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 void munlock_vma_page(struct page
*page
)
107 BUG_ON(!PageLocked(page
));
109 if (TestClearPageMlocked(page
)) {
110 mod_zone_page_state(page_zone(page
), NR_MLOCK
,
111 -hpage_nr_pages(page
));
112 if (!isolate_lru_page(page
)) {
113 int ret
= SWAP_AGAIN
;
116 * Optimization: if the page was mapped just once,
117 * that's our mapping and we don't need to check all the
120 if (page_mapcount(page
) > 1)
121 ret
= try_to_munlock(page
);
123 * did try_to_unlock() succeed or punt?
125 if (ret
!= SWAP_MLOCK
)
126 count_vm_event(UNEVICTABLE_PGMUNLOCKED
);
128 putback_lru_page(page
);
131 * Some other task has removed the page from the LRU.
132 * putback_lru_page() will take care of removing the
133 * page from the unevictable list, if necessary.
134 * vmscan [page_referenced()] will move the page back
135 * to the unevictable list if some other vma has it
138 if (PageUnevictable(page
))
139 count_vm_event(UNEVICTABLE_PGSTRANDED
);
141 count_vm_event(UNEVICTABLE_PGMUNLOCKED
);
147 * __mlock_vma_pages_range() - mlock a range of pages in the vma.
149 * @start: start address
152 * This takes care of making the pages present too.
154 * return 0 on success, negative error code on error.
156 * vma->vm_mm->mmap_sem must be held for at least read.
158 long __mlock_vma_pages_range(struct vm_area_struct
*vma
,
159 unsigned long start
, unsigned long end
, int *nonblocking
)
161 struct mm_struct
*mm
= vma
->vm_mm
;
162 unsigned long addr
= start
;
163 unsigned long nr_pages
= (end
- start
) / PAGE_SIZE
;
166 VM_BUG_ON(start
& ~PAGE_MASK
);
167 VM_BUG_ON(end
& ~PAGE_MASK
);
168 VM_BUG_ON(start
< vma
->vm_start
);
169 VM_BUG_ON(end
> vma
->vm_end
);
170 VM_BUG_ON(!rwsem_is_locked(&mm
->mmap_sem
));
172 gup_flags
= FOLL_TOUCH
| FOLL_MLOCK
;
174 * We want to touch writable mappings with a write fault in order
175 * to break COW, except for shared mappings because these don't COW
176 * and we would not want to dirty them for nothing.
178 if ((vma
->vm_flags
& (VM_WRITE
| VM_SHARED
)) == VM_WRITE
)
179 gup_flags
|= FOLL_WRITE
;
182 * We want mlock to succeed for regions that have any permissions
183 * other than PROT_NONE.
185 if (vma
->vm_flags
& (VM_READ
| VM_WRITE
| VM_EXEC
))
186 gup_flags
|= FOLL_FORCE
;
189 * We made sure addr is within a VMA, so the following will
190 * not result in a stack expansion that recurses back here.
192 return __get_user_pages(current
, mm
, addr
, nr_pages
, gup_flags
,
193 NULL
, NULL
, nonblocking
);
197 * convert get_user_pages() return value to posix mlock() error
199 static int __mlock_posix_error_return(long retval
)
201 if (retval
== -EFAULT
)
203 else if (retval
== -ENOMEM
)
209 * munlock_vma_pages_range() - munlock all pages in the vma range.'
210 * @vma - vma containing range to be munlock()ed.
211 * @start - start address in @vma of the range
212 * @end - end of range in @vma.
214 * For mremap(), munmap() and exit().
216 * Called with @vma VM_LOCKED.
218 * Returns with VM_LOCKED cleared. Callers must be prepared to
221 * We don't save and restore VM_LOCKED here because pages are
222 * still on lru. In unmap path, pages might be scanned by reclaim
223 * and re-mlocked by try_to_{munlock|unmap} before we unmap and
224 * free them. This will result in freeing mlocked pages.
226 void munlock_vma_pages_range(struct vm_area_struct
*vma
,
227 unsigned long start
, unsigned long end
)
232 vma
->vm_flags
&= ~VM_LOCKED
;
234 for (addr
= start
; addr
< end
; addr
+= PAGE_SIZE
) {
237 * Although FOLL_DUMP is intended for get_dump_page(),
238 * it just so happens that its special treatment of the
239 * ZERO_PAGE (returning an error instead of doing get_page)
240 * suits munlock very well (and if somehow an abnormal page
241 * has sneaked into the range, we won't oops here: great).
243 page
= follow_page(vma
, addr
, FOLL_GET
| FOLL_DUMP
);
244 if (page
&& !IS_ERR(page
)) {
246 munlock_vma_page(page
);
255 * mlock_fixup - handle mlock[all]/munlock[all] requests.
257 * Filters out "special" vmas -- VM_LOCKED never gets set for these, and
258 * munlock is a no-op. However, for some special vmas, we go ahead and
261 * For vmas that pass the filters, merge/split as appropriate.
263 static int mlock_fixup(struct vm_area_struct
*vma
, struct vm_area_struct
**prev
,
264 unsigned long start
, unsigned long end
, vm_flags_t newflags
)
266 struct mm_struct
*mm
= vma
->vm_mm
;
270 int lock
= !!(newflags
& VM_LOCKED
);
272 if (newflags
== vma
->vm_flags
|| (vma
->vm_flags
& VM_SPECIAL
) ||
273 is_vm_hugetlb_page(vma
) || vma
== get_gate_vma(current
->mm
))
274 goto out
; /* don't set VM_LOCKED, don't count */
276 pgoff
= vma
->vm_pgoff
+ ((start
- vma
->vm_start
) >> PAGE_SHIFT
);
277 *prev
= vma_merge(mm
, *prev
, start
, end
, newflags
, vma
->anon_vma
,
278 vma
->vm_file
, pgoff
, vma_policy(vma
));
284 if (start
!= vma
->vm_start
) {
285 ret
= split_vma(mm
, vma
, start
, 1);
290 if (end
!= vma
->vm_end
) {
291 ret
= split_vma(mm
, vma
, end
, 0);
298 * Keep track of amount of locked VM.
300 nr_pages
= (end
- start
) >> PAGE_SHIFT
;
302 nr_pages
= -nr_pages
;
303 mm
->locked_vm
+= nr_pages
;
306 * vm_flags is protected by the mmap_sem held in write mode.
307 * It's okay if try_to_unmap_one unmaps a page just after we
308 * set VM_LOCKED, __mlock_vma_pages_range will bring it back.
312 vma
->vm_flags
= newflags
;
314 munlock_vma_pages_range(vma
, start
, end
);
321 static int do_mlock(unsigned long start
, size_t len
, int on
)
323 unsigned long nstart
, end
, tmp
;
324 struct vm_area_struct
* vma
, * prev
;
327 VM_BUG_ON(start
& ~PAGE_MASK
);
328 VM_BUG_ON(len
!= PAGE_ALIGN(len
));
334 vma
= find_vma(current
->mm
, start
);
335 if (!vma
|| vma
->vm_start
> start
)
339 if (start
> vma
->vm_start
)
342 for (nstart
= start
; ; ) {
345 /* Here we know that vma->vm_start <= nstart < vma->vm_end. */
347 newflags
= vma
->vm_flags
& ~VM_LOCKED
;
349 newflags
|= VM_LOCKED
| VM_POPULATE
;
354 error
= mlock_fixup(vma
, &prev
, nstart
, tmp
, newflags
);
358 if (nstart
< prev
->vm_end
)
359 nstart
= prev
->vm_end
;
364 if (!vma
|| vma
->vm_start
!= nstart
) {
373 * __mm_populate - populate and/or mlock pages within a range of address space.
375 * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
376 * flags. VMAs must be already marked with the desired vm_flags, and
377 * mmap_sem must not be held.
379 int __mm_populate(unsigned long start
, unsigned long len
, int ignore_errors
)
381 struct mm_struct
*mm
= current
->mm
;
382 unsigned long end
, nstart
, nend
;
383 struct vm_area_struct
*vma
= NULL
;
387 VM_BUG_ON(start
& ~PAGE_MASK
);
388 VM_BUG_ON(len
!= PAGE_ALIGN(len
));
391 for (nstart
= start
; nstart
< end
; nstart
= nend
) {
393 * We want to fault in pages for [nstart; end) address range.
394 * Find first corresponding VMA.
398 down_read(&mm
->mmap_sem
);
399 vma
= find_vma(mm
, nstart
);
400 } else if (nstart
>= vma
->vm_end
)
402 if (!vma
|| vma
->vm_start
>= end
)
405 * Set [nstart; nend) to intersection of desired address
406 * range with the first VMA. Also, skip undesirable VMA types.
408 nend
= min(end
, vma
->vm_end
);
409 if ((vma
->vm_flags
& (VM_IO
| VM_PFNMAP
| VM_POPULATE
)) !=
412 if (nstart
< vma
->vm_start
)
413 nstart
= vma
->vm_start
;
415 * Now fault in a range of pages. __mlock_vma_pages_range()
416 * double checks the vma flags, so that it won't mlock pages
417 * if the vma was already munlocked.
419 ret
= __mlock_vma_pages_range(vma
, nstart
, nend
, &locked
);
423 continue; /* continue at next VMA */
425 ret
= __mlock_posix_error_return(ret
);
428 nend
= nstart
+ ret
* PAGE_SIZE
;
432 up_read(&mm
->mmap_sem
);
433 return ret
; /* 0 or negative error code */
436 SYSCALL_DEFINE2(mlock
, unsigned long, start
, size_t, len
)
438 unsigned long locked
;
439 unsigned long lock_limit
;
445 lru_add_drain_all(); /* flush pagevec */
447 down_write(¤t
->mm
->mmap_sem
);
448 len
= PAGE_ALIGN(len
+ (start
& ~PAGE_MASK
));
451 locked
= len
>> PAGE_SHIFT
;
452 locked
+= current
->mm
->locked_vm
;
454 lock_limit
= rlimit(RLIMIT_MEMLOCK
);
455 lock_limit
>>= PAGE_SHIFT
;
457 /* check against resource limits */
458 if ((locked
<= lock_limit
) || capable(CAP_IPC_LOCK
))
459 error
= do_mlock(start
, len
, 1);
460 up_write(¤t
->mm
->mmap_sem
);
462 error
= __mm_populate(start
, len
, 0);
466 SYSCALL_DEFINE2(munlock
, unsigned long, start
, size_t, len
)
470 down_write(¤t
->mm
->mmap_sem
);
471 len
= PAGE_ALIGN(len
+ (start
& ~PAGE_MASK
));
473 ret
= do_mlock(start
, len
, 0);
474 up_write(¤t
->mm
->mmap_sem
);
478 static int do_mlockall(int flags
)
480 struct vm_area_struct
* vma
, * prev
= NULL
;
482 if (flags
& MCL_FUTURE
)
483 current
->mm
->def_flags
|= VM_LOCKED
| VM_POPULATE
;
485 current
->mm
->def_flags
&= ~(VM_LOCKED
| VM_POPULATE
);
486 if (flags
== MCL_FUTURE
)
489 for (vma
= current
->mm
->mmap
; vma
; vma
= prev
->vm_next
) {
492 newflags
= vma
->vm_flags
& ~VM_LOCKED
;
493 if (flags
& MCL_CURRENT
)
494 newflags
|= VM_LOCKED
| VM_POPULATE
;
497 mlock_fixup(vma
, &prev
, vma
->vm_start
, vma
->vm_end
, newflags
);
503 SYSCALL_DEFINE1(mlockall
, int, flags
)
505 unsigned long lock_limit
;
508 if (!flags
|| (flags
& ~(MCL_CURRENT
| MCL_FUTURE
)))
515 if (flags
& MCL_CURRENT
)
516 lru_add_drain_all(); /* flush pagevec */
518 down_write(¤t
->mm
->mmap_sem
);
520 lock_limit
= rlimit(RLIMIT_MEMLOCK
);
521 lock_limit
>>= PAGE_SHIFT
;
524 if (!(flags
& MCL_CURRENT
) || (current
->mm
->total_vm
<= lock_limit
) ||
525 capable(CAP_IPC_LOCK
))
526 ret
= do_mlockall(flags
);
527 up_write(¤t
->mm
->mmap_sem
);
528 if (!ret
&& (flags
& MCL_CURRENT
))
529 mm_populate(0, TASK_SIZE
);
534 SYSCALL_DEFINE0(munlockall
)
538 down_write(¤t
->mm
->mmap_sem
);
539 ret
= do_mlockall(0);
540 up_write(¤t
->mm
->mmap_sem
);
545 * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
546 * shm segments) get accounted against the user_struct instead.
548 static DEFINE_SPINLOCK(shmlock_user_lock
);
550 int user_shm_lock(size_t size
, struct user_struct
*user
)
552 unsigned long lock_limit
, locked
;
555 locked
= (size
+ PAGE_SIZE
- 1) >> PAGE_SHIFT
;
556 lock_limit
= rlimit(RLIMIT_MEMLOCK
);
557 if (lock_limit
== RLIM_INFINITY
)
559 lock_limit
>>= PAGE_SHIFT
;
560 spin_lock(&shmlock_user_lock
);
562 locked
+ user
->locked_shm
> lock_limit
&& !capable(CAP_IPC_LOCK
))
565 user
->locked_shm
+= locked
;
568 spin_unlock(&shmlock_user_lock
);
572 void user_shm_unlock(size_t size
, struct user_struct
*user
)
574 spin_lock(&shmlock_user_lock
);
575 user
->locked_shm
-= (size
+ PAGE_SIZE
- 1) >> PAGE_SHIFT
;
576 spin_unlock(&shmlock_user_lock
);
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