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 if ((fault_flags
& FAULT_FLAG_KILLABLE
) &&
1222 fatal_signal_pending(current
))
1225 ret
= handle_mm_fault(vma
, address
, fault_flags
);
1226 major
|= ret
& VM_FAULT_MAJOR
;
1227 if (ret
& VM_FAULT_ERROR
) {
1228 int err
= vm_fault_to_errno(ret
, 0);
1235 if (ret
& VM_FAULT_RETRY
) {
1236 down_read(&mm
->mmap_sem
);
1238 fault_flags
|= FAULT_FLAG_TRIED
;
1250 EXPORT_SYMBOL_GPL(fixup_user_fault
);
1252 static __always_inline
long __get_user_pages_locked(struct task_struct
*tsk
,
1253 struct mm_struct
*mm
,
1254 unsigned long start
,
1255 unsigned long nr_pages
,
1256 struct page
**pages
,
1257 struct vm_area_struct
**vmas
,
1261 long ret
, pages_done
;
1265 /* if VM_FAULT_RETRY can be returned, vmas become invalid */
1267 /* check caller initialized locked */
1268 BUG_ON(*locked
!= 1);
1272 * FOLL_PIN and FOLL_GET are mutually exclusive. Traditional behavior
1273 * is to set FOLL_GET if the caller wants pages[] filled in (but has
1274 * carelessly failed to specify FOLL_GET), so keep doing that, but only
1275 * for FOLL_GET, not for the newer FOLL_PIN.
1277 * FOLL_PIN always expects pages to be non-null, but no need to assert
1278 * that here, as any failures will be obvious enough.
1280 if (pages
&& !(flags
& FOLL_PIN
))
1284 lock_dropped
= false;
1286 ret
= __get_user_pages(tsk
, mm
, start
, nr_pages
, flags
, pages
,
1289 /* VM_FAULT_RETRY couldn't trigger, bypass */
1292 /* VM_FAULT_RETRY cannot return errors */
1295 BUG_ON(ret
>= nr_pages
);
1306 * VM_FAULT_RETRY didn't trigger or it was a
1314 * VM_FAULT_RETRY triggered, so seek to the faulting offset.
1315 * For the prefault case (!pages) we only update counts.
1319 start
+= ret
<< PAGE_SHIFT
;
1320 lock_dropped
= true;
1324 * Repeat on the address that fired VM_FAULT_RETRY
1325 * with both FAULT_FLAG_ALLOW_RETRY and
1326 * FAULT_FLAG_TRIED. Note that GUP can be interrupted
1327 * by fatal signals, so we need to check it before we
1328 * start trying again otherwise it can loop forever.
1331 if (fatal_signal_pending(current
)) {
1333 pages_done
= -EINTR
;
1337 ret
= down_read_killable(&mm
->mmap_sem
);
1346 ret
= __get_user_pages(tsk
, mm
, start
, 1, flags
| FOLL_TRIED
,
1347 pages
, NULL
, locked
);
1349 /* Continue to retry until we succeeded */
1367 if (lock_dropped
&& *locked
) {
1369 * We must let the caller know we temporarily dropped the lock
1370 * and so the critical section protected by it was lost.
1372 up_read(&mm
->mmap_sem
);
1379 * populate_vma_page_range() - populate a range of pages in the vma.
1381 * @start: start address
1383 * @locked: whether the mmap_sem is still held
1385 * This takes care of mlocking the pages too if VM_LOCKED is set.
1387 * return 0 on success, negative error code on error.
1389 * vma->vm_mm->mmap_sem must be held.
1391 * If @locked is NULL, it may be held for read or write and will
1394 * If @locked is non-NULL, it must held for read only and may be
1395 * released. If it's released, *@locked will be set to 0.
1397 long populate_vma_page_range(struct vm_area_struct
*vma
,
1398 unsigned long start
, unsigned long end
, int *locked
)
1400 struct mm_struct
*mm
= vma
->vm_mm
;
1401 unsigned long nr_pages
= (end
- start
) / PAGE_SIZE
;
1404 VM_BUG_ON(start
& ~PAGE_MASK
);
1405 VM_BUG_ON(end
& ~PAGE_MASK
);
1406 VM_BUG_ON_VMA(start
< vma
->vm_start
, vma
);
1407 VM_BUG_ON_VMA(end
> vma
->vm_end
, vma
);
1408 VM_BUG_ON_MM(!rwsem_is_locked(&mm
->mmap_sem
), mm
);
1410 gup_flags
= FOLL_TOUCH
| FOLL_POPULATE
| FOLL_MLOCK
;
1411 if (vma
->vm_flags
& VM_LOCKONFAULT
)
1412 gup_flags
&= ~FOLL_POPULATE
;
1414 * We want to touch writable mappings with a write fault in order
1415 * to break COW, except for shared mappings because these don't COW
1416 * and we would not want to dirty them for nothing.
1418 if ((vma
->vm_flags
& (VM_WRITE
| VM_SHARED
)) == VM_WRITE
)
1419 gup_flags
|= FOLL_WRITE
;
1422 * We want mlock to succeed for regions that have any permissions
1423 * other than PROT_NONE.
1425 if (vma_is_accessible(vma
))
1426 gup_flags
|= FOLL_FORCE
;
1429 * We made sure addr is within a VMA, so the following will
1430 * not result in a stack expansion that recurses back here.
1432 return __get_user_pages(current
, mm
, start
, nr_pages
, gup_flags
,
1433 NULL
, NULL
, locked
);
1437 * __mm_populate - populate and/or mlock pages within a range of address space.
1439 * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
1440 * flags. VMAs must be already marked with the desired vm_flags, and
1441 * mmap_sem must not be held.
1443 int __mm_populate(unsigned long start
, unsigned long len
, int ignore_errors
)
1445 struct mm_struct
*mm
= current
->mm
;
1446 unsigned long end
, nstart
, nend
;
1447 struct vm_area_struct
*vma
= NULL
;
1453 for (nstart
= start
; nstart
< end
; nstart
= nend
) {
1455 * We want to fault in pages for [nstart; end) address range.
1456 * Find first corresponding VMA.
1460 down_read(&mm
->mmap_sem
);
1461 vma
= find_vma(mm
, nstart
);
1462 } else if (nstart
>= vma
->vm_end
)
1464 if (!vma
|| vma
->vm_start
>= end
)
1467 * Set [nstart; nend) to intersection of desired address
1468 * range with the first VMA. Also, skip undesirable VMA types.
1470 nend
= min(end
, vma
->vm_end
);
1471 if (vma
->vm_flags
& (VM_IO
| VM_PFNMAP
))
1473 if (nstart
< vma
->vm_start
)
1474 nstart
= vma
->vm_start
;
1476 * Now fault in a range of pages. populate_vma_page_range()
1477 * double checks the vma flags, so that it won't mlock pages
1478 * if the vma was already munlocked.
1480 ret
= populate_vma_page_range(vma
, nstart
, nend
, &locked
);
1482 if (ignore_errors
) {
1484 continue; /* continue at next VMA */
1488 nend
= nstart
+ ret
* PAGE_SIZE
;
1492 up_read(&mm
->mmap_sem
);
1493 return ret
; /* 0 or negative error code */
1497 * get_dump_page() - pin user page in memory while writing it to core dump
1498 * @addr: user address
1500 * Returns struct page pointer of user page pinned for dump,
1501 * to be freed afterwards by put_page().
1503 * Returns NULL on any kind of failure - a hole must then be inserted into
1504 * the corefile, to preserve alignment with its headers; and also returns
1505 * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
1506 * allowing a hole to be left in the corefile to save diskspace.
1508 * Called without mmap_sem, but after all other threads have been killed.
1510 #ifdef CONFIG_ELF_CORE
1511 struct page
*get_dump_page(unsigned long addr
)
1513 struct vm_area_struct
*vma
;
1516 if (__get_user_pages(current
, current
->mm
, addr
, 1,
1517 FOLL_FORCE
| FOLL_DUMP
| FOLL_GET
, &page
, &vma
,
1520 flush_cache_page(vma
, addr
, page_to_pfn(page
));
1523 #endif /* CONFIG_ELF_CORE */
1524 #else /* CONFIG_MMU */
1525 static long __get_user_pages_locked(struct task_struct
*tsk
,
1526 struct mm_struct
*mm
, unsigned long start
,
1527 unsigned long nr_pages
, struct page
**pages
,
1528 struct vm_area_struct
**vmas
, int *locked
,
1529 unsigned int foll_flags
)
1531 struct vm_area_struct
*vma
;
1532 unsigned long vm_flags
;
1535 /* calculate required read or write permissions.
1536 * If FOLL_FORCE is set, we only require the "MAY" flags.
1538 vm_flags
= (foll_flags
& FOLL_WRITE
) ?
1539 (VM_WRITE
| VM_MAYWRITE
) : (VM_READ
| VM_MAYREAD
);
1540 vm_flags
&= (foll_flags
& FOLL_FORCE
) ?
1541 (VM_MAYREAD
| VM_MAYWRITE
) : (VM_READ
| VM_WRITE
);
1543 for (i
= 0; i
< nr_pages
; i
++) {
1544 vma
= find_vma(mm
, start
);
1546 goto finish_or_fault
;
1548 /* protect what we can, including chardevs */
1549 if ((vma
->vm_flags
& (VM_IO
| VM_PFNMAP
)) ||
1550 !(vm_flags
& vma
->vm_flags
))
1551 goto finish_or_fault
;
1554 pages
[i
] = virt_to_page(start
);
1560 start
= (start
+ PAGE_SIZE
) & PAGE_MASK
;
1566 return i
? : -EFAULT
;
1568 #endif /* !CONFIG_MMU */
1570 #if defined(CONFIG_FS_DAX) || defined (CONFIG_CMA)
1571 static bool check_dax_vmas(struct vm_area_struct
**vmas
, long nr_pages
)
1574 struct vm_area_struct
*vma_prev
= NULL
;
1576 for (i
= 0; i
< nr_pages
; i
++) {
1577 struct vm_area_struct
*vma
= vmas
[i
];
1579 if (vma
== vma_prev
)
1584 if (vma_is_fsdax(vma
))
1591 static struct page
*new_non_cma_page(struct page
*page
, unsigned long private)
1594 * We want to make sure we allocate the new page from the same node
1595 * as the source page.
1597 int nid
= page_to_nid(page
);
1599 * Trying to allocate a page for migration. Ignore allocation
1600 * failure warnings. We don't force __GFP_THISNODE here because
1601 * this node here is the node where we have CMA reservation and
1602 * in some case these nodes will have really less non movable
1603 * allocation memory.
1605 gfp_t gfp_mask
= GFP_USER
| __GFP_NOWARN
;
1607 if (PageHighMem(page
))
1608 gfp_mask
|= __GFP_HIGHMEM
;
1610 #ifdef CONFIG_HUGETLB_PAGE
1611 if (PageHuge(page
)) {
1612 struct hstate
*h
= page_hstate(page
);
1614 * We don't want to dequeue from the pool because pool pages will
1615 * mostly be from the CMA region.
1617 return alloc_migrate_huge_page(h
, gfp_mask
, nid
, NULL
);
1620 if (PageTransHuge(page
)) {
1623 * ignore allocation failure warnings
1625 gfp_t thp_gfpmask
= GFP_TRANSHUGE
| __GFP_NOWARN
;
1628 * Remove the movable mask so that we don't allocate from
1631 thp_gfpmask
&= ~__GFP_MOVABLE
;
1632 thp
= __alloc_pages_node(nid
, thp_gfpmask
, HPAGE_PMD_ORDER
);
1635 prep_transhuge_page(thp
);
1639 return __alloc_pages_node(nid
, gfp_mask
, 0);
1642 static long check_and_migrate_cma_pages(struct task_struct
*tsk
,
1643 struct mm_struct
*mm
,
1644 unsigned long start
,
1645 unsigned long nr_pages
,
1646 struct page
**pages
,
1647 struct vm_area_struct
**vmas
,
1648 unsigned int gup_flags
)
1652 bool drain_allow
= true;
1653 bool migrate_allow
= true;
1654 LIST_HEAD(cma_page_list
);
1655 long ret
= nr_pages
;
1658 for (i
= 0; i
< nr_pages
;) {
1660 struct page
*head
= compound_head(pages
[i
]);
1663 * gup may start from a tail page. Advance step by the left
1666 step
= compound_nr(head
) - (pages
[i
] - head
);
1668 * If we get a page from the CMA zone, since we are going to
1669 * be pinning these entries, we might as well move them out
1670 * of the CMA zone if possible.
1672 if (is_migrate_cma_page(head
)) {
1674 isolate_huge_page(head
, &cma_page_list
);
1676 if (!PageLRU(head
) && drain_allow
) {
1677 lru_add_drain_all();
1678 drain_allow
= false;
1681 if (!isolate_lru_page(head
)) {
1682 list_add_tail(&head
->lru
, &cma_page_list
);
1683 mod_node_page_state(page_pgdat(head
),
1685 page_is_file_lru(head
),
1686 hpage_nr_pages(head
));
1694 if (!list_empty(&cma_page_list
)) {
1696 * drop the above get_user_pages reference.
1698 for (i
= 0; i
< nr_pages
; i
++)
1701 if (migrate_pages(&cma_page_list
, new_non_cma_page
,
1702 NULL
, 0, MIGRATE_SYNC
, MR_CONTIG_RANGE
)) {
1704 * some of the pages failed migration. Do get_user_pages
1705 * without migration.
1707 migrate_allow
= false;
1709 if (!list_empty(&cma_page_list
))
1710 putback_movable_pages(&cma_page_list
);
1713 * We did migrate all the pages, Try to get the page references
1714 * again migrating any new CMA pages which we failed to isolate
1717 ret
= __get_user_pages_locked(tsk
, mm
, start
, nr_pages
,
1721 if ((ret
> 0) && migrate_allow
) {
1731 static long check_and_migrate_cma_pages(struct task_struct
*tsk
,
1732 struct mm_struct
*mm
,
1733 unsigned long start
,
1734 unsigned long nr_pages
,
1735 struct page
**pages
,
1736 struct vm_area_struct
**vmas
,
1737 unsigned int gup_flags
)
1741 #endif /* CONFIG_CMA */
1744 * __gup_longterm_locked() is a wrapper for __get_user_pages_locked which
1745 * allows us to process the FOLL_LONGTERM flag.
1747 static long __gup_longterm_locked(struct task_struct
*tsk
,
1748 struct mm_struct
*mm
,
1749 unsigned long start
,
1750 unsigned long nr_pages
,
1751 struct page
**pages
,
1752 struct vm_area_struct
**vmas
,
1753 unsigned int gup_flags
)
1755 struct vm_area_struct
**vmas_tmp
= vmas
;
1756 unsigned long flags
= 0;
1759 if (gup_flags
& FOLL_LONGTERM
) {
1764 vmas_tmp
= kcalloc(nr_pages
,
1765 sizeof(struct vm_area_struct
*),
1770 flags
= memalloc_nocma_save();
1773 rc
= __get_user_pages_locked(tsk
, mm
, start
, nr_pages
, pages
,
1774 vmas_tmp
, NULL
, gup_flags
);
1776 if (gup_flags
& FOLL_LONGTERM
) {
1777 memalloc_nocma_restore(flags
);
1781 if (check_dax_vmas(vmas_tmp
, rc
)) {
1782 for (i
= 0; i
< rc
; i
++)
1788 rc
= check_and_migrate_cma_pages(tsk
, mm
, start
, rc
, pages
,
1789 vmas_tmp
, gup_flags
);
1793 if (vmas_tmp
!= vmas
)
1797 #else /* !CONFIG_FS_DAX && !CONFIG_CMA */
1798 static __always_inline
long __gup_longterm_locked(struct task_struct
*tsk
,
1799 struct mm_struct
*mm
,
1800 unsigned long start
,
1801 unsigned long nr_pages
,
1802 struct page
**pages
,
1803 struct vm_area_struct
**vmas
,
1806 return __get_user_pages_locked(tsk
, mm
, start
, nr_pages
, pages
, vmas
,
1809 #endif /* CONFIG_FS_DAX || CONFIG_CMA */
1812 static long __get_user_pages_remote(struct task_struct
*tsk
,
1813 struct mm_struct
*mm
,
1814 unsigned long start
, unsigned long nr_pages
,
1815 unsigned int gup_flags
, struct page
**pages
,
1816 struct vm_area_struct
**vmas
, int *locked
)
1819 * Parts of FOLL_LONGTERM behavior are incompatible with
1820 * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
1821 * vmas. However, this only comes up if locked is set, and there are
1822 * callers that do request FOLL_LONGTERM, but do not set locked. So,
1823 * allow what we can.
1825 if (gup_flags
& FOLL_LONGTERM
) {
1826 if (WARN_ON_ONCE(locked
))
1829 * This will check the vmas (even if our vmas arg is NULL)
1830 * and return -ENOTSUPP if DAX isn't allowed in this case:
1832 return __gup_longterm_locked(tsk
, mm
, start
, nr_pages
, pages
,
1833 vmas
, gup_flags
| FOLL_TOUCH
|
1837 return __get_user_pages_locked(tsk
, mm
, start
, nr_pages
, pages
, vmas
,
1839 gup_flags
| FOLL_TOUCH
| FOLL_REMOTE
);
1843 * get_user_pages_remote() - pin user pages in memory
1844 * @tsk: the task_struct to use for page fault accounting, or
1845 * NULL if faults are not to be recorded.
1846 * @mm: mm_struct of target mm
1847 * @start: starting user address
1848 * @nr_pages: number of pages from start to pin
1849 * @gup_flags: flags modifying lookup behaviour
1850 * @pages: array that receives pointers to the pages pinned.
1851 * Should be at least nr_pages long. Or NULL, if caller
1852 * only intends to ensure the pages are faulted in.
1853 * @vmas: array of pointers to vmas corresponding to each page.
1854 * Or NULL if the caller does not require them.
1855 * @locked: pointer to lock flag indicating whether lock is held and
1856 * subsequently whether VM_FAULT_RETRY functionality can be
1857 * utilised. Lock must initially be held.
1859 * Returns either number of pages pinned (which may be less than the
1860 * number requested), or an error. Details about the return value:
1862 * -- If nr_pages is 0, returns 0.
1863 * -- If nr_pages is >0, but no pages were pinned, returns -errno.
1864 * -- If nr_pages is >0, and some pages were pinned, returns the number of
1865 * pages pinned. Again, this may be less than nr_pages.
1867 * The caller is responsible for releasing returned @pages, via put_page().
1869 * @vmas are valid only as long as mmap_sem is held.
1871 * Must be called with mmap_sem held for read or write.
1873 * get_user_pages walks a process's page tables and takes a reference to
1874 * each struct page that each user address corresponds to at a given
1875 * instant. That is, it takes the page that would be accessed if a user
1876 * thread accesses the given user virtual address at that instant.
1878 * This does not guarantee that the page exists in the user mappings when
1879 * get_user_pages returns, and there may even be a completely different
1880 * page there in some cases (eg. if mmapped pagecache has been invalidated
1881 * and subsequently re faulted). However it does guarantee that the page
1882 * won't be freed completely. And mostly callers simply care that the page
1883 * contains data that was valid *at some point in time*. Typically, an IO
1884 * or similar operation cannot guarantee anything stronger anyway because
1885 * locks can't be held over the syscall boundary.
1887 * If gup_flags & FOLL_WRITE == 0, the page must not be written to. If the page
1888 * is written to, set_page_dirty (or set_page_dirty_lock, as appropriate) must
1889 * be called after the page is finished with, and before put_page is called.
1891 * get_user_pages is typically used for fewer-copy IO operations, to get a
1892 * handle on the memory by some means other than accesses via the user virtual
1893 * addresses. The pages may be submitted for DMA to devices or accessed via
1894 * their kernel linear mapping (via the kmap APIs). Care should be taken to
1895 * use the correct cache flushing APIs.
1897 * See also get_user_pages_fast, for performance critical applications.
1899 * get_user_pages should be phased out in favor of
1900 * get_user_pages_locked|unlocked or get_user_pages_fast. Nothing
1901 * should use get_user_pages because it cannot pass
1902 * FAULT_FLAG_ALLOW_RETRY to handle_mm_fault.
1904 long get_user_pages_remote(struct task_struct
*tsk
, struct mm_struct
*mm
,
1905 unsigned long start
, unsigned long nr_pages
,
1906 unsigned int gup_flags
, struct page
**pages
,
1907 struct vm_area_struct
**vmas
, int *locked
)
1910 * FOLL_PIN must only be set internally by the pin_user_pages*() APIs,
1911 * never directly by the caller, so enforce that with an assertion:
1913 if (WARN_ON_ONCE(gup_flags
& FOLL_PIN
))
1916 return __get_user_pages_remote(tsk
, mm
, start
, nr_pages
, gup_flags
,
1917 pages
, vmas
, locked
);
1919 EXPORT_SYMBOL(get_user_pages_remote
);
1921 #else /* CONFIG_MMU */
1922 long get_user_pages_remote(struct task_struct
*tsk
, struct mm_struct
*mm
,
1923 unsigned long start
, unsigned long nr_pages
,
1924 unsigned int gup_flags
, struct page
**pages
,
1925 struct vm_area_struct
**vmas
, int *locked
)
1930 static long __get_user_pages_remote(struct task_struct
*tsk
,
1931 struct mm_struct
*mm
,
1932 unsigned long start
, unsigned long nr_pages
,
1933 unsigned int gup_flags
, struct page
**pages
,
1934 struct vm_area_struct
**vmas
, int *locked
)
1938 #endif /* !CONFIG_MMU */
1941 * This is the same as get_user_pages_remote(), just with a
1942 * less-flexible calling convention where we assume that the task
1943 * and mm being operated on are the current task's and don't allow
1944 * passing of a locked parameter. We also obviously don't pass
1945 * FOLL_REMOTE in here.
1947 long get_user_pages(unsigned long start
, unsigned long nr_pages
,
1948 unsigned int gup_flags
, struct page
**pages
,
1949 struct vm_area_struct
**vmas
)
1952 * FOLL_PIN must only be set internally by the pin_user_pages*() APIs,
1953 * never directly by the caller, so enforce that with an assertion:
1955 if (WARN_ON_ONCE(gup_flags
& FOLL_PIN
))
1958 return __gup_longterm_locked(current
, current
->mm
, start
, nr_pages
,
1959 pages
, vmas
, gup_flags
| FOLL_TOUCH
);
1961 EXPORT_SYMBOL(get_user_pages
);
1964 * We can leverage the VM_FAULT_RETRY functionality in the page fault
1965 * paths better by using either get_user_pages_locked() or
1966 * get_user_pages_unlocked().
1968 * get_user_pages_locked() is suitable to replace the form:
1970 * down_read(&mm->mmap_sem);
1972 * get_user_pages(tsk, mm, ..., pages, NULL);
1973 * up_read(&mm->mmap_sem);
1978 * down_read(&mm->mmap_sem);
1980 * get_user_pages_locked(tsk, mm, ..., pages, &locked);
1982 * up_read(&mm->mmap_sem);
1984 long get_user_pages_locked(unsigned long start
, unsigned long nr_pages
,
1985 unsigned int gup_flags
, struct page
**pages
,
1989 * FIXME: Current FOLL_LONGTERM behavior is incompatible with
1990 * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
1991 * vmas. As there are no users of this flag in this call we simply
1992 * disallow this option for now.
1994 if (WARN_ON_ONCE(gup_flags
& FOLL_LONGTERM
))
1997 return __get_user_pages_locked(current
, current
->mm
, start
, nr_pages
,
1998 pages
, NULL
, locked
,
1999 gup_flags
| FOLL_TOUCH
);
2001 EXPORT_SYMBOL(get_user_pages_locked
);
2004 * get_user_pages_unlocked() is suitable to replace the form:
2006 * down_read(&mm->mmap_sem);
2007 * get_user_pages(tsk, mm, ..., pages, NULL);
2008 * up_read(&mm->mmap_sem);
2012 * get_user_pages_unlocked(tsk, mm, ..., pages);
2014 * It is functionally equivalent to get_user_pages_fast so
2015 * get_user_pages_fast should be used instead if specific gup_flags
2016 * (e.g. FOLL_FORCE) are not required.
2018 long get_user_pages_unlocked(unsigned long start
, unsigned long nr_pages
,
2019 struct page
**pages
, unsigned int gup_flags
)
2021 struct mm_struct
*mm
= current
->mm
;
2026 * FIXME: Current FOLL_LONGTERM behavior is incompatible with
2027 * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
2028 * vmas. As there are no users of this flag in this call we simply
2029 * disallow this option for now.
2031 if (WARN_ON_ONCE(gup_flags
& FOLL_LONGTERM
))
2034 down_read(&mm
->mmap_sem
);
2035 ret
= __get_user_pages_locked(current
, mm
, start
, nr_pages
, pages
, NULL
,
2036 &locked
, gup_flags
| FOLL_TOUCH
);
2038 up_read(&mm
->mmap_sem
);
2041 EXPORT_SYMBOL(get_user_pages_unlocked
);
2046 * get_user_pages_fast attempts to pin user pages by walking the page
2047 * tables directly and avoids taking locks. Thus the walker needs to be
2048 * protected from page table pages being freed from under it, and should
2049 * block any THP splits.
2051 * One way to achieve this is to have the walker disable interrupts, and
2052 * rely on IPIs from the TLB flushing code blocking before the page table
2053 * pages are freed. This is unsuitable for architectures that do not need
2054 * to broadcast an IPI when invalidating TLBs.
2056 * Another way to achieve this is to batch up page table containing pages
2057 * belonging to more than one mm_user, then rcu_sched a callback to free those
2058 * pages. Disabling interrupts will allow the fast_gup walker to both block
2059 * the rcu_sched callback, and an IPI that we broadcast for splitting THPs
2060 * (which is a relatively rare event). The code below adopts this strategy.
2062 * Before activating this code, please be aware that the following assumptions
2063 * are currently made:
2065 * *) Either MMU_GATHER_RCU_TABLE_FREE is enabled, and tlb_remove_table() is used to
2066 * free pages containing page tables or TLB flushing requires IPI broadcast.
2068 * *) ptes can be read atomically by the architecture.
2070 * *) access_ok is sufficient to validate userspace address ranges.
2072 * The last two assumptions can be relaxed by the addition of helper functions.
2074 * This code is based heavily on the PowerPC implementation by Nick Piggin.
2076 #ifdef CONFIG_HAVE_FAST_GUP
2078 static void put_compound_head(struct page
*page
, int refs
, unsigned int flags
)
2080 if (flags
& FOLL_PIN
) {
2081 mod_node_page_state(page_pgdat(page
), NR_FOLL_PIN_RELEASED
,
2084 if (hpage_pincount_available(page
))
2085 hpage_pincount_sub(page
, refs
);
2087 refs
*= GUP_PIN_COUNTING_BIAS
;
2090 VM_BUG_ON_PAGE(page_ref_count(page
) < refs
, page
);
2092 * Calling put_page() for each ref is unnecessarily slow. Only the last
2093 * ref needs a put_page().
2096 page_ref_sub(page
, refs
- 1);
2100 #ifdef CONFIG_GUP_GET_PTE_LOW_HIGH
2103 * WARNING: only to be used in the get_user_pages_fast() implementation.
2105 * With get_user_pages_fast(), we walk down the pagetables without taking any
2106 * locks. For this we would like to load the pointers atomically, but sometimes
2107 * that is not possible (e.g. without expensive cmpxchg8b on x86_32 PAE). What
2108 * we do have is the guarantee that a PTE will only either go from not present
2109 * to present, or present to not present or both -- it will not switch to a
2110 * completely different present page without a TLB flush in between; something
2111 * that we are blocking by holding interrupts off.
2113 * Setting ptes from not present to present goes:
2115 * ptep->pte_high = h;
2117 * ptep->pte_low = l;
2119 * And present to not present goes:
2121 * ptep->pte_low = 0;
2123 * ptep->pte_high = 0;
2125 * We must ensure here that the load of pte_low sees 'l' IFF pte_high sees 'h'.
2126 * We load pte_high *after* loading pte_low, which ensures we don't see an older
2127 * value of pte_high. *Then* we recheck pte_low, which ensures that we haven't
2128 * picked up a changed pte high. We might have gotten rubbish values from
2129 * pte_low and pte_high, but we are guaranteed that pte_low will not have the
2130 * present bit set *unless* it is 'l'. Because get_user_pages_fast() only
2131 * operates on present ptes we're safe.
2133 static inline pte_t
gup_get_pte(pte_t
*ptep
)
2138 pte
.pte_low
= ptep
->pte_low
;
2140 pte
.pte_high
= ptep
->pte_high
;
2142 } while (unlikely(pte
.pte_low
!= ptep
->pte_low
));
2146 #else /* CONFIG_GUP_GET_PTE_LOW_HIGH */
2148 * We require that the PTE can be read atomically.
2150 static inline pte_t
gup_get_pte(pte_t
*ptep
)
2152 return READ_ONCE(*ptep
);
2154 #endif /* CONFIG_GUP_GET_PTE_LOW_HIGH */
2156 static void __maybe_unused
undo_dev_pagemap(int *nr
, int nr_start
,
2158 struct page
**pages
)
2160 while ((*nr
) - nr_start
) {
2161 struct page
*page
= pages
[--(*nr
)];
2163 ClearPageReferenced(page
);
2164 if (flags
& FOLL_PIN
)
2165 unpin_user_page(page
);
2171 #ifdef CONFIG_ARCH_HAS_PTE_SPECIAL
2172 static int gup_pte_range(pmd_t pmd
, unsigned long addr
, unsigned long end
,
2173 unsigned int flags
, struct page
**pages
, int *nr
)
2175 struct dev_pagemap
*pgmap
= NULL
;
2176 int nr_start
= *nr
, ret
= 0;
2179 ptem
= ptep
= pte_offset_map(&pmd
, addr
);
2181 pte_t pte
= gup_get_pte(ptep
);
2182 struct page
*head
, *page
;
2185 * Similar to the PMD case below, NUMA hinting must take slow
2186 * path using the pte_protnone check.
2188 if (pte_protnone(pte
))
2191 if (!pte_access_permitted(pte
, flags
& FOLL_WRITE
))
2194 if (pte_devmap(pte
)) {
2195 if (unlikely(flags
& FOLL_LONGTERM
))
2198 pgmap
= get_dev_pagemap(pte_pfn(pte
), pgmap
);
2199 if (unlikely(!pgmap
)) {
2200 undo_dev_pagemap(nr
, nr_start
, flags
, pages
);
2203 } else if (pte_special(pte
))
2206 VM_BUG_ON(!pfn_valid(pte_pfn(pte
)));
2207 page
= pte_page(pte
);
2209 head
= try_grab_compound_head(page
, 1, flags
);
2213 if (unlikely(pte_val(pte
) != pte_val(*ptep
))) {
2214 put_compound_head(head
, 1, flags
);
2218 VM_BUG_ON_PAGE(compound_head(page
) != head
, page
);
2221 * We need to make the page accessible if and only if we are
2222 * going to access its content (the FOLL_PIN case). Please
2223 * see Documentation/core-api/pin_user_pages.rst for
2226 if (flags
& FOLL_PIN
) {
2227 ret
= arch_make_page_accessible(page
);
2229 unpin_user_page(page
);
2233 SetPageReferenced(page
);
2237 } while (ptep
++, addr
+= PAGE_SIZE
, addr
!= end
);
2243 put_dev_pagemap(pgmap
);
2250 * If we can't determine whether or not a pte is special, then fail immediately
2251 * for ptes. Note, we can still pin HugeTLB and THP as these are guaranteed not
2254 * For a futex to be placed on a THP tail page, get_futex_key requires a
2255 * __get_user_pages_fast implementation that can pin pages. Thus it's still
2256 * useful to have gup_huge_pmd even if we can't operate on ptes.
2258 static int gup_pte_range(pmd_t pmd
, unsigned long addr
, unsigned long end
,
2259 unsigned int flags
, struct page
**pages
, int *nr
)
2263 #endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */
2265 #if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
2266 static int __gup_device_huge(unsigned long pfn
, unsigned long addr
,
2267 unsigned long end
, unsigned int flags
,
2268 struct page
**pages
, int *nr
)
2271 struct dev_pagemap
*pgmap
= NULL
;
2274 struct page
*page
= pfn_to_page(pfn
);
2276 pgmap
= get_dev_pagemap(pfn
, pgmap
);
2277 if (unlikely(!pgmap
)) {
2278 undo_dev_pagemap(nr
, nr_start
, flags
, pages
);
2281 SetPageReferenced(page
);
2283 if (unlikely(!try_grab_page(page
, flags
))) {
2284 undo_dev_pagemap(nr
, nr_start
, flags
, pages
);
2289 } while (addr
+= PAGE_SIZE
, addr
!= end
);
2292 put_dev_pagemap(pgmap
);
2296 static int __gup_device_huge_pmd(pmd_t orig
, pmd_t
*pmdp
, unsigned long addr
,
2297 unsigned long end
, unsigned int flags
,
2298 struct page
**pages
, int *nr
)
2300 unsigned long fault_pfn
;
2303 fault_pfn
= pmd_pfn(orig
) + ((addr
& ~PMD_MASK
) >> PAGE_SHIFT
);
2304 if (!__gup_device_huge(fault_pfn
, addr
, end
, flags
, pages
, nr
))
2307 if (unlikely(pmd_val(orig
) != pmd_val(*pmdp
))) {
2308 undo_dev_pagemap(nr
, nr_start
, flags
, pages
);
2314 static int __gup_device_huge_pud(pud_t orig
, pud_t
*pudp
, unsigned long addr
,
2315 unsigned long end
, unsigned int flags
,
2316 struct page
**pages
, int *nr
)
2318 unsigned long fault_pfn
;
2321 fault_pfn
= pud_pfn(orig
) + ((addr
& ~PUD_MASK
) >> PAGE_SHIFT
);
2322 if (!__gup_device_huge(fault_pfn
, addr
, end
, flags
, pages
, nr
))
2325 if (unlikely(pud_val(orig
) != pud_val(*pudp
))) {
2326 undo_dev_pagemap(nr
, nr_start
, flags
, pages
);
2332 static int __gup_device_huge_pmd(pmd_t orig
, pmd_t
*pmdp
, unsigned long addr
,
2333 unsigned long end
, unsigned int flags
,
2334 struct page
**pages
, int *nr
)
2340 static int __gup_device_huge_pud(pud_t pud
, pud_t
*pudp
, unsigned long addr
,
2341 unsigned long end
, unsigned int flags
,
2342 struct page
**pages
, int *nr
)
2349 static int record_subpages(struct page
*page
, unsigned long addr
,
2350 unsigned long end
, struct page
**pages
)
2354 for (nr
= 0; addr
!= end
; addr
+= PAGE_SIZE
)
2355 pages
[nr
++] = page
++;
2360 #ifdef CONFIG_ARCH_HAS_HUGEPD
2361 static unsigned long hugepte_addr_end(unsigned long addr
, unsigned long end
,
2364 unsigned long __boundary
= (addr
+ sz
) & ~(sz
-1);
2365 return (__boundary
- 1 < end
- 1) ? __boundary
: end
;
2368 static int gup_hugepte(pte_t
*ptep
, unsigned long sz
, unsigned long addr
,
2369 unsigned long end
, unsigned int flags
,
2370 struct page
**pages
, int *nr
)
2372 unsigned long pte_end
;
2373 struct page
*head
, *page
;
2377 pte_end
= (addr
+ sz
) & ~(sz
-1);
2381 pte
= READ_ONCE(*ptep
);
2383 if (!pte_access_permitted(pte
, flags
& FOLL_WRITE
))
2386 /* hugepages are never "special" */
2387 VM_BUG_ON(!pfn_valid(pte_pfn(pte
)));
2389 head
= pte_page(pte
);
2390 page
= head
+ ((addr
& (sz
-1)) >> PAGE_SHIFT
);
2391 refs
= record_subpages(page
, addr
, end
, pages
+ *nr
);
2393 head
= try_grab_compound_head(head
, refs
, flags
);
2397 if (unlikely(pte_val(pte
) != pte_val(*ptep
))) {
2398 put_compound_head(head
, refs
, flags
);
2403 SetPageReferenced(head
);
2407 static int gup_huge_pd(hugepd_t hugepd
, unsigned long addr
,
2408 unsigned int pdshift
, unsigned long end
, unsigned int flags
,
2409 struct page
**pages
, int *nr
)
2412 unsigned long sz
= 1UL << hugepd_shift(hugepd
);
2415 ptep
= hugepte_offset(hugepd
, addr
, pdshift
);
2417 next
= hugepte_addr_end(addr
, end
, sz
);
2418 if (!gup_hugepte(ptep
, sz
, addr
, end
, flags
, pages
, nr
))
2420 } while (ptep
++, addr
= next
, addr
!= end
);
2425 static inline int gup_huge_pd(hugepd_t hugepd
, unsigned long addr
,
2426 unsigned int pdshift
, unsigned long end
, unsigned int flags
,
2427 struct page
**pages
, int *nr
)
2431 #endif /* CONFIG_ARCH_HAS_HUGEPD */
2433 static int gup_huge_pmd(pmd_t orig
, pmd_t
*pmdp
, unsigned long addr
,
2434 unsigned long end
, unsigned int flags
,
2435 struct page
**pages
, int *nr
)
2437 struct page
*head
, *page
;
2440 if (!pmd_access_permitted(orig
, flags
& FOLL_WRITE
))
2443 if (pmd_devmap(orig
)) {
2444 if (unlikely(flags
& FOLL_LONGTERM
))
2446 return __gup_device_huge_pmd(orig
, pmdp
, addr
, end
, flags
,
2450 page
= pmd_page(orig
) + ((addr
& ~PMD_MASK
) >> PAGE_SHIFT
);
2451 refs
= record_subpages(page
, addr
, end
, pages
+ *nr
);
2453 head
= try_grab_compound_head(pmd_page(orig
), refs
, flags
);
2457 if (unlikely(pmd_val(orig
) != pmd_val(*pmdp
))) {
2458 put_compound_head(head
, refs
, flags
);
2463 SetPageReferenced(head
);
2467 static int gup_huge_pud(pud_t orig
, pud_t
*pudp
, unsigned long addr
,
2468 unsigned long end
, unsigned int flags
,
2469 struct page
**pages
, int *nr
)
2471 struct page
*head
, *page
;
2474 if (!pud_access_permitted(orig
, flags
& FOLL_WRITE
))
2477 if (pud_devmap(orig
)) {
2478 if (unlikely(flags
& FOLL_LONGTERM
))
2480 return __gup_device_huge_pud(orig
, pudp
, addr
, end
, flags
,
2484 page
= pud_page(orig
) + ((addr
& ~PUD_MASK
) >> PAGE_SHIFT
);
2485 refs
= record_subpages(page
, addr
, end
, pages
+ *nr
);
2487 head
= try_grab_compound_head(pud_page(orig
), refs
, flags
);
2491 if (unlikely(pud_val(orig
) != pud_val(*pudp
))) {
2492 put_compound_head(head
, refs
, flags
);
2497 SetPageReferenced(head
);
2501 static int gup_huge_pgd(pgd_t orig
, pgd_t
*pgdp
, unsigned long addr
,
2502 unsigned long end
, unsigned int flags
,
2503 struct page
**pages
, int *nr
)
2506 struct page
*head
, *page
;
2508 if (!pgd_access_permitted(orig
, flags
& FOLL_WRITE
))
2511 BUILD_BUG_ON(pgd_devmap(orig
));
2513 page
= pgd_page(orig
) + ((addr
& ~PGDIR_MASK
) >> PAGE_SHIFT
);
2514 refs
= record_subpages(page
, addr
, end
, pages
+ *nr
);
2516 head
= try_grab_compound_head(pgd_page(orig
), refs
, flags
);
2520 if (unlikely(pgd_val(orig
) != pgd_val(*pgdp
))) {
2521 put_compound_head(head
, refs
, flags
);
2526 SetPageReferenced(head
);
2530 static int gup_pmd_range(pud_t pud
, unsigned long addr
, unsigned long end
,
2531 unsigned int flags
, struct page
**pages
, int *nr
)
2536 pmdp
= pmd_offset(&pud
, addr
);
2538 pmd_t pmd
= READ_ONCE(*pmdp
);
2540 next
= pmd_addr_end(addr
, end
);
2541 if (!pmd_present(pmd
))
2544 if (unlikely(pmd_trans_huge(pmd
) || pmd_huge(pmd
) ||
2547 * NUMA hinting faults need to be handled in the GUP
2548 * slowpath for accounting purposes and so that they
2549 * can be serialised against THP migration.
2551 if (pmd_protnone(pmd
))
2554 if (!gup_huge_pmd(pmd
, pmdp
, addr
, next
, flags
,
2558 } else if (unlikely(is_hugepd(__hugepd(pmd_val(pmd
))))) {
2560 * architecture have different format for hugetlbfs
2561 * pmd format and THP pmd format
2563 if (!gup_huge_pd(__hugepd(pmd_val(pmd
)), addr
,
2564 PMD_SHIFT
, next
, flags
, pages
, nr
))
2566 } else if (!gup_pte_range(pmd
, addr
, next
, flags
, pages
, nr
))
2568 } while (pmdp
++, addr
= next
, addr
!= end
);
2573 static int gup_pud_range(p4d_t p4d
, unsigned long addr
, unsigned long end
,
2574 unsigned int flags
, struct page
**pages
, int *nr
)
2579 pudp
= pud_offset(&p4d
, addr
);
2581 pud_t pud
= READ_ONCE(*pudp
);
2583 next
= pud_addr_end(addr
, end
);
2584 if (unlikely(!pud_present(pud
)))
2586 if (unlikely(pud_huge(pud
))) {
2587 if (!gup_huge_pud(pud
, pudp
, addr
, next
, flags
,
2590 } else if (unlikely(is_hugepd(__hugepd(pud_val(pud
))))) {
2591 if (!gup_huge_pd(__hugepd(pud_val(pud
)), addr
,
2592 PUD_SHIFT
, next
, flags
, pages
, nr
))
2594 } else if (!gup_pmd_range(pud
, addr
, next
, flags
, pages
, nr
))
2596 } while (pudp
++, addr
= next
, addr
!= end
);
2601 static int gup_p4d_range(pgd_t pgd
, unsigned long addr
, unsigned long end
,
2602 unsigned int flags
, struct page
**pages
, int *nr
)
2607 p4dp
= p4d_offset(&pgd
, addr
);
2609 p4d_t p4d
= READ_ONCE(*p4dp
);
2611 next
= p4d_addr_end(addr
, end
);
2614 BUILD_BUG_ON(p4d_huge(p4d
));
2615 if (unlikely(is_hugepd(__hugepd(p4d_val(p4d
))))) {
2616 if (!gup_huge_pd(__hugepd(p4d_val(p4d
)), addr
,
2617 P4D_SHIFT
, next
, flags
, pages
, nr
))
2619 } else if (!gup_pud_range(p4d
, addr
, next
, flags
, pages
, nr
))
2621 } while (p4dp
++, addr
= next
, addr
!= end
);
2626 static void gup_pgd_range(unsigned long addr
, unsigned long end
,
2627 unsigned int flags
, struct page
**pages
, int *nr
)
2632 pgdp
= pgd_offset(current
->mm
, addr
);
2634 pgd_t pgd
= READ_ONCE(*pgdp
);
2636 next
= pgd_addr_end(addr
, end
);
2639 if (unlikely(pgd_huge(pgd
))) {
2640 if (!gup_huge_pgd(pgd
, pgdp
, addr
, next
, flags
,
2643 } else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd
))))) {
2644 if (!gup_huge_pd(__hugepd(pgd_val(pgd
)), addr
,
2645 PGDIR_SHIFT
, next
, flags
, pages
, nr
))
2647 } else if (!gup_p4d_range(pgd
, addr
, next
, flags
, pages
, nr
))
2649 } while (pgdp
++, addr
= next
, addr
!= end
);
2652 static inline void gup_pgd_range(unsigned long addr
, unsigned long end
,
2653 unsigned int flags
, struct page
**pages
, int *nr
)
2656 #endif /* CONFIG_HAVE_FAST_GUP */
2658 #ifndef gup_fast_permitted
2660 * Check if it's allowed to use __get_user_pages_fast() for the range, or
2661 * we need to fall back to the slow version:
2663 static bool gup_fast_permitted(unsigned long start
, unsigned long end
)
2670 * Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to
2672 * Note a difference with get_user_pages_fast: this always returns the
2673 * number of pages pinned, 0 if no pages were pinned.
2675 * If the architecture does not support this function, simply return with no
2678 int __get_user_pages_fast(unsigned long start
, int nr_pages
, int write
,
2679 struct page
**pages
)
2681 unsigned long len
, end
;
2682 unsigned long flags
;
2685 * Internally (within mm/gup.c), gup fast variants must set FOLL_GET,
2686 * because gup fast is always a "pin with a +1 page refcount" request.
2688 unsigned int gup_flags
= FOLL_GET
;
2691 gup_flags
|= FOLL_WRITE
;
2693 start
= untagged_addr(start
) & PAGE_MASK
;
2694 len
= (unsigned long) nr_pages
<< PAGE_SHIFT
;
2699 if (unlikely(!access_ok((void __user
*)start
, len
)))
2703 * Disable interrupts. We use the nested form as we can already have
2704 * interrupts disabled by get_futex_key.
2706 * With interrupts disabled, we block page table pages from being
2707 * freed from under us. See struct mmu_table_batch comments in
2708 * include/asm-generic/tlb.h for more details.
2710 * We do not adopt an rcu_read_lock(.) here as we also want to
2711 * block IPIs that come from THPs splitting.
2714 if (IS_ENABLED(CONFIG_HAVE_FAST_GUP
) &&
2715 gup_fast_permitted(start
, end
)) {
2716 local_irq_save(flags
);
2717 gup_pgd_range(start
, end
, gup_flags
, pages
, &nr_pinned
);
2718 local_irq_restore(flags
);
2723 EXPORT_SYMBOL_GPL(__get_user_pages_fast
);
2725 static int __gup_longterm_unlocked(unsigned long start
, int nr_pages
,
2726 unsigned int gup_flags
, struct page
**pages
)
2731 * FIXME: FOLL_LONGTERM does not work with
2732 * get_user_pages_unlocked() (see comments in that function)
2734 if (gup_flags
& FOLL_LONGTERM
) {
2735 down_read(¤t
->mm
->mmap_sem
);
2736 ret
= __gup_longterm_locked(current
, current
->mm
,
2738 pages
, NULL
, gup_flags
);
2739 up_read(¤t
->mm
->mmap_sem
);
2741 ret
= get_user_pages_unlocked(start
, nr_pages
,
2748 static int internal_get_user_pages_fast(unsigned long start
, int nr_pages
,
2749 unsigned int gup_flags
,
2750 struct page
**pages
)
2752 unsigned long addr
, len
, end
;
2753 int nr_pinned
= 0, ret
= 0;
2755 if (WARN_ON_ONCE(gup_flags
& ~(FOLL_WRITE
| FOLL_LONGTERM
|
2756 FOLL_FORCE
| FOLL_PIN
| FOLL_GET
)))
2759 start
= untagged_addr(start
) & PAGE_MASK
;
2761 len
= (unsigned long) nr_pages
<< PAGE_SHIFT
;
2766 if (unlikely(!access_ok((void __user
*)start
, len
)))
2769 if (IS_ENABLED(CONFIG_HAVE_FAST_GUP
) &&
2770 gup_fast_permitted(start
, end
)) {
2771 local_irq_disable();
2772 gup_pgd_range(addr
, end
, gup_flags
, pages
, &nr_pinned
);
2777 if (nr_pinned
< nr_pages
) {
2778 /* Try to get the remaining pages with get_user_pages */
2779 start
+= nr_pinned
<< PAGE_SHIFT
;
2782 ret
= __gup_longterm_unlocked(start
, nr_pages
- nr_pinned
,
2785 /* Have to be a bit careful with return values */
2786 if (nr_pinned
> 0) {
2798 * get_user_pages_fast() - pin user pages in memory
2799 * @start: starting user address
2800 * @nr_pages: number of pages from start to pin
2801 * @gup_flags: flags modifying pin behaviour
2802 * @pages: array that receives pointers to the pages pinned.
2803 * Should be at least nr_pages long.
2805 * Attempt to pin user pages in memory without taking mm->mmap_sem.
2806 * If not successful, it will fall back to taking the lock and
2807 * calling get_user_pages().
2809 * Returns number of pages pinned. This may be fewer than the number requested.
2810 * If nr_pages is 0 or negative, returns 0. If no pages were pinned, returns
2813 int get_user_pages_fast(unsigned long start
, int nr_pages
,
2814 unsigned int gup_flags
, struct page
**pages
)
2817 * FOLL_PIN must only be set internally by the pin_user_pages*() APIs,
2818 * never directly by the caller, so enforce that:
2820 if (WARN_ON_ONCE(gup_flags
& FOLL_PIN
))
2824 * The caller may or may not have explicitly set FOLL_GET; either way is
2825 * OK. However, internally (within mm/gup.c), gup fast variants must set
2826 * FOLL_GET, because gup fast is always a "pin with a +1 page refcount"
2829 gup_flags
|= FOLL_GET
;
2830 return internal_get_user_pages_fast(start
, nr_pages
, gup_flags
, pages
);
2832 EXPORT_SYMBOL_GPL(get_user_pages_fast
);
2835 * pin_user_pages_fast() - pin user pages in memory without taking locks
2837 * @start: starting user address
2838 * @nr_pages: number of pages from start to pin
2839 * @gup_flags: flags modifying pin behaviour
2840 * @pages: array that receives pointers to the pages pinned.
2841 * Should be at least nr_pages long.
2843 * Nearly the same as get_user_pages_fast(), except that FOLL_PIN is set. See
2844 * get_user_pages_fast() for documentation on the function arguments, because
2845 * the arguments here are identical.
2847 * FOLL_PIN means that the pages must be released via unpin_user_page(). Please
2848 * see Documentation/vm/pin_user_pages.rst for further details.
2850 * This is intended for Case 1 (DIO) in Documentation/vm/pin_user_pages.rst. It
2851 * is NOT intended for Case 2 (RDMA: long-term pins).
2853 int pin_user_pages_fast(unsigned long start
, int nr_pages
,
2854 unsigned int gup_flags
, struct page
**pages
)
2856 /* FOLL_GET and FOLL_PIN are mutually exclusive. */
2857 if (WARN_ON_ONCE(gup_flags
& FOLL_GET
))
2860 gup_flags
|= FOLL_PIN
;
2861 return internal_get_user_pages_fast(start
, nr_pages
, gup_flags
, pages
);
2863 EXPORT_SYMBOL_GPL(pin_user_pages_fast
);
2866 * pin_user_pages_remote() - pin pages of a remote process (task != current)
2868 * @tsk: the task_struct to use for page fault accounting, or
2869 * NULL if faults are not to be recorded.
2870 * @mm: mm_struct of target mm
2871 * @start: starting user address
2872 * @nr_pages: number of pages from start to pin
2873 * @gup_flags: flags modifying lookup behaviour
2874 * @pages: array that receives pointers to the pages pinned.
2875 * Should be at least nr_pages long. Or NULL, if caller
2876 * only intends to ensure the pages are faulted in.
2877 * @vmas: array of pointers to vmas corresponding to each page.
2878 * Or NULL if the caller does not require them.
2879 * @locked: pointer to lock flag indicating whether lock is held and
2880 * subsequently whether VM_FAULT_RETRY functionality can be
2881 * utilised. Lock must initially be held.
2883 * Nearly the same as get_user_pages_remote(), except that FOLL_PIN is set. See
2884 * get_user_pages_remote() for documentation on the function arguments, because
2885 * the arguments here are identical.
2887 * FOLL_PIN means that the pages must be released via unpin_user_page(). Please
2888 * see Documentation/vm/pin_user_pages.rst for details.
2890 * This is intended for Case 1 (DIO) in Documentation/vm/pin_user_pages.rst. It
2891 * is NOT intended for Case 2 (RDMA: long-term pins).
2893 long pin_user_pages_remote(struct task_struct
*tsk
, struct mm_struct
*mm
,
2894 unsigned long start
, unsigned long nr_pages
,
2895 unsigned int gup_flags
, struct page
**pages
,
2896 struct vm_area_struct
**vmas
, int *locked
)
2898 /* FOLL_GET and FOLL_PIN are mutually exclusive. */
2899 if (WARN_ON_ONCE(gup_flags
& FOLL_GET
))
2902 gup_flags
|= FOLL_PIN
;
2903 return __get_user_pages_remote(tsk
, mm
, start
, nr_pages
, gup_flags
,
2904 pages
, vmas
, locked
);
2906 EXPORT_SYMBOL(pin_user_pages_remote
);
2909 * pin_user_pages() - pin user pages in memory for use by other devices
2911 * @start: starting user address
2912 * @nr_pages: number of pages from start to pin
2913 * @gup_flags: flags modifying lookup behaviour
2914 * @pages: array that receives pointers to the pages pinned.
2915 * Should be at least nr_pages long. Or NULL, if caller
2916 * only intends to ensure the pages are faulted in.
2917 * @vmas: array of pointers to vmas corresponding to each page.
2918 * Or NULL if the caller does not require them.
2920 * Nearly the same as get_user_pages(), except that FOLL_TOUCH is not set, and
2923 * FOLL_PIN means that the pages must be released via unpin_user_page(). Please
2924 * see Documentation/vm/pin_user_pages.rst for details.
2926 * This is intended for Case 1 (DIO) in Documentation/vm/pin_user_pages.rst. It
2927 * is NOT intended for Case 2 (RDMA: long-term pins).
2929 long pin_user_pages(unsigned long start
, unsigned long nr_pages
,
2930 unsigned int gup_flags
, struct page
**pages
,
2931 struct vm_area_struct
**vmas
)
2933 /* FOLL_GET and FOLL_PIN are mutually exclusive. */
2934 if (WARN_ON_ONCE(gup_flags
& FOLL_GET
))
2937 gup_flags
|= FOLL_PIN
;
2938 return __gup_longterm_locked(current
, current
->mm
, start
, nr_pages
,
2939 pages
, vmas
, gup_flags
);
2941 EXPORT_SYMBOL(pin_user_pages
);