ALSA: virtio: use module_virtio_driver() to simplify the code
[linux-2.6-microblaze.git] / mm / userfaultfd.c
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  *  mm/userfaultfd.c
4  *
5  *  Copyright (C) 2015  Red Hat, Inc.
6  */
7
8 #include <linux/mm.h>
9 #include <linux/sched/signal.h>
10 #include <linux/pagemap.h>
11 #include <linux/rmap.h>
12 #include <linux/swap.h>
13 #include <linux/swapops.h>
14 #include <linux/userfaultfd_k.h>
15 #include <linux/mmu_notifier.h>
16 #include <linux/hugetlb.h>
17 #include <linux/shmem_fs.h>
18 #include <asm/tlbflush.h>
19 #include "internal.h"
20
21 static __always_inline
22 struct vm_area_struct *find_dst_vma(struct mm_struct *dst_mm,
23                                     unsigned long dst_start,
24                                     unsigned long len)
25 {
26         /*
27          * Make sure that the dst range is both valid and fully within a
28          * single existing vma.
29          */
30         struct vm_area_struct *dst_vma;
31
32         dst_vma = find_vma(dst_mm, dst_start);
33         if (!dst_vma)
34                 return NULL;
35
36         if (dst_start < dst_vma->vm_start ||
37             dst_start + len > dst_vma->vm_end)
38                 return NULL;
39
40         /*
41          * Check the vma is registered in uffd, this is required to
42          * enforce the VM_MAYWRITE check done at uffd registration
43          * time.
44          */
45         if (!dst_vma->vm_userfaultfd_ctx.ctx)
46                 return NULL;
47
48         return dst_vma;
49 }
50
51 static int mcopy_atomic_pte(struct mm_struct *dst_mm,
52                             pmd_t *dst_pmd,
53                             struct vm_area_struct *dst_vma,
54                             unsigned long dst_addr,
55                             unsigned long src_addr,
56                             struct page **pagep,
57                             bool wp_copy)
58 {
59         pte_t _dst_pte, *dst_pte;
60         spinlock_t *ptl;
61         void *page_kaddr;
62         int ret;
63         struct page *page;
64         pgoff_t offset, max_off;
65         struct inode *inode;
66
67         if (!*pagep) {
68                 ret = -ENOMEM;
69                 page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, dst_vma, dst_addr);
70                 if (!page)
71                         goto out;
72
73                 page_kaddr = kmap_atomic(page);
74                 ret = copy_from_user(page_kaddr,
75                                      (const void __user *) src_addr,
76                                      PAGE_SIZE);
77                 kunmap_atomic(page_kaddr);
78
79                 /* fallback to copy_from_user outside mmap_lock */
80                 if (unlikely(ret)) {
81                         ret = -ENOENT;
82                         *pagep = page;
83                         /* don't free the page */
84                         goto out;
85                 }
86         } else {
87                 page = *pagep;
88                 *pagep = NULL;
89         }
90
91         /*
92          * The memory barrier inside __SetPageUptodate makes sure that
93          * preceding stores to the page contents become visible before
94          * the set_pte_at() write.
95          */
96         __SetPageUptodate(page);
97
98         ret = -ENOMEM;
99         if (mem_cgroup_charge(page, dst_mm, GFP_KERNEL))
100                 goto out_release;
101
102         _dst_pte = pte_mkdirty(mk_pte(page, dst_vma->vm_page_prot));
103         if (dst_vma->vm_flags & VM_WRITE) {
104                 if (wp_copy)
105                         _dst_pte = pte_mkuffd_wp(_dst_pte);
106                 else
107                         _dst_pte = pte_mkwrite(_dst_pte);
108         }
109
110         dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
111         if (dst_vma->vm_file) {
112                 /* the shmem MAP_PRIVATE case requires checking the i_size */
113                 inode = dst_vma->vm_file->f_inode;
114                 offset = linear_page_index(dst_vma, dst_addr);
115                 max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
116                 ret = -EFAULT;
117                 if (unlikely(offset >= max_off))
118                         goto out_release_uncharge_unlock;
119         }
120         ret = -EEXIST;
121         if (!pte_none(*dst_pte))
122                 goto out_release_uncharge_unlock;
123
124         inc_mm_counter(dst_mm, MM_ANONPAGES);
125         page_add_new_anon_rmap(page, dst_vma, dst_addr, false);
126         lru_cache_add_inactive_or_unevictable(page, dst_vma);
127
128         set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
129
130         /* No need to invalidate - it was non-present before */
131         update_mmu_cache(dst_vma, dst_addr, dst_pte);
132
133         pte_unmap_unlock(dst_pte, ptl);
134         ret = 0;
135 out:
136         return ret;
137 out_release_uncharge_unlock:
138         pte_unmap_unlock(dst_pte, ptl);
139 out_release:
140         put_page(page);
141         goto out;
142 }
143
144 static int mfill_zeropage_pte(struct mm_struct *dst_mm,
145                               pmd_t *dst_pmd,
146                               struct vm_area_struct *dst_vma,
147                               unsigned long dst_addr)
148 {
149         pte_t _dst_pte, *dst_pte;
150         spinlock_t *ptl;
151         int ret;
152         pgoff_t offset, max_off;
153         struct inode *inode;
154
155         _dst_pte = pte_mkspecial(pfn_pte(my_zero_pfn(dst_addr),
156                                          dst_vma->vm_page_prot));
157         dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
158         if (dst_vma->vm_file) {
159                 /* the shmem MAP_PRIVATE case requires checking the i_size */
160                 inode = dst_vma->vm_file->f_inode;
161                 offset = linear_page_index(dst_vma, dst_addr);
162                 max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
163                 ret = -EFAULT;
164                 if (unlikely(offset >= max_off))
165                         goto out_unlock;
166         }
167         ret = -EEXIST;
168         if (!pte_none(*dst_pte))
169                 goto out_unlock;
170         set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
171         /* No need to invalidate - it was non-present before */
172         update_mmu_cache(dst_vma, dst_addr, dst_pte);
173         ret = 0;
174 out_unlock:
175         pte_unmap_unlock(dst_pte, ptl);
176         return ret;
177 }
178
179 static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsigned long address)
180 {
181         pgd_t *pgd;
182         p4d_t *p4d;
183         pud_t *pud;
184
185         pgd = pgd_offset(mm, address);
186         p4d = p4d_alloc(mm, pgd, address);
187         if (!p4d)
188                 return NULL;
189         pud = pud_alloc(mm, p4d, address);
190         if (!pud)
191                 return NULL;
192         /*
193          * Note that we didn't run this because the pmd was
194          * missing, the *pmd may be already established and in
195          * turn it may also be a trans_huge_pmd.
196          */
197         return pmd_alloc(mm, pud, address);
198 }
199
200 #ifdef CONFIG_HUGETLB_PAGE
201 /*
202  * __mcopy_atomic processing for HUGETLB vmas.  Note that this routine is
203  * called with mmap_lock held, it will release mmap_lock before returning.
204  */
205 static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
206                                               struct vm_area_struct *dst_vma,
207                                               unsigned long dst_start,
208                                               unsigned long src_start,
209                                               unsigned long len,
210                                               bool zeropage)
211 {
212         int vm_alloc_shared = dst_vma->vm_flags & VM_SHARED;
213         int vm_shared = dst_vma->vm_flags & VM_SHARED;
214         ssize_t err;
215         pte_t *dst_pte;
216         unsigned long src_addr, dst_addr;
217         long copied;
218         struct page *page;
219         unsigned long vma_hpagesize;
220         pgoff_t idx;
221         u32 hash;
222         struct address_space *mapping;
223
224         /*
225          * There is no default zero huge page for all huge page sizes as
226          * supported by hugetlb.  A PMD_SIZE huge pages may exist as used
227          * by THP.  Since we can not reliably insert a zero page, this
228          * feature is not supported.
229          */
230         if (zeropage) {
231                 mmap_read_unlock(dst_mm);
232                 return -EINVAL;
233         }
234
235         src_addr = src_start;
236         dst_addr = dst_start;
237         copied = 0;
238         page = NULL;
239         vma_hpagesize = vma_kernel_pagesize(dst_vma);
240
241         /*
242          * Validate alignment based on huge page size
243          */
244         err = -EINVAL;
245         if (dst_start & (vma_hpagesize - 1) || len & (vma_hpagesize - 1))
246                 goto out_unlock;
247
248 retry:
249         /*
250          * On routine entry dst_vma is set.  If we had to drop mmap_lock and
251          * retry, dst_vma will be set to NULL and we must lookup again.
252          */
253         if (!dst_vma) {
254                 err = -ENOENT;
255                 dst_vma = find_dst_vma(dst_mm, dst_start, len);
256                 if (!dst_vma || !is_vm_hugetlb_page(dst_vma))
257                         goto out_unlock;
258
259                 err = -EINVAL;
260                 if (vma_hpagesize != vma_kernel_pagesize(dst_vma))
261                         goto out_unlock;
262
263                 vm_shared = dst_vma->vm_flags & VM_SHARED;
264         }
265
266         /*
267          * If not shared, ensure the dst_vma has a anon_vma.
268          */
269         err = -ENOMEM;
270         if (!vm_shared) {
271                 if (unlikely(anon_vma_prepare(dst_vma)))
272                         goto out_unlock;
273         }
274
275         while (src_addr < src_start + len) {
276                 pte_t dst_pteval;
277
278                 BUG_ON(dst_addr >= dst_start + len);
279
280                 /*
281                  * Serialize via i_mmap_rwsem and hugetlb_fault_mutex.
282                  * i_mmap_rwsem ensures the dst_pte remains valid even
283                  * in the case of shared pmds.  fault mutex prevents
284                  * races with other faulting threads.
285                  */
286                 mapping = dst_vma->vm_file->f_mapping;
287                 i_mmap_lock_read(mapping);
288                 idx = linear_page_index(dst_vma, dst_addr);
289                 hash = hugetlb_fault_mutex_hash(mapping, idx);
290                 mutex_lock(&hugetlb_fault_mutex_table[hash]);
291
292                 err = -ENOMEM;
293                 dst_pte = huge_pte_alloc(dst_mm, dst_addr, vma_hpagesize);
294                 if (!dst_pte) {
295                         mutex_unlock(&hugetlb_fault_mutex_table[hash]);
296                         i_mmap_unlock_read(mapping);
297                         goto out_unlock;
298                 }
299
300                 err = -EEXIST;
301                 dst_pteval = huge_ptep_get(dst_pte);
302                 if (!huge_pte_none(dst_pteval)) {
303                         mutex_unlock(&hugetlb_fault_mutex_table[hash]);
304                         i_mmap_unlock_read(mapping);
305                         goto out_unlock;
306                 }
307
308                 err = hugetlb_mcopy_atomic_pte(dst_mm, dst_pte, dst_vma,
309                                                 dst_addr, src_addr, &page);
310
311                 mutex_unlock(&hugetlb_fault_mutex_table[hash]);
312                 i_mmap_unlock_read(mapping);
313                 vm_alloc_shared = vm_shared;
314
315                 cond_resched();
316
317                 if (unlikely(err == -ENOENT)) {
318                         mmap_read_unlock(dst_mm);
319                         BUG_ON(!page);
320
321                         err = copy_huge_page_from_user(page,
322                                                 (const void __user *)src_addr,
323                                                 vma_hpagesize / PAGE_SIZE,
324                                                 true);
325                         if (unlikely(err)) {
326                                 err = -EFAULT;
327                                 goto out;
328                         }
329                         mmap_read_lock(dst_mm);
330
331                         dst_vma = NULL;
332                         goto retry;
333                 } else
334                         BUG_ON(page);
335
336                 if (!err) {
337                         dst_addr += vma_hpagesize;
338                         src_addr += vma_hpagesize;
339                         copied += vma_hpagesize;
340
341                         if (fatal_signal_pending(current))
342                                 err = -EINTR;
343                 }
344                 if (err)
345                         break;
346         }
347
348 out_unlock:
349         mmap_read_unlock(dst_mm);
350 out:
351         if (page) {
352                 /*
353                  * We encountered an error and are about to free a newly
354                  * allocated huge page.
355                  *
356                  * Reservation handling is very subtle, and is different for
357                  * private and shared mappings.  See the routine
358                  * restore_reserve_on_error for details.  Unfortunately, we
359                  * can not call restore_reserve_on_error now as it would
360                  * require holding mmap_lock.
361                  *
362                  * If a reservation for the page existed in the reservation
363                  * map of a private mapping, the map was modified to indicate
364                  * the reservation was consumed when the page was allocated.
365                  * We clear the PagePrivate flag now so that the global
366                  * reserve count will not be incremented in free_huge_page.
367                  * The reservation map will still indicate the reservation
368                  * was consumed and possibly prevent later page allocation.
369                  * This is better than leaking a global reservation.  If no
370                  * reservation existed, it is still safe to clear PagePrivate
371                  * as no adjustments to reservation counts were made during
372                  * allocation.
373                  *
374                  * The reservation map for shared mappings indicates which
375                  * pages have reservations.  When a huge page is allocated
376                  * for an address with a reservation, no change is made to
377                  * the reserve map.  In this case PagePrivate will be set
378                  * to indicate that the global reservation count should be
379                  * incremented when the page is freed.  This is the desired
380                  * behavior.  However, when a huge page is allocated for an
381                  * address without a reservation a reservation entry is added
382                  * to the reservation map, and PagePrivate will not be set.
383                  * When the page is freed, the global reserve count will NOT
384                  * be incremented and it will appear as though we have leaked
385                  * reserved page.  In this case, set PagePrivate so that the
386                  * global reserve count will be incremented to match the
387                  * reservation map entry which was created.
388                  *
389                  * Note that vm_alloc_shared is based on the flags of the vma
390                  * for which the page was originally allocated.  dst_vma could
391                  * be different or NULL on error.
392                  */
393                 if (vm_alloc_shared)
394                         SetPagePrivate(page);
395                 else
396                         ClearPagePrivate(page);
397                 put_page(page);
398         }
399         BUG_ON(copied < 0);
400         BUG_ON(err > 0);
401         BUG_ON(!copied && !err);
402         return copied ? copied : err;
403 }
404 #else /* !CONFIG_HUGETLB_PAGE */
405 /* fail at build time if gcc attempts to use this */
406 extern ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
407                                       struct vm_area_struct *dst_vma,
408                                       unsigned long dst_start,
409                                       unsigned long src_start,
410                                       unsigned long len,
411                                       bool zeropage);
412 #endif /* CONFIG_HUGETLB_PAGE */
413
414 static __always_inline ssize_t mfill_atomic_pte(struct mm_struct *dst_mm,
415                                                 pmd_t *dst_pmd,
416                                                 struct vm_area_struct *dst_vma,
417                                                 unsigned long dst_addr,
418                                                 unsigned long src_addr,
419                                                 struct page **page,
420                                                 bool zeropage,
421                                                 bool wp_copy)
422 {
423         ssize_t err;
424
425         /*
426          * The normal page fault path for a shmem will invoke the
427          * fault, fill the hole in the file and COW it right away. The
428          * result generates plain anonymous memory. So when we are
429          * asked to fill an hole in a MAP_PRIVATE shmem mapping, we'll
430          * generate anonymous memory directly without actually filling
431          * the hole. For the MAP_PRIVATE case the robustness check
432          * only happens in the pagetable (to verify it's still none)
433          * and not in the radix tree.
434          */
435         if (!(dst_vma->vm_flags & VM_SHARED)) {
436                 if (!zeropage)
437                         err = mcopy_atomic_pte(dst_mm, dst_pmd, dst_vma,
438                                                dst_addr, src_addr, page,
439                                                wp_copy);
440                 else
441                         err = mfill_zeropage_pte(dst_mm, dst_pmd,
442                                                  dst_vma, dst_addr);
443         } else {
444                 VM_WARN_ON_ONCE(wp_copy);
445                 if (!zeropage)
446                         err = shmem_mcopy_atomic_pte(dst_mm, dst_pmd,
447                                                      dst_vma, dst_addr,
448                                                      src_addr, page);
449                 else
450                         err = shmem_mfill_zeropage_pte(dst_mm, dst_pmd,
451                                                        dst_vma, dst_addr);
452         }
453
454         return err;
455 }
456
457 static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm,
458                                               unsigned long dst_start,
459                                               unsigned long src_start,
460                                               unsigned long len,
461                                               bool zeropage,
462                                               bool *mmap_changing,
463                                               __u64 mode)
464 {
465         struct vm_area_struct *dst_vma;
466         ssize_t err;
467         pmd_t *dst_pmd;
468         unsigned long src_addr, dst_addr;
469         long copied;
470         struct page *page;
471         bool wp_copy;
472
473         /*
474          * Sanitize the command parameters:
475          */
476         BUG_ON(dst_start & ~PAGE_MASK);
477         BUG_ON(len & ~PAGE_MASK);
478
479         /* Does the address range wrap, or is the span zero-sized? */
480         BUG_ON(src_start + len <= src_start);
481         BUG_ON(dst_start + len <= dst_start);
482
483         src_addr = src_start;
484         dst_addr = dst_start;
485         copied = 0;
486         page = NULL;
487 retry:
488         mmap_read_lock(dst_mm);
489
490         /*
491          * If memory mappings are changing because of non-cooperative
492          * operation (e.g. mremap) running in parallel, bail out and
493          * request the user to retry later
494          */
495         err = -EAGAIN;
496         if (mmap_changing && READ_ONCE(*mmap_changing))
497                 goto out_unlock;
498
499         /*
500          * Make sure the vma is not shared, that the dst range is
501          * both valid and fully within a single existing vma.
502          */
503         err = -ENOENT;
504         dst_vma = find_dst_vma(dst_mm, dst_start, len);
505         if (!dst_vma)
506                 goto out_unlock;
507
508         err = -EINVAL;
509         /*
510          * shmem_zero_setup is invoked in mmap for MAP_ANONYMOUS|MAP_SHARED but
511          * it will overwrite vm_ops, so vma_is_anonymous must return false.
512          */
513         if (WARN_ON_ONCE(vma_is_anonymous(dst_vma) &&
514             dst_vma->vm_flags & VM_SHARED))
515                 goto out_unlock;
516
517         /*
518          * validate 'mode' now that we know the dst_vma: don't allow
519          * a wrprotect copy if the userfaultfd didn't register as WP.
520          */
521         wp_copy = mode & UFFDIO_COPY_MODE_WP;
522         if (wp_copy && !(dst_vma->vm_flags & VM_UFFD_WP))
523                 goto out_unlock;
524
525         /*
526          * If this is a HUGETLB vma, pass off to appropriate routine
527          */
528         if (is_vm_hugetlb_page(dst_vma))
529                 return  __mcopy_atomic_hugetlb(dst_mm, dst_vma, dst_start,
530                                                 src_start, len, zeropage);
531
532         if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma))
533                 goto out_unlock;
534
535         /*
536          * Ensure the dst_vma has a anon_vma or this page
537          * would get a NULL anon_vma when moved in the
538          * dst_vma.
539          */
540         err = -ENOMEM;
541         if (!(dst_vma->vm_flags & VM_SHARED) &&
542             unlikely(anon_vma_prepare(dst_vma)))
543                 goto out_unlock;
544
545         while (src_addr < src_start + len) {
546                 pmd_t dst_pmdval;
547
548                 BUG_ON(dst_addr >= dst_start + len);
549
550                 dst_pmd = mm_alloc_pmd(dst_mm, dst_addr);
551                 if (unlikely(!dst_pmd)) {
552                         err = -ENOMEM;
553                         break;
554                 }
555
556                 dst_pmdval = pmd_read_atomic(dst_pmd);
557                 /*
558                  * If the dst_pmd is mapped as THP don't
559                  * override it and just be strict.
560                  */
561                 if (unlikely(pmd_trans_huge(dst_pmdval))) {
562                         err = -EEXIST;
563                         break;
564                 }
565                 if (unlikely(pmd_none(dst_pmdval)) &&
566                     unlikely(__pte_alloc(dst_mm, dst_pmd))) {
567                         err = -ENOMEM;
568                         break;
569                 }
570                 /* If an huge pmd materialized from under us fail */
571                 if (unlikely(pmd_trans_huge(*dst_pmd))) {
572                         err = -EFAULT;
573                         break;
574                 }
575
576                 BUG_ON(pmd_none(*dst_pmd));
577                 BUG_ON(pmd_trans_huge(*dst_pmd));
578
579                 err = mfill_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
580                                        src_addr, &page, zeropage, wp_copy);
581                 cond_resched();
582
583                 if (unlikely(err == -ENOENT)) {
584                         void *page_kaddr;
585
586                         mmap_read_unlock(dst_mm);
587                         BUG_ON(!page);
588
589                         page_kaddr = kmap(page);
590                         err = copy_from_user(page_kaddr,
591                                              (const void __user *) src_addr,
592                                              PAGE_SIZE);
593                         kunmap(page);
594                         if (unlikely(err)) {
595                                 err = -EFAULT;
596                                 goto out;
597                         }
598                         goto retry;
599                 } else
600                         BUG_ON(page);
601
602                 if (!err) {
603                         dst_addr += PAGE_SIZE;
604                         src_addr += PAGE_SIZE;
605                         copied += PAGE_SIZE;
606
607                         if (fatal_signal_pending(current))
608                                 err = -EINTR;
609                 }
610                 if (err)
611                         break;
612         }
613
614 out_unlock:
615         mmap_read_unlock(dst_mm);
616 out:
617         if (page)
618                 put_page(page);
619         BUG_ON(copied < 0);
620         BUG_ON(err > 0);
621         BUG_ON(!copied && !err);
622         return copied ? copied : err;
623 }
624
625 ssize_t mcopy_atomic(struct mm_struct *dst_mm, unsigned long dst_start,
626                      unsigned long src_start, unsigned long len,
627                      bool *mmap_changing, __u64 mode)
628 {
629         return __mcopy_atomic(dst_mm, dst_start, src_start, len, false,
630                               mmap_changing, mode);
631 }
632
633 ssize_t mfill_zeropage(struct mm_struct *dst_mm, unsigned long start,
634                        unsigned long len, bool *mmap_changing)
635 {
636         return __mcopy_atomic(dst_mm, start, 0, len, true, mmap_changing, 0);
637 }
638
639 int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start,
640                         unsigned long len, bool enable_wp, bool *mmap_changing)
641 {
642         struct vm_area_struct *dst_vma;
643         pgprot_t newprot;
644         int err;
645
646         /*
647          * Sanitize the command parameters:
648          */
649         BUG_ON(start & ~PAGE_MASK);
650         BUG_ON(len & ~PAGE_MASK);
651
652         /* Does the address range wrap, or is the span zero-sized? */
653         BUG_ON(start + len <= start);
654
655         mmap_read_lock(dst_mm);
656
657         /*
658          * If memory mappings are changing because of non-cooperative
659          * operation (e.g. mremap) running in parallel, bail out and
660          * request the user to retry later
661          */
662         err = -EAGAIN;
663         if (mmap_changing && READ_ONCE(*mmap_changing))
664                 goto out_unlock;
665
666         err = -ENOENT;
667         dst_vma = find_dst_vma(dst_mm, start, len);
668         /*
669          * Make sure the vma is not shared, that the dst range is
670          * both valid and fully within a single existing vma.
671          */
672         if (!dst_vma || (dst_vma->vm_flags & VM_SHARED))
673                 goto out_unlock;
674         if (!userfaultfd_wp(dst_vma))
675                 goto out_unlock;
676         if (!vma_is_anonymous(dst_vma))
677                 goto out_unlock;
678
679         if (enable_wp)
680                 newprot = vm_get_page_prot(dst_vma->vm_flags & ~(VM_WRITE));
681         else
682                 newprot = vm_get_page_prot(dst_vma->vm_flags);
683
684         change_protection(dst_vma, start, start + len, newprot,
685                           enable_wp ? MM_CP_UFFD_WP : MM_CP_UFFD_WP_RESOLVE);
686
687         err = 0;
688 out_unlock:
689         mmap_read_unlock(dst_mm);
690         return err;
691 }