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) &&
355 (vma_is_anonymous(vma) || !vma->vm_ops->fault))
356 return ERR_PTR(-EFAULT);
360 static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address,
361 pte_t *pte, unsigned int flags)
363 /* No page to get reference */
364 if (flags & FOLL_GET)
367 if (flags & FOLL_TOUCH) {
370 if (flags & FOLL_WRITE)
371 entry = pte_mkdirty(entry);
372 entry = pte_mkyoung(entry);
374 if (!pte_same(*pte, entry)) {
375 set_pte_at(vma->vm_mm, address, pte, entry);
376 update_mmu_cache(vma, address, pte);
380 /* Proper page table entry exists, but no corresponding struct page */
385 * FOLL_FORCE or a forced COW break can write even to unwritable pte's,
386 * but only after we've gone through a COW cycle and they are dirty.
388 static inline bool can_follow_write_pte(pte_t pte, unsigned int flags)
390 return pte_write(pte) || ((flags & FOLL_COW) && pte_dirty(pte));
394 * A (separate) COW fault might break the page the other way and
395 * get_user_pages() would return the page from what is now the wrong
396 * VM. So we need to force a COW break at GUP time even for reads.
398 static inline bool should_force_cow_break(struct vm_area_struct *vma, unsigned int flags)
400 return is_cow_mapping(vma->vm_flags) && (flags & (FOLL_GET | FOLL_PIN));
403 static struct page *follow_page_pte(struct vm_area_struct *vma,
404 unsigned long address, pmd_t *pmd, unsigned int flags,
405 struct dev_pagemap **pgmap)
407 struct mm_struct *mm = vma->vm_mm;
413 /* FOLL_GET and FOLL_PIN are mutually exclusive. */
414 if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) ==
415 (FOLL_PIN | FOLL_GET)))
416 return ERR_PTR(-EINVAL);
418 if (unlikely(pmd_bad(*pmd)))
419 return no_page_table(vma, flags);
421 ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
423 if (!pte_present(pte)) {
426 * KSM's break_ksm() relies upon recognizing a ksm page
427 * even while it is being migrated, so for that case we
428 * need migration_entry_wait().
430 if (likely(!(flags & FOLL_MIGRATION)))
434 entry = pte_to_swp_entry(pte);
435 if (!is_migration_entry(entry))
437 pte_unmap_unlock(ptep, ptl);
438 migration_entry_wait(mm, pmd, address);
441 if ((flags & FOLL_NUMA) && pte_protnone(pte))
443 if ((flags & FOLL_WRITE) && !can_follow_write_pte(pte, flags)) {
444 pte_unmap_unlock(ptep, ptl);
448 page = vm_normal_page(vma, address, pte);
449 if (!page && pte_devmap(pte) && (flags & (FOLL_GET | FOLL_PIN))) {
451 * Only return device mapping pages in the FOLL_GET or FOLL_PIN
452 * case since they are only valid while holding the pgmap
455 *pgmap = get_dev_pagemap(pte_pfn(pte), *pgmap);
457 page = pte_page(pte);
460 } else if (unlikely(!page)) {
461 if (flags & FOLL_DUMP) {
462 /* Avoid special (like zero) pages in core dumps */
463 page = ERR_PTR(-EFAULT);
467 if (is_zero_pfn(pte_pfn(pte))) {
468 page = pte_page(pte);
470 ret = follow_pfn_pte(vma, address, ptep, flags);
476 if (flags & FOLL_SPLIT && PageTransCompound(page)) {
478 pte_unmap_unlock(ptep, ptl);
480 ret = split_huge_page(page);
488 /* try_grab_page() does nothing unless FOLL_GET or FOLL_PIN is set. */
489 if (unlikely(!try_grab_page(page, flags))) {
490 page = ERR_PTR(-ENOMEM);
494 * We need to make the page accessible if and only if we are going
495 * to access its content (the FOLL_PIN case). Please see
496 * Documentation/core-api/pin_user_pages.rst for details.
498 if (flags & FOLL_PIN) {
499 ret = arch_make_page_accessible(page);
501 unpin_user_page(page);
506 if (flags & FOLL_TOUCH) {
507 if ((flags & FOLL_WRITE) &&
508 !pte_dirty(pte) && !PageDirty(page))
509 set_page_dirty(page);
511 * pte_mkyoung() would be more correct here, but atomic care
512 * is needed to avoid losing the dirty bit: it is easier to use
513 * mark_page_accessed().
515 mark_page_accessed(page);
517 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
518 /* Do not mlock pte-mapped THP */
519 if (PageTransCompound(page))
523 * The preliminary mapping check is mainly to avoid the
524 * pointless overhead of lock_page on the ZERO_PAGE
525 * which might bounce very badly if there is contention.
527 * If the page is already locked, we don't need to
528 * handle it now - vmscan will handle it later if and
529 * when it attempts to reclaim the page.
531 if (page->mapping && trylock_page(page)) {
532 lru_add_drain(); /* push cached pages to LRU */
534 * Because we lock page here, and migration is
535 * blocked by the pte's page reference, and we
536 * know the page is still mapped, we don't even
537 * need to check for file-cache page truncation.
539 mlock_vma_page(page);
544 pte_unmap_unlock(ptep, ptl);
547 pte_unmap_unlock(ptep, ptl);
550 return no_page_table(vma, flags);
553 static struct page *follow_pmd_mask(struct vm_area_struct *vma,
554 unsigned long address, pud_t *pudp,
556 struct follow_page_context *ctx)
561 struct mm_struct *mm = vma->vm_mm;
563 pmd = pmd_offset(pudp, address);
565 * The READ_ONCE() will stabilize the pmdval in a register or
566 * on the stack so that it will stop changing under the code.
568 pmdval = READ_ONCE(*pmd);
569 if (pmd_none(pmdval))
570 return no_page_table(vma, flags);
571 if (pmd_huge(pmdval) && is_vm_hugetlb_page(vma)) {
572 page = follow_huge_pmd(mm, address, pmd, flags);
575 return no_page_table(vma, flags);
577 if (is_hugepd(__hugepd(pmd_val(pmdval)))) {
578 page = follow_huge_pd(vma, address,
579 __hugepd(pmd_val(pmdval)), flags,
583 return no_page_table(vma, flags);
586 if (!pmd_present(pmdval)) {
587 if (likely(!(flags & FOLL_MIGRATION)))
588 return no_page_table(vma, flags);
589 VM_BUG_ON(thp_migration_supported() &&
590 !is_pmd_migration_entry(pmdval));
591 if (is_pmd_migration_entry(pmdval))
592 pmd_migration_entry_wait(mm, pmd);
593 pmdval = READ_ONCE(*pmd);
595 * MADV_DONTNEED may convert the pmd to null because
596 * mmap_sem is held in read mode
598 if (pmd_none(pmdval))
599 return no_page_table(vma, flags);
602 if (pmd_devmap(pmdval)) {
603 ptl = pmd_lock(mm, pmd);
604 page = follow_devmap_pmd(vma, address, pmd, flags, &ctx->pgmap);
609 if (likely(!pmd_trans_huge(pmdval)))
610 return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
612 if ((flags & FOLL_NUMA) && pmd_protnone(pmdval))
613 return no_page_table(vma, flags);
616 ptl = pmd_lock(mm, pmd);
617 if (unlikely(pmd_none(*pmd))) {
619 return no_page_table(vma, flags);
621 if (unlikely(!pmd_present(*pmd))) {
623 if (likely(!(flags & FOLL_MIGRATION)))
624 return no_page_table(vma, flags);
625 pmd_migration_entry_wait(mm, pmd);
628 if (unlikely(!pmd_trans_huge(*pmd))) {
630 return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
632 if (flags & (FOLL_SPLIT | FOLL_SPLIT_PMD)) {
634 page = pmd_page(*pmd);
635 if (is_huge_zero_page(page)) {
638 split_huge_pmd(vma, pmd, address);
639 if (pmd_trans_unstable(pmd))
641 } else if (flags & FOLL_SPLIT) {
642 if (unlikely(!try_get_page(page))) {
644 return ERR_PTR(-ENOMEM);
648 ret = split_huge_page(page);
652 return no_page_table(vma, flags);
653 } else { /* flags & FOLL_SPLIT_PMD */
655 split_huge_pmd(vma, pmd, address);
656 ret = pte_alloc(mm, pmd) ? -ENOMEM : 0;
659 return ret ? ERR_PTR(ret) :
660 follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
662 page = follow_trans_huge_pmd(vma, address, pmd, flags);
664 ctx->page_mask = HPAGE_PMD_NR - 1;
668 static struct page *follow_pud_mask(struct vm_area_struct *vma,
669 unsigned long address, p4d_t *p4dp,
671 struct follow_page_context *ctx)
676 struct mm_struct *mm = vma->vm_mm;
678 pud = pud_offset(p4dp, address);
680 return no_page_table(vma, flags);
681 if (pud_huge(*pud) && is_vm_hugetlb_page(vma)) {
682 page = follow_huge_pud(mm, address, pud, flags);
685 return no_page_table(vma, flags);
687 if (is_hugepd(__hugepd(pud_val(*pud)))) {
688 page = follow_huge_pd(vma, address,
689 __hugepd(pud_val(*pud)), flags,
693 return no_page_table(vma, flags);
695 if (pud_devmap(*pud)) {
696 ptl = pud_lock(mm, pud);
697 page = follow_devmap_pud(vma, address, pud, flags, &ctx->pgmap);
702 if (unlikely(pud_bad(*pud)))
703 return no_page_table(vma, flags);
705 return follow_pmd_mask(vma, address, pud, flags, ctx);
708 static struct page *follow_p4d_mask(struct vm_area_struct *vma,
709 unsigned long address, pgd_t *pgdp,
711 struct follow_page_context *ctx)
716 p4d = p4d_offset(pgdp, address);
718 return no_page_table(vma, flags);
719 BUILD_BUG_ON(p4d_huge(*p4d));
720 if (unlikely(p4d_bad(*p4d)))
721 return no_page_table(vma, flags);
723 if (is_hugepd(__hugepd(p4d_val(*p4d)))) {
724 page = follow_huge_pd(vma, address,
725 __hugepd(p4d_val(*p4d)), flags,
729 return no_page_table(vma, flags);
731 return follow_pud_mask(vma, address, p4d, flags, ctx);
735 * follow_page_mask - look up a page descriptor from a user-virtual address
736 * @vma: vm_area_struct mapping @address
737 * @address: virtual address to look up
738 * @flags: flags modifying lookup behaviour
739 * @ctx: contains dev_pagemap for %ZONE_DEVICE memory pinning and a
740 * pointer to output page_mask
742 * @flags can have FOLL_ flags set, defined in <linux/mm.h>
744 * When getting pages from ZONE_DEVICE memory, the @ctx->pgmap caches
745 * the device's dev_pagemap metadata to avoid repeating expensive lookups.
747 * On output, the @ctx->page_mask is set according to the size of the page.
749 * Return: the mapped (struct page *), %NULL if no mapping exists, or
750 * an error pointer if there is a mapping to something not represented
751 * by a page descriptor (see also vm_normal_page()).
753 static struct page *follow_page_mask(struct vm_area_struct *vma,
754 unsigned long address, unsigned int flags,
755 struct follow_page_context *ctx)
759 struct mm_struct *mm = vma->vm_mm;
763 /* make this handle hugepd */
764 page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
766 WARN_ON_ONCE(flags & (FOLL_GET | FOLL_PIN));
770 pgd = pgd_offset(mm, address);
772 if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
773 return no_page_table(vma, flags);
775 if (pgd_huge(*pgd)) {
776 page = follow_huge_pgd(mm, address, pgd, flags);
779 return no_page_table(vma, flags);
781 if (is_hugepd(__hugepd(pgd_val(*pgd)))) {
782 page = follow_huge_pd(vma, address,
783 __hugepd(pgd_val(*pgd)), flags,
787 return no_page_table(vma, flags);
790 return follow_p4d_mask(vma, address, pgd, flags, ctx);
793 struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
794 unsigned int foll_flags)
796 struct follow_page_context ctx = { NULL };
799 page = follow_page_mask(vma, address, foll_flags, &ctx);
801 put_dev_pagemap(ctx.pgmap);
805 static int get_gate_page(struct mm_struct *mm, unsigned long address,
806 unsigned int gup_flags, struct vm_area_struct **vma,
816 /* user gate pages are read-only */
817 if (gup_flags & FOLL_WRITE)
819 if (address > TASK_SIZE)
820 pgd = pgd_offset_k(address);
822 pgd = pgd_offset_gate(mm, address);
825 p4d = p4d_offset(pgd, address);
828 pud = pud_offset(p4d, address);
831 pmd = pmd_offset(pud, address);
832 if (!pmd_present(*pmd))
834 VM_BUG_ON(pmd_trans_huge(*pmd));
835 pte = pte_offset_map(pmd, address);
838 *vma = get_gate_vma(mm);
841 *page = vm_normal_page(*vma, address, *pte);
843 if ((gup_flags & FOLL_DUMP) || !is_zero_pfn(pte_pfn(*pte)))
845 *page = pte_page(*pte);
847 if (unlikely(!try_get_page(*page))) {
859 * mmap_sem must be held on entry. If @locked != NULL and *@flags
860 * does not include FOLL_NOWAIT, the mmap_sem may be released. If it
861 * is, *@locked will be set to 0 and -EBUSY returned.
863 static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma,
864 unsigned long address, unsigned int *flags, int *locked)
866 unsigned int fault_flags = 0;
869 /* mlock all present pages, but do not fault in new pages */
870 if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK)
872 if (*flags & FOLL_WRITE)
873 fault_flags |= FAULT_FLAG_WRITE;
874 if (*flags & FOLL_REMOTE)
875 fault_flags |= FAULT_FLAG_REMOTE;
877 fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
878 if (*flags & FOLL_NOWAIT)
879 fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT;
880 if (*flags & FOLL_TRIED) {
882 * Note: FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_TRIED
885 fault_flags |= FAULT_FLAG_TRIED;
888 ret = handle_mm_fault(vma, address, fault_flags);
889 if (ret & VM_FAULT_ERROR) {
890 int err = vm_fault_to_errno(ret, *flags);
898 if (ret & VM_FAULT_MAJOR)
904 if (ret & VM_FAULT_RETRY) {
905 if (locked && !(fault_flags & FAULT_FLAG_RETRY_NOWAIT))
911 * The VM_FAULT_WRITE bit tells us that do_wp_page has broken COW when
912 * necessary, even if maybe_mkwrite decided not to set pte_write. We
913 * can thus safely do subsequent page lookups as if they were reads.
914 * But only do so when looping for pte_write is futile: in some cases
915 * userspace may also be wanting to write to the gotten user page,
916 * which a read fault here might prevent (a readonly page might get
917 * reCOWed by userspace write).
919 if ((ret & VM_FAULT_WRITE) && !(vma->vm_flags & VM_WRITE))
924 static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)
926 vm_flags_t vm_flags = vma->vm_flags;
927 int write = (gup_flags & FOLL_WRITE);
928 int foreign = (gup_flags & FOLL_REMOTE);
930 if (vm_flags & (VM_IO | VM_PFNMAP))
933 if (gup_flags & FOLL_ANON && !vma_is_anonymous(vma))
937 if (!(vm_flags & VM_WRITE)) {
938 if (!(gup_flags & FOLL_FORCE))
941 * We used to let the write,force case do COW in a
942 * VM_MAYWRITE VM_SHARED !VM_WRITE vma, so ptrace could
943 * set a breakpoint in a read-only mapping of an
944 * executable, without corrupting the file (yet only
945 * when that file had been opened for writing!).
946 * Anon pages in shared mappings are surprising: now
949 if (!is_cow_mapping(vm_flags))
952 } else if (!(vm_flags & VM_READ)) {
953 if (!(gup_flags & FOLL_FORCE))
956 * Is there actually any vma we can reach here which does not
957 * have VM_MAYREAD set?
959 if (!(vm_flags & VM_MAYREAD))
963 * gups are always data accesses, not instruction
964 * fetches, so execute=false here
966 if (!arch_vma_access_permitted(vma, write, false, foreign))
972 * __get_user_pages() - pin user pages in memory
973 * @tsk: task_struct of target task
974 * @mm: mm_struct of target mm
975 * @start: starting user address
976 * @nr_pages: number of pages from start to pin
977 * @gup_flags: flags modifying pin behaviour
978 * @pages: array that receives pointers to the pages pinned.
979 * Should be at least nr_pages long. Or NULL, if caller
980 * only intends to ensure the pages are faulted in.
981 * @vmas: array of pointers to vmas corresponding to each page.
982 * Or NULL if the caller does not require them.
983 * @locked: whether we're still with the mmap_sem held
985 * Returns either number of pages pinned (which may be less than the
986 * number requested), or an error. Details about the return value:
988 * -- If nr_pages is 0, returns 0.
989 * -- If nr_pages is >0, but no pages were pinned, returns -errno.
990 * -- If nr_pages is >0, and some pages were pinned, returns the number of
991 * pages pinned. Again, this may be less than nr_pages.
992 * -- 0 return value is possible when the fault would need to be retried.
994 * The caller is responsible for releasing returned @pages, via put_page().
996 * @vmas are valid only as long as mmap_sem is held.
998 * Must be called with mmap_sem held. It may be released. See below.
1000 * __get_user_pages walks a process's page tables and takes a reference to
1001 * each struct page that each user address corresponds to at a given
1002 * instant. That is, it takes the page that would be accessed if a user
1003 * thread accesses the given user virtual address at that instant.
1005 * This does not guarantee that the page exists in the user mappings when
1006 * __get_user_pages returns, and there may even be a completely different
1007 * page there in some cases (eg. if mmapped pagecache has been invalidated
1008 * and subsequently re faulted). However it does guarantee that the page
1009 * won't be freed completely. And mostly callers simply care that the page
1010 * contains data that was valid *at some point in time*. Typically, an IO
1011 * or similar operation cannot guarantee anything stronger anyway because
1012 * locks can't be held over the syscall boundary.
1014 * If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If
1015 * the page is written to, set_page_dirty (or set_page_dirty_lock, as
1016 * appropriate) must be called after the page is finished with, and
1017 * before put_page is called.
1019 * If @locked != NULL, *@locked will be set to 0 when mmap_sem is
1020 * released by an up_read(). That can happen if @gup_flags does not
1023 * A caller using such a combination of @locked and @gup_flags
1024 * must therefore hold the mmap_sem for reading only, and recognize
1025 * when it's been released. Otherwise, it must be held for either
1026 * reading or writing and will not be released.
1028 * In most cases, get_user_pages or get_user_pages_fast should be used
1029 * instead of __get_user_pages. __get_user_pages should be used only if
1030 * you need some special @gup_flags.
1032 static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
1033 unsigned long start, unsigned long nr_pages,
1034 unsigned int gup_flags, struct page **pages,
1035 struct vm_area_struct **vmas, int *locked)
1037 long ret = 0, i = 0;
1038 struct vm_area_struct *vma = NULL;
1039 struct follow_page_context ctx = { NULL };
1044 start = untagged_addr(start);
1046 VM_BUG_ON(!!pages != !!(gup_flags & (FOLL_GET | FOLL_PIN)));
1049 * If FOLL_FORCE is set then do not force a full fault as the hinting
1050 * fault information is unrelated to the reference behaviour of a task
1051 * using the address space
1053 if (!(gup_flags & FOLL_FORCE))
1054 gup_flags |= FOLL_NUMA;
1058 unsigned int foll_flags = gup_flags;
1059 unsigned int page_increm;
1061 /* first iteration or cross vma bound */
1062 if (!vma || start >= vma->vm_end) {
1063 vma = find_extend_vma(mm, start);
1064 if (!vma && in_gate_area(mm, start)) {
1065 ret = get_gate_page(mm, start & PAGE_MASK,
1067 pages ? &pages[i] : NULL);
1074 if (!vma || check_vma_flags(vma, gup_flags)) {
1078 if (is_vm_hugetlb_page(vma)) {
1079 if (should_force_cow_break(vma, foll_flags))
1080 foll_flags |= FOLL_WRITE;
1081 i = follow_hugetlb_page(mm, vma, pages, vmas,
1082 &start, &nr_pages, i,
1083 foll_flags, locked);
1084 if (locked && *locked == 0) {
1086 * We've got a VM_FAULT_RETRY
1087 * and we've lost mmap_sem.
1088 * We must stop here.
1090 BUG_ON(gup_flags & FOLL_NOWAIT);
1098 if (should_force_cow_break(vma, foll_flags))
1099 foll_flags |= FOLL_WRITE;
1103 * If we have a pending SIGKILL, don't keep faulting pages and
1104 * potentially allocating memory.
1106 if (fatal_signal_pending(current)) {
1112 page = follow_page_mask(vma, start, foll_flags, &ctx);
1114 ret = faultin_page(tsk, vma, start, &foll_flags,
1130 } else if (PTR_ERR(page) == -EEXIST) {
1132 * Proper page table entry exists, but no corresponding
1136 } else if (IS_ERR(page)) {
1137 ret = PTR_ERR(page);
1142 flush_anon_page(vma, page, start);
1143 flush_dcache_page(page);
1151 page_increm = 1 + (~(start >> PAGE_SHIFT) & ctx.page_mask);
1152 if (page_increm > nr_pages)
1153 page_increm = nr_pages;
1155 start += page_increm * PAGE_SIZE;
1156 nr_pages -= page_increm;
1160 put_dev_pagemap(ctx.pgmap);
1164 static bool vma_permits_fault(struct vm_area_struct *vma,
1165 unsigned int fault_flags)
1167 bool write = !!(fault_flags & FAULT_FLAG_WRITE);
1168 bool foreign = !!(fault_flags & FAULT_FLAG_REMOTE);
1169 vm_flags_t vm_flags = write ? VM_WRITE : VM_READ;
1171 if (!(vm_flags & vma->vm_flags))
1175 * The architecture might have a hardware protection
1176 * mechanism other than read/write that can deny access.
1178 * gup always represents data access, not instruction
1179 * fetches, so execute=false here:
1181 if (!arch_vma_access_permitted(vma, write, false, foreign))
1188 * fixup_user_fault() - manually resolve a user page fault
1189 * @tsk: the task_struct to use for page fault accounting, or
1190 * NULL if faults are not to be recorded.
1191 * @mm: mm_struct of target mm
1192 * @address: user address
1193 * @fault_flags:flags to pass down to handle_mm_fault()
1194 * @unlocked: did we unlock the mmap_sem while retrying, maybe NULL if caller
1195 * does not allow retry. If NULL, the caller must guarantee
1196 * that fault_flags does not contain FAULT_FLAG_ALLOW_RETRY.
1198 * This is meant to be called in the specific scenario where for locking reasons
1199 * we try to access user memory in atomic context (within a pagefault_disable()
1200 * section), this returns -EFAULT, and we want to resolve the user fault before
1203 * Typically this is meant to be used by the futex code.
1205 * The main difference with get_user_pages() is that this function will
1206 * unconditionally call handle_mm_fault() which will in turn perform all the
1207 * necessary SW fixup of the dirty and young bits in the PTE, while
1208 * get_user_pages() only guarantees to update these in the struct page.
1210 * This is important for some architectures where those bits also gate the
1211 * access permission to the page because they are maintained in software. On
1212 * such architectures, gup() will not be enough to make a subsequent access
1215 * This function will not return with an unlocked mmap_sem. So it has not the
1216 * same semantics wrt the @mm->mmap_sem as does filemap_fault().
1218 int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
1219 unsigned long address, unsigned int fault_flags,
1222 struct vm_area_struct *vma;
1223 vm_fault_t ret, major = 0;
1225 address = untagged_addr(address);
1228 fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
1231 vma = find_extend_vma(mm, address);
1232 if (!vma || address < vma->vm_start)
1235 if (!vma_permits_fault(vma, fault_flags))
1238 if ((fault_flags & FAULT_FLAG_KILLABLE) &&
1239 fatal_signal_pending(current))
1242 ret = handle_mm_fault(vma, address, fault_flags);
1243 major |= ret & VM_FAULT_MAJOR;
1244 if (ret & VM_FAULT_ERROR) {
1245 int err = vm_fault_to_errno(ret, 0);
1252 if (ret & VM_FAULT_RETRY) {
1253 down_read(&mm->mmap_sem);
1255 fault_flags |= FAULT_FLAG_TRIED;
1267 EXPORT_SYMBOL_GPL(fixup_user_fault);
1270 * Please note that this function, unlike __get_user_pages will not
1271 * return 0 for nr_pages > 0 without FOLL_NOWAIT
1273 static __always_inline long __get_user_pages_locked(struct task_struct *tsk,
1274 struct mm_struct *mm,
1275 unsigned long start,
1276 unsigned long nr_pages,
1277 struct page **pages,
1278 struct vm_area_struct **vmas,
1282 long ret, pages_done;
1286 /* if VM_FAULT_RETRY can be returned, vmas become invalid */
1288 /* check caller initialized locked */
1289 BUG_ON(*locked != 1);
1293 * FOLL_PIN and FOLL_GET are mutually exclusive. Traditional behavior
1294 * is to set FOLL_GET if the caller wants pages[] filled in (but has
1295 * carelessly failed to specify FOLL_GET), so keep doing that, but only
1296 * for FOLL_GET, not for the newer FOLL_PIN.
1298 * FOLL_PIN always expects pages to be non-null, but no need to assert
1299 * that here, as any failures will be obvious enough.
1301 if (pages && !(flags & FOLL_PIN))
1305 lock_dropped = false;
1307 ret = __get_user_pages(tsk, mm, start, nr_pages, flags, pages,
1310 /* VM_FAULT_RETRY couldn't trigger, bypass */
1313 /* VM_FAULT_RETRY cannot return errors */
1316 BUG_ON(ret >= nr_pages);
1327 * VM_FAULT_RETRY didn't trigger or it was a
1335 * VM_FAULT_RETRY triggered, so seek to the faulting offset.
1336 * For the prefault case (!pages) we only update counts.
1340 start += ret << PAGE_SHIFT;
1341 lock_dropped = true;
1345 * Repeat on the address that fired VM_FAULT_RETRY
1346 * with both FAULT_FLAG_ALLOW_RETRY and
1347 * FAULT_FLAG_TRIED. Note that GUP can be interrupted
1348 * by fatal signals, so we need to check it before we
1349 * start trying again otherwise it can loop forever.
1352 if (fatal_signal_pending(current)) {
1354 pages_done = -EINTR;
1358 ret = down_read_killable(&mm->mmap_sem);
1367 ret = __get_user_pages(tsk, mm, start, 1, flags | FOLL_TRIED,
1368 pages, NULL, locked);
1370 /* Continue to retry until we succeeded */
1388 if (lock_dropped && *locked) {
1390 * We must let the caller know we temporarily dropped the lock
1391 * and so the critical section protected by it was lost.
1393 up_read(&mm->mmap_sem);
1400 * populate_vma_page_range() - populate a range of pages in the vma.
1402 * @start: start address
1404 * @locked: whether the mmap_sem is still held
1406 * This takes care of mlocking the pages too if VM_LOCKED is set.
1408 * return 0 on success, negative error code on error.
1410 * vma->vm_mm->mmap_sem must be held.
1412 * If @locked is NULL, it may be held for read or write and will
1415 * If @locked is non-NULL, it must held for read only and may be
1416 * released. If it's released, *@locked will be set to 0.
1418 long populate_vma_page_range(struct vm_area_struct *vma,
1419 unsigned long start, unsigned long end, int *locked)
1421 struct mm_struct *mm = vma->vm_mm;
1422 unsigned long nr_pages = (end - start) / PAGE_SIZE;
1425 VM_BUG_ON(start & ~PAGE_MASK);
1426 VM_BUG_ON(end & ~PAGE_MASK);
1427 VM_BUG_ON_VMA(start < vma->vm_start, vma);
1428 VM_BUG_ON_VMA(end > vma->vm_end, vma);
1429 VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm);
1431 gup_flags = FOLL_TOUCH | FOLL_POPULATE | FOLL_MLOCK;
1432 if (vma->vm_flags & VM_LOCKONFAULT)
1433 gup_flags &= ~FOLL_POPULATE;
1435 * We want to touch writable mappings with a write fault in order
1436 * to break COW, except for shared mappings because these don't COW
1437 * and we would not want to dirty them for nothing.
1439 if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
1440 gup_flags |= FOLL_WRITE;
1443 * We want mlock to succeed for regions that have any permissions
1444 * other than PROT_NONE.
1446 if (vma_is_accessible(vma))
1447 gup_flags |= FOLL_FORCE;
1450 * We made sure addr is within a VMA, so the following will
1451 * not result in a stack expansion that recurses back here.
1453 return __get_user_pages(current, mm, start, nr_pages, gup_flags,
1454 NULL, NULL, locked);
1458 * __mm_populate - populate and/or mlock pages within a range of address space.
1460 * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
1461 * flags. VMAs must be already marked with the desired vm_flags, and
1462 * mmap_sem must not be held.
1464 int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
1466 struct mm_struct *mm = current->mm;
1467 unsigned long end, nstart, nend;
1468 struct vm_area_struct *vma = NULL;
1474 for (nstart = start; nstart < end; nstart = nend) {
1476 * We want to fault in pages for [nstart; end) address range.
1477 * Find first corresponding VMA.
1481 down_read(&mm->mmap_sem);
1482 vma = find_vma(mm, nstart);
1483 } else if (nstart >= vma->vm_end)
1485 if (!vma || vma->vm_start >= end)
1488 * Set [nstart; nend) to intersection of desired address
1489 * range with the first VMA. Also, skip undesirable VMA types.
1491 nend = min(end, vma->vm_end);
1492 if (vma->vm_flags & (VM_IO | VM_PFNMAP))
1494 if (nstart < vma->vm_start)
1495 nstart = vma->vm_start;
1497 * Now fault in a range of pages. populate_vma_page_range()
1498 * double checks the vma flags, so that it won't mlock pages
1499 * if the vma was already munlocked.
1501 ret = populate_vma_page_range(vma, nstart, nend, &locked);
1503 if (ignore_errors) {
1505 continue; /* continue at next VMA */
1509 nend = nstart + ret * PAGE_SIZE;
1513 up_read(&mm->mmap_sem);
1514 return ret; /* 0 or negative error code */
1518 * get_dump_page() - pin user page in memory while writing it to core dump
1519 * @addr: user address
1521 * Returns struct page pointer of user page pinned for dump,
1522 * to be freed afterwards by put_page().
1524 * Returns NULL on any kind of failure - a hole must then be inserted into
1525 * the corefile, to preserve alignment with its headers; and also returns
1526 * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
1527 * allowing a hole to be left in the corefile to save diskspace.
1529 * Called without mmap_sem, but after all other threads have been killed.
1531 #ifdef CONFIG_ELF_CORE
1532 struct page *get_dump_page(unsigned long addr)
1534 struct vm_area_struct *vma;
1537 if (__get_user_pages(current, current->mm, addr, 1,
1538 FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma,
1541 flush_cache_page(vma, addr, page_to_pfn(page));
1544 #endif /* CONFIG_ELF_CORE */
1545 #else /* CONFIG_MMU */
1546 static long __get_user_pages_locked(struct task_struct *tsk,
1547 struct mm_struct *mm, unsigned long start,
1548 unsigned long nr_pages, struct page **pages,
1549 struct vm_area_struct **vmas, int *locked,
1550 unsigned int foll_flags)
1552 struct vm_area_struct *vma;
1553 unsigned long vm_flags;
1556 /* calculate required read or write permissions.
1557 * If FOLL_FORCE is set, we only require the "MAY" flags.
1559 vm_flags = (foll_flags & FOLL_WRITE) ?
1560 (VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
1561 vm_flags &= (foll_flags & FOLL_FORCE) ?
1562 (VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
1564 for (i = 0; i < nr_pages; i++) {
1565 vma = find_vma(mm, start);
1567 goto finish_or_fault;
1569 /* protect what we can, including chardevs */
1570 if ((vma->vm_flags & (VM_IO | VM_PFNMAP)) ||
1571 !(vm_flags & vma->vm_flags))
1572 goto finish_or_fault;
1575 pages[i] = virt_to_page(start);
1581 start = (start + PAGE_SIZE) & PAGE_MASK;
1587 return i ? : -EFAULT;
1589 #endif /* !CONFIG_MMU */
1591 #if defined(CONFIG_FS_DAX) || defined (CONFIG_CMA)
1592 static bool check_dax_vmas(struct vm_area_struct **vmas, long nr_pages)
1595 struct vm_area_struct *vma_prev = NULL;
1597 for (i = 0; i < nr_pages; i++) {
1598 struct vm_area_struct *vma = vmas[i];
1600 if (vma == vma_prev)
1605 if (vma_is_fsdax(vma))
1612 static struct page *new_non_cma_page(struct page *page, unsigned long private)
1615 * We want to make sure we allocate the new page from the same node
1616 * as the source page.
1618 int nid = page_to_nid(page);
1620 * Trying to allocate a page for migration. Ignore allocation
1621 * failure warnings. We don't force __GFP_THISNODE here because
1622 * this node here is the node where we have CMA reservation and
1623 * in some case these nodes will have really less non movable
1624 * allocation memory.
1626 gfp_t gfp_mask = GFP_USER | __GFP_NOWARN;
1628 if (PageHighMem(page))
1629 gfp_mask |= __GFP_HIGHMEM;
1631 #ifdef CONFIG_HUGETLB_PAGE
1632 if (PageHuge(page)) {
1633 struct hstate *h = page_hstate(page);
1635 * We don't want to dequeue from the pool because pool pages will
1636 * mostly be from the CMA region.
1638 return alloc_migrate_huge_page(h, gfp_mask, nid, NULL);
1641 if (PageTransHuge(page)) {
1644 * ignore allocation failure warnings
1646 gfp_t thp_gfpmask = GFP_TRANSHUGE | __GFP_NOWARN;
1649 * Remove the movable mask so that we don't allocate from
1652 thp_gfpmask &= ~__GFP_MOVABLE;
1653 thp = __alloc_pages_node(nid, thp_gfpmask, HPAGE_PMD_ORDER);
1656 prep_transhuge_page(thp);
1660 return __alloc_pages_node(nid, gfp_mask, 0);
1663 static long check_and_migrate_cma_pages(struct task_struct *tsk,
1664 struct mm_struct *mm,
1665 unsigned long start,
1666 unsigned long nr_pages,
1667 struct page **pages,
1668 struct vm_area_struct **vmas,
1669 unsigned int gup_flags)
1673 bool drain_allow = true;
1674 bool migrate_allow = true;
1675 LIST_HEAD(cma_page_list);
1676 long ret = nr_pages;
1679 for (i = 0; i < nr_pages;) {
1681 struct page *head = compound_head(pages[i]);
1684 * gup may start from a tail page. Advance step by the left
1687 step = compound_nr(head) - (pages[i] - head);
1689 * If we get a page from the CMA zone, since we are going to
1690 * be pinning these entries, we might as well move them out
1691 * of the CMA zone if possible.
1693 if (is_migrate_cma_page(head)) {
1695 isolate_huge_page(head, &cma_page_list);
1697 if (!PageLRU(head) && drain_allow) {
1698 lru_add_drain_all();
1699 drain_allow = false;
1702 if (!isolate_lru_page(head)) {
1703 list_add_tail(&head->lru, &cma_page_list);
1704 mod_node_page_state(page_pgdat(head),
1706 page_is_file_lru(head),
1707 hpage_nr_pages(head));
1715 if (!list_empty(&cma_page_list)) {
1717 * drop the above get_user_pages reference.
1719 for (i = 0; i < nr_pages; i++)
1722 if (migrate_pages(&cma_page_list, new_non_cma_page,
1723 NULL, 0, MIGRATE_SYNC, MR_CONTIG_RANGE)) {
1725 * some of the pages failed migration. Do get_user_pages
1726 * without migration.
1728 migrate_allow = false;
1730 if (!list_empty(&cma_page_list))
1731 putback_movable_pages(&cma_page_list);
1734 * We did migrate all the pages, Try to get the page references
1735 * again migrating any new CMA pages which we failed to isolate
1738 ret = __get_user_pages_locked(tsk, mm, start, nr_pages,
1742 if ((ret > 0) && migrate_allow) {
1752 static long check_and_migrate_cma_pages(struct task_struct *tsk,
1753 struct mm_struct *mm,
1754 unsigned long start,
1755 unsigned long nr_pages,
1756 struct page **pages,
1757 struct vm_area_struct **vmas,
1758 unsigned int gup_flags)
1762 #endif /* CONFIG_CMA */
1765 * __gup_longterm_locked() is a wrapper for __get_user_pages_locked which
1766 * allows us to process the FOLL_LONGTERM flag.
1768 static long __gup_longterm_locked(struct task_struct *tsk,
1769 struct mm_struct *mm,
1770 unsigned long start,
1771 unsigned long nr_pages,
1772 struct page **pages,
1773 struct vm_area_struct **vmas,
1774 unsigned int gup_flags)
1776 struct vm_area_struct **vmas_tmp = vmas;
1777 unsigned long flags = 0;
1780 if (gup_flags & FOLL_LONGTERM) {
1785 vmas_tmp = kcalloc(nr_pages,
1786 sizeof(struct vm_area_struct *),
1791 flags = memalloc_nocma_save();
1794 rc = __get_user_pages_locked(tsk, mm, start, nr_pages, pages,
1795 vmas_tmp, NULL, gup_flags);
1797 if (gup_flags & FOLL_LONGTERM) {
1798 memalloc_nocma_restore(flags);
1802 if (check_dax_vmas(vmas_tmp, rc)) {
1803 for (i = 0; i < rc; i++)
1809 rc = check_and_migrate_cma_pages(tsk, mm, start, rc, pages,
1810 vmas_tmp, gup_flags);
1814 if (vmas_tmp != vmas)
1818 #else /* !CONFIG_FS_DAX && !CONFIG_CMA */
1819 static __always_inline long __gup_longterm_locked(struct task_struct *tsk,
1820 struct mm_struct *mm,
1821 unsigned long start,
1822 unsigned long nr_pages,
1823 struct page **pages,
1824 struct vm_area_struct **vmas,
1827 return __get_user_pages_locked(tsk, mm, start, nr_pages, pages, vmas,
1830 #endif /* CONFIG_FS_DAX || CONFIG_CMA */
1833 static long __get_user_pages_remote(struct task_struct *tsk,
1834 struct mm_struct *mm,
1835 unsigned long start, unsigned long nr_pages,
1836 unsigned int gup_flags, struct page **pages,
1837 struct vm_area_struct **vmas, int *locked)
1840 * Parts of FOLL_LONGTERM behavior are incompatible with
1841 * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
1842 * vmas. However, this only comes up if locked is set, and there are
1843 * callers that do request FOLL_LONGTERM, but do not set locked. So,
1844 * allow what we can.
1846 if (gup_flags & FOLL_LONGTERM) {
1847 if (WARN_ON_ONCE(locked))
1850 * This will check the vmas (even if our vmas arg is NULL)
1851 * and return -ENOTSUPP if DAX isn't allowed in this case:
1853 return __gup_longterm_locked(tsk, mm, start, nr_pages, pages,
1854 vmas, gup_flags | FOLL_TOUCH |
1858 return __get_user_pages_locked(tsk, mm, start, nr_pages, pages, vmas,
1860 gup_flags | FOLL_TOUCH | FOLL_REMOTE);
1864 * get_user_pages_remote() - pin user pages in memory
1865 * @tsk: the task_struct to use for page fault accounting, or
1866 * NULL if faults are not to be recorded.
1867 * @mm: mm_struct of target mm
1868 * @start: starting user address
1869 * @nr_pages: number of pages from start to pin
1870 * @gup_flags: flags modifying lookup behaviour
1871 * @pages: array that receives pointers to the pages pinned.
1872 * Should be at least nr_pages long. Or NULL, if caller
1873 * only intends to ensure the pages are faulted in.
1874 * @vmas: array of pointers to vmas corresponding to each page.
1875 * Or NULL if the caller does not require them.
1876 * @locked: pointer to lock flag indicating whether lock is held and
1877 * subsequently whether VM_FAULT_RETRY functionality can be
1878 * utilised. Lock must initially be held.
1880 * Returns either number of pages pinned (which may be less than the
1881 * number requested), or an error. Details about the return value:
1883 * -- If nr_pages is 0, returns 0.
1884 * -- If nr_pages is >0, but no pages were pinned, returns -errno.
1885 * -- If nr_pages is >0, and some pages were pinned, returns the number of
1886 * pages pinned. Again, this may be less than nr_pages.
1888 * The caller is responsible for releasing returned @pages, via put_page().
1890 * @vmas are valid only as long as mmap_sem is held.
1892 * Must be called with mmap_sem held for read or write.
1894 * get_user_pages_remote walks a process's page tables and takes a reference
1895 * to each struct page that each user address corresponds to at a given
1896 * instant. That is, it takes the page that would be accessed if a user
1897 * thread accesses the given user virtual address at that instant.
1899 * This does not guarantee that the page exists in the user mappings when
1900 * get_user_pages_remote returns, and there may even be a completely different
1901 * page there in some cases (eg. if mmapped pagecache has been invalidated
1902 * and subsequently re faulted). However it does guarantee that the page
1903 * won't be freed completely. And mostly callers simply care that the page
1904 * contains data that was valid *at some point in time*. Typically, an IO
1905 * or similar operation cannot guarantee anything stronger anyway because
1906 * locks can't be held over the syscall boundary.
1908 * If gup_flags & FOLL_WRITE == 0, the page must not be written to. If the page
1909 * is written to, set_page_dirty (or set_page_dirty_lock, as appropriate) must
1910 * be called after the page is finished with, and before put_page is called.
1912 * get_user_pages_remote is typically used for fewer-copy IO operations,
1913 * to get a handle on the memory by some means other than accesses
1914 * via the user virtual addresses. The pages may be submitted for
1915 * DMA to devices or accessed via their kernel linear mapping (via the
1916 * kmap APIs). Care should be taken to use the correct cache flushing APIs.
1918 * See also get_user_pages_fast, for performance critical applications.
1920 * get_user_pages_remote should be phased out in favor of
1921 * get_user_pages_locked|unlocked or get_user_pages_fast. Nothing
1922 * should use get_user_pages_remote because it cannot pass
1923 * FAULT_FLAG_ALLOW_RETRY to handle_mm_fault.
1925 long get_user_pages_remote(struct task_struct *tsk, 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)
1931 * FOLL_PIN must only be set internally by the pin_user_pages*() APIs,
1932 * never directly by the caller, so enforce that with an assertion:
1934 if (WARN_ON_ONCE(gup_flags & FOLL_PIN))
1937 return __get_user_pages_remote(tsk, mm, start, nr_pages, gup_flags,
1938 pages, vmas, locked);
1940 EXPORT_SYMBOL(get_user_pages_remote);
1942 #else /* CONFIG_MMU */
1943 long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
1944 unsigned long start, unsigned long nr_pages,
1945 unsigned int gup_flags, struct page **pages,
1946 struct vm_area_struct **vmas, int *locked)
1951 static long __get_user_pages_remote(struct task_struct *tsk,
1952 struct mm_struct *mm,
1953 unsigned long start, unsigned long nr_pages,
1954 unsigned int gup_flags, struct page **pages,
1955 struct vm_area_struct **vmas, int *locked)
1959 #endif /* !CONFIG_MMU */
1962 * get_user_pages() - pin user pages in memory
1963 * @start: starting user address
1964 * @nr_pages: number of pages from start to pin
1965 * @gup_flags: flags modifying lookup behaviour
1966 * @pages: array that receives pointers to the pages pinned.
1967 * Should be at least nr_pages long. Or NULL, if caller
1968 * only intends to ensure the pages are faulted in.
1969 * @vmas: array of pointers to vmas corresponding to each page.
1970 * Or NULL if the caller does not require them.
1972 * This is the same as get_user_pages_remote(), just with a
1973 * less-flexible calling convention where we assume that the task
1974 * and mm being operated on are the current task's and don't allow
1975 * passing of a locked parameter. We also obviously don't pass
1976 * FOLL_REMOTE in here.
1978 long get_user_pages(unsigned long start, unsigned long nr_pages,
1979 unsigned int gup_flags, struct page **pages,
1980 struct vm_area_struct **vmas)
1983 * FOLL_PIN must only be set internally by the pin_user_pages*() APIs,
1984 * never directly by the caller, so enforce that with an assertion:
1986 if (WARN_ON_ONCE(gup_flags & FOLL_PIN))
1989 return __gup_longterm_locked(current, current->mm, start, nr_pages,
1990 pages, vmas, gup_flags | FOLL_TOUCH);
1992 EXPORT_SYMBOL(get_user_pages);
1995 * get_user_pages_locked() is suitable to replace the form:
1997 * down_read(&mm->mmap_sem);
1999 * get_user_pages(tsk, mm, ..., pages, NULL);
2000 * up_read(&mm->mmap_sem);
2005 * down_read(&mm->mmap_sem);
2007 * get_user_pages_locked(tsk, mm, ..., pages, &locked);
2009 * up_read(&mm->mmap_sem);
2011 * @start: starting user address
2012 * @nr_pages: number of pages from start to pin
2013 * @gup_flags: flags modifying lookup behaviour
2014 * @pages: array that receives pointers to the pages pinned.
2015 * Should be at least nr_pages long. Or NULL, if caller
2016 * only intends to ensure the pages are faulted in.
2017 * @locked: pointer to lock flag indicating whether lock is held and
2018 * subsequently whether VM_FAULT_RETRY functionality can be
2019 * utilised. Lock must initially be held.
2021 * We can leverage the VM_FAULT_RETRY functionality in the page fault
2022 * paths better by using either get_user_pages_locked() or
2023 * get_user_pages_unlocked().
2026 long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
2027 unsigned int gup_flags, struct page **pages,
2031 * FIXME: Current FOLL_LONGTERM behavior is incompatible with
2032 * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
2033 * vmas. As there are no users of this flag in this call we simply
2034 * disallow this option for now.
2036 if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
2039 * FOLL_PIN must only be set internally by the pin_user_pages*() APIs,
2040 * never directly by the caller, so enforce that:
2042 if (WARN_ON_ONCE(gup_flags & FOLL_PIN))
2045 return __get_user_pages_locked(current, current->mm, start, nr_pages,
2046 pages, NULL, locked,
2047 gup_flags | FOLL_TOUCH);
2049 EXPORT_SYMBOL(get_user_pages_locked);
2052 * get_user_pages_unlocked() is suitable to replace the form:
2054 * down_read(&mm->mmap_sem);
2055 * get_user_pages(tsk, mm, ..., pages, NULL);
2056 * up_read(&mm->mmap_sem);
2060 * get_user_pages_unlocked(tsk, mm, ..., pages);
2062 * It is functionally equivalent to get_user_pages_fast so
2063 * get_user_pages_fast should be used instead if specific gup_flags
2064 * (e.g. FOLL_FORCE) are not required.
2066 long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
2067 struct page **pages, unsigned int gup_flags)
2069 struct mm_struct *mm = current->mm;
2074 * FIXME: Current FOLL_LONGTERM behavior is incompatible with
2075 * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
2076 * vmas. As there are no users of this flag in this call we simply
2077 * disallow this option for now.
2079 if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
2082 down_read(&mm->mmap_sem);
2083 ret = __get_user_pages_locked(current, mm, start, nr_pages, pages, NULL,
2084 &locked, gup_flags | FOLL_TOUCH);
2086 up_read(&mm->mmap_sem);
2089 EXPORT_SYMBOL(get_user_pages_unlocked);
2094 * get_user_pages_fast attempts to pin user pages by walking the page
2095 * tables directly and avoids taking locks. Thus the walker needs to be
2096 * protected from page table pages being freed from under it, and should
2097 * block any THP splits.
2099 * One way to achieve this is to have the walker disable interrupts, and
2100 * rely on IPIs from the TLB flushing code blocking before the page table
2101 * pages are freed. This is unsuitable for architectures that do not need
2102 * to broadcast an IPI when invalidating TLBs.
2104 * Another way to achieve this is to batch up page table containing pages
2105 * belonging to more than one mm_user, then rcu_sched a callback to free those
2106 * pages. Disabling interrupts will allow the fast_gup walker to both block
2107 * the rcu_sched callback, and an IPI that we broadcast for splitting THPs
2108 * (which is a relatively rare event). The code below adopts this strategy.
2110 * Before activating this code, please be aware that the following assumptions
2111 * are currently made:
2113 * *) Either MMU_GATHER_RCU_TABLE_FREE is enabled, and tlb_remove_table() is used to
2114 * free pages containing page tables or TLB flushing requires IPI broadcast.
2116 * *) ptes can be read atomically by the architecture.
2118 * *) access_ok is sufficient to validate userspace address ranges.
2120 * The last two assumptions can be relaxed by the addition of helper functions.
2122 * This code is based heavily on the PowerPC implementation by Nick Piggin.
2124 #ifdef CONFIG_HAVE_FAST_GUP
2126 static void put_compound_head(struct page *page, int refs, unsigned int flags)
2128 if (flags & FOLL_PIN) {
2129 mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_RELEASED,
2132 if (hpage_pincount_available(page))
2133 hpage_pincount_sub(page, refs);
2135 refs *= GUP_PIN_COUNTING_BIAS;
2138 VM_BUG_ON_PAGE(page_ref_count(page) < refs, page);
2140 * Calling put_page() for each ref is unnecessarily slow. Only the last
2141 * ref needs a put_page().
2144 page_ref_sub(page, refs - 1);
2148 #ifdef CONFIG_GUP_GET_PTE_LOW_HIGH
2151 * WARNING: only to be used in the get_user_pages_fast() implementation.
2153 * With get_user_pages_fast(), we walk down the pagetables without taking any
2154 * locks. For this we would like to load the pointers atomically, but sometimes
2155 * that is not possible (e.g. without expensive cmpxchg8b on x86_32 PAE). What
2156 * we do have is the guarantee that a PTE will only either go from not present
2157 * to present, or present to not present or both -- it will not switch to a
2158 * completely different present page without a TLB flush in between; something
2159 * that we are blocking by holding interrupts off.
2161 * Setting ptes from not present to present goes:
2163 * ptep->pte_high = h;
2165 * ptep->pte_low = l;
2167 * And present to not present goes:
2169 * ptep->pte_low = 0;
2171 * ptep->pte_high = 0;
2173 * We must ensure here that the load of pte_low sees 'l' IFF pte_high sees 'h'.
2174 * We load pte_high *after* loading pte_low, which ensures we don't see an older
2175 * value of pte_high. *Then* we recheck pte_low, which ensures that we haven't
2176 * picked up a changed pte high. We might have gotten rubbish values from
2177 * pte_low and pte_high, but we are guaranteed that pte_low will not have the
2178 * present bit set *unless* it is 'l'. Because get_user_pages_fast() only
2179 * operates on present ptes we're safe.
2181 static inline pte_t gup_get_pte(pte_t *ptep)
2186 pte.pte_low = ptep->pte_low;
2188 pte.pte_high = ptep->pte_high;
2190 } while (unlikely(pte.pte_low != ptep->pte_low));
2194 #else /* CONFIG_GUP_GET_PTE_LOW_HIGH */
2196 * We require that the PTE can be read atomically.
2198 static inline pte_t gup_get_pte(pte_t *ptep)
2200 return READ_ONCE(*ptep);
2202 #endif /* CONFIG_GUP_GET_PTE_LOW_HIGH */
2204 static void __maybe_unused undo_dev_pagemap(int *nr, int nr_start,
2206 struct page **pages)
2208 while ((*nr) - nr_start) {
2209 struct page *page = pages[--(*nr)];
2211 ClearPageReferenced(page);
2212 if (flags & FOLL_PIN)
2213 unpin_user_page(page);
2219 #ifdef CONFIG_ARCH_HAS_PTE_SPECIAL
2220 static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
2221 unsigned int flags, struct page **pages, int *nr)
2223 struct dev_pagemap *pgmap = NULL;
2224 int nr_start = *nr, ret = 0;
2227 ptem = ptep = pte_offset_map(&pmd, addr);
2229 pte_t pte = gup_get_pte(ptep);
2230 struct page *head, *page;
2233 * Similar to the PMD case below, NUMA hinting must take slow
2234 * path using the pte_protnone check.
2236 if (pte_protnone(pte))
2239 if (!pte_access_permitted(pte, flags & FOLL_WRITE))
2242 if (pte_devmap(pte)) {
2243 if (unlikely(flags & FOLL_LONGTERM))
2246 pgmap = get_dev_pagemap(pte_pfn(pte), pgmap);
2247 if (unlikely(!pgmap)) {
2248 undo_dev_pagemap(nr, nr_start, flags, pages);
2251 } else if (pte_special(pte))
2254 VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
2255 page = pte_page(pte);
2257 head = try_grab_compound_head(page, 1, flags);
2261 if (unlikely(pte_val(pte) != pte_val(*ptep))) {
2262 put_compound_head(head, 1, flags);
2266 VM_BUG_ON_PAGE(compound_head(page) != head, page);
2269 * We need to make the page accessible if and only if we are
2270 * going to access its content (the FOLL_PIN case). Please
2271 * see Documentation/core-api/pin_user_pages.rst for
2274 if (flags & FOLL_PIN) {
2275 ret = arch_make_page_accessible(page);
2277 unpin_user_page(page);
2281 SetPageReferenced(page);
2285 } while (ptep++, addr += PAGE_SIZE, addr != end);
2291 put_dev_pagemap(pgmap);
2298 * If we can't determine whether or not a pte is special, then fail immediately
2299 * for ptes. Note, we can still pin HugeTLB and THP as these are guaranteed not
2302 * For a futex to be placed on a THP tail page, get_futex_key requires a
2303 * get_user_pages_fast_only implementation that can pin pages. Thus it's still
2304 * useful to have gup_huge_pmd even if we can't operate on ptes.
2306 static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
2307 unsigned int flags, struct page **pages, int *nr)
2311 #endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */
2313 #if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
2314 static int __gup_device_huge(unsigned long pfn, unsigned long addr,
2315 unsigned long end, unsigned int flags,
2316 struct page **pages, int *nr)
2319 struct dev_pagemap *pgmap = NULL;
2322 struct page *page = pfn_to_page(pfn);
2324 pgmap = get_dev_pagemap(pfn, pgmap);
2325 if (unlikely(!pgmap)) {
2326 undo_dev_pagemap(nr, nr_start, flags, pages);
2329 SetPageReferenced(page);
2331 if (unlikely(!try_grab_page(page, flags))) {
2332 undo_dev_pagemap(nr, nr_start, flags, pages);
2337 } while (addr += PAGE_SIZE, addr != end);
2340 put_dev_pagemap(pgmap);
2344 static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
2345 unsigned long end, unsigned int flags,
2346 struct page **pages, int *nr)
2348 unsigned long fault_pfn;
2351 fault_pfn = pmd_pfn(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
2352 if (!__gup_device_huge(fault_pfn, addr, end, flags, pages, nr))
2355 if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
2356 undo_dev_pagemap(nr, nr_start, flags, pages);
2362 static int __gup_device_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
2363 unsigned long end, unsigned int flags,
2364 struct page **pages, int *nr)
2366 unsigned long fault_pfn;
2369 fault_pfn = pud_pfn(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
2370 if (!__gup_device_huge(fault_pfn, addr, end, flags, pages, nr))
2373 if (unlikely(pud_val(orig) != pud_val(*pudp))) {
2374 undo_dev_pagemap(nr, nr_start, flags, pages);
2380 static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
2381 unsigned long end, unsigned int flags,
2382 struct page **pages, int *nr)
2388 static int __gup_device_huge_pud(pud_t pud, pud_t *pudp, unsigned long addr,
2389 unsigned long end, unsigned int flags,
2390 struct page **pages, int *nr)
2397 static int record_subpages(struct page *page, unsigned long addr,
2398 unsigned long end, struct page **pages)
2402 for (nr = 0; addr != end; addr += PAGE_SIZE)
2403 pages[nr++] = page++;
2408 #ifdef CONFIG_ARCH_HAS_HUGEPD
2409 static unsigned long hugepte_addr_end(unsigned long addr, unsigned long end,
2412 unsigned long __boundary = (addr + sz) & ~(sz-1);
2413 return (__boundary - 1 < end - 1) ? __boundary : end;
2416 static int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr,
2417 unsigned long end, unsigned int flags,
2418 struct page **pages, int *nr)
2420 unsigned long pte_end;
2421 struct page *head, *page;
2425 pte_end = (addr + sz) & ~(sz-1);
2429 pte = READ_ONCE(*ptep);
2431 if (!pte_access_permitted(pte, flags & FOLL_WRITE))
2434 /* hugepages are never "special" */
2435 VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
2437 head = pte_page(pte);
2438 page = head + ((addr & (sz-1)) >> PAGE_SHIFT);
2439 refs = record_subpages(page, addr, end, pages + *nr);
2441 head = try_grab_compound_head(head, refs, flags);
2445 if (unlikely(pte_val(pte) != pte_val(*ptep))) {
2446 put_compound_head(head, refs, flags);
2451 SetPageReferenced(head);
2455 static int gup_huge_pd(hugepd_t hugepd, unsigned long addr,
2456 unsigned int pdshift, unsigned long end, unsigned int flags,
2457 struct page **pages, int *nr)
2460 unsigned long sz = 1UL << hugepd_shift(hugepd);
2463 ptep = hugepte_offset(hugepd, addr, pdshift);
2465 next = hugepte_addr_end(addr, end, sz);
2466 if (!gup_hugepte(ptep, sz, addr, end, flags, pages, nr))
2468 } while (ptep++, addr = next, addr != end);
2473 static inline int gup_huge_pd(hugepd_t hugepd, unsigned long addr,
2474 unsigned int pdshift, unsigned long end, unsigned int flags,
2475 struct page **pages, int *nr)
2479 #endif /* CONFIG_ARCH_HAS_HUGEPD */
2481 static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
2482 unsigned long end, unsigned int flags,
2483 struct page **pages, int *nr)
2485 struct page *head, *page;
2488 if (!pmd_access_permitted(orig, flags & FOLL_WRITE))
2491 if (pmd_devmap(orig)) {
2492 if (unlikely(flags & FOLL_LONGTERM))
2494 return __gup_device_huge_pmd(orig, pmdp, addr, end, flags,
2498 page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
2499 refs = record_subpages(page, addr, end, pages + *nr);
2501 head = try_grab_compound_head(pmd_page(orig), refs, flags);
2505 if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
2506 put_compound_head(head, refs, flags);
2511 SetPageReferenced(head);
2515 static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
2516 unsigned long end, unsigned int flags,
2517 struct page **pages, int *nr)
2519 struct page *head, *page;
2522 if (!pud_access_permitted(orig, flags & FOLL_WRITE))
2525 if (pud_devmap(orig)) {
2526 if (unlikely(flags & FOLL_LONGTERM))
2528 return __gup_device_huge_pud(orig, pudp, addr, end, flags,
2532 page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
2533 refs = record_subpages(page, addr, end, pages + *nr);
2535 head = try_grab_compound_head(pud_page(orig), refs, flags);
2539 if (unlikely(pud_val(orig) != pud_val(*pudp))) {
2540 put_compound_head(head, refs, flags);
2545 SetPageReferenced(head);
2549 static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
2550 unsigned long end, unsigned int flags,
2551 struct page **pages, int *nr)
2554 struct page *head, *page;
2556 if (!pgd_access_permitted(orig, flags & FOLL_WRITE))
2559 BUILD_BUG_ON(pgd_devmap(orig));
2561 page = pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT);
2562 refs = record_subpages(page, addr, end, pages + *nr);
2564 head = try_grab_compound_head(pgd_page(orig), refs, flags);
2568 if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) {
2569 put_compound_head(head, refs, flags);
2574 SetPageReferenced(head);
2578 static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
2579 unsigned int flags, struct page **pages, int *nr)
2584 pmdp = pmd_offset(&pud, addr);
2586 pmd_t pmd = READ_ONCE(*pmdp);
2588 next = pmd_addr_end(addr, end);
2589 if (!pmd_present(pmd))
2592 if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd) ||
2595 * NUMA hinting faults need to be handled in the GUP
2596 * slowpath for accounting purposes and so that they
2597 * can be serialised against THP migration.
2599 if (pmd_protnone(pmd))
2602 if (!gup_huge_pmd(pmd, pmdp, addr, next, flags,
2606 } else if (unlikely(is_hugepd(__hugepd(pmd_val(pmd))))) {
2608 * architecture have different format for hugetlbfs
2609 * pmd format and THP pmd format
2611 if (!gup_huge_pd(__hugepd(pmd_val(pmd)), addr,
2612 PMD_SHIFT, next, flags, pages, nr))
2614 } else if (!gup_pte_range(pmd, addr, next, flags, pages, nr))
2616 } while (pmdp++, addr = next, addr != end);
2621 static int gup_pud_range(p4d_t p4d, unsigned long addr, unsigned long end,
2622 unsigned int flags, struct page **pages, int *nr)
2627 pudp = pud_offset(&p4d, addr);
2629 pud_t pud = READ_ONCE(*pudp);
2631 next = pud_addr_end(addr, end);
2632 if (unlikely(!pud_present(pud)))
2634 if (unlikely(pud_huge(pud))) {
2635 if (!gup_huge_pud(pud, pudp, addr, next, flags,
2638 } else if (unlikely(is_hugepd(__hugepd(pud_val(pud))))) {
2639 if (!gup_huge_pd(__hugepd(pud_val(pud)), addr,
2640 PUD_SHIFT, next, flags, pages, nr))
2642 } else if (!gup_pmd_range(pud, addr, next, flags, pages, nr))
2644 } while (pudp++, addr = next, addr != end);
2649 static int gup_p4d_range(pgd_t pgd, unsigned long addr, unsigned long end,
2650 unsigned int flags, struct page **pages, int *nr)
2655 p4dp = p4d_offset(&pgd, addr);
2657 p4d_t p4d = READ_ONCE(*p4dp);
2659 next = p4d_addr_end(addr, end);
2662 BUILD_BUG_ON(p4d_huge(p4d));
2663 if (unlikely(is_hugepd(__hugepd(p4d_val(p4d))))) {
2664 if (!gup_huge_pd(__hugepd(p4d_val(p4d)), addr,
2665 P4D_SHIFT, next, flags, pages, nr))
2667 } else if (!gup_pud_range(p4d, addr, next, flags, pages, nr))
2669 } while (p4dp++, addr = next, addr != end);
2674 static void gup_pgd_range(unsigned long addr, unsigned long end,
2675 unsigned int flags, struct page **pages, int *nr)
2680 pgdp = pgd_offset(current->mm, addr);
2682 pgd_t pgd = READ_ONCE(*pgdp);
2684 next = pgd_addr_end(addr, end);
2687 if (unlikely(pgd_huge(pgd))) {
2688 if (!gup_huge_pgd(pgd, pgdp, addr, next, flags,
2691 } else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd))))) {
2692 if (!gup_huge_pd(__hugepd(pgd_val(pgd)), addr,
2693 PGDIR_SHIFT, next, flags, pages, nr))
2695 } else if (!gup_p4d_range(pgd, addr, next, flags, pages, nr))
2697 } while (pgdp++, addr = next, addr != end);
2700 static inline void gup_pgd_range(unsigned long addr, unsigned long end,
2701 unsigned int flags, struct page **pages, int *nr)
2704 #endif /* CONFIG_HAVE_FAST_GUP */
2706 #ifndef gup_fast_permitted
2708 * Check if it's allowed to use get_user_pages_fast_only() for the range, or
2709 * we need to fall back to the slow version:
2711 static bool gup_fast_permitted(unsigned long start, unsigned long end)
2717 static int __gup_longterm_unlocked(unsigned long start, int nr_pages,
2718 unsigned int gup_flags, struct page **pages)
2723 * FIXME: FOLL_LONGTERM does not work with
2724 * get_user_pages_unlocked() (see comments in that function)
2726 if (gup_flags & FOLL_LONGTERM) {
2727 down_read(¤t->mm->mmap_sem);
2728 ret = __gup_longterm_locked(current, current->mm,
2730 pages, NULL, gup_flags);
2731 up_read(¤t->mm->mmap_sem);
2733 ret = get_user_pages_unlocked(start, nr_pages,
2740 static int internal_get_user_pages_fast(unsigned long start, int nr_pages,
2741 unsigned int gup_flags,
2742 struct page **pages)
2744 unsigned long addr, len, end;
2745 unsigned long flags;
2746 int nr_pinned = 0, ret = 0;
2748 if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM |
2749 FOLL_FORCE | FOLL_PIN | FOLL_GET |
2753 if (!(gup_flags & FOLL_FAST_ONLY))
2754 might_lock_read(¤t->mm->mmap_sem);
2756 start = untagged_addr(start) & PAGE_MASK;
2758 len = (unsigned long) nr_pages << PAGE_SHIFT;
2763 if (unlikely(!access_ok((void __user *)start, len)))
2767 * The FAST_GUP case requires FOLL_WRITE even for pure reads,
2768 * because get_user_pages() may need to cause an early COW in
2769 * order to avoid confusing the normal COW routines. So only
2770 * targets that are already writable are safe to do by just
2771 * looking at the page tables.
2773 * NOTE! With FOLL_FAST_ONLY we allow read-only gup_fast() here,
2774 * because there is no slow path to fall back on. But you'd
2775 * better be careful about possible COW pages - you'll get _a_
2776 * COW page, but not necessarily the one you intended to get
2777 * depending on what COW event happens after this. COW may break
2778 * the page copy in a random direction.
2780 * Disable interrupts. The nested form is used, in order to allow
2781 * full, general purpose use of this routine.
2783 * With interrupts disabled, we block page table pages from being
2784 * freed from under us. See struct mmu_table_batch comments in
2785 * include/asm-generic/tlb.h for more details.
2787 * We do not adopt an rcu_read_lock(.) here as we also want to
2788 * block IPIs that come from THPs splitting.
2790 if (IS_ENABLED(CONFIG_HAVE_FAST_GUP) && gup_fast_permitted(start, end)) {
2791 unsigned long fast_flags = gup_flags;
2792 if (!(gup_flags & FOLL_FAST_ONLY))
2793 fast_flags |= FOLL_WRITE;
2795 local_irq_save(flags);
2796 gup_pgd_range(addr, end, fast_flags, pages, &nr_pinned);
2797 local_irq_restore(flags);
2801 if (nr_pinned < nr_pages && !(gup_flags & FOLL_FAST_ONLY)) {
2802 /* Try to get the remaining pages with get_user_pages */
2803 start += nr_pinned << PAGE_SHIFT;
2806 ret = __gup_longterm_unlocked(start, nr_pages - nr_pinned,
2809 /* Have to be a bit careful with return values */
2810 if (nr_pinned > 0) {
2821 * get_user_pages_fast_only() - pin user pages in memory
2822 * @start: starting user address
2823 * @nr_pages: number of pages from start to pin
2824 * @gup_flags: flags modifying pin behaviour
2825 * @pages: array that receives pointers to the pages pinned.
2826 * Should be at least nr_pages long.
2828 * Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to
2830 * Note a difference with get_user_pages_fast: this always returns the
2831 * number of pages pinned, 0 if no pages were pinned.
2833 * If the architecture does not support this function, simply return with no
2836 * Careful, careful! COW breaking can go either way, so a non-write
2837 * access can get ambiguous page results. If you call this function without
2838 * 'write' set, you'd better be sure that you're ok with that ambiguity.
2840 int get_user_pages_fast_only(unsigned long start, int nr_pages,
2841 unsigned int gup_flags, struct page **pages)
2845 * Internally (within mm/gup.c), gup fast variants must set FOLL_GET,
2846 * because gup fast is always a "pin with a +1 page refcount" request.
2848 * FOLL_FAST_ONLY is required in order to match the API description of
2849 * this routine: no fall back to regular ("slow") GUP.
2851 gup_flags |= FOLL_GET | FOLL_FAST_ONLY;
2853 nr_pinned = internal_get_user_pages_fast(start, nr_pages, gup_flags,
2857 * As specified in the API description above, this routine is not
2858 * allowed to return negative values. However, the common core
2859 * routine internal_get_user_pages_fast() *can* return -errno.
2860 * Therefore, correct for that here:
2867 EXPORT_SYMBOL_GPL(get_user_pages_fast_only);
2870 * get_user_pages_fast() - pin user pages in memory
2871 * @start: starting user address
2872 * @nr_pages: number of pages from start to pin
2873 * @gup_flags: flags modifying pin behaviour
2874 * @pages: array that receives pointers to the pages pinned.
2875 * Should be at least nr_pages long.
2877 * Attempt to pin user pages in memory without taking mm->mmap_sem.
2878 * If not successful, it will fall back to taking the lock and
2879 * calling get_user_pages().
2881 * Returns number of pages pinned. This may be fewer than the number requested.
2882 * If nr_pages is 0 or negative, returns 0. If no pages were pinned, returns
2885 int get_user_pages_fast(unsigned long start, int nr_pages,
2886 unsigned int gup_flags, struct page **pages)
2889 * FOLL_PIN must only be set internally by the pin_user_pages*() APIs,
2890 * never directly by the caller, so enforce that:
2892 if (WARN_ON_ONCE(gup_flags & FOLL_PIN))
2896 * The caller may or may not have explicitly set FOLL_GET; either way is
2897 * OK. However, internally (within mm/gup.c), gup fast variants must set
2898 * FOLL_GET, because gup fast is always a "pin with a +1 page refcount"
2901 gup_flags |= FOLL_GET;
2902 return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages);
2904 EXPORT_SYMBOL_GPL(get_user_pages_fast);
2907 * pin_user_pages_fast() - pin user pages in memory without taking locks
2909 * @start: starting user address
2910 * @nr_pages: number of pages from start to pin
2911 * @gup_flags: flags modifying pin behaviour
2912 * @pages: array that receives pointers to the pages pinned.
2913 * Should be at least nr_pages long.
2915 * Nearly the same as get_user_pages_fast(), except that FOLL_PIN is set. See
2916 * get_user_pages_fast() for documentation on the function arguments, because
2917 * the arguments here are identical.
2919 * FOLL_PIN means that the pages must be released via unpin_user_page(). Please
2920 * see Documentation/core-api/pin_user_pages.rst for further details.
2922 int pin_user_pages_fast(unsigned long start, int nr_pages,
2923 unsigned int gup_flags, struct page **pages)
2925 /* FOLL_GET and FOLL_PIN are mutually exclusive. */
2926 if (WARN_ON_ONCE(gup_flags & FOLL_GET))
2929 gup_flags |= FOLL_PIN;
2930 return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages);
2932 EXPORT_SYMBOL_GPL(pin_user_pages_fast);
2935 * This is the FOLL_PIN equivalent of get_user_pages_fast_only(). Behavior
2936 * is the same, except that this one sets FOLL_PIN instead of FOLL_GET.
2938 * The API rules are the same, too: no negative values may be returned.
2940 int pin_user_pages_fast_only(unsigned long start, int nr_pages,
2941 unsigned int gup_flags, struct page **pages)
2946 * FOLL_GET and FOLL_PIN are mutually exclusive. Note that the API
2947 * rules require returning 0, rather than -errno:
2949 if (WARN_ON_ONCE(gup_flags & FOLL_GET))
2952 * FOLL_FAST_ONLY is required in order to match the API description of
2953 * this routine: no fall back to regular ("slow") GUP.
2955 gup_flags |= (FOLL_PIN | FOLL_FAST_ONLY);
2956 nr_pinned = internal_get_user_pages_fast(start, nr_pages, gup_flags,
2959 * This routine is not allowed to return negative values. However,
2960 * internal_get_user_pages_fast() *can* return -errno. Therefore,
2961 * correct for that here:
2968 EXPORT_SYMBOL_GPL(pin_user_pages_fast_only);
2971 * pin_user_pages_remote() - pin pages of a remote process (task != current)
2973 * @tsk: the task_struct to use for page fault accounting, or
2974 * NULL if faults are not to be recorded.
2975 * @mm: mm_struct of target mm
2976 * @start: starting user address
2977 * @nr_pages: number of pages from start to pin
2978 * @gup_flags: flags modifying lookup behaviour
2979 * @pages: array that receives pointers to the pages pinned.
2980 * Should be at least nr_pages long. Or NULL, if caller
2981 * only intends to ensure the pages are faulted in.
2982 * @vmas: array of pointers to vmas corresponding to each page.
2983 * Or NULL if the caller does not require them.
2984 * @locked: pointer to lock flag indicating whether lock is held and
2985 * subsequently whether VM_FAULT_RETRY functionality can be
2986 * utilised. Lock must initially be held.
2988 * Nearly the same as get_user_pages_remote(), except that FOLL_PIN is set. See
2989 * get_user_pages_remote() for documentation on the function arguments, because
2990 * the arguments here are identical.
2992 * FOLL_PIN means that the pages must be released via unpin_user_page(). Please
2993 * see Documentation/core-api/pin_user_pages.rst for details.
2995 long pin_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
2996 unsigned long start, unsigned long nr_pages,
2997 unsigned int gup_flags, struct page **pages,
2998 struct vm_area_struct **vmas, int *locked)
3000 /* FOLL_GET and FOLL_PIN are mutually exclusive. */
3001 if (WARN_ON_ONCE(gup_flags & FOLL_GET))
3004 gup_flags |= FOLL_PIN;
3005 return __get_user_pages_remote(tsk, mm, start, nr_pages, gup_flags,
3006 pages, vmas, locked);
3008 EXPORT_SYMBOL(pin_user_pages_remote);
3011 * pin_user_pages() - pin user pages in memory for use by other devices
3013 * @start: starting user address
3014 * @nr_pages: number of pages from start to pin
3015 * @gup_flags: flags modifying lookup behaviour
3016 * @pages: array that receives pointers to the pages pinned.
3017 * Should be at least nr_pages long. Or NULL, if caller
3018 * only intends to ensure the pages are faulted in.
3019 * @vmas: array of pointers to vmas corresponding to each page.
3020 * Or NULL if the caller does not require them.
3022 * Nearly the same as get_user_pages(), except that FOLL_TOUCH is not set, and
3025 * FOLL_PIN means that the pages must be released via unpin_user_page(). Please
3026 * see Documentation/core-api/pin_user_pages.rst for details.
3028 long pin_user_pages(unsigned long start, unsigned long nr_pages,
3029 unsigned int gup_flags, struct page **pages,
3030 struct vm_area_struct **vmas)
3032 /* FOLL_GET and FOLL_PIN are mutually exclusive. */
3033 if (WARN_ON_ONCE(gup_flags & FOLL_GET))
3036 gup_flags |= FOLL_PIN;
3037 return __gup_longterm_locked(current, current->mm, start, nr_pages,
3038 pages, vmas, gup_flags);
3040 EXPORT_SYMBOL(pin_user_pages);
3043 * pin_user_pages_unlocked() is the FOLL_PIN variant of
3044 * get_user_pages_unlocked(). Behavior is the same, except that this one sets
3045 * FOLL_PIN and rejects FOLL_GET.
3047 long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
3048 struct page **pages, unsigned int gup_flags)
3050 /* FOLL_GET and FOLL_PIN are mutually exclusive. */
3051 if (WARN_ON_ONCE(gup_flags & FOLL_GET))
3054 gup_flags |= FOLL_PIN;
3055 return get_user_pages_unlocked(start, nr_pages, pages, gup_flags);
3057 EXPORT_SYMBOL(pin_user_pages_unlocked);
3060 * pin_user_pages_locked() is the FOLL_PIN variant of get_user_pages_locked().
3061 * Behavior is the same, except that this one sets FOLL_PIN and rejects
3064 long pin_user_pages_locked(unsigned long start, unsigned long nr_pages,
3065 unsigned int gup_flags, struct page **pages,
3069 * FIXME: Current FOLL_LONGTERM behavior is incompatible with
3070 * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
3071 * vmas. As there are no users of this flag in this call we simply
3072 * disallow this option for now.
3074 if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
3077 /* FOLL_GET and FOLL_PIN are mutually exclusive. */
3078 if (WARN_ON_ONCE(gup_flags & FOLL_GET))
3081 gup_flags |= FOLL_PIN;
3082 return __get_user_pages_locked(current, current->mm, start, nr_pages,
3083 pages, NULL, locked,
3084 gup_flags | FOLL_TOUCH);
3086 EXPORT_SYMBOL(pin_user_pages_locked);