b1a7c8007c8946f94df7cfee9fff2a00d0506e86
4 * (C) Copyright 1995 Linus Torvalds
5 * (C) Copyright 2002 Christoph Hellwig
8 #include <linux/capability.h>
9 #include <linux/mman.h>
11 #include <linux/swap.h>
12 #include <linux/swapops.h>
13 #include <linux/pagemap.h>
14 #include <linux/pagevec.h>
15 #include <linux/mempolicy.h>
16 #include <linux/syscalls.h>
17 #include <linux/sched.h>
18 #include <linux/export.h>
19 #include <linux/rmap.h>
20 #include <linux/mmzone.h>
21 #include <linux/hugetlb.h>
22 #include <linux/memcontrol.h>
23 #include <linux/mm_inline.h>
27 int can_do_mlock(void)
29 if (capable(CAP_IPC_LOCK
))
31 if (rlimit(RLIMIT_MEMLOCK
) != 0)
35 EXPORT_SYMBOL(can_do_mlock
);
38 * Mlocked pages are marked with PageMlocked() flag for efficient testing
39 * in vmscan and, possibly, the fault path; and to support semi-accurate
42 * An mlocked page [PageMlocked(page)] is unevictable. As such, it will
43 * be placed on the LRU "unevictable" list, rather than the [in]active lists.
44 * The unevictable list is an LRU sibling list to the [in]active lists.
45 * PageUnevictable is set to indicate the unevictable state.
47 * When lazy mlocking via vmscan, it is important to ensure that the
48 * vma's VM_LOCKED status is not concurrently being modified, otherwise we
49 * may have mlocked a page that is being munlocked. So lazy mlock must take
50 * the mmap_sem for read, and verify that the vma really is locked
55 * LRU accounting for clear_page_mlock()
57 void clear_page_mlock(struct page
*page
)
59 if (!TestClearPageMlocked(page
))
62 mod_zone_page_state(page_zone(page
), NR_MLOCK
,
63 -hpage_nr_pages(page
));
64 count_vm_event(UNEVICTABLE_PGCLEARED
);
65 if (!isolate_lru_page(page
)) {
66 putback_lru_page(page
);
69 * We lost the race. the page already moved to evictable list.
71 if (PageUnevictable(page
))
72 count_vm_event(UNEVICTABLE_PGSTRANDED
);
77 * Mark page as mlocked if not already.
78 * If page on LRU, isolate and putback to move to unevictable list.
80 void mlock_vma_page(struct page
*page
)
82 BUG_ON(!PageLocked(page
));
84 if (!TestSetPageMlocked(page
)) {
85 mod_zone_page_state(page_zone(page
), NR_MLOCK
,
86 hpage_nr_pages(page
));
87 count_vm_event(UNEVICTABLE_PGMLOCKED
);
88 if (!isolate_lru_page(page
))
89 putback_lru_page(page
);
94 * Finish munlock after successful page isolation
96 * Page must be locked. This is a wrapper for try_to_munlock()
97 * and putback_lru_page() with munlock accounting.
99 static void __munlock_isolated_page(struct page
*page
)
101 int ret
= SWAP_AGAIN
;
104 * Optimization: if the page was mapped just once, that's our mapping
105 * and we don't need to check all the other vmas.
107 if (page_mapcount(page
) > 1)
108 ret
= try_to_munlock(page
);
110 /* Did try_to_unlock() succeed or punt? */
111 if (ret
!= SWAP_MLOCK
)
112 count_vm_event(UNEVICTABLE_PGMUNLOCKED
);
114 putback_lru_page(page
);
118 * Accounting for page isolation fail during munlock
120 * Performs accounting when page isolation fails in munlock. There is nothing
121 * else to do because it means some other task has already removed the page
122 * from the LRU. putback_lru_page() will take care of removing the page from
123 * the unevictable list, if necessary. vmscan [page_referenced()] will move
124 * the page back to the unevictable list if some other vma has it mlocked.
126 static void __munlock_isolation_failed(struct page
*page
)
128 if (PageUnevictable(page
))
129 count_vm_event(UNEVICTABLE_PGSTRANDED
);
131 count_vm_event(UNEVICTABLE_PGMUNLOCKED
);
135 * munlock_vma_page - munlock a vma page
136 * @page - page to be unlocked
138 * called from munlock()/munmap() path with page supposedly on the LRU.
139 * When we munlock a page, because the vma where we found the page is being
140 * munlock()ed or munmap()ed, we want to check whether other vmas hold the
141 * page locked so that we can leave it on the unevictable lru list and not
142 * bother vmscan with it. However, to walk the page's rmap list in
143 * try_to_munlock() we must isolate the page from the LRU. If some other
144 * task has removed the page from the LRU, we won't be able to do that.
145 * So we clear the PageMlocked as we might not get another chance. If we
146 * can't isolate the page, we leave it for putback_lru_page() and vmscan
147 * [page_referenced()/try_to_unmap()] to deal with.
149 unsigned int munlock_vma_page(struct page
*page
)
151 unsigned int page_mask
= 0;
153 BUG_ON(!PageLocked(page
));
155 if (TestClearPageMlocked(page
)) {
156 unsigned int nr_pages
= hpage_nr_pages(page
);
157 mod_zone_page_state(page_zone(page
), NR_MLOCK
, -nr_pages
);
158 page_mask
= nr_pages
- 1;
159 if (!isolate_lru_page(page
))
160 __munlock_isolated_page(page
);
162 __munlock_isolation_failed(page
);
169 * __mlock_vma_pages_range() - mlock a range of pages in the vma.
171 * @start: start address
174 * This takes care of making the pages present too.
176 * return 0 on success, negative error code on error.
178 * vma->vm_mm->mmap_sem must be held for at least read.
180 long __mlock_vma_pages_range(struct vm_area_struct
*vma
,
181 unsigned long start
, unsigned long end
, int *nonblocking
)
183 struct mm_struct
*mm
= vma
->vm_mm
;
184 unsigned long nr_pages
= (end
- start
) / PAGE_SIZE
;
187 VM_BUG_ON(start
& ~PAGE_MASK
);
188 VM_BUG_ON(end
& ~PAGE_MASK
);
189 VM_BUG_ON(start
< vma
->vm_start
);
190 VM_BUG_ON(end
> vma
->vm_end
);
191 VM_BUG_ON(!rwsem_is_locked(&mm
->mmap_sem
));
193 gup_flags
= FOLL_TOUCH
| FOLL_MLOCK
;
195 * We want to touch writable mappings with a write fault in order
196 * to break COW, except for shared mappings because these don't COW
197 * and we would not want to dirty them for nothing.
199 if ((vma
->vm_flags
& (VM_WRITE
| VM_SHARED
)) == VM_WRITE
)
200 gup_flags
|= FOLL_WRITE
;
203 * We want mlock to succeed for regions that have any permissions
204 * other than PROT_NONE.
206 if (vma
->vm_flags
& (VM_READ
| VM_WRITE
| VM_EXEC
))
207 gup_flags
|= FOLL_FORCE
;
210 * We made sure addr is within a VMA, so the following will
211 * not result in a stack expansion that recurses back here.
213 return __get_user_pages(current
, mm
, start
, nr_pages
, gup_flags
,
214 NULL
, NULL
, nonblocking
);
218 * convert get_user_pages() return value to posix mlock() error
220 static int __mlock_posix_error_return(long retval
)
222 if (retval
== -EFAULT
)
224 else if (retval
== -ENOMEM
)
230 * Munlock a batch of pages from the same zone
232 * The work is split to two main phases. First phase clears the Mlocked flag
233 * and attempts to isolate the pages, all under a single zone lru lock.
234 * The second phase finishes the munlock only for pages where isolation
237 * Note that pvec is modified during the process. Before returning
238 * pagevec_reinit() is called on it.
240 static void __munlock_pagevec(struct pagevec
*pvec
, struct zone
*zone
)
243 int nr
= pagevec_count(pvec
);
244 int delta_munlocked
= -nr
;
246 /* Phase 1: page isolation */
247 spin_lock_irq(&zone
->lru_lock
);
248 for (i
= 0; i
< nr
; i
++) {
249 struct page
*page
= pvec
->pages
[i
];
251 if (TestClearPageMlocked(page
)) {
252 struct lruvec
*lruvec
;
256 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
257 lru
= page_lru(page
);
261 del_page_from_lru_list(page
, lruvec
, lru
);
263 __munlock_isolation_failed(page
);
270 * We won't be munlocking this page in the next phase
271 * but we still need to release the follow_page_mask()
274 pvec
->pages
[i
] = NULL
;
279 __mod_zone_page_state(zone
, NR_MLOCK
, delta_munlocked
);
280 spin_unlock_irq(&zone
->lru_lock
);
282 /* Phase 2: page munlock and putback */
283 for (i
= 0; i
< nr
; i
++) {
284 struct page
*page
= pvec
->pages
[i
];
288 __munlock_isolated_page(page
);
290 put_page(page
); /* pin from follow_page_mask() */
293 pagevec_reinit(pvec
);
297 * munlock_vma_pages_range() - munlock all pages in the vma range.'
298 * @vma - vma containing range to be munlock()ed.
299 * @start - start address in @vma of the range
300 * @end - end of range in @vma.
302 * For mremap(), munmap() and exit().
304 * Called with @vma VM_LOCKED.
306 * Returns with VM_LOCKED cleared. Callers must be prepared to
309 * We don't save and restore VM_LOCKED here because pages are
310 * still on lru. In unmap path, pages might be scanned by reclaim
311 * and re-mlocked by try_to_{munlock|unmap} before we unmap and
312 * free them. This will result in freeing mlocked pages.
314 void munlock_vma_pages_range(struct vm_area_struct
*vma
,
315 unsigned long start
, unsigned long end
)
318 struct zone
*zone
= NULL
;
320 pagevec_init(&pvec
, 0);
321 vma
->vm_flags
&= ~VM_LOCKED
;
323 while (start
< end
) {
325 unsigned int page_mask
, page_increm
;
326 struct zone
*pagezone
;
329 * Although FOLL_DUMP is intended for get_dump_page(),
330 * it just so happens that its special treatment of the
331 * ZERO_PAGE (returning an error instead of doing get_page)
332 * suits munlock very well (and if somehow an abnormal page
333 * has sneaked into the range, we won't oops here: great).
335 page
= follow_page_mask(vma
, start
, FOLL_GET
| FOLL_DUMP
,
337 if (page
&& !IS_ERR(page
)) {
338 pagezone
= page_zone(page
);
339 /* The whole pagevec must be in the same zone */
340 if (pagezone
!= zone
) {
341 if (pagevec_count(&pvec
))
342 __munlock_pagevec(&pvec
, zone
);
345 if (PageTransHuge(page
)) {
347 * THP pages are not handled by pagevec due
348 * to their possible split (see below).
350 if (pagevec_count(&pvec
))
351 __munlock_pagevec(&pvec
, zone
);
354 * Any THP page found by follow_page_mask() may
355 * have gotten split before reaching
356 * munlock_vma_page(), so we need to recompute
357 * the page_mask here.
359 page_mask
= munlock_vma_page(page
);
361 put_page(page
); /* follow_page_mask() */
364 * Non-huge pages are handled in batches
365 * via pagevec. The pin from
366 * follow_page_mask() prevents them from
369 if (pagevec_add(&pvec
, page
) == 0)
370 __munlock_pagevec(&pvec
, zone
);
373 page_increm
= 1 + (~(start
>> PAGE_SHIFT
) & page_mask
);
374 start
+= page_increm
* PAGE_SIZE
;
377 if (pagevec_count(&pvec
))
378 __munlock_pagevec(&pvec
, zone
);
382 * mlock_fixup - handle mlock[all]/munlock[all] requests.
384 * Filters out "special" vmas -- VM_LOCKED never gets set for these, and
385 * munlock is a no-op. However, for some special vmas, we go ahead and
388 * For vmas that pass the filters, merge/split as appropriate.
390 static int mlock_fixup(struct vm_area_struct
*vma
, struct vm_area_struct
**prev
,
391 unsigned long start
, unsigned long end
, vm_flags_t newflags
)
393 struct mm_struct
*mm
= vma
->vm_mm
;
397 int lock
= !!(newflags
& VM_LOCKED
);
399 if (newflags
== vma
->vm_flags
|| (vma
->vm_flags
& VM_SPECIAL
) ||
400 is_vm_hugetlb_page(vma
) || vma
== get_gate_vma(current
->mm
))
401 goto out
; /* don't set VM_LOCKED, don't count */
403 pgoff
= vma
->vm_pgoff
+ ((start
- vma
->vm_start
) >> PAGE_SHIFT
);
404 *prev
= vma_merge(mm
, *prev
, start
, end
, newflags
, vma
->anon_vma
,
405 vma
->vm_file
, pgoff
, vma_policy(vma
));
411 if (start
!= vma
->vm_start
) {
412 ret
= split_vma(mm
, vma
, start
, 1);
417 if (end
!= vma
->vm_end
) {
418 ret
= split_vma(mm
, vma
, end
, 0);
425 * Keep track of amount of locked VM.
427 nr_pages
= (end
- start
) >> PAGE_SHIFT
;
429 nr_pages
= -nr_pages
;
430 mm
->locked_vm
+= nr_pages
;
433 * vm_flags is protected by the mmap_sem held in write mode.
434 * It's okay if try_to_unmap_one unmaps a page just after we
435 * set VM_LOCKED, __mlock_vma_pages_range will bring it back.
439 vma
->vm_flags
= newflags
;
441 munlock_vma_pages_range(vma
, start
, end
);
448 static int do_mlock(unsigned long start
, size_t len
, int on
)
450 unsigned long nstart
, end
, tmp
;
451 struct vm_area_struct
* vma
, * prev
;
454 VM_BUG_ON(start
& ~PAGE_MASK
);
455 VM_BUG_ON(len
!= PAGE_ALIGN(len
));
461 vma
= find_vma(current
->mm
, start
);
462 if (!vma
|| vma
->vm_start
> start
)
466 if (start
> vma
->vm_start
)
469 for (nstart
= start
; ; ) {
472 /* Here we know that vma->vm_start <= nstart < vma->vm_end. */
474 newflags
= vma
->vm_flags
& ~VM_LOCKED
;
476 newflags
|= VM_LOCKED
;
481 error
= mlock_fixup(vma
, &prev
, nstart
, tmp
, newflags
);
485 if (nstart
< prev
->vm_end
)
486 nstart
= prev
->vm_end
;
491 if (!vma
|| vma
->vm_start
!= nstart
) {
500 * __mm_populate - populate and/or mlock pages within a range of address space.
502 * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
503 * flags. VMAs must be already marked with the desired vm_flags, and
504 * mmap_sem must not be held.
506 int __mm_populate(unsigned long start
, unsigned long len
, int ignore_errors
)
508 struct mm_struct
*mm
= current
->mm
;
509 unsigned long end
, nstart
, nend
;
510 struct vm_area_struct
*vma
= NULL
;
514 VM_BUG_ON(start
& ~PAGE_MASK
);
515 VM_BUG_ON(len
!= PAGE_ALIGN(len
));
518 for (nstart
= start
; nstart
< end
; nstart
= nend
) {
520 * We want to fault in pages for [nstart; end) address range.
521 * Find first corresponding VMA.
525 down_read(&mm
->mmap_sem
);
526 vma
= find_vma(mm
, nstart
);
527 } else if (nstart
>= vma
->vm_end
)
529 if (!vma
|| vma
->vm_start
>= end
)
532 * Set [nstart; nend) to intersection of desired address
533 * range with the first VMA. Also, skip undesirable VMA types.
535 nend
= min(end
, vma
->vm_end
);
536 if (vma
->vm_flags
& (VM_IO
| VM_PFNMAP
))
538 if (nstart
< vma
->vm_start
)
539 nstart
= vma
->vm_start
;
541 * Now fault in a range of pages. __mlock_vma_pages_range()
542 * double checks the vma flags, so that it won't mlock pages
543 * if the vma was already munlocked.
545 ret
= __mlock_vma_pages_range(vma
, nstart
, nend
, &locked
);
549 continue; /* continue at next VMA */
551 ret
= __mlock_posix_error_return(ret
);
554 nend
= nstart
+ ret
* PAGE_SIZE
;
558 up_read(&mm
->mmap_sem
);
559 return ret
; /* 0 or negative error code */
562 SYSCALL_DEFINE2(mlock
, unsigned long, start
, size_t, len
)
564 unsigned long locked
;
565 unsigned long lock_limit
;
571 lru_add_drain_all(); /* flush pagevec */
573 down_write(¤t
->mm
->mmap_sem
);
574 len
= PAGE_ALIGN(len
+ (start
& ~PAGE_MASK
));
577 locked
= len
>> PAGE_SHIFT
;
578 locked
+= current
->mm
->locked_vm
;
580 lock_limit
= rlimit(RLIMIT_MEMLOCK
);
581 lock_limit
>>= PAGE_SHIFT
;
583 /* check against resource limits */
584 if ((locked
<= lock_limit
) || capable(CAP_IPC_LOCK
))
585 error
= do_mlock(start
, len
, 1);
586 up_write(¤t
->mm
->mmap_sem
);
588 error
= __mm_populate(start
, len
, 0);
592 SYSCALL_DEFINE2(munlock
, unsigned long, start
, size_t, len
)
596 down_write(¤t
->mm
->mmap_sem
);
597 len
= PAGE_ALIGN(len
+ (start
& ~PAGE_MASK
));
599 ret
= do_mlock(start
, len
, 0);
600 up_write(¤t
->mm
->mmap_sem
);
604 static int do_mlockall(int flags
)
606 struct vm_area_struct
* vma
, * prev
= NULL
;
608 if (flags
& MCL_FUTURE
)
609 current
->mm
->def_flags
|= VM_LOCKED
;
611 current
->mm
->def_flags
&= ~VM_LOCKED
;
612 if (flags
== MCL_FUTURE
)
615 for (vma
= current
->mm
->mmap
; vma
; vma
= prev
->vm_next
) {
618 newflags
= vma
->vm_flags
& ~VM_LOCKED
;
619 if (flags
& MCL_CURRENT
)
620 newflags
|= VM_LOCKED
;
623 mlock_fixup(vma
, &prev
, vma
->vm_start
, vma
->vm_end
, newflags
);
629 SYSCALL_DEFINE1(mlockall
, int, flags
)
631 unsigned long lock_limit
;
634 if (!flags
|| (flags
& ~(MCL_CURRENT
| MCL_FUTURE
)))
641 if (flags
& MCL_CURRENT
)
642 lru_add_drain_all(); /* flush pagevec */
644 down_write(¤t
->mm
->mmap_sem
);
646 lock_limit
= rlimit(RLIMIT_MEMLOCK
);
647 lock_limit
>>= PAGE_SHIFT
;
650 if (!(flags
& MCL_CURRENT
) || (current
->mm
->total_vm
<= lock_limit
) ||
651 capable(CAP_IPC_LOCK
))
652 ret
= do_mlockall(flags
);
653 up_write(¤t
->mm
->mmap_sem
);
654 if (!ret
&& (flags
& MCL_CURRENT
))
655 mm_populate(0, TASK_SIZE
);
660 SYSCALL_DEFINE0(munlockall
)
664 down_write(¤t
->mm
->mmap_sem
);
665 ret
= do_mlockall(0);
666 up_write(¤t
->mm
->mmap_sem
);
671 * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
672 * shm segments) get accounted against the user_struct instead.
674 static DEFINE_SPINLOCK(shmlock_user_lock
);
676 int user_shm_lock(size_t size
, struct user_struct
*user
)
678 unsigned long lock_limit
, locked
;
681 locked
= (size
+ PAGE_SIZE
- 1) >> PAGE_SHIFT
;
682 lock_limit
= rlimit(RLIMIT_MEMLOCK
);
683 if (lock_limit
== RLIM_INFINITY
)
685 lock_limit
>>= PAGE_SHIFT
;
686 spin_lock(&shmlock_user_lock
);
688 locked
+ user
->locked_shm
> lock_limit
&& !capable(CAP_IPC_LOCK
))
691 user
->locked_shm
+= locked
;
694 spin_unlock(&shmlock_user_lock
);
698 void user_shm_unlock(size_t size
, struct user_struct
*user
)
700 spin_lock(&shmlock_user_lock
);
701 user
->locked_shm
-= (size
+ PAGE_SIZE
- 1) >> PAGE_SHIFT
;
702 spin_unlock(&shmlock_user_lock
);
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