in the corefile to save diskspace.
1502 * Called without mmap_sem, but after all other threads have been killed.
1504 #ifdef CONFIG_ELF_CORE
1505 struct page *get_dump_page(unsigned long addr)
1507 struct vm_area_struct *vma;
1510 if (__get_user_pages(current, current->mm, addr, 1,
1511 FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma,
1514 flush_cache_page(vma, addr, page_to_pfn(page));
1517 #endif /* CONFIG_ELF_CORE */
1518 #else /* CONFIG_MMU */
1519 static long __get_user_pages_locked(struct task_struct *tsk,
1520 struct mm_struct *mm, unsigned long start,
1521 unsigned long nr_pages, struct page **pages,
1522 struct vm_area_struct **vmas, int *locked,
1523 unsigned int foll_flags)
1525 struct vm_area_struct *vma;
1526 unsigned long vm_flags;
1529 /* calculate required read or write permissions.
1530 * If FOLL_FORCE is set, we only require the "MAY" flags.
1532 vm_flags = (foll_flags & FOLL_WRITE) ?
1533 (VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
1534 vm_flags &= (foll_flags & FOLL_FORCE) ?
1535 (VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
1537 for (i = 0; i < nr_pages; i++) {
1538 vma = find_vma(mm, start);
1540 goto finish_or_fault;
1542 /* protect what we can, including chardevs */
1543 if ((vma->vm_flags & (VM_IO | VM_PFNMAP)) ||
1544 !(vm_flags & vma->vm_flags))
1545 goto finish_or_fault;
1548 pages[i] = virt_to_page(start);
1554 start = (start + PAGE_SIZE) & PAGE_MASK;
1560 return i ? : -EFAULT;
1562 #endif /* !CONFIG_MMU */
1564 #if defined(CONFIG_FS_DAX) || defined (CONFIG_CMA)
1565 static bool check_dax_vmas(struct vm_area_struct **vmas, long nr_pages)
1568 struct vm_area_struct *vma_prev = NULL;
1570 for (i = 0; i < nr_pages; i++) {
1571 struct vm_area_struct *vma = vmas[i];
1573 if (vma == vma_prev)
1578 if (vma_is_fsdax(vma))
1585 static struct page *new_non_cma_page(struct page *page, unsigned long private)
1588 * We want to make sure we allocate the new page from the same node
1589 * as the source page.
1591 int nid = page_to_nid(page);
1593 * Trying to allocate a page for migration. Ignore allocation
1594 * failure warnings. We don't force __GFP_THISNODE here because
1595 * this node here is the node where we have CMA reservation and
1596 * in some case these nodes will have really less non movable
1597 * allocation memory.
1599 gfp_t gfp_mask = GFP_USER | __GFP_NOWARN;
1601 if (PageHighMem(page))
1602 gfp_mask |= __GFP_HIGHMEM;
1604 #ifdef CONFIG_HUGETLB_PAGE
1605 if (PageHuge(page)) {
1606 struct hstate *h = page_hstate(page);
1608 * We don't want to dequeue from the pool because pool pages will
1609 * mostly be from the CMA region.
1611 return alloc_migrate_huge_page(h, gfp_mask, nid, NULL);
1614 if (PageTransHuge(page)) {
1617 * ignore allocation failure warnings
1619 gfp_t thp_gfpmask = GFP_TRANSHUGE | __GFP_NOWARN;
1622 * Remove the movable mask so that we don't allocate from
1625 thp_gfpmask &= ~__GFP_MOVABLE;
1626 thp = __alloc_pages_node(nid, thp_gfpmask, HPAGE_PMD_ORDER);
1629 prep_transhuge_page(thp);
1633 return __alloc_pages_node(nid, gfp_mask, 0);
1636 static long check_and_migrate_cma_pages(struct task_struct *tsk,
1637 struct mm_struct *mm,
1638 unsigned long start,
1639 unsigned long nr_pages,
1640 struct page **pages,
1641 struct vm_area_struct **vmas,
1642 unsigned int gup_flags)
1646 bool drain_allow = true;
1647 bool migrate_allow = true;
1648 LIST_HEAD(cma_page_list);
1649 long ret = nr_pages;
1652 for (i = 0; i < nr_pages;) {
1654 struct page *head = compound_head(pages[i]);
1657 * gup may start from a tail page. Advance step by the left
1660 step = compound_nr(head) - (pages[i] - head);
1662 * If we get a page from the CMA zone, since we are going to
1663 * be pinning these entries, we might as well move them out
1664 * of the CMA zone if possible.
1666 if (is_migrate_cma_page(head)) {
1668 isolate_huge_page(head, &cma_page_list);
1670 if (!PageLRU(head) && drain_allow) {
1671 lru_add_drain_all();
1672 drain_allow = false;
1675 if (!isolate_lru_page(head)) {
1676 list_add_tail(&head->lru, &cma_page_list);
1677 mod_node_page_state(page_pgdat(head),
1679 page_is_file_cache(head),
1680 hpage_nr_pages(head));
1688 if (!list_empty(&cma_page_list)) {
1690 * drop the above get_user_pages reference.
1692 for (i = 0; i < nr_pages; i++)
1695 if (migrate_pages(&cma_page_list, new_non_cma_page,
1696 NULL, 0, MIGRATE_SYNC, MR_CONTIG_RANGE)) {
1698 * some of the pages failed migration. Do get_user_pages
1699 * without migration.
1701 migrate_allow = false;
1703 if (!list_empty(&cma_page_list))
1704 putback_movable_pages(&cma_page_list);
1707 * We did migrate all the pages, Try to get the page references
1708 * again migrating any new CMA pages which we failed to isolate
1711 ret = __get_user_pages_locked(tsk, mm, start, nr_pages,
1715 if ((ret > 0) && migrate_allow) {
1725 static long check_and_migrate_cma_pages(struct task_struct *tsk,
1726 struct mm_struct *mm,
1727 unsigned long start,
1728 unsigned long nr_pages,
1729 struct page **pages,
1730 struct vm_area_struct **vmas,
1731 unsigned int gup_flags)
1735 #endif /* CONFIG_CMA */
1738 * __gup_longterm_locked() is a wrapper for __get_user_pages_locked which
1739 * allows us to process the FOLL_LONGTERM flag.
1741 static long __gup_longterm_locked(struct task_struct *tsk,
1742 struct mm_struct *mm,
1743 unsigned long start,
1744 unsigned long nr_pages,
1745 struct page **pages,
1746 struct vm_area_struct **vmas,
1747 unsigned int gup_flags)
1749 struct vm_area_struct **vmas_tmp = vmas;
1750 unsigned long flags = 0;
1753 if (gup_flags & FOLL_LONGTERM) {
1758 vmas_tmp = kcalloc(nr_pages,
1759 sizeof(struct vm_area_struct *),
1764 flags = memalloc_nocma_save();
1767 rc = __get_user_pages_locked(tsk, mm, start, nr_pages, pages,
1768 vmas_tmp, NULL, gup_flags);
1770 if (gup_flags & FOLL_LONGTERM) {
1771 memalloc_nocma_restore(flags);
1775 if (check_dax_vmas(vmas_tmp, rc)) {
1776 for (i = 0; i < rc; i++)
1782 rc = check_and_migrate_cma_pages(tsk, mm, start, rc, pages,
1783 vmas_tmp, gup_flags);
1787 if (vmas_tmp != vmas)
1791 #else /* !CONFIG_FS_DAX && !CONFIG_CMA */
1792 static __always_inline long __gup_longterm_locked(struct task_struct *tsk,
1793 struct mm_struct *mm,
1794 unsigned long start,
1795 unsigned long nr_pages,
1796 struct page **pages,
1797 struct vm_area_struct **vmas,
1800 return __get_user_pages_locked(tsk, mm, start, nr_pages, pages, vmas,
1803 #endif /* CONFIG_FS_DAX || CONFIG_CMA */
1806 static long __get_user_pages_remote(struct task_struct *tsk,
1807 struct mm_struct *mm,
1808 unsigned long start, unsigned long nr_pages,
1809 unsigned int gup_flags, struct page **pages,
1810 struct vm_area_struct **vmas, int *locked)
1813 * Parts of FOLL_LONGTERM behavior are incompatible with
1814 * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
1815 * vmas. However, this only comes up if locked is set, and there are
1816 * callers that do request FOLL_LONGTERM, but do not set locked. So,
1817 * allow what we can.
1819 if (gup_flags & FOLL_LONGTERM) {
1820 if (WARN_ON_ONCE(locked))
1823 * This will check the vmas (even if our vmas arg is NULL)
1824 * and return -ENOTSUPP if DAX isn't allowed in this case:
1826 return __gup_longterm_locked(tsk, mm, start, nr_pages, pages,
1827 vmas, gup_flags | FOLL_TOUCH |
1831 return __get_user_pages_locked(tsk, mm, start, nr_pages, pages, vmas,
1833 gup_flags | FOLL_TOUCH | FOLL_REMOTE);
1837 * get_user_pages_remote() - pin user pages in memory
1838 * @tsk: the task_struct to use for page fault accounting, or
1839 * NULL if faults are not to be recorded.
1840 * @mm: mm_struct of target mm
1841 * @start: starting user address
1842 * @nr_pages: number of pages from start to pin
1843 * @gup_flags: flags modifying lookup behaviour
1844 * @pages: array that receives pointers to the pages pinned.
1845 * Should be at least nr_pages long. Or NULL, if caller
1846 * only intends to ensure the pages are faulted in.
1847 * @vmas: array of pointers to vmas corresponding to each page.
1848 * Or NULL if the caller does not require them.
1849 * @locked: pointer to lock flag indicating whether lock is held and
1850 * subsequently whether VM_FAULT_RETRY functionality can be
1851 * utilised. Lock must initially be held.
1853 * Returns either number of pages pinned (which may be less than the
1854 * number requested), or an error. Details about the return value:
1856 * -- If nr_pages is 0, returns 0.
1857 * -- If nr_pages is >0, but no pages were pinned, returns -errno.
1858 * -- If nr_pages is >0, and some pages were pinned, returns the number of
1859 * pages pinned. Again, this may be less than nr_pages.
1861 * The caller is responsible for releasing returned @pages, via put_page().
1863 * @vmas are valid only as long as mmap_sem is held.
1865 * Must be called with mmap_sem held for read or write.
1867 * get_user_pages walks a process's page tables and takes a reference to
1868 * each struct page that each user address corresponds to at a given
1869 * instant. That is, it takes the page that would be accessed if a user
1870 * thread accesses the given user virtual address at that instant.
1872 * This does not guarantee that the page exists in the user mappings when
1873 * get_user_pages returns, and there may even be a completely different
1874 * page there in some cases (eg. if mmapped pagecache has been invalidated
1875 * and subsequently re faulted). However it does guarantee that the page
1876 * won't be freed completely. And mostly callers simply care that the page
1877 * contains data that was valid *at some point in time*. Typically, an IO
1878 * or similar operation cannot guarantee anything stronger anyway because
1879 * locks can't be held over the syscall boundary.
1881 * If gup_flags & FOLL_WRITE == 0, the page must not be written to. If the page
1882 * is written to, set_page_dirty (or set_page_dirty_lock, as appropriate) must
1883 * be called after the page is finished with, and before put_page is called.
1885 * get_user_pages is typically used for fewer-copy IO operations, to get a
1886 * handle on the memory by some means other than accesses via the user virtual
1887 * addresses. The pages may be submitted for DMA to devices or accessed via
1888 * their kernel linear mapping (via the kmap APIs). Care should be taken to
1889 * use the correct cache flushing APIs.
1891 * See also get_user_pages_fast, for performance critical applications.
1893 * get_user_pages should be phased out in favor of
1894 * get_user_pages_locked|unlocked or get_user_pages_fast. Nothing
1895 * should use get_user_pages because it cannot pass
1896 * FAULT_FLAG_ALLOW_RETRY to handle_mm_fault.
1898 long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
1899 unsigned long start, unsigned long nr_pages,
1900 unsigned int gup_flags, struct page **pages,
1901 struct vm_area_struct **vmas, int *locked)
1904 * FOLL_PIN must only be set internally by the pin_user_pages*() APIs,
1905 * never directly by the caller, so enforce that with an assertion:
1907 if (WARN_ON_ONCE(gup_flags & FOLL_PIN))
1910 return __get_user_pages_remote(tsk, mm, start, nr_pages, gup_flags,
1911 pages, vmas, locked);
1913 EXPORT_SYMBOL(get_user_pages_remote);
1915 #else /* CONFIG_MMU */
1916 long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
1917 unsigned long start, unsigned long nr_pages,
1918 unsigned int gup_flags, struct page **pages,
1919 struct vm_area_struct **vmas, int *locked)
1924 static long __get_user_pages_remote(struct task_struct *tsk,
1925 struct mm_struct *mm,
1926 unsigned long start, unsigned long nr_pages,
1927 unsigned int gup_flags, struct page **pages,
1928 struct vm_area_struct **vmas, int *locked)
1932 #endif /* !CONFIG_MMU */
1935 * This is the same as get_user_pages_remote(), just with a
1936 * less-flexible calling convention where we assume that the task
1937 * and mm being operated on are the current task's and don't allow
1938 * passing of a locked parameter. We also obviously don't pass
1939 * FOLL_REMOTE in here.
1941 long get_user_pages(unsigned long start, unsigned long nr_pages,
1942 unsigned int gup_flags, struct page **pages,
1943 struct vm_area_struct **vmas)
1946 * FOLL_PIN must only be set internally by the pin_user_pages*() APIs,
1947 * never directly by the caller, so enforce that with an assertion:
1949 if (WARN_ON_ONCE(gup_flags & FOLL_PIN))
1952 return __gup_longterm_locked(current, current->mm, start, nr_pages,
1953 pages, vmas, gup_flags | FOLL_TOUCH);
1955 EXPORT_SYMBOL(get_user_pages);
1958 * We can leverage the VM_FAULT_RETRY functionality in the page fault
1959 * paths better by using either get_user_pages_locked() or
1960 * get_user_pages_unlocked().
1962 * get_user_pages_locked() is suitable to replace the form:
1964 * down_read(&mm->mmap_sem);
1966 * get_user_pages(tsk, mm, ..., pages, NULL);
1967 * up_read(&mm->mmap_sem);
1972 * down_read(&mm->mmap_sem);
1974 * get_user_pages_locked(tsk, mm, ..., pages, &locked);
1976 * up_read(&mm->mmap_sem);
1978 long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
1979 unsigned int gup_flags, struct page **pages,
1983 * FIXME: Current FOLL_LONGTERM behavior is incompatible with
1984 * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
1985 * vmas. As there are no users of this flag in this call we simply
1986 * disallow this option for now.
1988 if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
1991 return __get_user_pages_locked(current, current->mm, start, nr_pages,
1992 pages, NULL, locked,
1993 gup_flags | FOLL_TOUCH);
1995 EXPORT_SYMBOL(get_user_pages_locked);
1998 * get_user_pages_unlocked() is suitable to replace the form:
2000 * down_read(&mm->mmap_sem);
2001 * get_user_pages(tsk, mm, ..., pages, NULL);
2002 * up_read(&mm->mmap_sem);
2006 * get_user_pages_unlocked(tsk, mm, ..., pages);
2008 * It is functionally equivalent to get_user_pages_fast so
2009 * get_user_pages_fast should be used instead if specific gup_flags
2010 * (e.g. FOLL_FORCE) are not required.
2012 long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
2013 struct page **pages, unsigned int gup_flags)
2015 struct mm_struct *mm = current->mm;
2020 * FIXME: Current FOLL_LONGTERM behavior is incompatible with
2021 * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
2022 * vmas. As there are no users of this flag in this call we simply
2023 * disallow this option for now.
2025 if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
2028 down_read(&mm->mmap_sem);
2029 ret = __get_user_pages_locked(current, mm, start, nr_pages, pages, NULL,
2030 &locked, gup_flags | FOLL_TOUCH);
2032 up_read(&mm->mmap_sem);
2035 EXPORT_SYMBOL(get_user_pages_unlocked);
2040 * get_user_pages_fast attempts to pin user pages by walking the page
2041 * tables directly and avoids taking locks. Thus the walker needs to be
2042 * protected from page table pages being freed from under it, and should
2043 * block any THP splits.
2045 * One way to achieve this is to have the walker disable interrupts, and
2046 * rely on IPIs from the TLB flushing code blocking before the page table
2047 * pages are freed. This is unsuitable for architectures that do not need
2048 * to broadcast an IPI when invalidating TLBs.
2050 * Another way to achieve this is to batch up page table containing pages
2051 * belonging to more than one mm_user, then rcu_sched a callback to free those
2052 * pages. Disabling interrupts will allow the fast_gup walker to both block
2053 * the rcu_sched callback, and an IPI that we broadcast for splitting THPs
2054 * (which is a relatively rare event). The code below adopts this strategy.
2056 * Before activating this code, please be aware that the following assumptions
2057 * are currently made:
2059 * *) Either MMU_GATHER_RCU_TABLE_FREE is enabled, and tlb_remove_table() is used to
2060 * free pages containing page tables or TLB flushing requires IPI broadcast.
2062 * *) ptes can be read atomically by the architecture.
2064 * *) access_ok is sufficient to validate userspace address ranges.
2066 * The last two assumptions can be relaxed by the addition of helper functions.
2068 * This code is based heavily on the PowerPC implementation by Nick Piggin.
2070 #ifdef CONFIG_HAVE_FAST_GUP
2072 static void put_compound_head(struct page *page, int refs, unsigned int flags)
2074 if (flags & FOLL_PIN) {
2075 mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_RELEASED,
2078 if (hpage_pincount_available(page))
2079 hpage_pincount_sub(page, refs);
2081 refs *= GUP_PIN_COUNTING_BIAS;
2084 VM_BUG_ON_PAGE(page_ref_count(page) < refs, page);
2086 * Calling put_page() for each ref is unnecessarily slow. Only the last
2087 * ref needs a put_page().
2090 page_ref_sub(page, refs - 1);
2094 #ifdef CONFIG_GUP_GET_PTE_LOW_HIGH
2097 * WARNING: only to be used in the get_user_pages_fast() implementation.
2099 * With get_user_pages_fast(), we walk down the pagetables without taking any
2100 * locks. For this we would like to load the pointers atomically, but sometimes
2101 * that is not possible (e.g. without expensive cmpxchg8b on x86_32 PAE). What
2102 * we do have is the guarantee that a PTE will only either go from not present
2103 * to present, or present to not present or both -- it will not switch to a
2104 * completely different present page without a TLB flush in between; something
2105 * that we are blocking by holding interrupts off.
2107 * Setting ptes from not present to present goes:
2109 * ptep->pte_high = h;
2111 * ptep->pte_low = l;
2113 * And present to not present goes:
2115 * ptep->pte_low = 0;
2117 * ptep->pte_high = 0;
2119 * We must ensure here that the load of pte_low sees 'l' IFF pte_high sees 'h'.
2120 * We load pte_high *after* loading pte_low, which ensures we don't see an older
2121 * value of pte_high. *Then* we recheck pte_low, which ensures that we haven't
2122 * picked up a changed pte high. We might have gotten rubbish values from
2123 * pte_low and pte_high, but we are guaranteed that pte_low will not have the
2124 * present bit set *unless* it is 'l'. Because get_user_pages_fast() only
2125 * operates on present ptes we're safe.
2127 static inline pte_t gup_get_pte(pte_t *ptep)
2132 pte.pte_low = ptep->pte_low;
2134 pte.pte_high = ptep->pte_high;
2136 } while (unlikely(pte.pte_low != ptep->pte_low));
2140 #else /* CONFIG_GUP_GET_PTE_LOW_HIGH */
2142 * We require that the PTE can be read atomically.
2144 static inline pte_t gup_get_pte(pte_t *ptep)
2146 return READ_ONCE(*ptep);
2148 #endif /* CONFIG_GUP_GET_PTE_LOW_HIGH */
2150 static void __maybe_unused undo_dev_pagemap(int *nr, int nr_start,
2152 struct page **pages)
2154 while ((*nr) - nr_start) {
2155 struct page *page = pages[--(*nr)];
2157 ClearPageReferenced(page);
2158 if (flags & FOLL_PIN)
2159 unpin_user_page(page);
2165 #ifdef CONFIG_ARCH_HAS_PTE_SPECIAL
2166 static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
2167 unsigned int flags, struct page **pages, int *nr)
2169 struct dev_pagemap *pgmap = NULL;
2170 int nr_start = *nr, ret = 0;
2173 ptem = ptep = pte_offset_map(&pmd, addr);
2175 pte_t pte = gup_get_pte(ptep);
2176 struct page *head, *page;
2179 * Similar to the PMD case below, NUMA hinting must take slow
2180 * path using the pte_protnone check.
2182 if (pte_protnone(pte))
2185 if (!pte_access_permitted(pte, flags & FOLL_WRITE))
2188 if (pte_devmap(pte)) {
2189 if (unlikely(flags & FOLL_LONGTERM))
2192 pgmap = get_dev_pagemap(pte_pfn(pte), pgmap);
2193 if (unlikely(!pgmap)) {
2194 undo_dev_pagemap(nr, nr_start, flags, pages);
2197 } else if (pte_special(pte))
2200 VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
2201 page = pte_page(pte);
2203 head = try_grab_compound_head(page, 1, flags);
2207 if (unlikely(pte_val(pte) != pte_val(*ptep))) {
2208 put_compound_head(head, 1, flags);
2212 VM_BUG_ON_PAGE(compound_head(page) != head, page);
2215 * We need to make the page accessible if and only if we are
2216 * going to access its content (the FOLL_PIN case). Please
2217 * see Documentation/core-api/pin_user_pages.rst for
2220 if (flags & FOLL_PIN) {
2221 ret = arch_make_page_accessible(page);
2223 unpin_user_page(page);
2227 SetPageReferenced(page);
2231 } while (ptep++, addr += PAGE_SIZE, addr != end);
2237 put_dev_pagemap(pgmap);
2244 * If we can't determine whether or not a pte is special, then fail immediately
2245 * for ptes. Note, we can still pin HugeTLB and THP as these are guaranteed not
2248 * For a futex to be placed on a THP tail page, get_futex_key requires a
2249 * __get_user_pages_fast implementation that can pin pages. Thus it's still
2250 * useful to have gup_huge_pmd even if we can't operate on ptes.
2252 static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
2253 unsigned int flags, struct page **pages, int *nr)
2257 #endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */
2259 #if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
2260 static int __gup_device_huge(unsigned long pfn, unsigned long addr,
2261 unsigned long end, unsigned int flags,
2262 struct page **pages, int *nr)
2265 struct dev_pagemap *pgmap = NULL;
2268 struct page *page = pfn_to_page(pfn);
2270 pgmap = get_dev_pagemap(pfn, pgmap);
2271 if (unlikely(!pgmap)) {
2272 undo_dev_pagemap(nr, nr_start, flags, pages);
2275 SetPageReferenced(page);
2277 if (unlikely(!try_grab_page(page, flags))) {
2278 undo_dev_pagemap(nr, nr_start, flags, pages);
2283 } while (addr += PAGE_SIZE, addr != end);
2286 put_dev_pagemap(pgmap);
2290 static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
2291 unsigned long end, unsigned int flags,
2292 struct page **pages, int *nr)
2294 unsigned long fault_pfn;
2297 fault_pfn = pmd_pfn(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
2298 if (!__gup_device_huge(fault_pfn, addr, end, flags, pages, nr))
2301 if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
2302 undo_dev_pagemap(nr, nr_start, flags, pages);
2308 static int __gup_device_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
2309 unsigned long end, unsigned int flags,
2310 struct page **pages, int *nr)
2312 unsigned long fault_pfn;
2315 fault_pfn = pud_pfn(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
2316 if (!__gup_device_huge(fault_pfn, addr, end, flags, pages, nr))
2319 if (unlikely(pud_val(orig) != pud_val(*pudp))) {
2320 undo_dev_pagemap(nr, nr_start, flags, pages);
2326 static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
2327 unsigned long end, unsigned int flags,
2328 struct page **pages, int *nr)
2334 static int __gup_device_huge_pud(pud_t pud, pud_t *pudp, unsigned long addr,
2335 unsigned long end, unsigned int flags,
2336 struct page **pages, int *nr)
2343 static int record_subpages(struct page *page, unsigned long addr,
2344 unsigned long end, struct page **pages)
2348 for (nr = 0; addr != end; addr += PAGE_SIZE)
2349 pages[nr++] = page++;
2354 #ifdef CONFIG_ARCH_HAS_HUGEPD
2355 static unsigned long hugepte_addr_end(unsigned long addr, unsigned long end,
2358 unsigned long __boundary = (addr + sz) & ~(sz-1);
2359 return (__boundary - 1 < end - 1) ? __boundary : end;
2362 static int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr,
2363 unsigned long end, unsigned int flags,
2364 struct page **pages, int *nr)
2366 unsigned long pte_end;
2367 struct page *head, *page;
2371 pte_end = (addr + sz) & ~(sz-1);
2375 pte = READ_ONCE(*ptep);
2377 if (!pte_access_permitted(pte, flags & FOLL_WRITE))
2380 /* hugepages are never "special" */
2381 VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
2383 head = pte_page(pte);
2384 page = head + ((addr & (sz-1)) >> PAGE_SHIFT);
2385 refs = record_subpages(page, addr, end, pages + *nr);
2387 head = try_grab_compound_head(head, refs, flags);
2391 if (unlikely(pte_val(pte) != pte_val(*ptep))) {
2392 put_compound_head(head, refs, flags);
2397 SetPageReferenced(head);
2401 static int gup_huge_pd(hugepd_t hugepd, unsigned long addr,
2402 unsigned int pdshift, unsigned long end, unsigned int flags,
2403 struct page **pages, int *nr)
2406 unsigned long sz = 1UL << hugepd_shift(hugepd);
2409 ptep = hugepte_offset(hugepd, addr, pdshift);
2411 next = hugepte_addr_end(addr, end, sz);
2412 if (!gup_hugepte(ptep, sz, addr, end, flags, pages, nr))
2414 } while (ptep++, addr = next, addr != end);
2419 static inline int gup_huge_pd(hugepd_t hugepd, unsigned long addr,
2420 unsigned int pdshift, unsigned long end, unsigned int flags,
2421 struct page **pages, int *nr)
2425 #endif /* CONFIG_ARCH_HAS_HUGEPD */
2427 static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
2428 unsigned long end, unsigned int flags,
2429 struct page **pages, int *nr)
2431 struct page *head, *page;
2434 if (!pmd_access_permitted(orig, flags & FOLL_WRITE))
2437 if (pmd_devmap(orig)) {
2438 if (unlikely(flags & FOLL_LONGTERM))
2440 return __gup_device_huge_pmd(orig, pmdp, addr, end, flags,
2444 page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
2445 refs = record_subpages(page, addr, end, pages + *nr);
2447 head = try_grab_compound_head(pmd_page(orig), refs, flags);
2451 if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
2452 put_compound_head(head, refs, flags);
2457 SetPageReferenced(head);
2461 static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
2462 unsigned long end, unsigned int flags,
2463 struct page **pages, int *nr)
2465 struct page *head, *page;
2468 if (!pud_access_permitted(orig, flags & FOLL_WRITE))
2471 if (pud_devmap(orig)) {
2472 if (unlikely(flags & FOLL_LONGTERM))
2474 return __gup_device_huge_pud(orig, pudp, addr, end, flags,
2478 page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
2479 refs = record_subpages(page, addr, end, pages + *nr);
2481 head = try_grab_compound_head(pud_page(orig), refs, flags);
2485 if (unlikely(pud_val(orig) != pud_val(*pudp))) {
2486 put_compound_head(head, refs, flags);
2491 SetPageReferenced(head);
2495 static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
2496 unsigned long end, unsigned int flags,
2497 struct page **pages, int *nr)
2500 struct page *head, *page;
2502 if (!pgd_access_permitted(orig, flags & FOLL_WRITE))
2505 BUILD_BUG_ON(pgd_devmap(orig));
2507 page = pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT);
2508 refs = record_subpages(page, addr, end, pages + *nr);
2510 head = try_grab_compound_head(pgd_page(orig), refs, flags);
2514 if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) {
2515 put_compound_head(head, refs, flags);
2520 SetPageReferenced(head);
2524 static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
2525 unsigned int flags, struct page **pages, int *nr)
2530 pmdp = pmd_offset(&pud, addr);
2532 pmd_t pmd = READ_ONCE(*pmdp);
2534 next = pmd_addr_end(addr, end);
2535 if (!pmd_present(pmd))
2538 if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd) ||
2541 * NUMA hinting faults need to be handled in the GUP
2542 * slowpath for accounting purposes and so that they
2543 * can be serialised against THP migration.
2545 if (pmd_protnone(pmd))
2548 if (!gup_huge_pmd(pmd, pmdp, addr, next, flags,
2552 } else if (unlikely(is_hugepd(__hugepd(pmd_val(pmd))))) {
2554 * architecture have different format for hugetlbfs
2555 * pmd format and THP pmd format
2557 if (!gup_huge_pd(__hugepd(pmd_val(pmd)), addr,
2558 PMD_SHIFT, next, flags, pages, nr))
2560 } else if (!gup_pte_range(pmd, addr, next, flags, pages, nr))
2562 } while (pmdp++, addr = next, addr != end);
2567 static int gup_pud_range(p4d_t p4d, unsigned long addr, unsigned long end,
2568 unsigned int flags, struct page **pages, int *nr)
2573 pudp = pud_offset(&p4d, addr);
2575 pud_t pud = READ_ONCE(*pudp);
2577 next = pud_addr_end(addr, end);
2578 if (unlikely(!pud_present(pud)))
2580 if (unlikely(pud_huge(pud))) {
2581 if (!gup_huge_pud(pud, pudp, addr, next, flags,
2584 } else if (unlikely(is_hugepd(__hugepd(pud_val(pud))))) {
2585 if (!gup_huge_pd(__hugepd(pud_val(pud)), addr,
2586 PUD_SHIFT, next, flags, pages, nr))
2588 } else if (!gup_pmd_range(pud, addr, next, flags, pages, nr))
2590 } while (pudp++, addr = next, addr != end);
2595 static int gup_p4d_range(pgd_t pgd, unsigned long addr, unsigned long end,
2596 unsigned int flags, struct page **pages, int *nr)
2601 p4dp = p4d_offset(&pgd, addr);
2603 p4d_t p4d = READ_ONCE(*p4dp);
2605 next = p4d_addr_end(addr, end);
2608 BUILD_BUG_ON(p4d_huge(p4d));
2609 if (unlikely(is_hugepd(__hugepd(p4d_val(p4d))))) {
2610 if (!gup_huge_pd(__hugepd(p4d_val(p4d)), addr,
2611 P4D_SHIFT, next, flags, pages, nr))
2613 } else if (!gup_pud_range(p4d, addr, next, flags, pages, nr))
2615 } while (p4dp++, addr = next, addr != end);
2620 static void gup_pgd_range(unsigned long addr, unsigned long end,
2621 unsigned int flags, struct page **pages, int *nr)
2626 pgdp = pgd_offset(current->mm, addr);
2628 pgd_t pgd = READ_ONCE(*pgdp);
2630 next = pgd_addr_end(addr, end);
2633 if (unlikely(pgd_huge(pgd))) {
2634 if (!gup_huge_pgd(pgd, pgdp, addr, next, flags,
2637 } else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd))))) {
2638 if (!gup_huge_pd(__hugepd(pgd_val(pgd)), addr,
2639 PGDIR_SHIFT, next, flags, pages, nr))
2641 } else if (!gup_p4d_range(pgd, addr, next, flags, pages, nr))
2643 } while (pgdp++, addr = next, addr != end);
2646 static inline void gup_pgd_range(unsigned long addr, unsigned long end,
2647 unsigned int flags, struct page **pages, int *nr)
2650 #endif /* CONFIG_HAVE_FAST_GUP */
2652 #ifndef gup_fast_permitted
2654 * Check if it's allowed to use __get_user_pages_fast() for the range, or
2655 * we need to fall back to the slow version:
2657 static bool gup_fast_permitted(unsigned long start, unsigned long end)
2664 * Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to
2666 * Note a difference with get_user_pages_fast: this always returns the
2667 * number of pages pinned, 0 if no pages were pinned.
2669 * If the architecture does not support this function, simply return with no
2672 int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
2673 struct page **pages)
2675 unsigned long len, end;
2676 unsigned long flags;
2679 * Internally (within mm/gup.c), gup fast variants must set FOLL_GET,
2680 * because gup fast is always a "pin with a +1 page refcount" request.
2682 unsigned int gup_flags = FOLL_GET;
2685 gup_flags |= FOLL_WRITE;
2687 start = untagged_addr(start) & PAGE_MASK;
2688 len = (unsigned long) nr_pages << PAGE_SHIFT;
2693 if (unlikely(!access_ok((void __user *)start, len)))
2697 * Disable interrupts. We use the nested form as we can already have
2698 * interrupts disabled by get_futex_key.
2700 * With interrupts disabled, we block page table pages from being
2701 * freed from under us. See struct mmu_table_batch comments in
2702 * include/asm-generic/tlb.h for more details.
2704 * We do not adopt an rcu_read_lock(.) here as we also want to
2705 * block IPIs that come from THPs splitting.
2708 if (IS_ENABLED(CONFIG_HAVE_FAST_GUP) &&
2709 gup_fast_permitted(start, end)) {
2710 local_irq_save(flags);
2711 gup_pgd_range(start, end, gup_flags, pages, &nr_pinned);
2712 local_irq_restore(flags);
2717 EXPORT_SYMBOL_GPL(__get_user_pages_fast);
2719 static int __gup_longterm_unlocked(unsigned long start, int nr_pages,
2720 unsigned int gup_flags, struct page **pages)
2725 * FIXME: FOLL_LONGTERM does not work with
2726 * get_user_pages_unlocked() (see comments in that function)
2728 if (gup_flags & FOLL_LONGTERM) {
2729 down_read(¤t->mm->mmap_sem);
2730 ret = __gup_longterm_locked(current, current->mm,
2732 pages, NULL, gup_flags);
2733 up_read(¤t->mm->mmap_sem);
2735 ret = get_user_pages_unlocked(start, nr_pages,
2742 static int internal_get_user_pages_fast(unsigned long start, int nr_pages,
2743 unsigned int gup_flags,
2744 struct page **pages)
2746 unsigned long addr, len, end;
2747 int nr_pinned = 0, ret = 0;
2749 if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM |
2750 FOLL_FORCE | FOLL_PIN | FOLL_GET)))
2753 start = untagged_addr(start) & PAGE_MASK;
2755 len = (unsigned long) nr_pages << PAGE_SHIFT;
2760 if (unlikely(!access_ok((void __user *)start, len)))
2763 if (IS_ENABLED(CONFIG_HAVE_FAST_GUP) &&
2764 gup_fast_permitted(start, end)) {
2765 local_irq_disable();
2766 gup_pgd_range(addr, end, gup_flags, pages, &nr_pinned);
2771 if (nr_pinned < nr_pages) {
2772 /* Try to get the remaining pages with get_user_pages */
2773 start += nr_pinned << PAGE_SHIFT;
2776 ret = __gup_longterm_unlocked(start, nr_pages - nr_pinned,
2779 /* Have to be a bit careful with return values */
2780 if (nr_pinned > 0) {
2792 * get_user_pages_fast() - pin user pages in memory
2793 * @start: starting user address
2794 * @nr_pages: number of pages from start to pin
2795 * @gup_flags: flags modifying pin behaviour
2796 * @pages: array that receives pointers to the pages pinned.
2797 * Should be at least nr_pages long.
2799 * Attempt to pin user pages in memory without taking mm->mmap_sem.
2800 * If not successful, it will fall back to taking the lock and
2801 * calling get_user_pages().
2803 * Returns number of pages pinned. This may be fewer than the number requested.
2804 * If nr_pages is 0 or negative, returns 0. If no pages were pinned, returns
2807 int get_user_pages_fast(unsigned long start, int nr_pages,
2808 unsigned int gup_flags, struct page **pages)
2811 * FOLL_PIN must only be set internally by the pin_user_pages*() APIs,
2812 * never directly by the caller, so enforce that:
2814 if (WARN_ON_ONCE(gup_flags & FOLL_PIN))
2818 * The caller may or may not have explicitly set FOLL_GET; either way is
2819 * OK. However, internally (within mm/gup.c), gup fast variants must set
2820 * FOLL_GET, because gup fast is always a "pin with a +1 page refcount"
2823 gup_flags |= FOLL_GET;
2824 return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages);
2826 EXPORT_SYMBOL_GPL(get_user_pages_fast);
2829 * pin_user_pages_fast() - pin user pages in memory without taking locks
2831 * @start: starting user address
2832 * @nr_pages: number of pages from start to pin
2833 * @gup_flags: flags modifying pin behaviour
2834 * @pages: array that receives pointers to the pages pinned.
2835 * Should be at least nr_pages long.
2837 * Nearly the same as get_user_pages_fast(), except that FOLL_PIN is set. See
2838 * get_user_pages_fast() for documentation on the function arguments, because
2839 * the arguments here are identical.
2841 * FOLL_PIN means that the pages must be released via unpin_user_page(). Please
2842 * see Documentation/vm/pin_user_pages.rst for further details.
2844 * This is intended for Case 1 (DIO) in Documentation/vm/pin_user_pages.rst. It
2845 * is NOT intended for Case 2 (RDMA: long-term pins).
2847 int pin_user_pages_fast(unsigned long start, int nr_pages,
2848 unsigned int gup_flags, struct page **pages)
2850 /* FOLL_GET and FOLL_PIN are mutually exclusive. */
2851 if (WARN_ON_ONCE(gup_flags & FOLL_GET))
2854 gup_flags |= FOLL_PIN;
2855 return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages);
2857 EXPORT_SYMBOL_GPL(pin_user_pages_fast);
2860 * pin_user_pages_remote() - pin pages of a remote process (task != current)
2862 * @tsk: the task_struct to use for page fault accounting, or
2863 * NULL if faults are not to be recorded.
2864 * @mm: mm_struct of target mm
2865 * @start: starting user address
2866 * @nr_pages: number of pages from start to pin
2867 * @gup_flags: flags modifying lookup behaviour
2868 * @pages: array that receives pointers to the pages pinned.
2869 * Should be at least nr_pages long. Or NULL, if caller
2870 * only intends to ensure the pages are faulted in.
2871 * @vmas: array of pointers to vmas corresponding to each page.
2872 * Or NULL if the caller does not require them.
2873 * @locked: pointer to lock flag indicating whether lock is held and
2874 * subsequently whether VM_FAULT_RETRY functionality can be
2875 * utilised. Lock must initially be held.
2877 * Nearly the same as get_user_pages_remote(), except that FOLL_PIN is set. See
2878 * get_user_pages_remote() for documentation on the function arguments, because
2879 * the arguments here are identical.
2881 * FOLL_PIN means that the pages must be released via unpin_user_page(). Please
2882 * see Documentation/vm/pin_user_pages.rst for details.
2884 * This is intended for Case 1 (DIO) in Documentation/vm/pin_user_pages.rst. It
2885 * is NOT intended for Case 2 (RDMA: long-term pins).
2887 long pin_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
2888 unsigned long start, unsigned long nr_pages,
2889 unsigned int gup_flags, struct page **pages,
2890 struct vm_area_struct **vmas, int *locked)
2892 /* FOLL_GET and FOLL_PIN are mutually exclusive. */
2893 if (WARN_ON_ONCE(gup_flags & FOLL_GET))
2896 gup_flags |= FOLL_PIN;
2897 return __get_user_pages_remote(tsk, mm, start, nr_pages, gup_flags,
2898 pages, vmas, locked);
2900 EXPORT_SYMBOL(pin_user_pages_remote);
2903 * pin_user_pages() - pin user pages in memory for use by other devices
2905 * @start: starting user address
2906 * @nr_pages: number of pages from start to pin
2907 * @gup_flags: flags modifying lookup behaviour
2908 * @pages: array that receives pointers to the pages pinned.
2909 * Should be at least nr_pages long. Or NULL, if caller
2910 * only intends to ensure the pages are faulted in.
2911 * @vmas: array of pointers to vmas corresponding to each page.
2912 * Or NULL if the caller does not require them.
2914 * Nearly the same as get_user_pages(), except that FOLL_TOUCH is not set, and
2917 * FOLL_PIN means that the pages must be released via unpin_user_page(). Please
2918 * see Documentation/vm/pin_user_pages.rst for details.
2920 * This is intended for Case 1 (DIO) in Documentation/vm/pin_user_pages.rst. It
2921 * is NOT intended for Case 2 (RDMA: long-term pins).
2923 long pin_user_pages(unsigned long start, unsigned long nr_pages,
2924 unsigned int gup_flags, struct page **pages,
2925 struct vm_area_struct **vmas)
2927 /* FOLL_GET and FOLL_PIN are mutually exclusive. */
2928 if (WARN_ON_ONCE(gup_flags & FOLL_GET))
2931 gup_flags |= FOLL_PIN;
2932 return __gup_longterm_locked(current, current->mm, start, nr_pages,
2933 pages, vmas, gup_flags);
2935 EXPORT_SYMBOL(pin_user_pages);