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 can write to even unwritable pte's, but only
386 * 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) ||
391 ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pte_dirty(pte));
394 static struct page *follow_page_pte(struct vm_area_struct *vma,
395 unsigned long address, pmd_t *pmd, unsigned int flags,
396 struct dev_pagemap **pgmap)
398 struct mm_struct *mm = vma->vm_mm;
404 /* FOLL_GET and FOLL_PIN are mutually exclusive. */
405 if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) ==
406 (FOLL_PIN | FOLL_GET)))
407 return ERR_PTR(-EINVAL);
409 if (unlikely(pmd_bad(*pmd)))
410 return no_page_table(vma, flags);
412 ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
414 if (!pte_present(pte)) {
417 * KSM's break_ksm() relies upon recognizing a ksm page
418 * even while it is being migrated, so for that case we
419 * need migration_entry_wait().
421 if (likely(!(flags & FOLL_MIGRATION)))
425 entry = pte_to_swp_entry(pte);
426 if (!is_migration_entry(entry))
428 pte_unmap_unlock(ptep, ptl);
429 migration_entry_wait(mm, pmd, address);
432 if ((flags & FOLL_NUMA) && pte_protnone(pte))
434 if ((flags & FOLL_WRITE) && !can_follow_write_pte(pte, flags)) {
435 pte_unmap_unlock(ptep, ptl);
439 page = vm_normal_page(vma, address, pte);
440 if (!page && pte_devmap(pte) && (flags & (FOLL_GET | FOLL_PIN))) {
442 * Only return device mapping pages in the FOLL_GET or FOLL_PIN
443 * case since they are only valid while holding the pgmap
446 *pgmap = get_dev_pagemap(pte_pfn(pte), *pgmap);
448 page = pte_page(pte);
451 } else if (unlikely(!page)) {
452 if (flags & FOLL_DUMP) {
453 /* Avoid special (like zero) pages in core dumps */
454 page = ERR_PTR(-EFAULT);
458 if (is_zero_pfn(pte_pfn(pte))) {
459 page = pte_page(pte);
461 ret = follow_pfn_pte(vma, address, ptep, flags);
467 if (flags & FOLL_SPLIT && PageTransCompound(page)) {
469 pte_unmap_unlock(ptep, ptl);
471 ret = split_huge_page(page);
479 /* try_grab_page() does nothing unless FOLL_GET or FOLL_PIN is set. */
480 if (unlikely(!try_grab_page(page, flags))) {
481 page = ERR_PTR(-ENOMEM);
485 * We need to make the page accessible if and only if we are going
486 * to access its content (the FOLL_PIN case). Please see
487 * Documentation/core-api/pin_user_pages.rst for details.
489 if (flags & FOLL_PIN) {
490 ret = arch_make_page_accessible(page);
492 unpin_user_page(page);
497 if (flags & FOLL_TOUCH) {
498 if ((flags & FOLL_WRITE) &&
499 !pte_dirty(pte) && !PageDirty(page))
500 set_page_dirty(page);
502 * pte_mkyoung() would be more correct here, but atomic care
503 * is needed to avoid losing the dirty bit: it is easier to use
504 * mark_page_accessed().
506 mark_page_accessed(page);
508 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
509 /* Do not mlock pte-mapped THP */
510 if (PageTransCompound(page))
514 * The preliminary mapping check is mainly to avoid the
515 * pointless overhead of lock_page on the ZERO_PAGE
516 * which might bounce very badly if there is contention.
518 * If the page is already locked, we don't need to
519 * handle it now - vmscan will handle it later if and
520 * when it attempts to reclaim the page.
522 if (page->mapping && trylock_page(page)) {
523 lru_add_drain(); /* push cached pages to LRU */
525 * Because we lock page here, and migration is
526 * blocked by the pte's page reference, and we
527 * know the page is still mapped, we don't even
528 * need to check for file-cache page truncation.
530 mlock_vma_page(page);
535 pte_unmap_unlock(ptep, ptl);
538 pte_unmap_unlock(ptep, ptl);
541 return no_page_table(vma, flags);
544 static struct page *follow_pmd_mask(struct vm_area_struct *vma,
545 unsigned long address, pud_t *pudp,
547 struct follow_page_context *ctx)
552 struct mm_struct *mm = vma->vm_mm;
554 pmd = pmd_offset(pudp, address);
556 * The READ_ONCE() will stabilize the pmdval in a register or
557 * on the stack so that it will stop changing under the code.
559 pmdval = READ_ONCE(*pmd);
560 if (pmd_none(pmdval))
561 return no_page_table(vma, flags);
562 if (pmd_huge(pmdval) && is_vm_hugetlb_page(vma)) {
563 page = follow_huge_pmd(mm, address, pmd, flags);
566 return no_page_table(vma, flags);
568 if (is_hugepd(__hugepd(pmd_val(pmdval)))) {
569 page = follow_huge_pd(vma, address,
570 __hugepd(pmd_val(pmdval)), flags,
574 return no_page_table(vma, flags);
577 if (!pmd_present(pmdval)) {
578 if (likely(!(flags & FOLL_MIGRATION)))
579 return no_page_table(vma, flags);
580 VM_BUG_ON(thp_migration_supported() &&
581 !is_pmd_migration_entry(pmdval));
582 if (is_pmd_migration_entry(pmdval))
583 pmd_migration_entry_wait(mm, pmd);
584 pmdval = READ_ONCE(*pmd);
586 * MADV_DONTNEED may convert the pmd to null because
587 * mmap_sem is held in read mode
589 if (pmd_none(pmdval))
590 return no_page_table(vma, flags);
593 if (pmd_devmap(pmdval)) {
594 ptl = pmd_lock(mm, pmd);
595 page = follow_devmap_pmd(vma, address, pmd, flags, &ctx->pgmap);
600 if (likely(!pmd_trans_huge(pmdval)))
601 return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
603 if ((flags & FOLL_NUMA) && pmd_protnone(pmdval))
604 return no_page_table(vma, flags);
607 ptl = pmd_lock(mm, pmd);
608 if (unlikely(pmd_none(*pmd))) {
610 return no_page_table(vma, flags);
612 if (unlikely(!pmd_present(*pmd))) {
614 if (likely(!(flags & FOLL_MIGRATION)))
615 return no_page_table(vma, flags);
616 pmd_migration_entry_wait(mm, pmd);
619 if (unlikely(!pmd_trans_huge(*pmd))) {
621 return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
623 if (flags & (FOLL_SPLIT | FOLL_SPLIT_PMD)) {
625 page = pmd_page(*pmd);
626 if (is_huge_zero_page(page)) {
629 split_huge_pmd(vma, pmd, address);
630 if (pmd_trans_unstable(pmd))
632 } else if (flags & FOLL_SPLIT) {
633 if (unlikely(!try_get_page(page))) {
635 return ERR_PTR(-ENOMEM);
639 ret = split_huge_page(page);
643 return no_page_table(vma, flags);
644 } else { /* flags & FOLL_SPLIT_PMD */
646 split_huge_pmd(vma, pmd, address);
647 ret = pte_alloc(mm, pmd) ? -ENOMEM : 0;
650 return ret ? ERR_PTR(ret) :
651 follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
653 page = follow_trans_huge_pmd(vma, address, pmd, flags);
655 ctx->page_mask = HPAGE_PMD_NR - 1;
659 static struct page *follow_pud_mask(struct vm_area_struct *vma,
660 unsigned long address, p4d_t *p4dp,
662 struct follow_page_context *ctx)
667 struct mm_struct *mm = vma->vm_mm;
669 pud = pud_offset(p4dp, address);
671 return no_page_table(vma, flags);
672 if (pud_huge(*pud) && is_vm_hugetlb_page(vma)) {
673 page = follow_huge_pud(mm, address, pud, flags);
676 return no_page_table(vma, flags);
678 if (is_hugepd(__hugepd(pud_val(*pud)))) {
679 page = follow_huge_pd(vma, address,
680 __hugepd(pud_val(*pud)), flags,
684 return no_page_table(vma, flags);
686 if (pud_devmap(*pud)) {
687 ptl = pud_lock(mm, pud);
688 page = follow_devmap_pud(vma, address, pud, flags, &ctx->pgmap);
693 if (unlikely(pud_bad(*pud)))
694 return no_page_table(vma, flags);
696 return follow_pmd_mask(vma, address, pud, flags, ctx);
699 static struct page *follow_p4d_mask(struct vm_area_struct *vma,
700 unsigned long address, pgd_t *pgdp,
702 struct follow_page_context *ctx)
707 p4d = p4d_offset(pgdp, address);
709 return no_page_table(vma, flags);
710 BUILD_BUG_ON(p4d_huge(*p4d));
711 if (unlikely(p4d_bad(*p4d)))
712 return no_page_table(vma, flags);
714 if (is_hugepd(__hugepd(p4d_val(*p4d)))) {
715 page = follow_huge_pd(vma, address,
716 __hugepd(p4d_val(*p4d)), flags,
720 return no_page_table(vma, flags);
722 return follow_pud_mask(vma, address, p4d, flags, ctx);
726 * follow_page_mask - look up a page descriptor from a user-virtual address
727 * @vma: vm_area_struct mapping @address
728 * @address: virtual address to look up
729 * @flags: flags modifying lookup behaviour
730 * @ctx: contains dev_pagemap for %ZONE_DEVICE memory pinning and a
731 * pointer to output page_mask
733 * @flags can have FOLL_ flags set, defined in <linux/mm.h>
735 * When getting pages from ZONE_DEVICE memory, the @ctx->pgmap caches
736 * the device's dev_pagemap metadata to avoid repeating expensive lookups.
738 * On output, the @ctx->page_mask is set according to the size of the page.
740 * Return: the mapped (struct page *), %NULL if no mapping exists, or
741 * an error pointer if there is a mapping to something not represented
742 * by a page descriptor (see also vm_normal_page()).
744 static struct page *follow_page_mask(struct vm_area_struct *vma,
745 unsigned long address, unsigned int flags,
746 struct follow_page_context *ctx)
750 struct mm_struct *mm = vma->vm_mm;
754 /* make this handle hugepd */
755 page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
757 WARN_ON_ONCE(flags & (FOLL_GET | FOLL_PIN));
761 pgd = pgd_offset(mm, address);
763 if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
764 return no_page_table(vma, flags);
766 if (pgd_huge(*pgd)) {
767 page = follow_huge_pgd(mm, address, pgd, flags);
770 return no_page_table(vma, flags);
772 if (is_hugepd(__hugepd(pgd_val(*pgd)))) {
773 page = follow_huge_pd(vma, address,
774 __hugepd(pgd_val(*pgd)), flags,
778 return no_page_table(vma, flags);
781 return follow_p4d_mask(vma, address, pgd, flags, ctx);
784 struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
785 unsigned int foll_flags)
787 struct follow_page_context ctx = { NULL };
790 page = follow_page_mask(vma, address, foll_flags, &ctx);
792 put_dev_pagemap(ctx.pgmap);
796 static int get_gate_page(struct mm_struct *mm, unsigned long address,
797 unsigned int gup_flags, struct vm_area_struct **vma,
807 /* user gate pages are read-only */
808 if (gup_flags & FOLL_WRITE)
810 if (address > TASK_SIZE)
811 pgd = pgd_offset_k(address);
813 pgd = pgd_offset_gate(mm, address);
816 p4d = p4d_offset(pgd, address);
819 pud = pud_offset(p4d, address);
822 pmd = pmd_offset(pud, address);
823 if (!pmd_present(*pmd))
825 VM_BUG_ON(pmd_trans_huge(*pmd));
826 pte = pte_offset_map(pmd, address);
829 *vma = get_gate_vma(mm);
832 *page = vm_normal_page(*vma, address, *pte);
834 if ((gup_flags & FOLL_DUMP) || !is_zero_pfn(pte_pfn(*pte)))
836 *page = pte_page(*pte);
838 if (unlikely(!try_get_page(*page))) {
850 * mmap_sem must be held on entry. If @locked != NULL and *@flags
851 * does not include FOLL_NOWAIT, the mmap_sem may be released. If it
852 * is, *@locked will be set to 0 and -EBUSY returned.
854 static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma,
855 unsigned long address, unsigned int *flags, int *locked)
857 unsigned int fault_flags = 0;
860 /* mlock all present pages, but do not fault in new pages */
861 if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK)
863 if (*flags & FOLL_WRITE)
864 fault_flags |= FAULT_FLAG_WRITE;
865 if (*flags & FOLL_REMOTE)
866 fault_flags |= FAULT_FLAG_REMOTE;
868 fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
869 if (*flags & FOLL_NOWAIT)
870 fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT;
871 if (*flags & FOLL_TRIED) {
873 * Note: FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_TRIED
876 fault_flags |= FAULT_FLAG_TRIED;
879 ret = handle_mm_fault(vma, address, fault_flags);
880 if (ret & VM_FAULT_ERROR) {
881 int err = vm_fault_to_errno(ret, *flags);
889 if (ret & VM_FAULT_MAJOR)
895 if (ret & VM_FAULT_RETRY) {
896 if (locked && !(fault_flags & FAULT_FLAG_RETRY_NOWAIT))
902 * The VM_FAULT_WRITE bit tells us that do_wp_page has broken COW when
903 * necessary, even if maybe_mkwrite decided not to set pte_write. We
904 * can thus safely do subsequent page lookups as if they were reads.
905 * But only do so when looping for pte_write is futile: in some cases
906 * userspace may also be wanting to write to the gotten user page,
907 * which a read fault here might prevent (a readonly page might get
908 * reCOWed by userspace write).
910 if ((ret & VM_FAULT_WRITE) && !(vma->vm_flags & VM_WRITE))
915 static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)
917 vm_flags_t vm_flags = vma->vm_flags;
918 int write = (gup_flags & FOLL_WRITE);
919 int foreign = (gup_flags & FOLL_REMOTE);
921 if (vm_flags & (VM_IO | VM_PFNMAP))
924 if (gup_flags & FOLL_ANON && !vma_is_anonymous(vma))
928 if (!(vm_flags & VM_WRITE)) {
929 if (!(gup_flags & FOLL_FORCE))
932 * We used to let the write,force case do COW in a
933 * VM_MAYWRITE VM_SHARED !VM_WRITE vma, so ptrace could
934 * set a breakpoint in a read-only mapping of an
935 * executable, without corrupting the file (yet only
936 * when that file had been opened for writing!).
937 * Anon pages in shared mappings are surprising: now
940 if (!is_cow_mapping(vm_flags))
943 } else if (!(vm_flags & VM_READ)) {
944 if (!(gup_flags & FOLL_FORCE))
947 * Is there actually any vma we can reach here which does not
948 * have VM_MAYREAD set?
950 if (!(vm_flags & VM_MAYREAD))
954 * gups are always data accesses, not instruction
955 * fetches, so execute=false here
957 if (!arch_vma_access_permitted(vma, write, false, foreign))
963 * __get_user_pages() - pin user pages in memory
964 * @tsk: task_struct of target task
965 * @mm: mm_struct of target mm
966 * @start: starting user address
967 * @nr_pages: number of pages from start to pin
968 * @gup_flags: flags modifying pin behaviour
969 * @pages: array that receives pointers to the pages pinned.
970 * Should be at least nr_pages long. Or NULL, if caller
971 * only intends to ensure the pages are faulted in.
972 * @vmas: array of pointers to vmas corresponding to each page.
973 * Or NULL if the caller does not require them.
974 * @locked: whether we're still with the mmap_sem held
976 * Returns either number of pages pinned (which may be less than the
977 * number requested), or an error. Details about the return value:
979 * -- If nr_pages is 0, returns 0.
980 * -- If nr_pages is >0, but no pages were pinned, returns -errno.
981 * -- If nr_pages is >0, and some pages were pinned, returns the number of
982 * pages pinned. Again, this may be less than nr_pages.
984 * The caller is responsible for releasing returned @pages, via put_page().
986 * @vmas are valid only as long as mmap_sem is held.
988 * Must be called with mmap_sem held. It may be released. See below.
990 * __get_user_pages walks a process's page tables and takes a reference to
991 * each struct page that each user address corresponds to at a given
992 * instant. That is, it takes the page that would be accessed if a user
993 * thread accesses the given user virtual address at that instant.
995 * This does not guarantee that the page exists in the user mappings when
996 * __get_user_pages returns, and there may even be a completely different
997 * page there in some cases (eg. if mmapped pagecache has been invalidated
998 * and subsequently re faulted). However it does guarantee that the page
999 * won't be freed completely. And mostly callers simply care that the page
1000 * contains data that was valid *at some point in time*. Typically, an IO
1001 * or similar operation cannot guarantee anything stronger anyway because
1002 * locks can't be held over the syscall boundary.
1004 * If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If
1005 * the page is written to, set_page_dirty (or set_page_dirty_lock, as
1006 * appropriate) must be called after the page is finished with, and
1007 * before put_page is called.
1009 * If @locked != NULL, *@locked will be set to 0 when mmap_sem is
1010 * released by an up_read(). That can happen if @gup_flags does not
1013 * A caller using such a combination of @locked and @gup_flags
1014 * must therefore hold the mmap_sem for reading only, and recognize
1015 * when it's been released. Otherwise, it must be held for either
1016 * reading or writing and will not be released.
1018 * In most cases, get_user_pages or get_user_pages_fast should be used
1019 * instead of __get_user_pages. __get_user_pages should be used only if
1020 * you need some special @gup_flags.
1022 static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
1023 unsigned long start, unsigned long nr_pages,
1024 unsigned int gup_flags, struct page **pages,
1025 struct vm_area_struct **vmas, int *locked)
1027 long ret = 0, i = 0;
1028 struct vm_area_struct *vma = NULL;
1029 struct follow_page_context ctx = { NULL };
1034 start = untagged_addr(start);
1036 VM_BUG_ON(!!pages != !!(gup_flags & (FOLL_GET | FOLL_PIN)));
1039 * If FOLL_FORCE is set then do not force a full fault as the hinting
1040 * fault information is unrelated to the reference behaviour of a task
1041 * using the address space
1043 if (!(gup_flags & FOLL_FORCE))
1044 gup_flags |= FOLL_NUMA;
1048 unsigned int foll_flags = gup_flags;
1049 unsigned int page_increm;
1051 /* first iteration or cross vma bound */
1052 if (!vma || start >= vma->vm_end) {
1053 vma = find_extend_vma(mm, start);
1054 if (!vma && in_gate_area(mm, start)) {
1055 ret = get_gate_page(mm, start & PAGE_MASK,
1057 pages ? &pages[i] : NULL);
1064 if (!vma || check_vma_flags(vma, gup_flags)) {
1068 if (is_vm_hugetlb_page(vma)) {
1069 i = follow_hugetlb_page(mm, vma, pages, vmas,
1070 &start, &nr_pages, i,
1072 if (locked && *locked == 0) {
1074 * We've got a VM_FAULT_RETRY
1075 * and we've lost mmap_sem.
1076 * We must stop here.
1078 BUG_ON(gup_flags & FOLL_NOWAIT);
1087 * If we have a pending SIGKILL, don't keep faulting pages and
1088 * potentially allocating memory.
1090 if (fatal_signal_pending(current)) {
1096 page = follow_page_mask(vma, start, foll_flags, &ctx);
1098 ret = faultin_page(tsk, vma, start, &foll_flags,
1114 } else if (PTR_ERR(page) == -EEXIST) {
1116 * Proper page table entry exists, but no corresponding
1120 } else if (IS_ERR(page)) {
1121 ret = PTR_ERR(page);
1126 flush_anon_page(vma, page, start);
1127 flush_dcache_page(page);
1135 page_increm = 1 + (~(start >> PAGE_SHIFT) & ctx.page_mask);
1136 if (page_increm > nr_pages)
1137 page_increm = nr_pages;
1139 start += page_increm * PAGE_SIZE;
1140 nr_pages -= page_increm;
1144 put_dev_pagemap(ctx.pgmap);
1148 static bool vma_permits_fault(struct vm_area_struct *vma,
1149 unsigned int fault_flags)
1151 bool write = !!(fault_flags & FAULT_FLAG_WRITE);
1152 bool foreign = !!(fault_flags & FAULT_FLAG_REMOTE);
1153 vm_flags_t vm_flags = write ? VM_WRITE : VM_READ;
1155 if (!(vm_flags & vma->vm_flags))
1159 * The architecture might have a hardware protection
1160 * mechanism other than read/write that can deny access.
1162 * gup always represents data access, not instruction
1163 * fetches, so execute=false here:
1165 if (!arch_vma_access_permitted(vma, write, false, foreign))
1172 * fixup_user_fault() - manually resolve a user page fault
1173 * @tsk: the task_struct to use for page fault accounting, or
1174 * NULL if faults are not to be recorded.
1175 * @mm: mm_struct of target mm
1176 * @address: user address
1177 * @fault_flags:flags to pass down to handle_mm_fault()
1178 * @unlocked: did we unlock the mmap_sem while retrying, maybe NULL if caller
1179 * does not allow retry
1181 * This is meant to be called in the specific scenario where for locking reasons
1182 * we try to access user memory in atomic context (within a pagefault_disable()
1183 * section), this returns -EFAULT, and we want to resolve the user fault before
1186 * Typically this is meant to be used by the futex code.
1188 * The main difference with get_user_pages() is that this function will
1189 * unconditionally call handle_mm_fault() which will in turn perform all the
1190 * necessary SW fixup of the dirty and young bits in the PTE, while
1191 * get_user_pages() only guarantees to update these in the struct page.
1193 * This is important for some architectures where those bits also gate the
1194 * access permission to the page because they are maintained in software. On
1195 * such architectures, gup() will not be enough to make a subsequent access
1198 * This function will not return with an unlocked mmap_sem. So it has not the
1199 * same semantics wrt the @mm->mmap_sem as does filemap_fault().
1201 int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
1202 unsigned long address, unsigned int fault_flags,
1205 struct vm_area_struct *vma;
1206 vm_fault_t ret, major = 0;
1208 address = untagged_addr(address);
1211 fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
1214 vma = find_extend_vma(mm, address);
1215 if (!vma || address < vma->vm_start)
1218 if (!vma_permits_fault(vma, fault_flags))
1221 ret = handle_mm_fault(vma, address, fault_flags);
1222 major |= ret & VM_FAULT_MAJOR;
1223 if (ret & VM_FAULT_ERROR) {
1224 int err = vm_fault_to_errno(ret, 0);
1231 if (ret & VM_FAULT_RETRY) {
1232 down_read(&mm->mmap_sem);
1233 if (!(fault_flags & FAULT_FLAG_TRIED)) {
1235 fault_flags |= FAULT_FLAG_TRIED;
1248 EXPORT_SYMBOL_GPL(fixup_user_fault);
1250 static __always_inline long __get_user_pages_locked(struct task_struct *tsk,
1251 struct mm_struct *mm,
1252 unsigned long start,
1253 unsigned long nr_pages,
1254 struct page **pages,
1255 struct vm_area_struct **vmas,
1259 long ret, pages_done;
1263 /* if VM_FAULT_RETRY can be returned, vmas become invalid */
1265 /* check caller initialized locked */
1266 BUG_ON(*locked != 1);
1270 * FOLL_PIN and FOLL_GET are mutually exclusive. Traditional behavior
1271 * is to set FOLL_GET if the caller wants pages[] filled in (but has
1272 * carelessly failed to specify FOLL_GET), so keep doing that, but only
1273 * for FOLL_GET, not for the newer FOLL_PIN.
1275 * FOLL_PIN always expects pages to be non-null, but no need to assert
1276 * that here, as any failures will be obvious enough.
1278 if (pages && !(flags & FOLL_PIN))
1282 lock_dropped = false;
1284 ret = __get_user_pages(tsk, mm, start, nr_pages, flags, pages,
1287 /* VM_FAULT_RETRY couldn't trigger, bypass */
1290 /* VM_FAULT_RETRY cannot return errors */
1293 BUG_ON(ret >= nr_pages);
1304 * VM_FAULT_RETRY didn't trigger or it was a
1312 * VM_FAULT_RETRY triggered, so seek to the faulting offset.
1313 * For the prefault case (!pages) we only update counts.
1317 start += ret << PAGE_SHIFT;
1318 lock_dropped = true;
1322 * Repeat on the address that fired VM_FAULT_RETRY
1323 * with both FAULT_FLAG_ALLOW_RETRY and
1324 * FAULT_FLAG_TRIED. Note that GUP can be interrupted
1325 * by fatal signals, so we need to check it before we
1326 * start trying again otherwise it can loop forever.
1329 if (fatal_signal_pending(current))
1333 ret = down_read_killable(&mm->mmap_sem);
1341 ret = __get_user_pages(tsk, mm, start, 1, flags | FOLL_TRIED,
1342 pages, NULL, locked);
1344 /* Continue to retry until we succeeded */
1362 if (lock_dropped && *locked) {
1364 * We must let the caller know we temporarily dropped the lock
1365 * and so the critical section protected by it was lost.
1367 up_read(&mm->mmap_sem);
1374 * populate_vma_page_range() - populate a range of pages in the vma.
1376 * @start: start address
1378 * @locked: whether the mmap_sem is still held
1380 * This takes care of mlocking the pages too if VM_LOCKED is set.
1382 * return 0 on success, negative error code on error.
1384 * vma->vm_mm->mmap_sem must be held.
1386 * If @locked is NULL, it may be held for read or write and will
1389 * If @locked is non-NULL, it must held for read only and may be
1390 * released. If it's released, *@locked will be set to 0.
1392 long populate_vma_page_range(struct vm_area_struct *vma,
1393 unsigned long start, unsigned long end, int *locked)
1395 struct mm_struct *mm = vma->vm_mm;
1396 unsigned long nr_pages = (end - start) / PAGE_SIZE;
1399 VM_BUG_ON(start & ~PAGE_MASK);
1400 VM_BUG_ON(end & ~PAGE_MASK);
1401 VM_BUG_ON_VMA(start < vma->vm_start, vma);
1402 VM_BUG_ON_VMA(end > vma->vm_end, vma);
1403 VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm);
1405 gup_flags = FOLL_TOUCH | FOLL_POPULATE | FOLL_MLOCK;
1406 if (vma->vm_flags & VM_LOCKONFAULT)
1407 gup_flags &= ~FOLL_POPULATE;
1409 * We want to touch writable mappings with a write fault in order
1410 * to break COW, except for shared mappings because these don't COW
1411 * and we would not want to dirty them for nothing.
1413 if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
1414 gup_flags |= FOLL_WRITE;
1417 * We want mlock to succeed for regions that have any permissions
1418 * other than PROT_NONE.
1420 if (vma_is_accessible(vma))
1421 gup_flags |= FOLL_FORCE;
1424 * We made sure addr is within a VMA, so the following will
1425 * not result in a stack expansion that recurses back here.
1427 return __get_user_pages(current, mm, start, nr_pages, gup_flags,
1428 NULL, NULL, locked);
1432 * __mm_populate - populate and/or mlock pages within a range of address space.
1434 * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
1435 * flags. VMAs must be already marked with the desired vm_flags, and
1436 * mmap_sem must not be held.
1438 int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
1440 struct mm_struct *mm = current->mm;
1441 unsigned long end, nstart, nend;
1442 struct vm_area_struct *vma = NULL;
1448 for (nstart = start; nstart < end; nstart = nend) {
1450 * We want to fault in pages for [nstart; end) address range.
1451 * Find first corresponding VMA.
1455 down_read(&mm->mmap_sem);
1456 vma = find_vma(mm, nstart);
1457 } else if (nstart >= vma->vm_end)
1459 if (!vma || vma->vm_start >= end)
1462 * Set [nstart; nend) to intersection of desired address
1463 * range with the first VMA. Also, skip undesirable VMA types.
1465 nend = min(end, vma->vm_end);
1466 if (vma->vm_flags & (VM_IO | VM_PFNMAP))
1468 if (nstart < vma->vm_start)
1469 nstart = vma->vm_start;
1471 * Now fault in a range of pages. populate_vma_page_range()
1472 * double checks the vma flags, so that it won't mlock pages
1473 * if the vma was already munlocked.
1475 ret = populate_vma_page_range(vma, nstart, nend, &locked);
1477 if (ignore_errors) {
1479 continue; /* continue at next VMA */
1483 nend = nstart + ret * PAGE_SIZE;
1487 up_read(&mm->mmap_sem);
1488 return ret; /* 0 or negative error code */
1492 * get_dump_page() - pin user page in memory while writing it to core dump
1493 * @addr: user address
1495 * Returns struct page pointer of user page pinned for dump,
1496 * to be freed afterwards by put_page().
1498 * Returns NULL on any kind of failure - a hole must then be inserted into
1499 * the corefile, to preserve alignment with its headers; and also returns
1500 * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
1501 * allowing a hole to be left in the corefile to save diskspace.
1503 * Called without mmap_sem, but after all other threads have been killed.
1505 #ifdef CONFIG_ELF_CORE
1506 struct page *get_dump_page(unsigned long addr)
1508 struct vm_area_struct *vma;
1511 if (__get_user_pages(current, current->mm, addr, 1,
1512 FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma,
1515 flush_cache_page(vma, addr, page_to_pfn(page));
1518 #endif /* CONFIG_ELF_CORE */
1519 #else /* CONFIG_MMU */
1520 static long __get_user_pages_locked(struct task_struct *tsk,
1521 struct mm_struct *mm, unsigned long start,
1522 unsigned long nr_pages, struct page **pages,
1523 struct vm_area_struct **vmas, int *locked,
1524 unsigned int foll_flags)
1526 struct vm_area_struct *vma;
1527 unsigned long vm_flags;
1530 /* calculate required read or write permissions.
1531 * If FOLL_FORCE is set, we only require the "MAY" flags.
1533 vm_flags = (foll_flags & FOLL_WRITE) ?
1534 (VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
1535 vm_flags &= (foll_flags & FOLL_FORCE) ?
1536 (VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
1538 for (i = 0; i < nr_pages; i++) {
1539 vma = find_vma(mm, start);
1541 goto finish_or_fault;
1543 /* protect what we can, including chardevs */
1544 if ((vma->vm_flags & (VM_IO | VM_PFNMAP)) ||
1545 !(vm_flags & vma->vm_flags))
1546 goto finish_or_fault;
1549 pages[i] = virt_to_page(start);
1555 start = (start + PAGE_SIZE) & PAGE_MASK;
1561 return i ? : -EFAULT;
1563 #endif /* !CONFIG_MMU */
1565 #if defined(CONFIG_FS_DAX) || defined (CONFIG_CMA)
1566 static bool check_dax_vmas(struct vm_area_struct **vmas, long nr_pages)
1569 struct vm_area_struct *vma_prev = NULL;
1571 for (i = 0; i < nr_pages; i++) {
1572 struct vm_area_struct *vma = vmas[i];
1574 if (vma == vma_prev)
1579 if (vma_is_fsdax(vma))
1586 static struct page *new_non_cma_page(struct page *page, unsigned long private)
1589 * We want to make sure we allocate the new page from the same node
1590 * as the source page.
1592 int nid = page_to_nid(page);
1594 * Trying to allocate a page for migration. Ignore allocation
1595 * failure warnings. We don't force __GFP_THISNODE here because
1596 * this node here is the node where we have CMA reservation and
1597 * in some case these nodes will have really less non movable
1598 * allocation memory.
1600 gfp_t gfp_mask = GFP_USER | __GFP_NOWARN;
1602 if (PageHighMem(page))
1603 gfp_mask |= __GFP_HIGHMEM;
1605 #ifdef CONFIG_HUGETLB_PAGE
1606 if (PageHuge(page)) {
1607 struct hstate *h = page_hstate(page);
1609 * We don't want to dequeue from the pool because pool pages will
1610 * mostly be from the CMA region.
1612 return alloc_migrate_huge_page(h, gfp_mask, nid, NULL);
1615 if (PageTransHuge(page)) {
1618 * ignore allocation failure warnings
1620 gfp_t thp_gfpmask = GFP_TRANSHUGE | __GFP_NOWARN;
1623 * Remove the movable mask so that we don't allocate from
1626 thp_gfpmask &= ~__GFP_MOVABLE;
1627 thp = __alloc_pages_node(nid, thp_gfpmask, HPAGE_PMD_ORDER);
1630 prep_transhuge_page(thp);
1634 return __alloc_pages_node(nid, gfp_mask, 0);
1637 static long check_and_migrate_cma_pages(struct task_struct *tsk,
1638 struct mm_struct *mm,
1639 unsigned long start,
1640 unsigned long nr_pages,
1641 struct page **pages,
1642 struct vm_area_struct **vmas,
1643 unsigned int gup_flags)
1647 bool drain_allow = true;
1648 bool migrate_allow = true;
1649 LIST_HEAD(cma_page_list);
1650 long ret = nr_pages;
1653 for (i = 0; i < nr_pages;) {
1655 struct page *head = compound_head(pages[i]);
1658 * gup may start from a tail page. Advance step by the left
1661 step = compound_nr(head) - (pages[i] - head);
1663 * If we get a page from the CMA zone, since we are going to
1664 * be pinning these entries, we might as well move them out
1665 * of the CMA zone if possible.
1667 if (is_migrate_cma_page(head)) {
1669 isolate_huge_page(head, &cma_page_list);
1671 if (!PageLRU(head) && drain_allow) {
1672 lru_add_drain_all();
1673 drain_allow = false;
1676 if (!isolate_lru_page(head)) {
1677 list_add_tail(&head->lru, &cma_page_list);
1678 mod_node_page_state(page_pgdat(head),
1680 page_is_file_lru(head),
1681 hpage_nr_pages(head));
1689 if (!list_empty(&cma_page_list)) {
1691 * drop the above get_user_pages reference.
1693 for (i = 0; i < nr_pages; i++)
1696 if (migrate_pages(&cma_page_list, new_non_cma_page,
1697 NULL, 0, MIGRATE_SYNC, MR_CONTIG_RANGE)) {
1699 * some of the pages failed migration. Do get_user_pages
1700 * without migration.
1702 migrate_allow = false;
1704 if (!list_empty(&cma_page_list))
1705 putback_movable_pages(&cma_page_list);
1708 * We did migrate all the pages, Try to get the page references
1709 * again migrating any new CMA pages which we failed to isolate
1712 ret = __get_user_pages_locked(tsk, mm, start, nr_pages,
1716 if ((ret > 0) && migrate_allow) {
1726 static long check_and_migrate_cma_pages(struct task_struct *tsk,
1727 struct mm_struct *mm,
1728 unsigned long start,
1729 unsigned long nr_pages,
1730 struct page **pages,
1731 struct vm_area_struct **vmas,
1732 unsigned int gup_flags)
1736 #endif /* CONFIG_CMA */
1739 * __gup_longterm_locked() is a wrapper for __get_user_pages_locked which
1740 * allows us to process the FOLL_LONGTERM flag.
1742 static long __gup_longterm_locked(struct task_struct *tsk,
1743 struct mm_struct *mm,
1744 unsigned long start,
1745 unsigned long nr_pages,
1746 struct page **pages,
1747 struct vm_area_struct **vmas,
1748 unsigned int gup_flags)
1750 struct vm_area_struct **vmas_tmp = vmas;
1751 unsigned long flags = 0;
1754 if (gup_flags & FOLL_LONGTERM) {
1759 vmas_tmp = kcalloc(nr_pages,
1760 sizeof(struct vm_area_struct *),
1765 flags = memalloc_nocma_save();
1768 rc = __get_user_pages_locked(tsk, mm, start, nr_pages, pages,
1769 vmas_tmp, NULL, gup_flags);
1771 if (gup_flags & FOLL_LONGTERM) {
1772 memalloc_nocma_restore(flags);
1776 if (check_dax_vmas(vmas_tmp, rc)) {
1777 for (i = 0; i < rc; i++)
1783 rc = check_and_migrate_cma_pages(tsk, mm, start, rc, pages,
1784 vmas_tmp, gup_flags);
1788 if (vmas_tmp != vmas)
1792 #else /* !CONFIG_FS_DAX && !CONFIG_CMA */
1793 static __always_inline long __gup_longterm_locked(struct task_struct *tsk,
1794 struct mm_struct *mm,
1795 unsigned long start,
1796 unsigned long nr_pages,
1797 struct page **pages,
1798 struct vm_area_struct **vmas,
1801 return __get_user_pages_locked(tsk, mm, start, nr_pages, pages, vmas,
1804 #endif /* CONFIG_FS_DAX || CONFIG_CMA */
1807 static long __get_user_pages_remote(struct task_struct *tsk,
1808 struct mm_struct *mm,
1809 unsigned long start, unsigned long nr_pages,
1810 unsigned int gup_flags, struct page **pages,
1811 struct vm_area_struct **vmas, int *locked)
1814 * Parts of FOLL_LONGTERM behavior are incompatible with
1815 * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
1816 * vmas. However, this only comes up if locked is set, and there are
1817 * callers that do request FOLL_LONGTERM, but do not set locked. So,
1818 * allow what we can.
1820 if (gup_flags & FOLL_LONGTERM) {
1821 if (WARN_ON_ONCE(locked))
1824 * This will check the vmas (even if our vmas arg is NULL)
1825 * and return -ENOTSUPP if DAX isn't allowed in this case:
1827 return __gup_longterm_locked(tsk, mm, start, nr_pages, pages,
1828 vmas, gup_flags | FOLL_TOUCH |
1832 return __get_user_pages_locked(tsk, mm, start, nr_pages, pages, vmas,
1834 gup_flags | FOLL_TOUCH | FOLL_REMOTE);
1838 * get_user_pages_remote() - pin user pages in memory
1839 * @tsk: the task_struct to use for page fault accounting, or
1840 * NULL if faults are not to be recorded.
1841 * @mm: mm_struct of target mm
1842 * @start: starting user address
1843 * @nr_pages: number of pages from start to pin
1844 * @gup_flags: flags modifying lookup behaviour
1845 * @pages: array that receives pointers to the pages pinned.
1846 * Should be at least nr_pages long. Or NULL, if caller
1847 * only intends to ensure the pages are faulted in.
1848 * @vmas: array of pointers to vmas corresponding to each page.
1849 * Or NULL if the caller does not require them.
1850 * @locked: pointer to lock flag indicating whether lock is held and
1851 * subsequently whether VM_FAULT_RETRY functionality can be
1852 * utilised. Lock must initially be held.
1854 * Returns either number of pages pinned (which may be less than the
1855 * number requested), or an error. Details about the return value:
1857 * -- If nr_pages is 0, returns 0.
1858 * -- If nr_pages is >0, but no pages were pinned, returns -errno.
1859 * -- If nr_pages is >0, and some pages were pinned, returns the number of
1860 * pages pinned. Again, this may be less than nr_pages.
1862 * The caller is responsible for releasing returned @pages, via put_page().
1864 * @vmas are valid only as long as mmap_sem is held.
1866 * Must be called with mmap_sem held for read or write.
1868 * get_user_pages walks a process's page tables and takes a reference to
1869 * each struct page that each user address corresponds to at a given
1870 * instant. That is, it takes the page that would be accessed if a user
1871 * thread accesses the given user virtual address at that instant.
1873 * This does not guarantee that the page exists in the user mappings when
1874 * get_user_pages returns, and there may even be a completely different
1875 * page there in some cases (eg. if mmapped pagecache has been invalidated
1876 * and subsequently re faulted). However it does guarantee that the page
1877 * won't be freed completely. And mostly callers simply care that the page
1878 * contains data that was valid *at some point in time*. Typically, an IO
1879 * or similar operation cannot guarantee anything stronger anyway because
1880 * locks can't be held over the syscall boundary.
1882 * If gup_flags & FOLL_WRITE == 0, the page must not be written to. If the page
1883 * is written to, set_page_dirty (or set_page_dirty_lock, as appropriate) must
1884 * be called after the page is finished with, and before put_page is called.
1886 * get_user_pages is typically used for fewer-copy IO operations, to get a
1887 * handle on the memory by some means other than accesses via the user virtual
1888 * addresses. The pages may be submitted for DMA to devices or accessed via
1889 * their kernel linear mapping (via the kmap APIs). Care should be taken to
1890 * use the correct cache flushing APIs.
1892 * See also get_user_pages_fast, for performance critical applications.
1894 * get_user_pages should be phased out in favor of
1895 * get_user_pages_locked|unlocked or get_user_pages_fast. Nothing
1896 * should use get_user_pages because it cannot pass
1897 * FAULT_FLAG_ALLOW_RETRY to handle_mm_fault.
1899 long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
1900 unsigned long start, unsigned long nr_pages,
1901 unsigned int gup_flags, struct page **pages,
1902 struct vm_area_struct **vmas, int *locked)
1905 * FOLL_PIN must only be set internally by the pin_user_pages*() APIs,
1906 * never directly by the caller, so enforce that with an assertion:
1908 if (WARN_ON_ONCE(gup_flags & FOLL_PIN))
1911 return __get_user_pages_remote(tsk, mm, start, nr_pages, gup_flags,
1912 pages, vmas, locked);
1914 EXPORT_SYMBOL(get_user_pages_remote);
1916 #else /* CONFIG_MMU */
1917 long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
1918 unsigned long start, unsigned long nr_pages,
1919 unsigned int gup_flags, struct page **pages,
1920 struct vm_area_struct **vmas, int *locked)
1925 static long __get_user_pages_remote(struct task_struct *tsk,
1926 struct mm_struct *mm,
1927 unsigned long start, unsigned long nr_pages,
1928 unsigned int gup_flags, struct page **pages,
1929 struct vm_area_struct **vmas, int *locked)
1933 #endif /* !CONFIG_MMU */
1936 * This is the same as get_user_pages_remote(), just with a
1937 * less-flexible calling convention where we assume that the task
1938 * and mm being operated on are the current task's and don't allow
1939 * passing of a locked parameter. We also obviously don't pass
1940 * FOLL_REMOTE in here.
1942 long get_user_pages(unsigned long start, unsigned long nr_pages,
1943 unsigned int gup_flags, struct page **pages,
1944 struct vm_area_struct **vmas)
1947 * FOLL_PIN must only be set internally by the pin_user_pages*() APIs,
1948 * never directly by the caller, so enforce that with an assertion:
1950 if (WARN_ON_ONCE(gup_flags & FOLL_PIN))
1953 return __gup_longterm_locked(current, current->mm, start, nr_pages,
1954 pages, vmas, gup_flags | FOLL_TOUCH);
1956 EXPORT_SYMBOL(get_user_pages);
1959 * We can leverage the VM_FAULT_RETRY functionality in the page fault
1960 * paths better by using either get_user_pages_locked() or
1961 * get_user_pages_unlocked().
1963 * get_user_pages_locked() is suitable to replace the form:
1965 * down_read(&mm->mmap_sem);
1967 * get_user_pages(tsk, mm, ..., pages, NULL);
1968 * up_read(&mm->mmap_sem);
1973 * down_read(&mm->mmap_sem);
1975 * get_user_pages_locked(tsk, mm, ..., pages, &locked);
1977 * up_read(&mm->mmap_sem);
1979 long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
1980 unsigned int gup_flags, struct page **pages,
1984 * FIXME: Current FOLL_LONGTERM behavior is incompatible with
1985 * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
1986 * vmas. As there are no users of this flag in this call we simply
1987 * disallow this option for now.
1989 if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
1992 return __get_user_pages_locked(current, current->mm, start, nr_pages,
1993 pages, NULL, locked,
1994 gup_flags | FOLL_TOUCH);
1996 EXPORT_SYMBOL(get_user_pages_locked);
1999 * get_user_pages_unlocked() is suitable to replace the form:
2001 * down_read(&mm->mmap_sem);
2002 * get_user_pages(tsk, mm, ..., pages, NULL);
2003 * up_read(&mm->mmap_sem);
2007 * get_user_pages_unlocked(tsk, mm, ..., pages);
2009 * It is functionally equivalent to get_user_pages_fast so
2010 * get_user_pages_fast should be used instead if specific gup_flags
2011 * (e.g. FOLL_FORCE) are not required.
2013 long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
2014 struct page **pages, unsigned int gup_flags)
2016 struct mm_struct *mm = current->mm;
2021 * FIXME: Current FOLL_LONGTERM behavior is incompatible with
2022 * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
2023 * vmas. As there are no users of this flag in this call we simply
2024 * disallow this option for now.
2026 if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
2029 down_read(&mm->mmap_sem);
2030 ret = __get_user_pages_locked(current, mm, start, nr_pages, pages, NULL,
2031 &locked, gup_flags | FOLL_TOUCH);
2033 up_read(&mm->mmap_sem);
2036 EXPORT_SYMBOL(get_user_pages_unlocked);
2041 * get_user_pages_fast attempts to pin user pages by walking the page
2042 * tables directly and avoids taking locks. Thus the walker needs to be
2043 * protected from page table pages being freed from under it, and should
2044 * block any THP splits.
2046 * One way to achieve this is to have the walker disable interrupts, and
2047 * rely on IPIs from the TLB flushing code blocking before the page table
2048 * pages are freed. This is unsuitable for architectures that do not need
2049 * to broadcast an IPI when invalidating TLBs.
2051 * Another way to achieve this is to batch up page table containing pages
2052 * belonging to more than one mm_user, then rcu_sched a callback to free those
2053 * pages. Disabling interrupts will allow the fast_gup walker to both block
2054 * the rcu_sched callback, and an IPI that we broadcast for splitting THPs
2055 * (which is a relatively rare event). The code below adopts this strategy.
2057 * Before activating this code, please be aware that the following assumptions
2058 * are currently made:
2060 * *) Either MMU_GATHER_RCU_TABLE_FREE is enabled, and tlb_remove_table() is used to
2061 * free pages containing page tables or TLB flushing requires IPI broadcast.
2063 * *) ptes can be read atomically by the architecture.
2065 * *) access_ok is sufficient to validate userspace address ranges.
2067 * The last two assumptions can be relaxed by the addition of helper functions.
2069 * This code is based heavily on the PowerPC implementation by Nick Piggin.
2071 #ifdef CONFIG_HAVE_FAST_GUP
2073 static void put_compound_head(struct page *page, int refs, unsigned int flags)
2075 if (flags & FOLL_PIN) {
2076 mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_RELEASED,
2079 if (hpage_pincount_available(page))
2080 hpage_pincount_sub(page, refs);
2082 refs *= GUP_PIN_COUNTING_BIAS;
2085 VM_BUG_ON_PAGE(page_ref_count(page) < refs, page);
2087 * Calling put_page() for each ref is unnecessarily slow. Only the last
2088 * ref needs a put_page().
2091 page_ref_sub(page, refs - 1);
2095 #ifdef CONFIG_GUP_GET_PTE_LOW_HIGH
2098 * WARNING: only to be used in the get_user_pages_fast() implementation.
2100 * With get_user_pages_fast(), we walk down the pagetables without taking any
2101 * locks. For this we would like to load the pointers atomically, but sometimes
2102 * that is not possible (e.g. without expensive cmpxchg8b on x86_32 PAE). What
2103 * we do have is the guarantee that a PTE will only either go from not present
2104 * to present, or present to not present or both -- it will not switch to a
2105 * completely different present page without a TLB flush in between; something
2106 * that we are blocking by holding interrupts off.
2108 * Setting ptes from not present to present goes:
2110 * ptep->pte_high = h;
2112 * ptep->pte_low = l;
2114 * And present to not present goes:
2116 * ptep->pte_low = 0;
2118 * ptep->pte_high = 0;
2120 * We must ensure here that the load of pte_low sees 'l' IFF pte_high sees 'h'.
2121 * We load pte_high *after* loading pte_low, which ensures we don't see an older
2122 * value of pte_high. *Then* we recheck pte_low, which ensures that we haven't
2123 * picked up a changed pte high. We might have gotten rubbish values from
2124 * pte_low and pte_high, but we are guaranteed that pte_low will not have the
2125 * present bit set *unless* it is 'l'. Because get_user_pages_fast() only
2126 * operates on present ptes we're safe.
2128 static inline pte_t gup_get_pte(pte_t *ptep)
2133 pte.pte_low = ptep->pte_low;
2135 pte.pte_high = ptep->pte_high;
2137 } while (unlikely(pte.pte_low != ptep->pte_low));
2141 #else /* CONFIG_GUP_GET_PTE_LOW_HIGH */
2143 * We require that the PTE can be read atomically.
2145 static inline pte_t gup_get_pte(pte_t *ptep)
2147 return READ_ONCE(*ptep);
2149 #endif /* CONFIG_GUP_GET_PTE_LOW_HIGH */
2151 static void __maybe_unused undo_dev_pagemap(int *nr, int nr_start,
2153 struct page **pages)
2155 while ((*nr) - nr_start) {
2156 struct page *page = pages[--(*nr)];
2158 ClearPageReferenced(page);
2159 if (flags & FOLL_PIN)
2160 unpin_user_page(page);
2166 #ifdef CONFIG_ARCH_HAS_PTE_SPECIAL
2167 static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
2168 unsigned int flags, struct page **pages, int *nr)
2170 struct dev_pagemap *pgmap = NULL;
2171 int nr_start = *nr, ret = 0;
2174 ptem = ptep = pte_offset_map(&pmd, addr);
2176 pte_t pte = gup_get_pte(ptep);
2177 struct page *head, *page;
2180 * Similar to the PMD case below, NUMA hinting must take slow
2181 * path using the pte_protnone check.
2183 if (pte_protnone(pte))
2186 if (!pte_access_permitted(pte, flags & FOLL_WRITE))
2189 if (pte_devmap(pte)) {
2190 if (unlikely(flags & FOLL_LONGTERM))
2193 pgmap = get_dev_pagemap(pte_pfn(pte), pgmap);
2194 if (unlikely(!pgmap)) {
2195 undo_dev_pagemap(nr, nr_start, flags, pages);
2198 } else if (pte_special(pte))
2201 VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
2202 page = pte_page(pte);
2204 head = try_grab_compound_head(page, 1, flags);
2208 if (unlikely(pte_val(pte) != pte_val(*ptep))) {
2209 put_compound_head(head, 1, flags);
2213 VM_BUG_ON_PAGE(compound_head(page) != head, page);
2216 * We need to make the page accessible if and only if we are
2217 * going to access its content (the FOLL_PIN case). Please
2218 * see Documentation/core-api/pin_user_pages.rst for
2221 if (flags & FOLL_PIN) {
2222 ret = arch_make_page_accessible(page);
2224 unpin_user_page(page);
2228 SetPageReferenced(page);
2232 } while (ptep++, addr += PAGE_SIZE, addr != end);
2238 put_dev_pagemap(pgmap);
2245 * If we can't determine whether or not a pte is special, then fail immediately
2246 * for ptes. Note, we can still pin HugeTLB and THP as these are guaranteed not
2249 * For a futex to be placed on a THP tail page, get_futex_key requires a
2250 * __get_user_pages_fast implementation that can pin pages. Thus it's still
2251 * useful to have gup_huge_pmd even if we can't operate on ptes.
2253 static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
2254 unsigned int flags, struct page **pages, int *nr)
2258 #endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */
2260 #if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
2261 static int __gup_device_huge(unsigned long pfn, unsigned long addr,
2262 unsigned long end, unsigned int flags,
2263 struct page **pages, int *nr)
2266 struct dev_pagemap *pgmap = NULL;
2269 struct page *page = pfn_to_page(pfn);
2271 pgmap = get_dev_pagemap(pfn, pgmap);
2272 if (unlikely(!pgmap)) {
2273 undo_dev_pagemap(nr, nr_start, flags, pages);
2276 SetPageReferenced(page);
2278 if (unlikely(!try_grab_page(page, flags))) {
2279 undo_dev_pagemap(nr, nr_start, flags, pages);
2284 } while (addr += PAGE_SIZE, addr != end);
2287 put_dev_pagemap(pgmap);
2291 static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
2292 unsigned long end, unsigned int flags,
2293 struct page **pages, int *nr)
2295 unsigned long fault_pfn;
2298 fault_pfn = pmd_pfn(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
2299 if (!__gup_device_huge(fault_pfn, addr, end, flags, pages, nr))
2302 if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
2303 undo_dev_pagemap(nr, nr_start, flags, pages);
2309 static int __gup_device_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
2310 unsigned long end, unsigned int flags,
2311 struct page **pages, int *nr)
2313 unsigned long fault_pfn;
2316 fault_pfn = pud_pfn(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
2317 if (!__gup_device_huge(fault_pfn, addr, end, flags, pages, nr))
2320 if (unlikely(pud_val(orig) != pud_val(*pudp))) {
2321 undo_dev_pagemap(nr, nr_start, flags, pages);
2327 static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
2328 unsigned long end, unsigned int flags,
2329 struct page **pages, int *nr)
2335 static int __gup_device_huge_pud(pud_t pud, pud_t *pudp, unsigned long addr,
2336 unsigned long end, unsigned int flags,
2337 struct page **pages, int *nr)
2344 static int record_subpages(struct page *page, unsigned long addr,
2345 unsigned long end, struct page **pages)
2349 for (nr = 0; addr != end; addr += PAGE_SIZE)
2350 pages[nr++] = page++;
2355 #ifdef CONFIG_ARCH_HAS_HUGEPD
2356 static unsigned long hugepte_addr_end(unsigned long addr, unsigned long end,
2359 unsigned long __boundary = (addr + sz) & ~(sz-1);
2360 return (__boundary - 1 < end - 1) ? __boundary : end;
2363 static int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr,
2364 unsigned long end, unsigned int flags,
2365 struct page **pages, int *nr)
2367 unsigned long pte_end;
2368 struct page *head, *page;
2372 pte_end = (addr + sz) & ~(sz-1);
2376 pte = READ_ONCE(*ptep);
2378 if (!pte_access_permitted(pte, flags & FOLL_WRITE))
2381 /* hugepages are never "special" */
2382 VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
2384 head = pte_page(pte);
2385 page = head + ((addr & (sz-1)) >> PAGE_SHIFT);
2386 refs = record_subpages(page, addr, end, pages + *nr);
2388 head = try_grab_compound_head(head, refs, flags);
2392 if (unlikely(pte_val(pte) != pte_val(*ptep))) {
2393 put_compound_head(head, refs, flags);
2398 SetPageReferenced(head);
2402 static int gup_huge_pd(hugepd_t hugepd, unsigned long addr,
2403 unsigned int pdshift, unsigned long end, unsigned int flags,
2404 struct page **pages, int *nr)
2407 unsigned long sz = 1UL << hugepd_shift(hugepd);
2410 ptep = hugepte_offset(hugepd, addr, pdshift);
2412 next = hugepte_addr_end(addr, end, sz);
2413 if (!gup_hugepte(ptep, sz, addr, end, flags, pages, nr))
2415 } while (ptep++, addr = next, addr != end);
2420 static inline int gup_huge_pd(hugepd_t hugepd, unsigned long addr,
2421 unsigned int pdshift, unsigned long end, unsigned int flags,
2422 struct page **pages, int *nr)
2426 #endif /* CONFIG_ARCH_HAS_HUGEPD */
2428 static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
2429 unsigned long end, unsigned int flags,
2430 struct page **pages, int *nr)
2432 struct page *head, *page;
2435 if (!pmd_access_permitted(orig, flags & FOLL_WRITE))
2438 if (pmd_devmap(orig)) {
2439 if (unlikely(flags & FOLL_LONGTERM))
2441 return __gup_device_huge_pmd(orig, pmdp, addr, end, flags,
2445 page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
2446 refs = record_subpages(page, addr, end, pages + *nr);
2448 head = try_grab_compound_head(pmd_page(orig), refs, flags);
2452 if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
2453 put_compound_head(head, refs, flags);
2458 SetPageReferenced(head);
2462 static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
2463 unsigned long end, unsigned int flags,
2464 struct page **pages, int *nr)
2466 struct page *head, *page;
2469 if (!pud_access_permitted(orig, flags & FOLL_WRITE))
2472 if (pud_devmap(orig)) {
2473 if (unlikely(flags & FOLL_LONGTERM))
2475 return __gup_device_huge_pud(orig, pudp, addr, end, flags,
2479 page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
2480 refs = record_subpages(page, addr, end, pages + *nr);
2482 head = try_grab_compound_head(pud_page(orig), refs, flags);
2486 if (unlikely(pud_val(orig) != pud_val(*pudp))) {
2487 put_compound_head(head, refs, flags);
2492 SetPageReferenced(head);
2496 static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
2497 unsigned long end, unsigned int flags,
2498 struct page **pages, int *nr)
2501 struct page *head, *page;
2503 if (!pgd_access_permitted(orig, flags & FOLL_WRITE))
2506 BUILD_BUG_ON(pgd_devmap(orig));
2508 page = pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT);
2509 refs = record_subpages(page, addr, end, pages + *nr);
2511 head = try_grab_compound_head(pgd_page(orig), refs, flags);
2515 if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) {
2516 put_compound_head(head, refs, flags);
2521 SetPageReferenced(head);
2525 static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
2526 unsigned int flags, struct page **pages, int *nr)
2531 pmdp = pmd_offset(&pud, addr);
2533 pmd_t pmd = READ_ONCE(*pmdp);
2535 next = pmd_addr_end(addr, end);
2536 if (!pmd_present(pmd))
2539 if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd) ||
2542 * NUMA hinting faults need to be handled in the GUP
2543 * slowpath for accounting purposes and so that they
2544 * can be serialised against THP migration.
2546 if (pmd_protnone(pmd))
2549 if (!gup_huge_pmd(pmd, pmdp, addr, next, flags,
2553 } else if (unlikely(is_hugepd(__hugepd(pmd_val(pmd))))) {
2555 * architecture have different format for hugetlbfs
2556 * pmd format and THP pmd format
2558 if (!gup_huge_pd(__hugepd(pmd_val(pmd)), addr,
2559 PMD_SHIFT, next, flags, pages, nr))
2561 } else if (!gup_pte_range(pmd, addr, next, flags, pages, nr))
2563 } while (pmdp++, addr = next, addr != end);
2568 static int gup_pud_range(p4d_t p4d, unsigned long addr, unsigned long end,
2569 unsigned int flags, struct page **pages, int *nr)
2574 pudp = pud_offset(&p4d, addr);
2576 pud_t pud = READ_ONCE(*pudp);
2578 next = pud_addr_end(addr, end);
2579 if (unlikely(!pud_present(pud)))
2581 if (unlikely(pud_huge(pud))) {
2582 if (!gup_huge_pud(pud, pudp, addr, next, flags,
2585 } else if (unlikely(is_hugepd(__hugepd(pud_val(pud))))) {
2586 if (!gup_huge_pd(__hugepd(pud_val(pud)), addr,
2587 PUD_SHIFT, next, flags, pages, nr))
2589 } else if (!gup_pmd_range(pud, addr, next, flags, pages, nr))
2591 } while (pudp++, addr = next, addr != end);
2596 static int gup_p4d_range(pgd_t pgd, unsigned long addr, unsigned long end,
2597 unsigned int flags, struct page **pages, int *nr)
2602 p4dp = p4d_offset(&pgd, addr);
2604 p4d_t p4d = READ_ONCE(*p4dp);
2606 next = p4d_addr_end(addr, end);
2609 BUILD_BUG_ON(p4d_huge(p4d));
2610 if (unlikely(is_hugepd(__hugepd(p4d_val(p4d))))) {
2611 if (!gup_huge_pd(__hugepd(p4d_val(p4d)), addr,
2612 P4D_SHIFT, next, flags, pages, nr))
2614 } else if (!gup_pud_range(p4d, addr, next, flags, pages, nr))
2616 } while (p4dp++, addr = next, addr != end);
2621 static void gup_pgd_range(unsigned long addr, unsigned long end,
2622 unsigned int flags, struct page **pages, int *nr)
2627 pgdp = pgd_offset(current->mm, addr);
2629 pgd_t pgd = READ_ONCE(*pgdp);
2631 next = pgd_addr_end(addr, end);
2634 if (unlikely(pgd_huge(pgd))) {
2635 if (!gup_huge_pgd(pgd, pgdp, addr, next, flags,
2638 } else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd))))) {
2639 if (!gup_huge_pd(__hugepd(pgd_val(pgd)), addr,
2640 PGDIR_SHIFT, next, flags, pages, nr))
2642 } else if (!gup_p4d_range(pgd, addr, next, flags, pages, nr))
2644 } while (pgdp++, addr = next, addr != end);
2647 static inline void gup_pgd_range(unsigned long addr, unsigned long end,
2648 unsigned int flags, struct page **pages, int *nr)
2651 #endif /* CONFIG_HAVE_FAST_GUP */
2653 #ifndef gup_fast_permitted
2655 * Check if it's allowed to use __get_user_pages_fast() for the range, or
2656 * we need to fall back to the slow version:
2658 static bool gup_fast_permitted(unsigned long start, unsigned long end)
2665 * Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to
2667 * Note a difference with get_user_pages_fast: this always returns the
2668 * number of pages pinned, 0 if no pages were pinned.
2670 * If the architecture does not support this function, simply return with no
2673 int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
2674 struct page **pages)
2676 unsigned long len, end;
2677 unsigned long flags;
2680 * Internally (within mm/gup.c), gup fast variants must set FOLL_GET,
2681 * because gup fast is always a "pin with a +1 page refcount" request.
2683 unsigned int gup_flags = FOLL_GET;
2686 gup_flags |= FOLL_WRITE;
2688 start = untagged_addr(start) & PAGE_MASK;
2689 len = (unsigned long) nr_pages << PAGE_SHIFT;
2694 if (unlikely(!access_ok((void __user *)start, len)))
2698 * Disable interrupts. We use the nested form as we can already have
2699 * interrupts disabled by get_futex_key.
2701 * With interrupts disabled, we block page table pages from being
2702 * freed from under us. See struct mmu_table_batch comments in
2703 * include/asm-generic/tlb.h for more details.
2705 * We do not adopt an rcu_read_lock(.) here as we also want to
2706 * block IPIs that come from THPs splitting.
2709 if (IS_ENABLED(CONFIG_HAVE_FAST_GUP) &&
2710 gup_fast_permitted(start, end)) {
2711 local_irq_save(flags);
2712 gup_pgd_range(start, end, gup_flags, pages, &nr_pinned);
2713 local_irq_restore(flags);
2718 EXPORT_SYMBOL_GPL(__get_user_pages_fast);
2720 static int __gup_longterm_unlocked(unsigned long start, int nr_pages,
2721 unsigned int gup_flags, struct page **pages)
2726 * FIXME: FOLL_LONGTERM does not work with
2727 * get_user_pages_unlocked() (see comments in that function)
2729 if (gup_flags & FOLL_LONGTERM) {
2730 down_read(¤t->mm->mmap_sem);
2731 ret = __gup_longterm_locked(current, current->mm,
2733 pages, NULL, gup_flags);
2734 up_read(¤t->mm->mmap_sem);
2736 ret = get_user_pages_unlocked(start, nr_pages,
2743 static int internal_get_user_pages_fast(unsigned long start, int nr_pages,
2744 unsigned int gup_flags,
2745 struct page **pages)
2747 unsigned long addr, len, end;
2748 int nr_pinned = 0, ret = 0;
2750 if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM |
2751 FOLL_FORCE | FOLL_PIN | FOLL_GET)))
2754 start = untagged_addr(start) & PAGE_MASK;
2756 len = (unsigned long) nr_pages << PAGE_SHIFT;
2761 if (unlikely(!access_ok((void __user *)start, len)))
2764 if (IS_ENABLED(CONFIG_HAVE_FAST_GUP) &&
2765 gup_fast_permitted(start, end)) {
2766 local_irq_disable();
2767 gup_pgd_range(addr, end, gup_flags, pages, &nr_pinned);
2772 if (nr_pinned < nr_pages) {
2773 /* Try to get the remaining pages with get_user_pages */
2774 start += nr_pinned << PAGE_SHIFT;
2777 ret = __gup_longterm_unlocked(start, nr_pages - nr_pinned,
2780 /* Have to be a bit careful with return values */
2781 if (nr_pinned > 0) {
2793 * get_user_pages_fast() - pin user pages in memory
2794 * @start: starting user address
2795 * @nr_pages: number of pages from start to pin
2796 * @gup_flags: flags modifying pin behaviour
2797 * @pages: array that receives pointers to the pages pinned.
2798 * Should be at least nr_pages long.
2800 * Attempt to pin user pages in memory without taking mm->mmap_sem.
2801 * If not successful, it will fall back to taking the lock and
2802 * calling get_user_pages().
2804 * Returns number of pages pinned. This may be fewer than the number requested.
2805 * If nr_pages is 0 or negative, returns 0. If no pages were pinned, returns
2808 int get_user_pages_fast(unsigned long start, int nr_pages,
2809 unsigned int gup_flags, struct page **pages)
2812 * FOLL_PIN must only be set internally by the pin_user_pages*() APIs,
2813 * never directly by the caller, so enforce that:
2815 if (WARN_ON_ONCE(gup_flags & FOLL_PIN))
2819 * The caller may or may not have explicitly set FOLL_GET; either way is
2820 * OK. However, internally (within mm/gup.c), gup fast variants must set
2821 * FOLL_GET, because gup fast is always a "pin with a +1 page refcount"
2824 gup_flags |= FOLL_GET;
2825 return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages);
2827 EXPORT_SYMBOL_GPL(get_user_pages_fast);
2830 * pin_user_pages_fast() - pin user pages in memory without taking locks
2832 * @start: starting user address
2833 * @nr_pages: number of pages from start to pin
2834 * @gup_flags: flags modifying pin behaviour
2835 * @pages: array that receives pointers to the pages pinned.
2836 * Should be at least nr_pages long.
2838 * Nearly the same as get_user_pages_fast(), except that FOLL_PIN is set. See
2839 * get_user_pages_fast() for documentation on the function arguments, because
2840 * the arguments here are identical.
2842 * FOLL_PIN means that the pages must be released via unpin_user_page(). Please
2843 * see Documentation/vm/pin_user_pages.rst for further details.
2845 * This is intended for Case 1 (DIO) in Documentation/vm/pin_user_pages.rst. It
2846 * is NOT intended for Case 2 (RDMA: long-term pins).
2848 int pin_user_pages_fast(unsigned long start, int nr_pages,
2849 unsigned int gup_flags, struct page **pages)
2851 /* FOLL_GET and FOLL_PIN are mutually exclusive. */
2852 if (WARN_ON_ONCE(gup_flags & FOLL_GET))
2855 gup_flags |= FOLL_PIN;
2856 return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages);
2858 EXPORT_SYMBOL_GPL(pin_user_pages_fast);
2861 * pin_user_pages_remote() - pin pages of a remote process (task != current)
2863 * @tsk: the task_struct to use for page fault accounting, or
2864 * NULL if faults are not to be recorded.
2865 * @mm: mm_struct of target mm
2866 * @start: starting user address
2867 * @nr_pages: number of pages from start to pin
2868 * @gup_flags: flags modifying lookup behaviour
2869 * @pages: array that receives pointers to the pages pinned.
2870 * Should be at least nr_pages long. Or NULL, if caller
2871 * only intends to ensure the pages are faulted in.
2872 * @vmas: array of pointers to vmas corresponding to each page.
2873 * Or NULL if the caller does not require them.
2874 * @locked: pointer to lock flag indicating whether lock is held and
2875 * subsequently whether VM_FAULT_RETRY functionality can be
2876 * utilised. Lock must initially be held.
2878 * Nearly the same as get_user_pages_remote(), except that FOLL_PIN is set. See
2879 * get_user_pages_remote() for documentation on the function arguments, because
2880 * the arguments here are identical.
2882 * FOLL_PIN means that the pages must be released via unpin_user_page(). Please
2883 * see Documentation/vm/pin_user_pages.rst for details.
2885 * This is intended for Case 1 (DIO) in Documentation/vm/pin_user_pages.rst. It
2886 * is NOT intended for Case 2 (RDMA: long-term pins).
2888 long pin_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
2889 unsigned long start, unsigned long nr_pages,
2890 unsigned int gup_flags, struct page **pages,
2891 struct vm_area_struct **vmas, int *locked)
2893 /* FOLL_GET and FOLL_PIN are mutually exclusive. */
2894 if (WARN_ON_ONCE(gup_flags & FOLL_GET))
2897 gup_flags |= FOLL_PIN;
2898 return __get_user_pages_remote(tsk, mm, start, nr_pages, gup_flags,
2899 pages, vmas, locked);
2901 EXPORT_SYMBOL(pin_user_pages_remote);
2904 * pin_user_pages() - pin user pages in memory for use by other devices
2906 * @start: starting user address
2907 * @nr_pages: number of pages from start to pin
2908 * @gup_flags: flags modifying lookup behaviour
2909 * @pages: array that receives pointers to the pages pinned.
2910 * Should be at least nr_pages long. Or NULL, if caller
2911 * only intends to ensure the pages are faulted in.
2912 * @vmas: array of pointers to vmas corresponding to each page.
2913 * Or NULL if the caller does not require them.
2915 * Nearly the same as get_user_pages(), except that FOLL_TOUCH is not set, and
2918 * FOLL_PIN means that the pages must be released via unpin_user_page(). Please
2919 * see Documentation/vm/pin_user_pages.rst for details.
2921 * This is intended for Case 1 (DIO) in Documentation/vm/pin_user_pages.rst. It
2922 * is NOT intended for Case 2 (RDMA: long-term pins).
2924 long pin_user_pages(unsigned long start, unsigned long nr_pages,
2925 unsigned int gup_flags, struct page **pages,
2926 struct vm_area_struct **vmas)
2928 /* FOLL_GET and FOLL_PIN are mutually exclusive. */
2929 if (WARN_ON_ONCE(gup_flags & FOLL_GET))
2932 gup_flags |= FOLL_PIN;
2933 return __gup_longterm_locked(current, current->mm, start, nr_pages,
2934 pages, vmas, gup_flags);
2936 EXPORT_SYMBOL(pin_user_pages);