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1/*
2 * linux/mm/mlock.c
3 *
4 * (C) Copyright 1995 Linus Torvalds
5 * (C) Copyright 2002 Christoph Hellwig
6 */
7
8#include <linux/capability.h>
9#include <linux/mman.h>
10#include <linux/mm.h>
11#include <linux/swap.h>
12#include <linux/swapops.h>
13#include <linux/pagemap.h>
14#include <linux/mempolicy.h>
15#include <linux/syscalls.h>
16#include <linux/sched.h>
17#include <linux/module.h>
18#include <linux/rmap.h>
19#include <linux/mmzone.h>
20#include <linux/hugetlb.h>
21
22#include "internal.h"
23
24int can_do_mlock(void)
25{
26 if (capable(CAP_IPC_LOCK))
27 return 1;
28 if (rlimit(RLIMIT_MEMLOCK) != 0)
29 return 1;
30 return 0;
31}
32EXPORT_SYMBOL(can_do_mlock);
33
34/*
35 * Mlocked pages are marked with PageMlocked() flag for efficient testing
36 * in vmscan and, possibly, the fault path; and to support semi-accurate
37 * statistics.
38 *
39 * An mlocked page [PageMlocked(page)] is unevictable. As such, it will
40 * be placed on the LRU "unevictable" list, rather than the [in]active lists.
41 * The unevictable list is an LRU sibling list to the [in]active lists.
42 * PageUnevictable is set to indicate the unevictable state.
43 *
44 * When lazy mlocking via vmscan, it is important to ensure that the
45 * vma's VM_LOCKED status is not concurrently being modified, otherwise we
46 * may have mlocked a page that is being munlocked. So lazy mlock must take
47 * the mmap_sem for read, and verify that the vma really is locked
48 * (see mm/rmap.c).
49 */
50
51/*
52 * LRU accounting for clear_page_mlock()
53 */
54void __clear_page_mlock(struct page *page)
55{
56 VM_BUG_ON(!PageLocked(page));
57
58 if (!page->mapping) { /* truncated ? */
59 return;
60 }
61
62 dec_zone_page_state(page, NR_MLOCK);
63 count_vm_event(UNEVICTABLE_PGCLEARED);
64 if (!isolate_lru_page(page)) {
65 putback_lru_page(page);
66 } else {
67 /*
68 * We lost the race. the page already moved to evictable list.
69 */
70 if (PageUnevictable(page))
71 count_vm_event(UNEVICTABLE_PGSTRANDED);
72 }
73}
74
75/*
76 * Mark page as mlocked if not already.
77 * If page on LRU, isolate and putback to move to unevictable list.
78 */
79void mlock_vma_page(struct page *page)
80{
81 BUG_ON(!PageLocked(page));
82
83 if (!TestSetPageMlocked(page)) {
84 inc_zone_page_state(page, NR_MLOCK);
85 count_vm_event(UNEVICTABLE_PGMLOCKED);
86 if (!isolate_lru_page(page))
87 putback_lru_page(page);
88 }
89}
90
91/**
92 * munlock_vma_page - munlock a vma page
93 * @page - page to be unlocked
94 *
95 * called from munlock()/munmap() path with page supposedly on the LRU.
96 * When we munlock a page, because the vma where we found the page is being
97 * munlock()ed or munmap()ed, we want to check whether other vmas hold the
98 * page locked so that we can leave it on the unevictable lru list and not
99 * bother vmscan with it. However, to walk the page's rmap list in
100 * try_to_munlock() we must isolate the page from the LRU. If some other
101 * task has removed the page from the LRU, we won't be able to do that.
102 * So we clear the PageMlocked as we might not get another chance. If we
103 * can't isolate the page, we leave it for putback_lru_page() and vmscan
104 * [page_referenced()/try_to_unmap()] to deal with.
105 */
106void munlock_vma_page(struct page *page)
107{
108 BUG_ON(!PageLocked(page));
109
110 if (TestClearPageMlocked(page)) {
111 dec_zone_page_state(page, NR_MLOCK);
112 if (!isolate_lru_page(page)) {
113 int ret = try_to_munlock(page);
114 /*
115 * did try_to_unlock() succeed or punt?
116 */
117 if (ret != SWAP_MLOCK)
118 count_vm_event(UNEVICTABLE_PGMUNLOCKED);
119
120 putback_lru_page(page);
121 } else {
122 /*
123 * Some other task has removed the page from the LRU.
124 * putback_lru_page() will take care of removing the
125 * page from the unevictable list, if necessary.
126 * vmscan [page_referenced()] will move the page back
127 * to the unevictable list if some other vma has it
128 * mlocked.
129 */
130 if (PageUnevictable(page))
131 count_vm_event(UNEVICTABLE_PGSTRANDED);
132 else
133 count_vm_event(UNEVICTABLE_PGMUNLOCKED);
134 }
135 }
136}
137
138/**
139 * __mlock_vma_pages_range() - mlock a range of pages in the vma.
140 * @vma: target vma
141 * @start: start address
142 * @end: end address
143 *
144 * This takes care of making the pages present too.
145 *
146 * return 0 on success, negative error code on error.
147 *
148 * vma->vm_mm->mmap_sem must be held for at least read.
149 */
150static long __mlock_vma_pages_range(struct vm_area_struct *vma,
151 unsigned long start, unsigned long end,
152 int *nonblocking)
153{
154 struct mm_struct *mm = vma->vm_mm;
155 unsigned long addr = start;
156 int nr_pages = (end - start) / PAGE_SIZE;
157 int gup_flags;
158
159 VM_BUG_ON(start & ~PAGE_MASK);
160 VM_BUG_ON(end & ~PAGE_MASK);
161 VM_BUG_ON(start < vma->vm_start);
162 VM_BUG_ON(end > vma->vm_end);
163 VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem));
164
165 gup_flags = FOLL_TOUCH | FOLL_MLOCK;
166 /*
167 * We want to touch writable mappings with a write fault in order
168 * to break COW, except for shared mappings because these don't COW
169 * and we would not want to dirty them for nothing.
170 */
171 if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
172 gup_flags |= FOLL_WRITE;
173
174 /*
175 * We want mlock to succeed for regions that have any permissions
176 * other than PROT_NONE.
177 */
178 if (vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))
179 gup_flags |= FOLL_FORCE;
180
181 return __get_user_pages(current, mm, addr, nr_pages, gup_flags,
182 NULL, NULL, nonblocking);
183}
184
185/*
186 * convert get_user_pages() return value to posix mlock() error
187 */
188static int __mlock_posix_error_return(long retval)
189{
190 if (retval == -EFAULT)
191 retval = -ENOMEM;
192 else if (retval == -ENOMEM)
193 retval = -EAGAIN;
194 return retval;
195}
196
197/**
198 * mlock_vma_pages_range() - mlock pages in specified vma range.
199 * @vma - the vma containing the specfied address range
200 * @start - starting address in @vma to mlock
201 * @end - end address [+1] in @vma to mlock
202 *
203 * For mmap()/mremap()/expansion of mlocked vma.
204 *
205 * return 0 on success for "normal" vmas.
206 *
207 * return number of pages [> 0] to be removed from locked_vm on success
208 * of "special" vmas.
209 */
210long mlock_vma_pages_range(struct vm_area_struct *vma,
211 unsigned long start, unsigned long end)
212{
213 int nr_pages = (end - start) / PAGE_SIZE;
214 BUG_ON(!(vma->vm_flags & VM_LOCKED));
215
216 /*
217 * filter unlockable vmas
218 */
219 if (vma->vm_flags & (VM_IO | VM_PFNMAP))
220 goto no_mlock;
221
222 if (!((vma->vm_flags & (VM_DONTEXPAND | VM_RESERVED)) ||
223 is_vm_hugetlb_page(vma) ||
224 vma == get_gate_vma(current->mm))) {
225
226 __mlock_vma_pages_range(vma, start, end, NULL);
227
228 /* Hide errors from mmap() and other callers */
229 return 0;
230 }
231
232 /*
233 * User mapped kernel pages or huge pages:
234 * make these pages present to populate the ptes, but
235 * fall thru' to reset VM_LOCKED--no need to unlock, and
236 * return nr_pages so these don't get counted against task's
237 * locked limit. huge pages are already counted against
238 * locked vm limit.
239 */
240 make_pages_present(start, end);
241
242no_mlock:
243 vma->vm_flags &= ~VM_LOCKED; /* and don't come back! */
244 return nr_pages; /* error or pages NOT mlocked */
245}
246
247/*
248 * munlock_vma_pages_range() - munlock all pages in the vma range.'
249 * @vma - vma containing range to be munlock()ed.
250 * @start - start address in @vma of the range
251 * @end - end of range in @vma.
252 *
253 * For mremap(), munmap() and exit().
254 *
255 * Called with @vma VM_LOCKED.
256 *
257 * Returns with VM_LOCKED cleared. Callers must be prepared to
258 * deal with this.
259 *
260 * We don't save and restore VM_LOCKED here because pages are
261 * still on lru. In unmap path, pages might be scanned by reclaim
262 * and re-mlocked by try_to_{munlock|unmap} before we unmap and
263 * free them. This will result in freeing mlocked pages.
264 */
265void munlock_vma_pages_range(struct vm_area_struct *vma,
266 unsigned long start, unsigned long end)
267{
268 unsigned long addr;
269
270 lru_add_drain();
271 vma->vm_flags &= ~VM_LOCKED;
272
273 for (addr = start; addr < end; addr += PAGE_SIZE) {
274 struct page *page;
275 /*
276 * Although FOLL_DUMP is intended for get_dump_page(),
277 * it just so happens that its special treatment of the
278 * ZERO_PAGE (returning an error instead of doing get_page)
279 * suits munlock very well (and if somehow an abnormal page
280 * has sneaked into the range, we won't oops here: great).
281 */
282 page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP);
283 if (page && !IS_ERR(page)) {
284 lock_page(page);
285 /*
286 * Like in __mlock_vma_pages_range(),
287 * because we lock page here and migration is
288 * blocked by the elevated reference, we need
289 * only check for file-cache page truncation.
290 */
291 if (page->mapping)
292 munlock_vma_page(page);
293 unlock_page(page);
294 put_page(page);
295 }
296 cond_resched();
297 }
298}
299
300/*
301 * mlock_fixup - handle mlock[all]/munlock[all] requests.
302 *
303 * Filters out "special" vmas -- VM_LOCKED never gets set for these, and
304 * munlock is a no-op. However, for some special vmas, we go ahead and
305 * populate the ptes via make_pages_present().
306 *
307 * For vmas that pass the filters, merge/split as appropriate.
308 */
309static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
310 unsigned long start, unsigned long end, vm_flags_t newflags)
311{
312 struct mm_struct *mm = vma->vm_mm;
313 pgoff_t pgoff;
314 int nr_pages;
315 int ret = 0;
316 int lock = !!(newflags & VM_LOCKED);
317
318 if (newflags == vma->vm_flags || (vma->vm_flags & VM_SPECIAL) ||
319 is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm))
320 goto out; /* don't set VM_LOCKED, don't count */
321
322 pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
323 *prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma,
324 vma->vm_file, pgoff, vma_policy(vma));
325 if (*prev) {
326 vma = *prev;
327 goto success;
328 }
329
330 if (start != vma->vm_start) {
331 ret = split_vma(mm, vma, start, 1);
332 if (ret)
333 goto out;
334 }
335
336 if (end != vma->vm_end) {
337 ret = split_vma(mm, vma, end, 0);
338 if (ret)
339 goto out;
340 }
341
342success:
343 /*
344 * Keep track of amount of locked VM.
345 */
346 nr_pages = (end - start) >> PAGE_SHIFT;
347 if (!lock)
348 nr_pages = -nr_pages;
349 mm->locked_vm += nr_pages;
350
351 /*
352 * vm_flags is protected by the mmap_sem held in write mode.
353 * It's okay if try_to_unmap_one unmaps a page just after we
354 * set VM_LOCKED, __mlock_vma_pages_range will bring it back.
355 */
356
357 if (lock)
358 vma->vm_flags = newflags;
359 else
360 munlock_vma_pages_range(vma, start, end);
361
362out:
363 *prev = vma;
364 return ret;
365}
366
367static int do_mlock(unsigned long start, size_t len, int on)
368{
369 unsigned long nstart, end, tmp;
370 struct vm_area_struct * vma, * prev;
371 int error;
372
373 VM_BUG_ON(start & ~PAGE_MASK);
374 VM_BUG_ON(len != PAGE_ALIGN(len));
375 end = start + len;
376 if (end < start)
377 return -EINVAL;
378 if (end == start)
379 return 0;
380 vma = find_vma_prev(current->mm, start, &prev);
381 if (!vma || vma->vm_start > start)
382 return -ENOMEM;
383
384 if (start > vma->vm_start)
385 prev = vma;
386
387 for (nstart = start ; ; ) {
388 vm_flags_t newflags;
389
390 /* Here we know that vma->vm_start <= nstart < vma->vm_end. */
391
392 newflags = vma->vm_flags | VM_LOCKED;
393 if (!on)
394 newflags &= ~VM_LOCKED;
395
396 tmp = vma->vm_end;
397 if (tmp > end)
398 tmp = end;
399 error = mlock_fixup(vma, &prev, nstart, tmp, newflags);
400 if (error)
401 break;
402 nstart = tmp;
403 if (nstart < prev->vm_end)
404 nstart = prev->vm_end;
405 if (nstart >= end)
406 break;
407
408 vma = prev->vm_next;
409 if (!vma || vma->vm_start != nstart) {
410 error = -ENOMEM;
411 break;
412 }
413 }
414 return error;
415}
416
417static int do_mlock_pages(unsigned long start, size_t len, int ignore_errors)
418{
419 struct mm_struct *mm = current->mm;
420 unsigned long end, nstart, nend;
421 struct vm_area_struct *vma = NULL;
422 int locked = 0;
423 int ret = 0;
424
425 VM_BUG_ON(start & ~PAGE_MASK);
426 VM_BUG_ON(len != PAGE_ALIGN(len));
427 end = start + len;
428
429 for (nstart = start; nstart < end; nstart = nend) {
430 /*
431 * We want to fault in pages for [nstart; end) address range.
432 * Find first corresponding VMA.
433 */
434 if (!locked) {
435 locked = 1;
436 down_read(&mm->mmap_sem);
437 vma = find_vma(mm, nstart);
438 } else if (nstart >= vma->vm_end)
439 vma = vma->vm_next;
440 if (!vma || vma->vm_start >= end)
441 break;
442 /*
443 * Set [nstart; nend) to intersection of desired address
444 * range with the first VMA. Also, skip undesirable VMA types.
445 */
446 nend = min(end, vma->vm_end);
447 if (vma->vm_flags & (VM_IO | VM_PFNMAP))
448 continue;
449 if (nstart < vma->vm_start)
450 nstart = vma->vm_start;
451 /*
452 * Now fault in a range of pages. __mlock_vma_pages_range()
453 * double checks the vma flags, so that it won't mlock pages
454 * if the vma was already munlocked.
455 */
456 ret = __mlock_vma_pages_range(vma, nstart, nend, &locked);
457 if (ret < 0) {
458 if (ignore_errors) {
459 ret = 0;
460 continue; /* continue at next VMA */
461 }
462 ret = __mlock_posix_error_return(ret);
463 break;
464 }
465 nend = nstart + ret * PAGE_SIZE;
466 ret = 0;
467 }
468 if (locked)
469 up_read(&mm->mmap_sem);
470 return ret; /* 0 or negative error code */
471}
472
473SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
474{
475 unsigned long locked;
476 unsigned long lock_limit;
477 int error = -ENOMEM;
478
479 if (!can_do_mlock())
480 return -EPERM;
481
482 lru_add_drain_all(); /* flush pagevec */
483
484 down_write(¤t->mm->mmap_sem);
485 len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
486 start &= PAGE_MASK;
487
488 locked = len >> PAGE_SHIFT;
489 locked += current->mm->locked_vm;
490
491 lock_limit = rlimit(RLIMIT_MEMLOCK);
492 lock_limit >>= PAGE_SHIFT;
493
494 /* check against resource limits */
495 if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
496 error = do_mlock(start, len, 1);
497 up_write(¤t->mm->mmap_sem);
498 if (!error)
499 error = do_mlock_pages(start, len, 0);
500 return error;
501}
502
503SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
504{
505 int ret;
506
507 down_write(¤t->mm->mmap_sem);
508 len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
509 start &= PAGE_MASK;
510 ret = do_mlock(start, len, 0);
511 up_write(¤t->mm->mmap_sem);
512 return ret;
513}
514
515static int do_mlockall(int flags)
516{
517 struct vm_area_struct * vma, * prev = NULL;
518 unsigned int def_flags = 0;
519
520 if (flags & MCL_FUTURE)
521 def_flags = VM_LOCKED;
522 current->mm->def_flags = def_flags;
523 if (flags == MCL_FUTURE)
524 goto out;
525
526 for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
527 vm_flags_t newflags;
528
529 newflags = vma->vm_flags | VM_LOCKED;
530 if (!(flags & MCL_CURRENT))
531 newflags &= ~VM_LOCKED;
532
533 /* Ignore errors */
534 mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
535 }
536out:
537 return 0;
538}
539
540SYSCALL_DEFINE1(mlockall, int, flags)
541{
542 unsigned long lock_limit;
543 int ret = -EINVAL;
544
545 if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE)))
546 goto out;
547
548 ret = -EPERM;
549 if (!can_do_mlock())
550 goto out;
551
552 lru_add_drain_all(); /* flush pagevec */
553
554 down_write(¤t->mm->mmap_sem);
555
556 lock_limit = rlimit(RLIMIT_MEMLOCK);
557 lock_limit >>= PAGE_SHIFT;
558
559 ret = -ENOMEM;
560 if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
561 capable(CAP_IPC_LOCK))
562 ret = do_mlockall(flags);
563 up_write(¤t->mm->mmap_sem);
564 if (!ret && (flags & MCL_CURRENT)) {
565 /* Ignore errors */
566 do_mlock_pages(0, TASK_SIZE, 1);
567 }
568out:
569 return ret;
570}
571
572SYSCALL_DEFINE0(munlockall)
573{
574 int ret;
575
576 down_write(¤t->mm->mmap_sem);
577 ret = do_mlockall(0);
578 up_write(¤t->mm->mmap_sem);
579 return ret;
580}
581
582/*
583 * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
584 * shm segments) get accounted against the user_struct instead.
585 */
586static DEFINE_SPINLOCK(shmlock_user_lock);
587
588int user_shm_lock(size_t size, struct user_struct *user)
589{
590 unsigned long lock_limit, locked;
591 int allowed = 0;
592
593 locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
594 lock_limit = rlimit(RLIMIT_MEMLOCK);
595 if (lock_limit == RLIM_INFINITY)
596 allowed = 1;
597 lock_limit >>= PAGE_SHIFT;
598 spin_lock(&shmlock_user_lock);
599 if (!allowed &&
600 locked + user->locked_shm > lock_limit && !capable(CAP_IPC_LOCK))
601 goto out;
602 get_uid(user);
603 user->locked_shm += locked;
604 allowed = 1;
605out:
606 spin_unlock(&shmlock_user_lock);
607 return allowed;
608}
609
610void user_shm_unlock(size_t size, struct user_struct *user)
611{
612 spin_lock(&shmlock_user_lock);
613 user->locked_shm -= (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
614 spin_unlock(&shmlock_user_lock);
615 free_uid(user);
616}
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * linux/mm/mlock.c
4 *
5 * (C) Copyright 1995 Linus Torvalds
6 * (C) Copyright 2002 Christoph Hellwig
7 */
8
9#include <linux/capability.h>
10#include <linux/mman.h>
11#include <linux/mm.h>
12#include <linux/sched/user.h>
13#include <linux/swap.h>
14#include <linux/swapops.h>
15#include <linux/pagemap.h>
16#include <linux/pagevec.h>
17#include <linux/mempolicy.h>
18#include <linux/syscalls.h>
19#include <linux/sched.h>
20#include <linux/export.h>
21#include <linux/rmap.h>
22#include <linux/mmzone.h>
23#include <linux/hugetlb.h>
24#include <linux/memcontrol.h>
25#include <linux/mm_inline.h>
26
27#include "internal.h"
28
29bool can_do_mlock(void)
30{
31 if (rlimit(RLIMIT_MEMLOCK) != 0)
32 return true;
33 if (capable(CAP_IPC_LOCK))
34 return true;
35 return false;
36}
37EXPORT_SYMBOL(can_do_mlock);
38
39/*
40 * Mlocked pages are marked with PageMlocked() flag for efficient testing
41 * in vmscan and, possibly, the fault path; and to support semi-accurate
42 * statistics.
43 *
44 * An mlocked page [PageMlocked(page)] is unevictable. As such, it will
45 * be placed on the LRU "unevictable" list, rather than the [in]active lists.
46 * The unevictable list is an LRU sibling list to the [in]active lists.
47 * PageUnevictable is set to indicate the unevictable state.
48 *
49 * When lazy mlocking via vmscan, it is important to ensure that the
50 * vma's VM_LOCKED status is not concurrently being modified, otherwise we
51 * may have mlocked a page that is being munlocked. So lazy mlock must take
52 * the mmap_sem for read, and verify that the vma really is locked
53 * (see mm/rmap.c).
54 */
55
56/*
57 * LRU accounting for clear_page_mlock()
58 */
59void clear_page_mlock(struct page *page)
60{
61 if (!TestClearPageMlocked(page))
62 return;
63
64 mod_zone_page_state(page_zone(page), NR_MLOCK,
65 -hpage_nr_pages(page));
66 count_vm_event(UNEVICTABLE_PGCLEARED);
67 /*
68 * The previous TestClearPageMlocked() corresponds to the smp_mb()
69 * in __pagevec_lru_add_fn().
70 *
71 * See __pagevec_lru_add_fn for more explanation.
72 */
73 if (!isolate_lru_page(page)) {
74 putback_lru_page(page);
75 } else {
76 /*
77 * We lost the race. the page already moved to evictable list.
78 */
79 if (PageUnevictable(page))
80 count_vm_event(UNEVICTABLE_PGSTRANDED);
81 }
82}
83
84/*
85 * Mark page as mlocked if not already.
86 * If page on LRU, isolate and putback to move to unevictable list.
87 */
88void mlock_vma_page(struct page *page)
89{
90 /* Serialize with page migration */
91 BUG_ON(!PageLocked(page));
92
93 VM_BUG_ON_PAGE(PageTail(page), page);
94 VM_BUG_ON_PAGE(PageCompound(page) && PageDoubleMap(page), page);
95
96 if (!TestSetPageMlocked(page)) {
97 mod_zone_page_state(page_zone(page), NR_MLOCK,
98 hpage_nr_pages(page));
99 count_vm_event(UNEVICTABLE_PGMLOCKED);
100 if (!isolate_lru_page(page))
101 putback_lru_page(page);
102 }
103}
104
105/*
106 * Isolate a page from LRU with optional get_page() pin.
107 * Assumes lru_lock already held and page already pinned.
108 */
109static bool __munlock_isolate_lru_page(struct page *page, bool getpage)
110{
111 if (PageLRU(page)) {
112 struct lruvec *lruvec;
113
114 lruvec = mem_cgroup_page_lruvec(page, page_pgdat(page));
115 if (getpage)
116 get_page(page);
117 ClearPageLRU(page);
118 del_page_from_lru_list(page, lruvec, page_lru(page));
119 return true;
120 }
121
122 return false;
123}
124
125/*
126 * Finish munlock after successful page isolation
127 *
128 * Page must be locked. This is a wrapper for try_to_munlock()
129 * and putback_lru_page() with munlock accounting.
130 */
131static void __munlock_isolated_page(struct page *page)
132{
133 /*
134 * Optimization: if the page was mapped just once, that's our mapping
135 * and we don't need to check all the other vmas.
136 */
137 if (page_mapcount(page) > 1)
138 try_to_munlock(page);
139
140 /* Did try_to_unlock() succeed or punt? */
141 if (!PageMlocked(page))
142 count_vm_event(UNEVICTABLE_PGMUNLOCKED);
143
144 putback_lru_page(page);
145}
146
147/*
148 * Accounting for page isolation fail during munlock
149 *
150 * Performs accounting when page isolation fails in munlock. There is nothing
151 * else to do because it means some other task has already removed the page
152 * from the LRU. putback_lru_page() will take care of removing the page from
153 * the unevictable list, if necessary. vmscan [page_referenced()] will move
154 * the page back to the unevictable list if some other vma has it mlocked.
155 */
156static void __munlock_isolation_failed(struct page *page)
157{
158 if (PageUnevictable(page))
159 __count_vm_event(UNEVICTABLE_PGSTRANDED);
160 else
161 __count_vm_event(UNEVICTABLE_PGMUNLOCKED);
162}
163
164/**
165 * munlock_vma_page - munlock a vma page
166 * @page: page to be unlocked, either a normal page or THP page head
167 *
168 * returns the size of the page as a page mask (0 for normal page,
169 * HPAGE_PMD_NR - 1 for THP head page)
170 *
171 * called from munlock()/munmap() path with page supposedly on the LRU.
172 * When we munlock a page, because the vma where we found the page is being
173 * munlock()ed or munmap()ed, we want to check whether other vmas hold the
174 * page locked so that we can leave it on the unevictable lru list and not
175 * bother vmscan with it. However, to walk the page's rmap list in
176 * try_to_munlock() we must isolate the page from the LRU. If some other
177 * task has removed the page from the LRU, we won't be able to do that.
178 * So we clear the PageMlocked as we might not get another chance. If we
179 * can't isolate the page, we leave it for putback_lru_page() and vmscan
180 * [page_referenced()/try_to_unmap()] to deal with.
181 */
182unsigned int munlock_vma_page(struct page *page)
183{
184 int nr_pages;
185 struct zone *zone = page_zone(page);
186
187 /* For try_to_munlock() and to serialize with page migration */
188 BUG_ON(!PageLocked(page));
189
190 VM_BUG_ON_PAGE(PageTail(page), page);
191
192 /*
193 * Serialize with any parallel __split_huge_page_refcount() which
194 * might otherwise copy PageMlocked to part of the tail pages before
195 * we clear it in the head page. It also stabilizes hpage_nr_pages().
196 */
197 spin_lock_irq(zone_lru_lock(zone));
198
199 if (!TestClearPageMlocked(page)) {
200 /* Potentially, PTE-mapped THP: do not skip the rest PTEs */
201 nr_pages = 1;
202 goto unlock_out;
203 }
204
205 nr_pages = hpage_nr_pages(page);
206 __mod_zone_page_state(zone, NR_MLOCK, -nr_pages);
207
208 if (__munlock_isolate_lru_page(page, true)) {
209 spin_unlock_irq(zone_lru_lock(zone));
210 __munlock_isolated_page(page);
211 goto out;
212 }
213 __munlock_isolation_failed(page);
214
215unlock_out:
216 spin_unlock_irq(zone_lru_lock(zone));
217
218out:
219 return nr_pages - 1;
220}
221
222/*
223 * convert get_user_pages() return value to posix mlock() error
224 */
225static int __mlock_posix_error_return(long retval)
226{
227 if (retval == -EFAULT)
228 retval = -ENOMEM;
229 else if (retval == -ENOMEM)
230 retval = -EAGAIN;
231 return retval;
232}
233
234/*
235 * Prepare page for fast batched LRU putback via putback_lru_evictable_pagevec()
236 *
237 * The fast path is available only for evictable pages with single mapping.
238 * Then we can bypass the per-cpu pvec and get better performance.
239 * when mapcount > 1 we need try_to_munlock() which can fail.
240 * when !page_evictable(), we need the full redo logic of putback_lru_page to
241 * avoid leaving evictable page in unevictable list.
242 *
243 * In case of success, @page is added to @pvec and @pgrescued is incremented
244 * in case that the page was previously unevictable. @page is also unlocked.
245 */
246static bool __putback_lru_fast_prepare(struct page *page, struct pagevec *pvec,
247 int *pgrescued)
248{
249 VM_BUG_ON_PAGE(PageLRU(page), page);
250 VM_BUG_ON_PAGE(!PageLocked(page), page);
251
252 if (page_mapcount(page) <= 1 && page_evictable(page)) {
253 pagevec_add(pvec, page);
254 if (TestClearPageUnevictable(page))
255 (*pgrescued)++;
256 unlock_page(page);
257 return true;
258 }
259
260 return false;
261}
262
263/*
264 * Putback multiple evictable pages to the LRU
265 *
266 * Batched putback of evictable pages that bypasses the per-cpu pvec. Some of
267 * the pages might have meanwhile become unevictable but that is OK.
268 */
269static void __putback_lru_fast(struct pagevec *pvec, int pgrescued)
270{
271 count_vm_events(UNEVICTABLE_PGMUNLOCKED, pagevec_count(pvec));
272 /*
273 *__pagevec_lru_add() calls release_pages() so we don't call
274 * put_page() explicitly
275 */
276 __pagevec_lru_add(pvec);
277 count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
278}
279
280/*
281 * Munlock a batch of pages from the same zone
282 *
283 * The work is split to two main phases. First phase clears the Mlocked flag
284 * and attempts to isolate the pages, all under a single zone lru lock.
285 * The second phase finishes the munlock only for pages where isolation
286 * succeeded.
287 *
288 * Note that the pagevec may be modified during the process.
289 */
290static void __munlock_pagevec(struct pagevec *pvec, struct zone *zone)
291{
292 int i;
293 int nr = pagevec_count(pvec);
294 int delta_munlocked = -nr;
295 struct pagevec pvec_putback;
296 int pgrescued = 0;
297
298 pagevec_init(&pvec_putback);
299
300 /* Phase 1: page isolation */
301 spin_lock_irq(zone_lru_lock(zone));
302 for (i = 0; i < nr; i++) {
303 struct page *page = pvec->pages[i];
304
305 if (TestClearPageMlocked(page)) {
306 /*
307 * We already have pin from follow_page_mask()
308 * so we can spare the get_page() here.
309 */
310 if (__munlock_isolate_lru_page(page, false))
311 continue;
312 else
313 __munlock_isolation_failed(page);
314 } else {
315 delta_munlocked++;
316 }
317
318 /*
319 * We won't be munlocking this page in the next phase
320 * but we still need to release the follow_page_mask()
321 * pin. We cannot do it under lru_lock however. If it's
322 * the last pin, __page_cache_release() would deadlock.
323 */
324 pagevec_add(&pvec_putback, pvec->pages[i]);
325 pvec->pages[i] = NULL;
326 }
327 __mod_zone_page_state(zone, NR_MLOCK, delta_munlocked);
328 spin_unlock_irq(zone_lru_lock(zone));
329
330 /* Now we can release pins of pages that we are not munlocking */
331 pagevec_release(&pvec_putback);
332
333 /* Phase 2: page munlock */
334 for (i = 0; i < nr; i++) {
335 struct page *page = pvec->pages[i];
336
337 if (page) {
338 lock_page(page);
339 if (!__putback_lru_fast_prepare(page, &pvec_putback,
340 &pgrescued)) {
341 /*
342 * Slow path. We don't want to lose the last
343 * pin before unlock_page()
344 */
345 get_page(page); /* for putback_lru_page() */
346 __munlock_isolated_page(page);
347 unlock_page(page);
348 put_page(page); /* from follow_page_mask() */
349 }
350 }
351 }
352
353 /*
354 * Phase 3: page putback for pages that qualified for the fast path
355 * This will also call put_page() to return pin from follow_page_mask()
356 */
357 if (pagevec_count(&pvec_putback))
358 __putback_lru_fast(&pvec_putback, pgrescued);
359}
360
361/*
362 * Fill up pagevec for __munlock_pagevec using pte walk
363 *
364 * The function expects that the struct page corresponding to @start address is
365 * a non-TPH page already pinned and in the @pvec, and that it belongs to @zone.
366 *
367 * The rest of @pvec is filled by subsequent pages within the same pmd and same
368 * zone, as long as the pte's are present and vm_normal_page() succeeds. These
369 * pages also get pinned.
370 *
371 * Returns the address of the next page that should be scanned. This equals
372 * @start + PAGE_SIZE when no page could be added by the pte walk.
373 */
374static unsigned long __munlock_pagevec_fill(struct pagevec *pvec,
375 struct vm_area_struct *vma, struct zone *zone,
376 unsigned long start, unsigned long end)
377{
378 pte_t *pte;
379 spinlock_t *ptl;
380
381 /*
382 * Initialize pte walk starting at the already pinned page where we
383 * are sure that there is a pte, as it was pinned under the same
384 * mmap_sem write op.
385 */
386 pte = get_locked_pte(vma->vm_mm, start, &ptl);
387 /* Make sure we do not cross the page table boundary */
388 end = pgd_addr_end(start, end);
389 end = p4d_addr_end(start, end);
390 end = pud_addr_end(start, end);
391 end = pmd_addr_end(start, end);
392
393 /* The page next to the pinned page is the first we will try to get */
394 start += PAGE_SIZE;
395 while (start < end) {
396 struct page *page = NULL;
397 pte++;
398 if (pte_present(*pte))
399 page = vm_normal_page(vma, start, *pte);
400 /*
401 * Break if page could not be obtained or the page's node+zone does not
402 * match
403 */
404 if (!page || page_zone(page) != zone)
405 break;
406
407 /*
408 * Do not use pagevec for PTE-mapped THP,
409 * munlock_vma_pages_range() will handle them.
410 */
411 if (PageTransCompound(page))
412 break;
413
414 get_page(page);
415 /*
416 * Increase the address that will be returned *before* the
417 * eventual break due to pvec becoming full by adding the page
418 */
419 start += PAGE_SIZE;
420 if (pagevec_add(pvec, page) == 0)
421 break;
422 }
423 pte_unmap_unlock(pte, ptl);
424 return start;
425}
426
427/*
428 * munlock_vma_pages_range() - munlock all pages in the vma range.'
429 * @vma - vma containing range to be munlock()ed.
430 * @start - start address in @vma of the range
431 * @end - end of range in @vma.
432 *
433 * For mremap(), munmap() and exit().
434 *
435 * Called with @vma VM_LOCKED.
436 *
437 * Returns with VM_LOCKED cleared. Callers must be prepared to
438 * deal with this.
439 *
440 * We don't save and restore VM_LOCKED here because pages are
441 * still on lru. In unmap path, pages might be scanned by reclaim
442 * and re-mlocked by try_to_{munlock|unmap} before we unmap and
443 * free them. This will result in freeing mlocked pages.
444 */
445void munlock_vma_pages_range(struct vm_area_struct *vma,
446 unsigned long start, unsigned long end)
447{
448 vma->vm_flags &= VM_LOCKED_CLEAR_MASK;
449
450 while (start < end) {
451 struct page *page;
452 unsigned int page_mask = 0;
453 unsigned long page_increm;
454 struct pagevec pvec;
455 struct zone *zone;
456
457 pagevec_init(&pvec);
458 /*
459 * Although FOLL_DUMP is intended for get_dump_page(),
460 * it just so happens that its special treatment of the
461 * ZERO_PAGE (returning an error instead of doing get_page)
462 * suits munlock very well (and if somehow an abnormal page
463 * has sneaked into the range, we won't oops here: great).
464 */
465 page = follow_page(vma, start, FOLL_GET | FOLL_DUMP);
466
467 if (page && !IS_ERR(page)) {
468 if (PageTransTail(page)) {
469 VM_BUG_ON_PAGE(PageMlocked(page), page);
470 put_page(page); /* follow_page_mask() */
471 } else if (PageTransHuge(page)) {
472 lock_page(page);
473 /*
474 * Any THP page found by follow_page_mask() may
475 * have gotten split before reaching
476 * munlock_vma_page(), so we need to compute
477 * the page_mask here instead.
478 */
479 page_mask = munlock_vma_page(page);
480 unlock_page(page);
481 put_page(page); /* follow_page_mask() */
482 } else {
483 /*
484 * Non-huge pages are handled in batches via
485 * pagevec. The pin from follow_page_mask()
486 * prevents them from collapsing by THP.
487 */
488 pagevec_add(&pvec, page);
489 zone = page_zone(page);
490
491 /*
492 * Try to fill the rest of pagevec using fast
493 * pte walk. This will also update start to
494 * the next page to process. Then munlock the
495 * pagevec.
496 */
497 start = __munlock_pagevec_fill(&pvec, vma,
498 zone, start, end);
499 __munlock_pagevec(&pvec, zone);
500 goto next;
501 }
502 }
503 page_increm = 1 + page_mask;
504 start += page_increm * PAGE_SIZE;
505next:
506 cond_resched();
507 }
508}
509
510/*
511 * mlock_fixup - handle mlock[all]/munlock[all] requests.
512 *
513 * Filters out "special" vmas -- VM_LOCKED never gets set for these, and
514 * munlock is a no-op. However, for some special vmas, we go ahead and
515 * populate the ptes.
516 *
517 * For vmas that pass the filters, merge/split as appropriate.
518 */
519static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
520 unsigned long start, unsigned long end, vm_flags_t newflags)
521{
522 struct mm_struct *mm = vma->vm_mm;
523 pgoff_t pgoff;
524 int nr_pages;
525 int ret = 0;
526 int lock = !!(newflags & VM_LOCKED);
527 vm_flags_t old_flags = vma->vm_flags;
528
529 if (newflags == vma->vm_flags || (vma->vm_flags & VM_SPECIAL) ||
530 is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm))
531 /* don't set VM_LOCKED or VM_LOCKONFAULT and don't count */
532 goto out;
533
534 pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
535 *prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma,
536 vma->vm_file, pgoff, vma_policy(vma),
537 vma->vm_userfaultfd_ctx);
538 if (*prev) {
539 vma = *prev;
540 goto success;
541 }
542
543 if (start != vma->vm_start) {
544 ret = split_vma(mm, vma, start, 1);
545 if (ret)
546 goto out;
547 }
548
549 if (end != vma->vm_end) {
550 ret = split_vma(mm, vma, end, 0);
551 if (ret)
552 goto out;
553 }
554
555success:
556 /*
557 * Keep track of amount of locked VM.
558 */
559 nr_pages = (end - start) >> PAGE_SHIFT;
560 if (!lock)
561 nr_pages = -nr_pages;
562 else if (old_flags & VM_LOCKED)
563 nr_pages = 0;
564 mm->locked_vm += nr_pages;
565
566 /*
567 * vm_flags is protected by the mmap_sem held in write mode.
568 * It's okay if try_to_unmap_one unmaps a page just after we
569 * set VM_LOCKED, populate_vma_page_range will bring it back.
570 */
571
572 if (lock)
573 vma->vm_flags = newflags;
574 else
575 munlock_vma_pages_range(vma, start, end);
576
577out:
578 *prev = vma;
579 return ret;
580}
581
582static int apply_vma_lock_flags(unsigned long start, size_t len,
583 vm_flags_t flags)
584{
585 unsigned long nstart, end, tmp;
586 struct vm_area_struct * vma, * prev;
587 int error;
588
589 VM_BUG_ON(offset_in_page(start));
590 VM_BUG_ON(len != PAGE_ALIGN(len));
591 end = start + len;
592 if (end < start)
593 return -EINVAL;
594 if (end == start)
595 return 0;
596 vma = find_vma(current->mm, start);
597 if (!vma || vma->vm_start > start)
598 return -ENOMEM;
599
600 prev = vma->vm_prev;
601 if (start > vma->vm_start)
602 prev = vma;
603
604 for (nstart = start ; ; ) {
605 vm_flags_t newflags = vma->vm_flags & VM_LOCKED_CLEAR_MASK;
606
607 newflags |= flags;
608
609 /* Here we know that vma->vm_start <= nstart < vma->vm_end. */
610 tmp = vma->vm_end;
611 if (tmp > end)
612 tmp = end;
613 error = mlock_fixup(vma, &prev, nstart, tmp, newflags);
614 if (error)
615 break;
616 nstart = tmp;
617 if (nstart < prev->vm_end)
618 nstart = prev->vm_end;
619 if (nstart >= end)
620 break;
621
622 vma = prev->vm_next;
623 if (!vma || vma->vm_start != nstart) {
624 error = -ENOMEM;
625 break;
626 }
627 }
628 return error;
629}
630
631/*
632 * Go through vma areas and sum size of mlocked
633 * vma pages, as return value.
634 * Note deferred memory locking case(mlock2(,,MLOCK_ONFAULT)
635 * is also counted.
636 * Return value: previously mlocked page counts
637 */
638static int count_mm_mlocked_page_nr(struct mm_struct *mm,
639 unsigned long start, size_t len)
640{
641 struct vm_area_struct *vma;
642 int count = 0;
643
644 if (mm == NULL)
645 mm = current->mm;
646
647 vma = find_vma(mm, start);
648 if (vma == NULL)
649 vma = mm->mmap;
650
651 for (; vma ; vma = vma->vm_next) {
652 if (start >= vma->vm_end)
653 continue;
654 if (start + len <= vma->vm_start)
655 break;
656 if (vma->vm_flags & VM_LOCKED) {
657 if (start > vma->vm_start)
658 count -= (start - vma->vm_start);
659 if (start + len < vma->vm_end) {
660 count += start + len - vma->vm_start;
661 break;
662 }
663 count += vma->vm_end - vma->vm_start;
664 }
665 }
666
667 return count >> PAGE_SHIFT;
668}
669
670static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t flags)
671{
672 unsigned long locked;
673 unsigned long lock_limit;
674 int error = -ENOMEM;
675
676 if (!can_do_mlock())
677 return -EPERM;
678
679 len = PAGE_ALIGN(len + (offset_in_page(start)));
680 start &= PAGE_MASK;
681
682 lock_limit = rlimit(RLIMIT_MEMLOCK);
683 lock_limit >>= PAGE_SHIFT;
684 locked = len >> PAGE_SHIFT;
685
686 if (down_write_killable(¤t->mm->mmap_sem))
687 return -EINTR;
688
689 locked += current->mm->locked_vm;
690 if ((locked > lock_limit) && (!capable(CAP_IPC_LOCK))) {
691 /*
692 * It is possible that the regions requested intersect with
693 * previously mlocked areas, that part area in "mm->locked_vm"
694 * should not be counted to new mlock increment count. So check
695 * and adjust locked count if necessary.
696 */
697 locked -= count_mm_mlocked_page_nr(current->mm,
698 start, len);
699 }
700
701 /* check against resource limits */
702 if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
703 error = apply_vma_lock_flags(start, len, flags);
704
705 up_write(¤t->mm->mmap_sem);
706 if (error)
707 return error;
708
709 error = __mm_populate(start, len, 0);
710 if (error)
711 return __mlock_posix_error_return(error);
712 return 0;
713}
714
715SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
716{
717 return do_mlock(start, len, VM_LOCKED);
718}
719
720SYSCALL_DEFINE3(mlock2, unsigned long, start, size_t, len, int, flags)
721{
722 vm_flags_t vm_flags = VM_LOCKED;
723
724 if (flags & ~MLOCK_ONFAULT)
725 return -EINVAL;
726
727 if (flags & MLOCK_ONFAULT)
728 vm_flags |= VM_LOCKONFAULT;
729
730 return do_mlock(start, len, vm_flags);
731}
732
733SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
734{
735 int ret;
736
737 len = PAGE_ALIGN(len + (offset_in_page(start)));
738 start &= PAGE_MASK;
739
740 if (down_write_killable(¤t->mm->mmap_sem))
741 return -EINTR;
742 ret = apply_vma_lock_flags(start, len, 0);
743 up_write(¤t->mm->mmap_sem);
744
745 return ret;
746}
747
748/*
749 * Take the MCL_* flags passed into mlockall (or 0 if called from munlockall)
750 * and translate into the appropriate modifications to mm->def_flags and/or the
751 * flags for all current VMAs.
752 *
753 * There are a couple of subtleties with this. If mlockall() is called multiple
754 * times with different flags, the values do not necessarily stack. If mlockall
755 * is called once including the MCL_FUTURE flag and then a second time without
756 * it, VM_LOCKED and VM_LOCKONFAULT will be cleared from mm->def_flags.
757 */
758static int apply_mlockall_flags(int flags)
759{
760 struct vm_area_struct * vma, * prev = NULL;
761 vm_flags_t to_add = 0;
762
763 current->mm->def_flags &= VM_LOCKED_CLEAR_MASK;
764 if (flags & MCL_FUTURE) {
765 current->mm->def_flags |= VM_LOCKED;
766
767 if (flags & MCL_ONFAULT)
768 current->mm->def_flags |= VM_LOCKONFAULT;
769
770 if (!(flags & MCL_CURRENT))
771 goto out;
772 }
773
774 if (flags & MCL_CURRENT) {
775 to_add |= VM_LOCKED;
776 if (flags & MCL_ONFAULT)
777 to_add |= VM_LOCKONFAULT;
778 }
779
780 for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
781 vm_flags_t newflags;
782
783 newflags = vma->vm_flags & VM_LOCKED_CLEAR_MASK;
784 newflags |= to_add;
785
786 /* Ignore errors */
787 mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
788 cond_resched();
789 }
790out:
791 return 0;
792}
793
794SYSCALL_DEFINE1(mlockall, int, flags)
795{
796 unsigned long lock_limit;
797 int ret;
798
799 if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE | MCL_ONFAULT)))
800 return -EINVAL;
801
802 if (!can_do_mlock())
803 return -EPERM;
804
805 lock_limit = rlimit(RLIMIT_MEMLOCK);
806 lock_limit >>= PAGE_SHIFT;
807
808 if (down_write_killable(¤t->mm->mmap_sem))
809 return -EINTR;
810
811 ret = -ENOMEM;
812 if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
813 capable(CAP_IPC_LOCK))
814 ret = apply_mlockall_flags(flags);
815 up_write(¤t->mm->mmap_sem);
816 if (!ret && (flags & MCL_CURRENT))
817 mm_populate(0, TASK_SIZE);
818
819 return ret;
820}
821
822SYSCALL_DEFINE0(munlockall)
823{
824 int ret;
825
826 if (down_write_killable(¤t->mm->mmap_sem))
827 return -EINTR;
828 ret = apply_mlockall_flags(0);
829 up_write(¤t->mm->mmap_sem);
830 return ret;
831}
832
833/*
834 * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
835 * shm segments) get accounted against the user_struct instead.
836 */
837static DEFINE_SPINLOCK(shmlock_user_lock);
838
839int user_shm_lock(size_t size, struct user_struct *user)
840{
841 unsigned long lock_limit, locked;
842 int allowed = 0;
843
844 locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
845 lock_limit = rlimit(RLIMIT_MEMLOCK);
846 if (lock_limit == RLIM_INFINITY)
847 allowed = 1;
848 lock_limit >>= PAGE_SHIFT;
849 spin_lock(&shmlock_user_lock);
850 if (!allowed &&
851 locked + user->locked_shm > lock_limit && !capable(CAP_IPC_LOCK))
852 goto out;
853 get_uid(user);
854 user->locked_shm += locked;
855 allowed = 1;
856out:
857 spin_unlock(&shmlock_user_lock);
858 return allowed;
859}
860
861void user_shm_unlock(size_t size, struct user_struct *user)
862{
863 spin_lock(&shmlock_user_lock);
864 user->locked_shm -= (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
865 spin_unlock(&shmlock_user_lock);
866 free_uid(user);
867}