blob: 373d1ec006e4f12a17578a9405d5e191a5718f1d [file] [log] [blame]
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -07001#include <linux/kernel.h>
2#include <linux/errno.h>
3#include <linux/err.h>
4#include <linux/spinlock.h>
5
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -07006#include <linux/mm.h>
Dan Williams3565fce2016-01-15 16:56:55 -08007#include <linux/memremap.h>
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -07008#include <linux/pagemap.h>
9#include <linux/rmap.h>
10#include <linux/swap.h>
11#include <linux/swapops.h>
12
Steve Capper2667f502014-10-09 15:29:14 -070013#include <linux/sched.h>
14#include <linux/rwsem.h>
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +053015#include <linux/hugetlb.h>
Kirill A. Shutemov1027e442015-09-04 15:47:55 -070016
Dave Hansen33a709b2016-02-12 13:02:19 -080017#include <asm/mmu_context.h>
Steve Capper2667f502014-10-09 15:29:14 -070018#include <asm/pgtable.h>
Kirill A. Shutemov1027e442015-09-04 15:47:55 -070019#include <asm/tlbflush.h>
Steve Capper2667f502014-10-09 15:29:14 -070020
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -070021#include "internal.h"
22
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -070023static struct page *no_page_table(struct vm_area_struct *vma,
24 unsigned int flags)
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -070025{
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -070026 /*
27 * When core dumping an enormous anonymous area that nobody
28 * has touched so far, we don't want to allocate unnecessary pages or
29 * page tables. Return error instead of NULL to skip handle_mm_fault,
30 * then get_dump_page() will return NULL to leave a hole in the dump.
31 * But we can only make this optimization where a hole would surely
32 * be zero-filled if handle_mm_fault() actually did handle it.
33 */
34 if ((flags & FOLL_DUMP) && (!vma->vm_ops || !vma->vm_ops->fault))
35 return ERR_PTR(-EFAULT);
36 return NULL;
37}
38
Kirill A. Shutemov1027e442015-09-04 15:47:55 -070039static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address,
40 pte_t *pte, unsigned int flags)
41{
42 /* No page to get reference */
43 if (flags & FOLL_GET)
44 return -EFAULT;
45
46 if (flags & FOLL_TOUCH) {
47 pte_t entry = *pte;
48
49 if (flags & FOLL_WRITE)
50 entry = pte_mkdirty(entry);
51 entry = pte_mkyoung(entry);
52
53 if (!pte_same(*pte, entry)) {
54 set_pte_at(vma->vm_mm, address, pte, entry);
55 update_mmu_cache(vma, address, pte);
56 }
57 }
58
59 /* Proper page table entry exists, but no corresponding struct page */
60 return -EEXIST;
61}
62
Linus Torvalds19be0ea2016-10-13 13:07:36 -070063/*
64 * FOLL_FORCE can write to even unwritable pte's, but only
65 * after we've gone through a COW cycle and they are dirty.
66 */
67static inline bool can_follow_write_pte(pte_t pte, unsigned int flags)
68{
69 return pte_write(pte) ||
70 ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pte_dirty(pte));
71}
72
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -070073static struct page *follow_page_pte(struct vm_area_struct *vma,
74 unsigned long address, pmd_t *pmd, unsigned int flags)
75{
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -070076 struct mm_struct *mm = vma->vm_mm;
Dan Williams3565fce2016-01-15 16:56:55 -080077 struct dev_pagemap *pgmap = NULL;
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -070078 struct page *page;
79 spinlock_t *ptl;
80 pte_t *ptep, pte;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -070081
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -070082retry:
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -070083 if (unlikely(pmd_bad(*pmd)))
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -070084 return no_page_table(vma, flags);
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -070085
86 ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -070087 pte = *ptep;
88 if (!pte_present(pte)) {
89 swp_entry_t entry;
90 /*
91 * KSM's break_ksm() relies upon recognizing a ksm page
92 * even while it is being migrated, so for that case we
93 * need migration_entry_wait().
94 */
95 if (likely(!(flags & FOLL_MIGRATION)))
96 goto no_page;
Kirill A. Shutemov0661a332015-02-10 14:10:04 -080097 if (pte_none(pte))
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -070098 goto no_page;
99 entry = pte_to_swp_entry(pte);
100 if (!is_migration_entry(entry))
101 goto no_page;
102 pte_unmap_unlock(ptep, ptl);
103 migration_entry_wait(mm, pmd, address);
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -0700104 goto retry;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700105 }
Mel Gorman8a0516e2015-02-12 14:58:22 -0800106 if ((flags & FOLL_NUMA) && pte_protnone(pte))
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700107 goto no_page;
Linus Torvalds19be0ea2016-10-13 13:07:36 -0700108 if ((flags & FOLL_WRITE) && !can_follow_write_pte(pte, flags)) {
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -0700109 pte_unmap_unlock(ptep, ptl);
110 return NULL;
111 }
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700112
113 page = vm_normal_page(vma, address, pte);
Dan Williams3565fce2016-01-15 16:56:55 -0800114 if (!page && pte_devmap(pte) && (flags & FOLL_GET)) {
115 /*
116 * Only return device mapping pages in the FOLL_GET case since
117 * they are only valid while holding the pgmap reference.
118 */
119 pgmap = get_dev_pagemap(pte_pfn(pte), NULL);
120 if (pgmap)
121 page = pte_page(pte);
122 else
123 goto no_page;
124 } else if (unlikely(!page)) {
Kirill A. Shutemov1027e442015-09-04 15:47:55 -0700125 if (flags & FOLL_DUMP) {
126 /* Avoid special (like zero) pages in core dumps */
127 page = ERR_PTR(-EFAULT);
128 goto out;
129 }
130
131 if (is_zero_pfn(pte_pfn(pte))) {
132 page = pte_page(pte);
133 } else {
134 int ret;
135
136 ret = follow_pfn_pte(vma, address, ptep, flags);
137 page = ERR_PTR(ret);
138 goto out;
139 }
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700140 }
141
Kirill A. Shutemov6742d292016-01-15 16:52:28 -0800142 if (flags & FOLL_SPLIT && PageTransCompound(page)) {
143 int ret;
144 get_page(page);
145 pte_unmap_unlock(ptep, ptl);
146 lock_page(page);
147 ret = split_huge_page(page);
148 unlock_page(page);
149 put_page(page);
150 if (ret)
151 return ERR_PTR(ret);
152 goto retry;
153 }
154
Dan Williams3565fce2016-01-15 16:56:55 -0800155 if (flags & FOLL_GET) {
Kirill A. Shutemovddc58f22016-01-15 16:52:56 -0800156 get_page(page);
Dan Williams3565fce2016-01-15 16:56:55 -0800157
158 /* drop the pgmap reference now that we hold the page */
159 if (pgmap) {
160 put_dev_pagemap(pgmap);
161 pgmap = NULL;
162 }
163 }
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700164 if (flags & FOLL_TOUCH) {
165 if ((flags & FOLL_WRITE) &&
166 !pte_dirty(pte) && !PageDirty(page))
167 set_page_dirty(page);
168 /*
169 * pte_mkyoung() would be more correct here, but atomic care
170 * is needed to avoid losing the dirty bit: it is easier to use
171 * mark_page_accessed().
172 */
173 mark_page_accessed(page);
174 }
Eric B Munsonde60f5f2015-11-05 18:51:36 -0800175 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
Kirill A. Shutemove90309c2016-01-15 16:54:33 -0800176 /* Do not mlock pte-mapped THP */
177 if (PageTransCompound(page))
178 goto out;
179
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700180 /*
181 * The preliminary mapping check is mainly to avoid the
182 * pointless overhead of lock_page on the ZERO_PAGE
183 * which might bounce very badly if there is contention.
184 *
185 * If the page is already locked, we don't need to
186 * handle it now - vmscan will handle it later if and
187 * when it attempts to reclaim the page.
188 */
189 if (page->mapping && trylock_page(page)) {
190 lru_add_drain(); /* push cached pages to LRU */
191 /*
192 * Because we lock page here, and migration is
193 * blocked by the pte's page reference, and we
194 * know the page is still mapped, we don't even
195 * need to check for file-cache page truncation.
196 */
197 mlock_vma_page(page);
198 unlock_page(page);
199 }
200 }
Kirill A. Shutemov1027e442015-09-04 15:47:55 -0700201out:
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700202 pte_unmap_unlock(ptep, ptl);
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700203 return page;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700204no_page:
205 pte_unmap_unlock(ptep, ptl);
206 if (!pte_none(pte))
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -0700207 return NULL;
208 return no_page_table(vma, flags);
209}
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700210
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -0700211/**
212 * follow_page_mask - look up a page descriptor from a user-virtual address
213 * @vma: vm_area_struct mapping @address
214 * @address: virtual address to look up
215 * @flags: flags modifying lookup behaviour
216 * @page_mask: on output, *page_mask is set according to the size of the page
217 *
218 * @flags can have FOLL_ flags set, defined in <linux/mm.h>
219 *
220 * Returns the mapped (struct page *), %NULL if no mapping exists, or
221 * an error pointer if there is a mapping to something not represented
222 * by a page descriptor (see also vm_normal_page()).
223 */
224struct page *follow_page_mask(struct vm_area_struct *vma,
225 unsigned long address, unsigned int flags,
226 unsigned int *page_mask)
227{
228 pgd_t *pgd;
229 pud_t *pud;
230 pmd_t *pmd;
231 spinlock_t *ptl;
232 struct page *page;
233 struct mm_struct *mm = vma->vm_mm;
234
235 *page_mask = 0;
236
237 page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
238 if (!IS_ERR(page)) {
239 BUG_ON(flags & FOLL_GET);
240 return page;
241 }
242
243 pgd = pgd_offset(mm, address);
244 if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
245 return no_page_table(vma, flags);
246
247 pud = pud_offset(pgd, address);
248 if (pud_none(*pud))
249 return no_page_table(vma, flags);
250 if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) {
Naoya Horiguchie66f17f2015-02-11 15:25:22 -0800251 page = follow_huge_pud(mm, address, pud, flags);
252 if (page)
253 return page;
254 return no_page_table(vma, flags);
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -0700255 }
256 if (unlikely(pud_bad(*pud)))
257 return no_page_table(vma, flags);
258
259 pmd = pmd_offset(pud, address);
260 if (pmd_none(*pmd))
261 return no_page_table(vma, flags);
262 if (pmd_huge(*pmd) && vma->vm_flags & VM_HUGETLB) {
Naoya Horiguchie66f17f2015-02-11 15:25:22 -0800263 page = follow_huge_pmd(mm, address, pmd, flags);
264 if (page)
265 return page;
266 return no_page_table(vma, flags);
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -0700267 }
Mel Gorman8a0516e2015-02-12 14:58:22 -0800268 if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -0700269 return no_page_table(vma, flags);
Dan Williams3565fce2016-01-15 16:56:55 -0800270 if (pmd_devmap(*pmd)) {
271 ptl = pmd_lock(mm, pmd);
272 page = follow_devmap_pmd(vma, address, pmd, flags);
273 spin_unlock(ptl);
274 if (page)
275 return page;
276 }
Kirill A. Shutemov6742d292016-01-15 16:52:28 -0800277 if (likely(!pmd_trans_huge(*pmd)))
278 return follow_page_pte(vma, address, pmd, flags);
279
280 ptl = pmd_lock(mm, pmd);
281 if (unlikely(!pmd_trans_huge(*pmd))) {
282 spin_unlock(ptl);
283 return follow_page_pte(vma, address, pmd, flags);
Kirill A. Shutemov69e68b42014-06-04 16:08:11 -0700284 }
Kirill A. Shutemov6742d292016-01-15 16:52:28 -0800285 if (flags & FOLL_SPLIT) {
286 int ret;
287 page = pmd_page(*pmd);
288 if (is_huge_zero_page(page)) {
289 spin_unlock(ptl);
290 ret = 0;
Kirill A. Shutemov78ddc532016-01-15 16:52:42 -0800291 split_huge_pmd(vma, pmd, address);
Naoya Horiguchi337d9ab2016-07-26 15:24:03 -0700292 if (pmd_trans_unstable(pmd))
293 ret = -EBUSY;
Kirill A. Shutemov6742d292016-01-15 16:52:28 -0800294 } else {
295 get_page(page);
296 spin_unlock(ptl);
297 lock_page(page);
298 ret = split_huge_page(page);
299 unlock_page(page);
300 put_page(page);
Kirill A. Shutemovbaa355f2016-07-26 15:25:51 -0700301 if (pmd_none(*pmd))
302 return no_page_table(vma, flags);
Kirill A. Shutemov6742d292016-01-15 16:52:28 -0800303 }
304
305 return ret ? ERR_PTR(ret) :
306 follow_page_pte(vma, address, pmd, flags);
307 }
308
309 page = follow_trans_huge_pmd(vma, address, pmd, flags);
310 spin_unlock(ptl);
311 *page_mask = HPAGE_PMD_NR - 1;
312 return page;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700313}
314
Kirill A. Shutemovf2b495c2014-06-04 16:08:11 -0700315static int get_gate_page(struct mm_struct *mm, unsigned long address,
316 unsigned int gup_flags, struct vm_area_struct **vma,
317 struct page **page)
318{
319 pgd_t *pgd;
320 pud_t *pud;
321 pmd_t *pmd;
322 pte_t *pte;
323 int ret = -EFAULT;
324
325 /* user gate pages are read-only */
326 if (gup_flags & FOLL_WRITE)
327 return -EFAULT;
328 if (address > TASK_SIZE)
329 pgd = pgd_offset_k(address);
330 else
331 pgd = pgd_offset_gate(mm, address);
332 BUG_ON(pgd_none(*pgd));
333 pud = pud_offset(pgd, address);
334 BUG_ON(pud_none(*pud));
335 pmd = pmd_offset(pud, address);
336 if (pmd_none(*pmd))
337 return -EFAULT;
338 VM_BUG_ON(pmd_trans_huge(*pmd));
339 pte = pte_offset_map(pmd, address);
340 if (pte_none(*pte))
341 goto unmap;
342 *vma = get_gate_vma(mm);
343 if (!page)
344 goto out;
345 *page = vm_normal_page(*vma, address, *pte);
346 if (!*page) {
347 if ((gup_flags & FOLL_DUMP) || !is_zero_pfn(pte_pfn(*pte)))
348 goto unmap;
349 *page = pte_page(*pte);
350 }
351 get_page(*page);
352out:
353 ret = 0;
354unmap:
355 pte_unmap(pte);
356 return ret;
357}
358
Paul Cassella9a95f3c2014-08-06 16:07:24 -0700359/*
360 * mmap_sem must be held on entry. If @nonblocking != NULL and
361 * *@flags does not include FOLL_NOWAIT, the mmap_sem may be released.
362 * If it is, *@nonblocking will be set to 0 and -EBUSY returned.
363 */
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700364static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma,
365 unsigned long address, unsigned int *flags, int *nonblocking)
366{
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700367 unsigned int fault_flags = 0;
368 int ret;
369
Eric B Munsonde60f5f2015-11-05 18:51:36 -0800370 /* mlock all present pages, but do not fault in new pages */
371 if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK)
372 return -ENOENT;
Kirill A. Shutemov84d33df2015-04-14 15:44:37 -0700373 /* For mm_populate(), just skip the stack guard page. */
374 if ((*flags & FOLL_POPULATE) &&
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700375 (stack_guard_page_start(vma, address) ||
376 stack_guard_page_end(vma, address + PAGE_SIZE)))
377 return -ENOENT;
378 if (*flags & FOLL_WRITE)
379 fault_flags |= FAULT_FLAG_WRITE;
Dave Hansen1b2ee122016-02-12 13:02:21 -0800380 if (*flags & FOLL_REMOTE)
381 fault_flags |= FAULT_FLAG_REMOTE;
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700382 if (nonblocking)
383 fault_flags |= FAULT_FLAG_ALLOW_RETRY;
384 if (*flags & FOLL_NOWAIT)
385 fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT;
Andres Lagar-Cavilla234b2392014-09-17 10:51:48 -0700386 if (*flags & FOLL_TRIED) {
387 VM_WARN_ON_ONCE(fault_flags & FAULT_FLAG_ALLOW_RETRY);
388 fault_flags |= FAULT_FLAG_TRIED;
389 }
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700390
Kirill A. Shutemovdcddffd2016-07-26 15:25:18 -0700391 ret = handle_mm_fault(vma, address, fault_flags);
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700392 if (ret & VM_FAULT_ERROR) {
393 if (ret & VM_FAULT_OOM)
394 return -ENOMEM;
395 if (ret & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE))
396 return *flags & FOLL_HWPOISON ? -EHWPOISON : -EFAULT;
Linus Torvalds33692f22015-01-29 10:51:32 -0800397 if (ret & (VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV))
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700398 return -EFAULT;
399 BUG();
400 }
401
402 if (tsk) {
403 if (ret & VM_FAULT_MAJOR)
404 tsk->maj_flt++;
405 else
406 tsk->min_flt++;
407 }
408
409 if (ret & VM_FAULT_RETRY) {
410 if (nonblocking)
411 *nonblocking = 0;
412 return -EBUSY;
413 }
414
415 /*
416 * The VM_FAULT_WRITE bit tells us that do_wp_page has broken COW when
417 * necessary, even if maybe_mkwrite decided not to set pte_write. We
418 * can thus safely do subsequent page lookups as if they were reads.
419 * But only do so when looping for pte_write is futile: in some cases
420 * userspace may also be wanting to write to the gotten user page,
421 * which a read fault here might prevent (a readonly page might get
422 * reCOWed by userspace write).
423 */
424 if ((ret & VM_FAULT_WRITE) && !(vma->vm_flags & VM_WRITE))
Linus Torvalds19be0ea2016-10-13 13:07:36 -0700425 *flags |= FOLL_COW;
Kirill A. Shutemov16744482014-06-04 16:08:12 -0700426 return 0;
427}
428
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700429static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)
430{
431 vm_flags_t vm_flags = vma->vm_flags;
Dave Hansen1b2ee122016-02-12 13:02:21 -0800432 int write = (gup_flags & FOLL_WRITE);
433 int foreign = (gup_flags & FOLL_REMOTE);
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700434
435 if (vm_flags & (VM_IO | VM_PFNMAP))
436 return -EFAULT;
437
Dave Hansen1b2ee122016-02-12 13:02:21 -0800438 if (write) {
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700439 if (!(vm_flags & VM_WRITE)) {
440 if (!(gup_flags & FOLL_FORCE))
441 return -EFAULT;
442 /*
443 * We used to let the write,force case do COW in a
444 * VM_MAYWRITE VM_SHARED !VM_WRITE vma, so ptrace could
445 * set a breakpoint in a read-only mapping of an
446 * executable, without corrupting the file (yet only
447 * when that file had been opened for writing!).
448 * Anon pages in shared mappings are surprising: now
449 * just reject it.
450 */
Hugh Dickins46435362016-01-30 18:03:16 -0800451 if (!is_cow_mapping(vm_flags))
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700452 return -EFAULT;
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700453 }
454 } else if (!(vm_flags & VM_READ)) {
455 if (!(gup_flags & FOLL_FORCE))
456 return -EFAULT;
457 /*
458 * Is there actually any vma we can reach here which does not
459 * have VM_MAYREAD set?
460 */
461 if (!(vm_flags & VM_MAYREAD))
462 return -EFAULT;
463 }
Dave Hansend61172b2016-02-12 13:02:24 -0800464 /*
465 * gups are always data accesses, not instruction
466 * fetches, so execute=false here
467 */
468 if (!arch_vma_access_permitted(vma, write, false, foreign))
Dave Hansen33a709b2016-02-12 13:02:19 -0800469 return -EFAULT;
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700470 return 0;
471}
472
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700473/**
474 * __get_user_pages() - pin user pages in memory
475 * @tsk: task_struct of target task
476 * @mm: mm_struct of target mm
477 * @start: starting user address
478 * @nr_pages: number of pages from start to pin
479 * @gup_flags: flags modifying pin behaviour
480 * @pages: array that receives pointers to the pages pinned.
481 * Should be at least nr_pages long. Or NULL, if caller
482 * only intends to ensure the pages are faulted in.
483 * @vmas: array of pointers to vmas corresponding to each page.
484 * Or NULL if the caller does not require them.
485 * @nonblocking: whether waiting for disk IO or mmap_sem contention
486 *
487 * Returns number of pages pinned. This may be fewer than the number
488 * requested. If nr_pages is 0 or negative, returns 0. If no pages
489 * were pinned, returns -errno. Each page returned must be released
490 * with a put_page() call when it is finished with. vmas will only
491 * remain valid while mmap_sem is held.
492 *
Paul Cassella9a95f3c2014-08-06 16:07:24 -0700493 * Must be called with mmap_sem held. It may be released. See below.
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700494 *
495 * __get_user_pages walks a process's page tables and takes a reference to
496 * each struct page that each user address corresponds to at a given
497 * instant. That is, it takes the page that would be accessed if a user
498 * thread accesses the given user virtual address at that instant.
499 *
500 * This does not guarantee that the page exists in the user mappings when
501 * __get_user_pages returns, and there may even be a completely different
502 * page there in some cases (eg. if mmapped pagecache has been invalidated
503 * and subsequently re faulted). However it does guarantee that the page
504 * won't be freed completely. And mostly callers simply care that the page
505 * contains data that was valid *at some point in time*. Typically, an IO
506 * or similar operation cannot guarantee anything stronger anyway because
507 * locks can't be held over the syscall boundary.
508 *
509 * If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If
510 * the page is written to, set_page_dirty (or set_page_dirty_lock, as
511 * appropriate) must be called after the page is finished with, and
512 * before put_page is called.
513 *
514 * If @nonblocking != NULL, __get_user_pages will not wait for disk IO
515 * or mmap_sem contention, and if waiting is needed to pin all pages,
Paul Cassella9a95f3c2014-08-06 16:07:24 -0700516 * *@nonblocking will be set to 0. Further, if @gup_flags does not
517 * include FOLL_NOWAIT, the mmap_sem will be released via up_read() in
518 * this case.
519 *
520 * A caller using such a combination of @nonblocking and @gup_flags
521 * must therefore hold the mmap_sem for reading only, and recognize
522 * when it's been released. Otherwise, it must be held for either
523 * reading or writing and will not be released.
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700524 *
525 * In most cases, get_user_pages or get_user_pages_fast should be used
526 * instead of __get_user_pages. __get_user_pages should be used only if
527 * you need some special @gup_flags.
528 */
529long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
530 unsigned long start, unsigned long nr_pages,
531 unsigned int gup_flags, struct page **pages,
532 struct vm_area_struct **vmas, int *nonblocking)
533{
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700534 long i = 0;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700535 unsigned int page_mask;
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700536 struct vm_area_struct *vma = NULL;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700537
538 if (!nr_pages)
539 return 0;
540
541 VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));
542
543 /*
544 * If FOLL_FORCE is set then do not force a full fault as the hinting
545 * fault information is unrelated to the reference behaviour of a task
546 * using the address space
547 */
548 if (!(gup_flags & FOLL_FORCE))
549 gup_flags |= FOLL_NUMA;
550
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700551 do {
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700552 struct page *page;
553 unsigned int foll_flags = gup_flags;
554 unsigned int page_increm;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700555
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700556 /* first iteration or cross vma bound */
557 if (!vma || start >= vma->vm_end) {
558 vma = find_extend_vma(mm, start);
559 if (!vma && in_gate_area(mm, start)) {
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700560 int ret;
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700561 ret = get_gate_page(mm, start & PAGE_MASK,
562 gup_flags, &vma,
563 pages ? &pages[i] : NULL);
564 if (ret)
565 return i ? : ret;
566 page_mask = 0;
567 goto next_page;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700568 }
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700569
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700570 if (!vma || check_vma_flags(vma, gup_flags))
571 return i ? : -EFAULT;
572 if (is_vm_hugetlb_page(vma)) {
573 i = follow_hugetlb_page(mm, vma, pages, vmas,
574 &start, &nr_pages, i,
575 gup_flags);
576 continue;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700577 }
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700578 }
579retry:
580 /*
581 * If we have a pending SIGKILL, don't keep faulting pages and
582 * potentially allocating memory.
583 */
584 if (unlikely(fatal_signal_pending(current)))
585 return i ? i : -ERESTARTSYS;
586 cond_resched();
587 page = follow_page_mask(vma, start, foll_flags, &page_mask);
588 if (!page) {
589 int ret;
590 ret = faultin_page(tsk, vma, start, &foll_flags,
591 nonblocking);
592 switch (ret) {
593 case 0:
594 goto retry;
595 case -EFAULT:
596 case -ENOMEM:
597 case -EHWPOISON:
598 return i ? i : ret;
599 case -EBUSY:
600 return i;
601 case -ENOENT:
602 goto next_page;
603 }
604 BUG();
Kirill A. Shutemov1027e442015-09-04 15:47:55 -0700605 } else if (PTR_ERR(page) == -EEXIST) {
606 /*
607 * Proper page table entry exists, but no corresponding
608 * struct page.
609 */
610 goto next_page;
611 } else if (IS_ERR(page)) {
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700612 return i ? i : PTR_ERR(page);
Kirill A. Shutemov1027e442015-09-04 15:47:55 -0700613 }
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700614 if (pages) {
615 pages[i] = page;
616 flush_anon_page(vma, page, start);
617 flush_dcache_page(page);
618 page_mask = 0;
619 }
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700620next_page:
Kirill A. Shutemovfa5bb202014-06-04 16:08:13 -0700621 if (vmas) {
622 vmas[i] = vma;
623 page_mask = 0;
624 }
625 page_increm = 1 + (~(start >> PAGE_SHIFT) & page_mask);
626 if (page_increm > nr_pages)
627 page_increm = nr_pages;
628 i += page_increm;
629 start += page_increm * PAGE_SIZE;
630 nr_pages -= page_increm;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700631 } while (nr_pages);
632 return i;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700633}
634EXPORT_SYMBOL(__get_user_pages);
635
Dave Hansend4925e02016-02-12 13:02:16 -0800636bool vma_permits_fault(struct vm_area_struct *vma, unsigned int fault_flags)
637{
Dave Hansen1b2ee122016-02-12 13:02:21 -0800638 bool write = !!(fault_flags & FAULT_FLAG_WRITE);
639 bool foreign = !!(fault_flags & FAULT_FLAG_REMOTE);
Dave Hansen33a709b2016-02-12 13:02:19 -0800640 vm_flags_t vm_flags = write ? VM_WRITE : VM_READ;
Dave Hansend4925e02016-02-12 13:02:16 -0800641
642 if (!(vm_flags & vma->vm_flags))
643 return false;
644
Dave Hansen33a709b2016-02-12 13:02:19 -0800645 /*
646 * The architecture might have a hardware protection
Dave Hansen1b2ee122016-02-12 13:02:21 -0800647 * mechanism other than read/write that can deny access.
Dave Hansend61172b2016-02-12 13:02:24 -0800648 *
649 * gup always represents data access, not instruction
650 * fetches, so execute=false here:
Dave Hansen33a709b2016-02-12 13:02:19 -0800651 */
Dave Hansend61172b2016-02-12 13:02:24 -0800652 if (!arch_vma_access_permitted(vma, write, false, foreign))
Dave Hansen33a709b2016-02-12 13:02:19 -0800653 return false;
654
Dave Hansend4925e02016-02-12 13:02:16 -0800655 return true;
656}
657
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700658/*
659 * fixup_user_fault() - manually resolve a user page fault
660 * @tsk: the task_struct to use for page fault accounting, or
661 * NULL if faults are not to be recorded.
662 * @mm: mm_struct of target mm
663 * @address: user address
664 * @fault_flags:flags to pass down to handle_mm_fault()
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800665 * @unlocked: did we unlock the mmap_sem while retrying, maybe NULL if caller
666 * does not allow retry
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700667 *
668 * This is meant to be called in the specific scenario where for locking reasons
669 * we try to access user memory in atomic context (within a pagefault_disable()
670 * section), this returns -EFAULT, and we want to resolve the user fault before
671 * trying again.
672 *
673 * Typically this is meant to be used by the futex code.
674 *
675 * The main difference with get_user_pages() is that this function will
676 * unconditionally call handle_mm_fault() which will in turn perform all the
677 * necessary SW fixup of the dirty and young bits in the PTE, while
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800678 * get_user_pages() only guarantees to update these in the struct page.
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700679 *
680 * This is important for some architectures where those bits also gate the
681 * access permission to the page because they are maintained in software. On
682 * such architectures, gup() will not be enough to make a subsequent access
683 * succeed.
684 *
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800685 * This function will not return with an unlocked mmap_sem. So it has not the
686 * same semantics wrt the @mm->mmap_sem as does filemap_fault().
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700687 */
688int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800689 unsigned long address, unsigned int fault_flags,
690 bool *unlocked)
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700691{
692 struct vm_area_struct *vma;
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800693 int ret, major = 0;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700694
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800695 if (unlocked)
696 fault_flags |= FAULT_FLAG_ALLOW_RETRY;
697
698retry:
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700699 vma = find_extend_vma(mm, address);
700 if (!vma || address < vma->vm_start)
701 return -EFAULT;
702
Dave Hansend4925e02016-02-12 13:02:16 -0800703 if (!vma_permits_fault(vma, fault_flags))
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700704 return -EFAULT;
705
Kirill A. Shutemovdcddffd2016-07-26 15:25:18 -0700706 ret = handle_mm_fault(vma, address, fault_flags);
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800707 major |= ret & VM_FAULT_MAJOR;
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700708 if (ret & VM_FAULT_ERROR) {
709 if (ret & VM_FAULT_OOM)
710 return -ENOMEM;
711 if (ret & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE))
712 return -EHWPOISON;
Linus Torvalds33692f22015-01-29 10:51:32 -0800713 if (ret & (VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV))
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700714 return -EFAULT;
715 BUG();
716 }
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800717
718 if (ret & VM_FAULT_RETRY) {
719 down_read(&mm->mmap_sem);
720 if (!(fault_flags & FAULT_FLAG_TRIED)) {
721 *unlocked = true;
722 fault_flags &= ~FAULT_FLAG_ALLOW_RETRY;
723 fault_flags |= FAULT_FLAG_TRIED;
724 goto retry;
725 }
726 }
727
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700728 if (tsk) {
Dominik Dingel4a9e1cd2016-01-15 16:57:04 -0800729 if (major)
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700730 tsk->maj_flt++;
731 else
732 tsk->min_flt++;
733 }
734 return 0;
735}
Paolo Bonziniadd6a0c2016-06-07 17:51:18 +0200736EXPORT_SYMBOL_GPL(fixup_user_fault);
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700737
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800738static __always_inline long __get_user_pages_locked(struct task_struct *tsk,
739 struct mm_struct *mm,
740 unsigned long start,
741 unsigned long nr_pages,
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800742 struct page **pages,
743 struct vm_area_struct **vmas,
Andrea Arcangeli0fd71a52015-02-11 15:27:20 -0800744 int *locked, bool notify_drop,
745 unsigned int flags)
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800746{
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800747 long ret, pages_done;
748 bool lock_dropped;
749
750 if (locked) {
751 /* if VM_FAULT_RETRY can be returned, vmas become invalid */
752 BUG_ON(vmas);
753 /* check caller initialized locked */
754 BUG_ON(*locked != 1);
755 }
756
757 if (pages)
758 flags |= FOLL_GET;
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800759
760 pages_done = 0;
761 lock_dropped = false;
762 for (;;) {
763 ret = __get_user_pages(tsk, mm, start, nr_pages, flags, pages,
764 vmas, locked);
765 if (!locked)
766 /* VM_FAULT_RETRY couldn't trigger, bypass */
767 return ret;
768
769 /* VM_FAULT_RETRY cannot return errors */
770 if (!*locked) {
771 BUG_ON(ret < 0);
772 BUG_ON(ret >= nr_pages);
773 }
774
775 if (!pages)
776 /* If it's a prefault don't insist harder */
777 return ret;
778
779 if (ret > 0) {
780 nr_pages -= ret;
781 pages_done += ret;
782 if (!nr_pages)
783 break;
784 }
785 if (*locked) {
786 /* VM_FAULT_RETRY didn't trigger */
787 if (!pages_done)
788 pages_done = ret;
789 break;
790 }
791 /* VM_FAULT_RETRY triggered, so seek to the faulting offset */
792 pages += ret;
793 start += ret << PAGE_SHIFT;
794
795 /*
796 * Repeat on the address that fired VM_FAULT_RETRY
797 * without FAULT_FLAG_ALLOW_RETRY but with
798 * FAULT_FLAG_TRIED.
799 */
800 *locked = 1;
801 lock_dropped = true;
802 down_read(&mm->mmap_sem);
803 ret = __get_user_pages(tsk, mm, start, 1, flags | FOLL_TRIED,
804 pages, NULL, NULL);
805 if (ret != 1) {
806 BUG_ON(ret > 1);
807 if (!pages_done)
808 pages_done = ret;
809 break;
810 }
811 nr_pages--;
812 pages_done++;
813 if (!nr_pages)
814 break;
815 pages++;
816 start += PAGE_SIZE;
817 }
818 if (notify_drop && lock_dropped && *locked) {
819 /*
820 * We must let the caller know we temporarily dropped the lock
821 * and so the critical section protected by it was lost.
822 */
823 up_read(&mm->mmap_sem);
824 *locked = 0;
825 }
826 return pages_done;
827}
828
829/*
830 * We can leverage the VM_FAULT_RETRY functionality in the page fault
831 * paths better by using either get_user_pages_locked() or
832 * get_user_pages_unlocked().
833 *
834 * get_user_pages_locked() is suitable to replace the form:
835 *
836 * down_read(&mm->mmap_sem);
837 * do_something()
838 * get_user_pages(tsk, mm, ..., pages, NULL);
839 * up_read(&mm->mmap_sem);
840 *
841 * to:
842 *
843 * int locked = 1;
844 * down_read(&mm->mmap_sem);
845 * do_something()
846 * get_user_pages_locked(tsk, mm, ..., pages, &locked);
847 * if (locked)
848 * up_read(&mm->mmap_sem);
849 */
Ingo Molnarc12d2da2016-04-04 10:24:58 +0200850long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800851 int write, int force, struct page **pages,
852 int *locked)
853{
Lorenzo Stoakes859110d2016-10-13 01:20:11 +0100854 unsigned int flags = FOLL_TOUCH;
855
856 if (write)
857 flags |= FOLL_WRITE;
858 if (force)
859 flags |= FOLL_FORCE;
860
Dave Hansencde70142016-02-12 13:01:55 -0800861 return __get_user_pages_locked(current, current->mm, start, nr_pages,
Lorenzo Stoakes859110d2016-10-13 01:20:11 +0100862 pages, NULL, locked, true, flags);
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800863}
Ingo Molnarc12d2da2016-04-04 10:24:58 +0200864EXPORT_SYMBOL(get_user_pages_locked);
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800865
866/*
Andrea Arcangeli0fd71a52015-02-11 15:27:20 -0800867 * Same as get_user_pages_unlocked(...., FOLL_TOUCH) but it allows to
868 * pass additional gup_flags as last parameter (like FOLL_HWPOISON).
869 *
870 * NOTE: here FOLL_TOUCH is not set implicitly and must be set by the
871 * caller if required (just like with __get_user_pages). "FOLL_GET",
872 * "FOLL_WRITE" and "FOLL_FORCE" are set implicitly as needed
873 * according to the parameters "pages", "write", "force"
874 * respectively.
875 */
876__always_inline long __get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm,
877 unsigned long start, unsigned long nr_pages,
Lorenzo Stoakesd4944b02016-10-13 01:20:12 +0100878 struct page **pages, unsigned int gup_flags)
Andrea Arcangeli0fd71a52015-02-11 15:27:20 -0800879{
880 long ret;
881 int locked = 1;
Lorenzo Stoakes859110d2016-10-13 01:20:11 +0100882
Andrea Arcangeli0fd71a52015-02-11 15:27:20 -0800883 down_read(&mm->mmap_sem);
Lorenzo Stoakes859110d2016-10-13 01:20:11 +0100884 ret = __get_user_pages_locked(tsk, mm, start, nr_pages, pages, NULL,
885 &locked, false, gup_flags);
Andrea Arcangeli0fd71a52015-02-11 15:27:20 -0800886 if (locked)
887 up_read(&mm->mmap_sem);
888 return ret;
889}
890EXPORT_SYMBOL(__get_user_pages_unlocked);
891
892/*
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800893 * get_user_pages_unlocked() is suitable to replace the form:
894 *
895 * down_read(&mm->mmap_sem);
896 * get_user_pages(tsk, mm, ..., pages, NULL);
897 * up_read(&mm->mmap_sem);
898 *
899 * with:
900 *
901 * get_user_pages_unlocked(tsk, mm, ..., pages);
902 *
903 * It is functionally equivalent to get_user_pages_fast so
904 * get_user_pages_fast should be used instead, if the two parameters
905 * "tsk" and "mm" are respectively equal to current and current->mm,
906 * or if "force" shall be set to 1 (get_user_pages_fast misses the
907 * "force" parameter).
908 */
Ingo Molnarc12d2da2016-04-04 10:24:58 +0200909long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
Lorenzo Stoakesc1641542016-10-13 01:20:13 +0100910 struct page **pages, unsigned int gup_flags)
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800911{
Dave Hansencde70142016-02-12 13:01:55 -0800912 return __get_user_pages_unlocked(current, current->mm, start, nr_pages,
Lorenzo Stoakesc1641542016-10-13 01:20:13 +0100913 pages, gup_flags | FOLL_TOUCH);
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800914}
Ingo Molnarc12d2da2016-04-04 10:24:58 +0200915EXPORT_SYMBOL(get_user_pages_unlocked);
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800916
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700917/*
Dave Hansen1e987792016-02-12 13:01:54 -0800918 * get_user_pages_remote() - pin user pages in memory
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700919 * @tsk: the task_struct to use for page fault accounting, or
920 * NULL if faults are not to be recorded.
921 * @mm: mm_struct of target mm
922 * @start: starting user address
923 * @nr_pages: number of pages from start to pin
924 * @write: whether pages will be written to by the caller
925 * @force: whether to force access even when user mapping is currently
926 * protected (but never forces write access to shared mapping).
927 * @pages: array that receives pointers to the pages pinned.
928 * Should be at least nr_pages long. Or NULL, if caller
929 * only intends to ensure the pages are faulted in.
930 * @vmas: array of pointers to vmas corresponding to each page.
931 * Or NULL if the caller does not require them.
932 *
933 * Returns number of pages pinned. This may be fewer than the number
934 * requested. If nr_pages is 0 or negative, returns 0. If no pages
935 * were pinned, returns -errno. Each page returned must be released
936 * with a put_page() call when it is finished with. vmas will only
937 * remain valid while mmap_sem is held.
938 *
939 * Must be called with mmap_sem held for read or write.
940 *
941 * get_user_pages walks a process's page tables and takes a reference to
942 * each struct page that each user address corresponds to at a given
943 * instant. That is, it takes the page that would be accessed if a user
944 * thread accesses the given user virtual address at that instant.
945 *
946 * This does not guarantee that the page exists in the user mappings when
947 * get_user_pages returns, and there may even be a completely different
948 * page there in some cases (eg. if mmapped pagecache has been invalidated
949 * and subsequently re faulted). However it does guarantee that the page
950 * won't be freed completely. And mostly callers simply care that the page
951 * contains data that was valid *at some point in time*. Typically, an IO
952 * or similar operation cannot guarantee anything stronger anyway because
953 * locks can't be held over the syscall boundary.
954 *
955 * If write=0, the page must not be written to. If the page is written to,
956 * set_page_dirty (or set_page_dirty_lock, as appropriate) must be called
957 * after the page is finished with, and before put_page is called.
958 *
959 * get_user_pages is typically used for fewer-copy IO operations, to get a
960 * handle on the memory by some means other than accesses via the user virtual
961 * addresses. The pages may be submitted for DMA to devices or accessed via
962 * their kernel linear mapping (via the kmap APIs). Care should be taken to
963 * use the correct cache flushing APIs.
964 *
965 * See also get_user_pages_fast, for performance critical applications.
Andrea Arcangelif0818f42015-02-11 15:27:17 -0800966 *
967 * get_user_pages should be phased out in favor of
968 * get_user_pages_locked|unlocked or get_user_pages_fast. Nothing
969 * should use get_user_pages because it cannot pass
970 * FAULT_FLAG_ALLOW_RETRY to handle_mm_fault.
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700971 */
Dave Hansen1e987792016-02-12 13:01:54 -0800972long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
973 unsigned long start, unsigned long nr_pages,
974 int write, int force, struct page **pages,
975 struct vm_area_struct **vmas)
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -0700976{
Lorenzo Stoakes859110d2016-10-13 01:20:11 +0100977 unsigned int flags = FOLL_TOUCH | FOLL_REMOTE;
978
979 if (write)
980 flags |= FOLL_WRITE;
981 if (force)
982 flags |= FOLL_FORCE;
983
984 return __get_user_pages_locked(tsk, mm, start, nr_pages, pages, vmas,
985 NULL, false, flags);
Dave Hansen1e987792016-02-12 13:01:54 -0800986}
987EXPORT_SYMBOL(get_user_pages_remote);
988
989/*
Dave Hansend4edcf02016-02-12 13:01:56 -0800990 * This is the same as get_user_pages_remote(), just with a
991 * less-flexible calling convention where we assume that the task
992 * and mm being operated on are the current task's. We also
993 * obviously don't pass FOLL_REMOTE in here.
Dave Hansen1e987792016-02-12 13:01:54 -0800994 */
Ingo Molnarc12d2da2016-04-04 10:24:58 +0200995long get_user_pages(unsigned long start, unsigned long nr_pages,
Dave Hansen1e987792016-02-12 13:01:54 -0800996 int write, int force, struct page **pages,
997 struct vm_area_struct **vmas)
998{
Lorenzo Stoakes859110d2016-10-13 01:20:11 +0100999 unsigned int flags = FOLL_TOUCH;
1000
1001 if (write)
1002 flags |= FOLL_WRITE;
1003 if (force)
1004 flags |= FOLL_FORCE;
1005
Dave Hansencde70142016-02-12 13:01:55 -08001006 return __get_user_pages_locked(current, current->mm, start, nr_pages,
Lorenzo Stoakes859110d2016-10-13 01:20:11 +01001007 pages, vmas, NULL, false, flags);
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -07001008}
Ingo Molnarc12d2da2016-04-04 10:24:58 +02001009EXPORT_SYMBOL(get_user_pages);
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -07001010
1011/**
Kirill A. Shutemovacc3c8d2015-04-14 15:44:45 -07001012 * populate_vma_page_range() - populate a range of pages in the vma.
1013 * @vma: target vma
1014 * @start: start address
1015 * @end: end address
1016 * @nonblocking:
1017 *
1018 * This takes care of mlocking the pages too if VM_LOCKED is set.
1019 *
1020 * return 0 on success, negative error code on error.
1021 *
1022 * vma->vm_mm->mmap_sem must be held.
1023 *
1024 * If @nonblocking is NULL, it may be held for read or write and will
1025 * be unperturbed.
1026 *
1027 * If @nonblocking is non-NULL, it must held for read only and may be
1028 * released. If it's released, *@nonblocking will be set to 0.
1029 */
1030long populate_vma_page_range(struct vm_area_struct *vma,
1031 unsigned long start, unsigned long end, int *nonblocking)
1032{
1033 struct mm_struct *mm = vma->vm_mm;
1034 unsigned long nr_pages = (end - start) / PAGE_SIZE;
1035 int gup_flags;
1036
1037 VM_BUG_ON(start & ~PAGE_MASK);
1038 VM_BUG_ON(end & ~PAGE_MASK);
1039 VM_BUG_ON_VMA(start < vma->vm_start, vma);
1040 VM_BUG_ON_VMA(end > vma->vm_end, vma);
1041 VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm);
1042
Eric B Munsonde60f5f2015-11-05 18:51:36 -08001043 gup_flags = FOLL_TOUCH | FOLL_POPULATE | FOLL_MLOCK;
1044 if (vma->vm_flags & VM_LOCKONFAULT)
1045 gup_flags &= ~FOLL_POPULATE;
Kirill A. Shutemovacc3c8d2015-04-14 15:44:45 -07001046 /*
1047 * We want to touch writable mappings with a write fault in order
1048 * to break COW, except for shared mappings because these don't COW
1049 * and we would not want to dirty them for nothing.
1050 */
1051 if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
1052 gup_flags |= FOLL_WRITE;
1053
1054 /*
1055 * We want mlock to succeed for regions that have any permissions
1056 * other than PROT_NONE.
1057 */
1058 if (vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))
1059 gup_flags |= FOLL_FORCE;
1060
1061 /*
1062 * We made sure addr is within a VMA, so the following will
1063 * not result in a stack expansion that recurses back here.
1064 */
1065 return __get_user_pages(current, mm, start, nr_pages, gup_flags,
1066 NULL, NULL, nonblocking);
1067}
1068
1069/*
1070 * __mm_populate - populate and/or mlock pages within a range of address space.
1071 *
1072 * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
1073 * flags. VMAs must be already marked with the desired vm_flags, and
1074 * mmap_sem must not be held.
1075 */
1076int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
1077{
1078 struct mm_struct *mm = current->mm;
1079 unsigned long end, nstart, nend;
1080 struct vm_area_struct *vma = NULL;
1081 int locked = 0;
1082 long ret = 0;
1083
1084 VM_BUG_ON(start & ~PAGE_MASK);
1085 VM_BUG_ON(len != PAGE_ALIGN(len));
1086 end = start + len;
1087
1088 for (nstart = start; nstart < end; nstart = nend) {
1089 /*
1090 * We want to fault in pages for [nstart; end) address range.
1091 * Find first corresponding VMA.
1092 */
1093 if (!locked) {
1094 locked = 1;
1095 down_read(&mm->mmap_sem);
1096 vma = find_vma(mm, nstart);
1097 } else if (nstart >= vma->vm_end)
1098 vma = vma->vm_next;
1099 if (!vma || vma->vm_start >= end)
1100 break;
1101 /*
1102 * Set [nstart; nend) to intersection of desired address
1103 * range with the first VMA. Also, skip undesirable VMA types.
1104 */
1105 nend = min(end, vma->vm_end);
1106 if (vma->vm_flags & (VM_IO | VM_PFNMAP))
1107 continue;
1108 if (nstart < vma->vm_start)
1109 nstart = vma->vm_start;
1110 /*
1111 * Now fault in a range of pages. populate_vma_page_range()
1112 * double checks the vma flags, so that it won't mlock pages
1113 * if the vma was already munlocked.
1114 */
1115 ret = populate_vma_page_range(vma, nstart, nend, &locked);
1116 if (ret < 0) {
1117 if (ignore_errors) {
1118 ret = 0;
1119 continue; /* continue at next VMA */
1120 }
1121 break;
1122 }
1123 nend = nstart + ret * PAGE_SIZE;
1124 ret = 0;
1125 }
1126 if (locked)
1127 up_read(&mm->mmap_sem);
1128 return ret; /* 0 or negative error code */
1129}
1130
1131/**
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -07001132 * get_dump_page() - pin user page in memory while writing it to core dump
1133 * @addr: user address
1134 *
1135 * Returns struct page pointer of user page pinned for dump,
Kirill A. Shutemovea1754a2016-04-01 15:29:48 +03001136 * to be freed afterwards by put_page().
Kirill A. Shutemov4bbd4c72014-06-04 16:08:10 -07001137 *
1138 * Returns NULL on any kind of failure - a hole must then be inserted into
1139 * the corefile, to preserve alignment with its headers; and also returns
1140 * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
1141 * allowing a hole to be left in the corefile to save diskspace.
1142 *
1143 * Called without mmap_sem, but after all other threads have been killed.
1144 */
1145#ifdef CONFIG_ELF_CORE
1146struct page *get_dump_page(unsigned long addr)
1147{
1148 struct vm_area_struct *vma;
1149 struct page *page;
1150
1151 if (__get_user_pages(current, current->mm, addr, 1,
1152 FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma,
1153 NULL) < 1)
1154 return NULL;
1155 flush_cache_page(vma, addr, page_to_pfn(page));
1156 return page;
1157}
1158#endif /* CONFIG_ELF_CORE */
Steve Capper2667f502014-10-09 15:29:14 -07001159
1160/*
1161 * Generic RCU Fast GUP
1162 *
1163 * get_user_pages_fast attempts to pin user pages by walking the page
1164 * tables directly and avoids taking locks. Thus the walker needs to be
1165 * protected from page table pages being freed from under it, and should
1166 * block any THP splits.
1167 *
1168 * One way to achieve this is to have the walker disable interrupts, and
1169 * rely on IPIs from the TLB flushing code blocking before the page table
1170 * pages are freed. This is unsuitable for architectures that do not need
1171 * to broadcast an IPI when invalidating TLBs.
1172 *
1173 * Another way to achieve this is to batch up page table containing pages
1174 * belonging to more than one mm_user, then rcu_sched a callback to free those
1175 * pages. Disabling interrupts will allow the fast_gup walker to both block
1176 * the rcu_sched callback, and an IPI that we broadcast for splitting THPs
1177 * (which is a relatively rare event). The code below adopts this strategy.
1178 *
1179 * Before activating this code, please be aware that the following assumptions
1180 * are currently made:
1181 *
1182 * *) HAVE_RCU_TABLE_FREE is enabled, and tlb_remove_table is used to free
1183 * pages containing page tables.
1184 *
Steve Capper2667f502014-10-09 15:29:14 -07001185 * *) ptes can be read atomically by the architecture.
1186 *
1187 * *) access_ok is sufficient to validate userspace address ranges.
1188 *
1189 * The last two assumptions can be relaxed by the addition of helper functions.
1190 *
1191 * This code is based heavily on the PowerPC implementation by Nick Piggin.
1192 */
1193#ifdef CONFIG_HAVE_GENERIC_RCU_GUP
1194
1195#ifdef __HAVE_ARCH_PTE_SPECIAL
1196static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
1197 int write, struct page **pages, int *nr)
1198{
1199 pte_t *ptep, *ptem;
1200 int ret = 0;
1201
1202 ptem = ptep = pte_offset_map(&pmd, addr);
1203 do {
1204 /*
1205 * In the line below we are assuming that the pte can be read
1206 * atomically. If this is not the case for your architecture,
1207 * please wrap this in a helper function!
1208 *
1209 * for an example see gup_get_pte in arch/x86/mm/gup.c
1210 */
Jason Low9d8c47e2015-04-15 16:14:05 -07001211 pte_t pte = READ_ONCE(*ptep);
Kirill A. Shutemov7aef4172016-01-15 16:52:32 -08001212 struct page *head, *page;
Steve Capper2667f502014-10-09 15:29:14 -07001213
1214 /*
1215 * Similar to the PMD case below, NUMA hinting must take slow
Mel Gorman8a0516e2015-02-12 14:58:22 -08001216 * path using the pte_protnone check.
Steve Capper2667f502014-10-09 15:29:14 -07001217 */
1218 if (!pte_present(pte) || pte_special(pte) ||
Mel Gorman8a0516e2015-02-12 14:58:22 -08001219 pte_protnone(pte) || (write && !pte_write(pte)))
Steve Capper2667f502014-10-09 15:29:14 -07001220 goto pte_unmap;
1221
Dave Hansen33a709b2016-02-12 13:02:19 -08001222 if (!arch_pte_access_permitted(pte, write))
1223 goto pte_unmap;
1224
Steve Capper2667f502014-10-09 15:29:14 -07001225 VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
1226 page = pte_page(pte);
Kirill A. Shutemov7aef4172016-01-15 16:52:32 -08001227 head = compound_head(page);
Steve Capper2667f502014-10-09 15:29:14 -07001228
Kirill A. Shutemov7aef4172016-01-15 16:52:32 -08001229 if (!page_cache_get_speculative(head))
Steve Capper2667f502014-10-09 15:29:14 -07001230 goto pte_unmap;
1231
1232 if (unlikely(pte_val(pte) != pte_val(*ptep))) {
Kirill A. Shutemov7aef4172016-01-15 16:52:32 -08001233 put_page(head);
Steve Capper2667f502014-10-09 15:29:14 -07001234 goto pte_unmap;
1235 }
1236
Kirill A. Shutemov7aef4172016-01-15 16:52:32 -08001237 VM_BUG_ON_PAGE(compound_head(page) != head, page);
Steve Capper2667f502014-10-09 15:29:14 -07001238 pages[*nr] = page;
1239 (*nr)++;
1240
1241 } while (ptep++, addr += PAGE_SIZE, addr != end);
1242
1243 ret = 1;
1244
1245pte_unmap:
1246 pte_unmap(ptem);
1247 return ret;
1248}
1249#else
1250
1251/*
1252 * If we can't determine whether or not a pte is special, then fail immediately
1253 * for ptes. Note, we can still pin HugeTLB and THP as these are guaranteed not
1254 * to be special.
1255 *
1256 * For a futex to be placed on a THP tail page, get_futex_key requires a
1257 * __get_user_pages_fast implementation that can pin pages. Thus it's still
1258 * useful to have gup_huge_pmd even if we can't operate on ptes.
1259 */
1260static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
1261 int write, struct page **pages, int *nr)
1262{
1263 return 0;
1264}
1265#endif /* __HAVE_ARCH_PTE_SPECIAL */
1266
1267static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
1268 unsigned long end, int write, struct page **pages, int *nr)
1269{
Kirill A. Shutemovddc58f22016-01-15 16:52:56 -08001270 struct page *head, *page;
Steve Capper2667f502014-10-09 15:29:14 -07001271 int refs;
1272
1273 if (write && !pmd_write(orig))
1274 return 0;
1275
1276 refs = 0;
1277 head = pmd_page(orig);
1278 page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
Steve Capper2667f502014-10-09 15:29:14 -07001279 do {
1280 VM_BUG_ON_PAGE(compound_head(page) != head, page);
1281 pages[*nr] = page;
1282 (*nr)++;
1283 page++;
1284 refs++;
1285 } while (addr += PAGE_SIZE, addr != end);
1286
1287 if (!page_cache_add_speculative(head, refs)) {
1288 *nr -= refs;
1289 return 0;
1290 }
1291
1292 if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
1293 *nr -= refs;
1294 while (refs--)
1295 put_page(head);
1296 return 0;
1297 }
1298
Steve Capper2667f502014-10-09 15:29:14 -07001299 return 1;
1300}
1301
1302static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
1303 unsigned long end, int write, struct page **pages, int *nr)
1304{
Kirill A. Shutemovddc58f22016-01-15 16:52:56 -08001305 struct page *head, *page;
Steve Capper2667f502014-10-09 15:29:14 -07001306 int refs;
1307
1308 if (write && !pud_write(orig))
1309 return 0;
1310
1311 refs = 0;
1312 head = pud_page(orig);
1313 page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
Steve Capper2667f502014-10-09 15:29:14 -07001314 do {
1315 VM_BUG_ON_PAGE(compound_head(page) != head, page);
1316 pages[*nr] = page;
1317 (*nr)++;
1318 page++;
1319 refs++;
1320 } while (addr += PAGE_SIZE, addr != end);
1321
1322 if (!page_cache_add_speculative(head, refs)) {
1323 *nr -= refs;
1324 return 0;
1325 }
1326
1327 if (unlikely(pud_val(orig) != pud_val(*pudp))) {
1328 *nr -= refs;
1329 while (refs--)
1330 put_page(head);
1331 return 0;
1332 }
1333
Steve Capper2667f502014-10-09 15:29:14 -07001334 return 1;
1335}
1336
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301337static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
1338 unsigned long end, int write,
1339 struct page **pages, int *nr)
1340{
1341 int refs;
Kirill A. Shutemovddc58f22016-01-15 16:52:56 -08001342 struct page *head, *page;
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301343
1344 if (write && !pgd_write(orig))
1345 return 0;
1346
1347 refs = 0;
1348 head = pgd_page(orig);
1349 page = head + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT);
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301350 do {
1351 VM_BUG_ON_PAGE(compound_head(page) != head, page);
1352 pages[*nr] = page;
1353 (*nr)++;
1354 page++;
1355 refs++;
1356 } while (addr += PAGE_SIZE, addr != end);
1357
1358 if (!page_cache_add_speculative(head, refs)) {
1359 *nr -= refs;
1360 return 0;
1361 }
1362
1363 if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) {
1364 *nr -= refs;
1365 while (refs--)
1366 put_page(head);
1367 return 0;
1368 }
1369
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301370 return 1;
1371}
1372
Steve Capper2667f502014-10-09 15:29:14 -07001373static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
1374 int write, struct page **pages, int *nr)
1375{
1376 unsigned long next;
1377 pmd_t *pmdp;
1378
1379 pmdp = pmd_offset(&pud, addr);
1380 do {
Christian Borntraeger38c5ce92015-01-06 22:54:46 +01001381 pmd_t pmd = READ_ONCE(*pmdp);
Steve Capper2667f502014-10-09 15:29:14 -07001382
1383 next = pmd_addr_end(addr, end);
Kirill A. Shutemov4b471e82016-01-15 16:53:39 -08001384 if (pmd_none(pmd))
Steve Capper2667f502014-10-09 15:29:14 -07001385 return 0;
1386
1387 if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd))) {
1388 /*
1389 * NUMA hinting faults need to be handled in the GUP
1390 * slowpath for accounting purposes and so that they
1391 * can be serialised against THP migration.
1392 */
Mel Gorman8a0516e2015-02-12 14:58:22 -08001393 if (pmd_protnone(pmd))
Steve Capper2667f502014-10-09 15:29:14 -07001394 return 0;
1395
1396 if (!gup_huge_pmd(pmd, pmdp, addr, next, write,
1397 pages, nr))
1398 return 0;
1399
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301400 } else if (unlikely(is_hugepd(__hugepd(pmd_val(pmd))))) {
1401 /*
1402 * architecture have different format for hugetlbfs
1403 * pmd format and THP pmd format
1404 */
1405 if (!gup_huge_pd(__hugepd(pmd_val(pmd)), addr,
1406 PMD_SHIFT, next, write, pages, nr))
1407 return 0;
Steve Capper2667f502014-10-09 15:29:14 -07001408 } else if (!gup_pte_range(pmd, addr, next, write, pages, nr))
1409 return 0;
1410 } while (pmdp++, addr = next, addr != end);
1411
1412 return 1;
1413}
1414
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301415static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end,
1416 int write, struct page **pages, int *nr)
Steve Capper2667f502014-10-09 15:29:14 -07001417{
1418 unsigned long next;
1419 pud_t *pudp;
1420
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301421 pudp = pud_offset(&pgd, addr);
Steve Capper2667f502014-10-09 15:29:14 -07001422 do {
Christian Borntraegere37c6982014-12-07 21:41:33 +01001423 pud_t pud = READ_ONCE(*pudp);
Steve Capper2667f502014-10-09 15:29:14 -07001424
1425 next = pud_addr_end(addr, end);
1426 if (pud_none(pud))
1427 return 0;
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301428 if (unlikely(pud_huge(pud))) {
Steve Capper2667f502014-10-09 15:29:14 -07001429 if (!gup_huge_pud(pud, pudp, addr, next, write,
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301430 pages, nr))
1431 return 0;
1432 } else if (unlikely(is_hugepd(__hugepd(pud_val(pud))))) {
1433 if (!gup_huge_pd(__hugepd(pud_val(pud)), addr,
1434 PUD_SHIFT, next, write, pages, nr))
Steve Capper2667f502014-10-09 15:29:14 -07001435 return 0;
1436 } else if (!gup_pmd_range(pud, addr, next, write, pages, nr))
1437 return 0;
1438 } while (pudp++, addr = next, addr != end);
1439
1440 return 1;
1441}
1442
1443/*
1444 * Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to
1445 * the regular GUP. It will only return non-negative values.
1446 */
1447int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
1448 struct page **pages)
1449{
1450 struct mm_struct *mm = current->mm;
1451 unsigned long addr, len, end;
1452 unsigned long next, flags;
1453 pgd_t *pgdp;
1454 int nr = 0;
1455
1456 start &= PAGE_MASK;
1457 addr = start;
1458 len = (unsigned long) nr_pages << PAGE_SHIFT;
1459 end = start + len;
1460
1461 if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ,
1462 start, len)))
1463 return 0;
1464
1465 /*
1466 * Disable interrupts. We use the nested form as we can already have
1467 * interrupts disabled by get_futex_key.
1468 *
1469 * With interrupts disabled, we block page table pages from being
1470 * freed from under us. See mmu_gather_tlb in asm-generic/tlb.h
1471 * for more details.
1472 *
1473 * We do not adopt an rcu_read_lock(.) here as we also want to
1474 * block IPIs that come from THPs splitting.
1475 */
1476
1477 local_irq_save(flags);
1478 pgdp = pgd_offset(mm, addr);
1479 do {
Jason Low9d8c47e2015-04-15 16:14:05 -07001480 pgd_t pgd = READ_ONCE(*pgdp);
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301481
Steve Capper2667f502014-10-09 15:29:14 -07001482 next = pgd_addr_end(addr, end);
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301483 if (pgd_none(pgd))
Steve Capper2667f502014-10-09 15:29:14 -07001484 break;
Aneesh Kumar K.Vf30c59e2014-11-05 21:57:40 +05301485 if (unlikely(pgd_huge(pgd))) {
1486 if (!gup_huge_pgd(pgd, pgdp, addr, next, write,
1487 pages, &nr))
1488 break;
1489 } else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd))))) {
1490 if (!gup_huge_pd(__hugepd(pgd_val(pgd)), addr,
1491 PGDIR_SHIFT, next, write, pages, &nr))
1492 break;
1493 } else if (!gup_pud_range(pgd, addr, next, write, pages, &nr))
Steve Capper2667f502014-10-09 15:29:14 -07001494 break;
1495 } while (pgdp++, addr = next, addr != end);
1496 local_irq_restore(flags);
1497
1498 return nr;
1499}
1500
1501/**
1502 * get_user_pages_fast() - pin user pages in memory
1503 * @start: starting user address
1504 * @nr_pages: number of pages from start to pin
1505 * @write: whether pages will be written to
1506 * @pages: array that receives pointers to the pages pinned.
1507 * Should be at least nr_pages long.
1508 *
1509 * Attempt to pin user pages in memory without taking mm->mmap_sem.
1510 * If not successful, it will fall back to taking the lock and
1511 * calling get_user_pages().
1512 *
1513 * Returns number of pages pinned. This may be fewer than the number
1514 * requested. If nr_pages is 0 or negative, returns 0. If no pages
1515 * were pinned, returns -errno.
1516 */
1517int get_user_pages_fast(unsigned long start, int nr_pages, int write,
1518 struct page **pages)
1519{
Steve Capper2667f502014-10-09 15:29:14 -07001520 int nr, ret;
1521
1522 start &= PAGE_MASK;
1523 nr = __get_user_pages_fast(start, nr_pages, write, pages);
1524 ret = nr;
1525
1526 if (nr < nr_pages) {
1527 /* Try to get the remaining pages with get_user_pages */
1528 start += nr << PAGE_SHIFT;
1529 pages += nr;
1530
Lorenzo Stoakesc1641542016-10-13 01:20:13 +01001531 ret = get_user_pages_unlocked(start, nr_pages - nr, pages,
1532 write ? FOLL_WRITE : 0);
Steve Capper2667f502014-10-09 15:29:14 -07001533
1534 /* Have to be a bit careful with return values */
1535 if (nr > 0) {
1536 if (ret < 0)
1537 ret = nr;
1538 else
1539 ret += nr;
1540 }
1541 }
1542
1543 return ret;
1544}
1545
1546#endif /* CONFIG_HAVE_GENERIC_RCU_GUP */