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/mempolicy.h>
15 #include <linux/syscalls.h>
16 #include <linux/sched.h>
17 #include <linux/export.h>
18 #include <linux/rmap.h>
19 #include <linux/mmzone.h>
20 #include <linux/hugetlb.h>
24 int can_do_mlock(void)
26 if (capable(CAP_IPC_LOCK
))
28 if (rlimit(RLIMIT_MEMLOCK
) != 0)
32 EXPORT_SYMBOL(can_do_mlock
);
35 * Mlocked pages are marked with PageMlocked() flag for efficient testing
36 * in vmscan and, possibly, the fault path; and to support semi-accurate
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.
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
52 * LRU accounting for clear_page_mlock()
54 void clear_page_mlock(struct page
*page
)
56 if (!TestClearPageMlocked(page
))
59 mod_zone_page_state(page_zone(page
), NR_MLOCK
,
60 -hpage_nr_pages(page
));
61 count_vm_event(UNEVICTABLE_PGCLEARED
);
62 if (!isolate_lru_page(page
)) {
63 putback_lru_page(page
);
66 * We lost the race. the page already moved to evictable list.
68 if (PageUnevictable(page
))
69 count_vm_event(UNEVICTABLE_PGSTRANDED
);
74 * Mark page as mlocked if not already.
75 * If page on LRU, isolate and putback to move to unevictable list.
77 void mlock_vma_page(struct page
*page
)
79 BUG_ON(!PageLocked(page
));
81 if (!TestSetPageMlocked(page
)) {
82 mod_zone_page_state(page_zone(page
), NR_MLOCK
,
83 hpage_nr_pages(page
));
84 count_vm_event(UNEVICTABLE_PGMLOCKED
);
85 if (!isolate_lru_page(page
))
86 putback_lru_page(page
);
91 * munlock_vma_page - munlock a vma page
92 * @page - page to be unlocked
94 * called from munlock()/munmap() path with page supposedly on the LRU.
95 * When we munlock a page, because the vma where we found the page is being
96 * munlock()ed or munmap()ed, we want to check whether other vmas hold the
97 * page locked so that we can leave it on the unevictable lru list and not
98 * bother vmscan with it. However, to walk the page's rmap list in
99 * try_to_munlock() we must isolate the page from the LRU. If some other
100 * task has removed the page from the LRU, we won't be able to do that.
101 * So we clear the PageMlocked as we might not get another chance. If we
102 * can't isolate the page, we leave it for putback_lru_page() and vmscan
103 * [page_referenced()/try_to_unmap()] to deal with.
105 unsigned int munlock_vma_page(struct page
*page
)
107 unsigned int page_mask
= 0;
109 BUG_ON(!PageLocked(page
));
111 if (TestClearPageMlocked(page
)) {
112 unsigned int nr_pages
= hpage_nr_pages(page
);
113 mod_zone_page_state(page_zone(page
), NR_MLOCK
, -nr_pages
);
114 page_mask
= nr_pages
- 1;
115 if (!isolate_lru_page(page
)) {
116 int ret
= SWAP_AGAIN
;
119 * Optimization: if the page was mapped just once,
120 * that's our mapping and we don't need to check all the
123 if (page_mapcount(page
) > 1)
124 ret
= try_to_munlock(page
);
126 * did try_to_unlock() succeed or punt?
128 if (ret
!= SWAP_MLOCK
)
129 count_vm_event(UNEVICTABLE_PGMUNLOCKED
);
131 putback_lru_page(page
);
134 * Some other task has removed the page from the LRU.
135 * putback_lru_page() will take care of removing the
136 * page from the unevictable list, if necessary.
137 * vmscan [page_referenced()] will move the page back
138 * to the unevictable list if some other vma has it
141 if (PageUnevictable(page
))
142 count_vm_event(UNEVICTABLE_PGSTRANDED
);
144 count_vm_event(UNEVICTABLE_PGMUNLOCKED
);
152 * __mlock_vma_pages_range() - mlock a range of pages in the vma.
154 * @start: start address
157 * This takes care of making the pages present too.
159 * return 0 on success, negative error code on error.
161 * vma->vm_mm->mmap_sem must be held for at least read.
163 long __mlock_vma_pages_range(struct vm_area_struct
*vma
,
164 unsigned long start
, unsigned long end
, int *nonblocking
)
166 struct mm_struct
*mm
= vma
->vm_mm
;
167 unsigned long nr_pages
= (end
- start
) / PAGE_SIZE
;
170 VM_BUG_ON(start
& ~PAGE_MASK
);
171 VM_BUG_ON(end
& ~PAGE_MASK
);
172 VM_BUG_ON(start
< vma
->vm_start
);
173 VM_BUG_ON(end
> vma
->vm_end
);
174 VM_BUG_ON(!rwsem_is_locked(&mm
->mmap_sem
));
176 gup_flags
= FOLL_TOUCH
| FOLL_MLOCK
;
178 * We want to touch writable mappings with a write fault in order
179 * to break COW, except for shared mappings because these don't COW
180 * and we would not want to dirty them for nothing.
182 if ((vma
->vm_flags
& (VM_WRITE
| VM_SHARED
)) == VM_WRITE
)
183 gup_flags
|= FOLL_WRITE
;
186 * We want mlock to succeed for regions that have any permissions
187 * other than PROT_NONE.
189 if (vma
->vm_flags
& (VM_READ
| VM_WRITE
| VM_EXEC
))
190 gup_flags
|= FOLL_FORCE
;
193 * We made sure addr is within a VMA, so the following will
194 * not result in a stack expansion that recurses back here.
196 return __get_user_pages(current
, mm
, start
, nr_pages
, gup_flags
,
197 NULL
, NULL
, nonblocking
);
201 * convert get_user_pages() return value to posix mlock() error
203 static int __mlock_posix_error_return(long retval
)
205 if (retval
== -EFAULT
)
207 else if (retval
== -ENOMEM
)
213 * munlock_vma_pages_range() - munlock all pages in the vma range.'
214 * @vma - vma containing range to be munlock()ed.
215 * @start - start address in @vma of the range
216 * @end - end of range in @vma.
218 * For mremap(), munmap() and exit().
220 * Called with @vma VM_LOCKED.
222 * Returns with VM_LOCKED cleared. Callers must be prepared to
225 * We don't save and restore VM_LOCKED here because pages are
226 * still on lru. In unmap path, pages might be scanned by reclaim
227 * and re-mlocked by try_to_{munlock|unmap} before we unmap and
228 * free them. This will result in freeing mlocked pages.
230 void munlock_vma_pages_range(struct vm_area_struct
*vma
,
231 unsigned long start
, unsigned long end
)
233 vma
->vm_flags
&= ~VM_LOCKED
;
235 while (start
< end
) {
237 unsigned int page_mask
, page_increm
;
240 * Although FOLL_DUMP is intended for get_dump_page(),
241 * it just so happens that its special treatment of the
242 * ZERO_PAGE (returning an error instead of doing get_page)
243 * suits munlock very well (and if somehow an abnormal page
244 * has sneaked into the range, we won't oops here: great).
246 page
= follow_page_mask(vma
, start
, FOLL_GET
| FOLL_DUMP
,
248 if (page
&& !IS_ERR(page
)) {
252 * Any THP page found by follow_page_mask() may have
253 * gotten split before reaching munlock_vma_page(),
254 * so we need to recompute the page_mask here.
256 page_mask
= munlock_vma_page(page
);
260 page_increm
= 1 + (~(start
>> PAGE_SHIFT
) & page_mask
);
261 start
+= page_increm
* PAGE_SIZE
;
267 * mlock_fixup - handle mlock[all]/munlock[all] requests.
269 * Filters out "special" vmas -- VM_LOCKED never gets set for these, and
270 * munlock is a no-op. However, for some special vmas, we go ahead and
273 * For vmas that pass the filters, merge/split as appropriate.
275 static int mlock_fixup(struct vm_area_struct
*vma
, struct vm_area_struct
**prev
,
276 unsigned long start
, unsigned long end
, vm_flags_t newflags
)
278 struct mm_struct
*mm
= vma
->vm_mm
;
282 int lock
= !!(newflags
& VM_LOCKED
);
284 if (newflags
== vma
->vm_flags
|| (vma
->vm_flags
& VM_SPECIAL
) ||
285 is_vm_hugetlb_page(vma
) || vma
== get_gate_vma(current
->mm
))
286 goto out
; /* don't set VM_LOCKED, don't count */
288 pgoff
= vma
->vm_pgoff
+ ((start
- vma
->vm_start
) >> PAGE_SHIFT
);
289 *prev
= vma_merge(mm
, *prev
, start
, end
, newflags
, vma
->anon_vma
,
290 vma
->vm_file
, pgoff
, vma_policy(vma
));
296 if (start
!= vma
->vm_start
) {
297 ret
= split_vma(mm
, vma
, start
, 1);
302 if (end
!= vma
->vm_end
) {
303 ret
= split_vma(mm
, vma
, end
, 0);
310 * Keep track of amount of locked VM.
312 nr_pages
= (end
- start
) >> PAGE_SHIFT
;
314 nr_pages
= -nr_pages
;
315 mm
->locked_vm
+= nr_pages
;
318 * vm_flags is protected by the mmap_sem held in write mode.
319 * It's okay if try_to_unmap_one unmaps a page just after we
320 * set VM_LOCKED, __mlock_vma_pages_range will bring it back.
324 vma
->vm_flags
= newflags
;
326 munlock_vma_pages_range(vma
, start
, end
);
333 static int do_mlock(unsigned long start
, size_t len
, int on
)
335 unsigned long nstart
, end
, tmp
;
336 struct vm_area_struct
* vma
, * prev
;
339 VM_BUG_ON(start
& ~PAGE_MASK
);
340 VM_BUG_ON(len
!= PAGE_ALIGN(len
));
346 vma
= find_vma(current
->mm
, start
);
347 if (!vma
|| vma
->vm_start
> start
)
351 if (start
> vma
->vm_start
)
354 for (nstart
= start
; ; ) {
357 /* Here we know that vma->vm_start <= nstart < vma->vm_end. */
359 newflags
= vma
->vm_flags
& ~VM_LOCKED
;
361 newflags
|= VM_LOCKED
;
366 error
= mlock_fixup(vma
, &prev
, nstart
, tmp
, newflags
);
370 if (nstart
< prev
->vm_end
)
371 nstart
= prev
->vm_end
;
376 if (!vma
|| vma
->vm_start
!= nstart
) {
385 * __mm_populate - populate and/or mlock pages within a range of address space.
387 * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
388 * flags. VMAs must be already marked with the desired vm_flags, and
389 * mmap_sem must not be held.
391 int __mm_populate(unsigned long start
, unsigned long len
, int ignore_errors
)
393 struct mm_struct
*mm
= current
->mm
;
394 unsigned long end
, nstart
, nend
;
395 struct vm_area_struct
*vma
= NULL
;
399 VM_BUG_ON(start
& ~PAGE_MASK
);
400 VM_BUG_ON(len
!= PAGE_ALIGN(len
));
403 for (nstart
= start
; nstart
< end
; nstart
= nend
) {
405 * We want to fault in pages for [nstart; end) address range.
406 * Find first corresponding VMA.
410 down_read(&mm
->mmap_sem
);
411 vma
= find_vma(mm
, nstart
);
412 } else if (nstart
>= vma
->vm_end
)
414 if (!vma
|| vma
->vm_start
>= end
)
417 * Set [nstart; nend) to intersection of desired address
418 * range with the first VMA. Also, skip undesirable VMA types.
420 nend
= min(end
, vma
->vm_end
);
421 if (vma
->vm_flags
& (VM_IO
| VM_PFNMAP
))
423 if (nstart
< vma
->vm_start
)
424 nstart
= vma
->vm_start
;
426 * Now fault in a range of pages. __mlock_vma_pages_range()
427 * double checks the vma flags, so that it won't mlock pages
428 * if the vma was already munlocked.
430 ret
= __mlock_vma_pages_range(vma
, nstart
, nend
, &locked
);
434 continue; /* continue at next VMA */
436 ret
= __mlock_posix_error_return(ret
);
439 nend
= nstart
+ ret
* PAGE_SIZE
;
443 up_read(&mm
->mmap_sem
);
444 return ret
; /* 0 or negative error code */
447 SYSCALL_DEFINE2(mlock
, unsigned long, start
, size_t, len
)
449 unsigned long locked
;
450 unsigned long lock_limit
;
456 lru_add_drain_all(); /* flush pagevec */
458 down_write(¤t
->mm
->mmap_sem
);
459 len
= PAGE_ALIGN(len
+ (start
& ~PAGE_MASK
));
462 locked
= len
>> PAGE_SHIFT
;
463 locked
+= current
->mm
->locked_vm
;
465 lock_limit
= rlimit(RLIMIT_MEMLOCK
);
466 lock_limit
>>= PAGE_SHIFT
;
468 /* check against resource limits */
469 if ((locked
<= lock_limit
) || capable(CAP_IPC_LOCK
))
470 error
= do_mlock(start
, len
, 1);
471 up_write(¤t
->mm
->mmap_sem
);
473 error
= __mm_populate(start
, len
, 0);
477 SYSCALL_DEFINE2(munlock
, unsigned long, start
, size_t, len
)
481 down_write(¤t
->mm
->mmap_sem
);
482 len
= PAGE_ALIGN(len
+ (start
& ~PAGE_MASK
));
484 ret
= do_mlock(start
, len
, 0);
485 up_write(¤t
->mm
->mmap_sem
);
489 static int do_mlockall(int flags
)
491 struct vm_area_struct
* vma
, * prev
= NULL
;
493 if (flags
& MCL_FUTURE
)
494 current
->mm
->def_flags
|= VM_LOCKED
;
496 current
->mm
->def_flags
&= ~VM_LOCKED
;
497 if (flags
== MCL_FUTURE
)
500 for (vma
= current
->mm
->mmap
; vma
; vma
= prev
->vm_next
) {
503 newflags
= vma
->vm_flags
& ~VM_LOCKED
;
504 if (flags
& MCL_CURRENT
)
505 newflags
|= VM_LOCKED
;
508 mlock_fixup(vma
, &prev
, vma
->vm_start
, vma
->vm_end
, newflags
);
514 SYSCALL_DEFINE1(mlockall
, int, flags
)
516 unsigned long lock_limit
;
519 if (!flags
|| (flags
& ~(MCL_CURRENT
| MCL_FUTURE
)))
526 if (flags
& MCL_CURRENT
)
527 lru_add_drain_all(); /* flush pagevec */
529 down_write(¤t
->mm
->mmap_sem
);
531 lock_limit
= rlimit(RLIMIT_MEMLOCK
);
532 lock_limit
>>= PAGE_SHIFT
;
535 if (!(flags
& MCL_CURRENT
) || (current
->mm
->total_vm
<= lock_limit
) ||
536 capable(CAP_IPC_LOCK
))
537 ret
= do_mlockall(flags
);
538 up_write(¤t
->mm
->mmap_sem
);
539 if (!ret
&& (flags
& MCL_CURRENT
))
540 mm_populate(0, TASK_SIZE
);
545 SYSCALL_DEFINE0(munlockall
)
549 down_write(¤t
->mm
->mmap_sem
);
550 ret
= do_mlockall(0);
551 up_write(¤t
->mm
->mmap_sem
);
556 * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
557 * shm segments) get accounted against the user_struct instead.
559 static DEFINE_SPINLOCK(shmlock_user_lock
);
561 int user_shm_lock(size_t size
, struct user_struct
*user
)
563 unsigned long lock_limit
, locked
;
566 locked
= (size
+ PAGE_SIZE
- 1) >> PAGE_SHIFT
;
567 lock_limit
= rlimit(RLIMIT_MEMLOCK
);
568 if (lock_limit
== RLIM_INFINITY
)
570 lock_limit
>>= PAGE_SHIFT
;
571 spin_lock(&shmlock_user_lock
);
573 locked
+ user
->locked_shm
> lock_limit
&& !capable(CAP_IPC_LOCK
))
576 user
->locked_shm
+= locked
;
579 spin_unlock(&shmlock_user_lock
);
583 void user_shm_unlock(size_t size
, struct user_struct
*user
)
585 spin_lock(&shmlock_user_lock
);
586 user
->locked_shm
-= (size
+ PAGE_SIZE
- 1) >> PAGE_SHIFT
;
587 spin_unlock(&shmlock_user_lock
);
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