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/module.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 VM_BUG_ON(!PageLocked(page
));
58 if (!page
->mapping
) { /* truncated ? */
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
);
68 * We lost the race. the page already moved to evictable list.
70 if (PageUnevictable(page
))
71 count_vm_event(UNEVICTABLE_PGSTRANDED
);
76 * Mark page as mlocked if not already.
77 * If page on LRU, isolate and putback to move to unevictable list.
79 void mlock_vma_page(struct page
*page
)
81 BUG_ON(!PageLocked(page
));
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
);
92 * munlock_vma_page - munlock a vma page
93 * @page - page to be unlocked
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.
106 void munlock_vma_page(struct page
*page
)
108 BUG_ON(!PageLocked(page
));
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
);
115 * did try_to_unlock() succeed or punt?
117 if (ret
!= SWAP_MLOCK
)
118 count_vm_event(UNEVICTABLE_PGMUNLOCKED
);
120 putback_lru_page(page
);
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
130 if (PageUnevictable(page
))
131 count_vm_event(UNEVICTABLE_PGSTRANDED
);
133 count_vm_event(UNEVICTABLE_PGMUNLOCKED
);
139 * __mlock_vma_pages_range() - mlock a range of pages in the vma.
141 * @start: start address
144 * This takes care of making the pages present too.
146 * return 0 on success, negative error code on error.
148 * vma->vm_mm->mmap_sem must be held for at least read.
150 static long __mlock_vma_pages_range(struct vm_area_struct
*vma
,
151 unsigned long start
, unsigned long end
,
154 struct mm_struct
*mm
= vma
->vm_mm
;
155 unsigned long addr
= start
;
156 int nr_pages
= (end
- start
) / PAGE_SIZE
;
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
));
165 gup_flags
= FOLL_TOUCH
| FOLL_MLOCK
;
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.
171 if ((vma
->vm_flags
& (VM_WRITE
| VM_SHARED
)) == VM_WRITE
)
172 gup_flags
|= FOLL_WRITE
;
175 * We want mlock to succeed for regions that have any permissions
176 * other than PROT_NONE.
178 if (vma
->vm_flags
& (VM_READ
| VM_WRITE
| VM_EXEC
))
179 gup_flags
|= FOLL_FORCE
;
181 return __get_user_pages(current
, mm
, addr
, nr_pages
, gup_flags
,
182 NULL
, NULL
, nonblocking
);
186 * convert get_user_pages() return value to posix mlock() error
188 static int __mlock_posix_error_return(long retval
)
190 if (retval
== -EFAULT
)
192 else if (retval
== -ENOMEM
)
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
203 * For mmap()/mremap()/expansion of mlocked vma.
205 * return 0 on success for "normal" vmas.
207 * return number of pages [> 0] to be removed from locked_vm on success
210 long mlock_vma_pages_range(struct vm_area_struct
*vma
,
211 unsigned long start
, unsigned long end
)
213 int nr_pages
= (end
- start
) / PAGE_SIZE
;
214 BUG_ON(!(vma
->vm_flags
& VM_LOCKED
));
217 * filter unlockable vmas
219 if (vma
->vm_flags
& (VM_IO
| VM_PFNMAP
))
222 if (!((vma
->vm_flags
& (VM_DONTEXPAND
| VM_RESERVED
)) ||
223 is_vm_hugetlb_page(vma
) ||
224 vma
== get_gate_vma(current
->mm
))) {
226 __mlock_vma_pages_range(vma
, start
, end
, NULL
);
228 /* Hide errors from mmap() and other callers */
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
240 make_pages_present(start
, end
);
243 vma
->vm_flags
&= ~VM_LOCKED
; /* and don't come back! */
244 return nr_pages
; /* error or pages NOT mlocked */
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.
253 * For mremap(), munmap() and exit().
255 * Called with @vma VM_LOCKED.
257 * Returns with VM_LOCKED cleared. Callers must be prepared to
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.
265 void munlock_vma_pages_range(struct vm_area_struct
*vma
,
266 unsigned long start
, unsigned long end
)
271 vma
->vm_flags
&= ~VM_LOCKED
;
273 for (addr
= start
; addr
< end
; addr
+= PAGE_SIZE
) {
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).
282 page
= follow_page(vma
, addr
, FOLL_GET
| FOLL_DUMP
);
283 if (page
&& !IS_ERR(page
)) {
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.
292 munlock_vma_page(page
);
301 * mlock_fixup - handle mlock[all]/munlock[all] requests.
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().
307 * For vmas that pass the filters, merge/split as appropriate.
309 static int mlock_fixup(struct vm_area_struct
*vma
, struct vm_area_struct
**prev
,
310 unsigned long start
, unsigned long end
, vm_flags_t newflags
)
312 struct mm_struct
*mm
= vma
->vm_mm
;
316 int lock
= !!(newflags
& VM_LOCKED
);
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 */
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
));
330 if (start
!= vma
->vm_start
) {
331 ret
= split_vma(mm
, vma
, start
, 1);
336 if (end
!= vma
->vm_end
) {
337 ret
= split_vma(mm
, vma
, end
, 0);
344 * Keep track of amount of locked VM.
346 nr_pages
= (end
- start
) >> PAGE_SHIFT
;
348 nr_pages
= -nr_pages
;
349 mm
->locked_vm
+= nr_pages
;
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.
358 vma
->vm_flags
= newflags
;
360 munlock_vma_pages_range(vma
, start
, end
);
367 static int do_mlock(unsigned long start
, size_t len
, int on
)
369 unsigned long nstart
, end
, tmp
;
370 struct vm_area_struct
* vma
, * prev
;
373 VM_BUG_ON(start
& ~PAGE_MASK
);
374 VM_BUG_ON(len
!= PAGE_ALIGN(len
));
380 vma
= find_vma_prev(current
->mm
, start
, &prev
);
381 if (!vma
|| vma
->vm_start
> start
)
384 if (start
> vma
->vm_start
)
387 for (nstart
= start
; ; ) {
390 /* Here we know that vma->vm_start <= nstart < vma->vm_end. */
392 newflags
= vma
->vm_flags
| VM_LOCKED
;
394 newflags
&= ~VM_LOCKED
;
399 error
= mlock_fixup(vma
, &prev
, nstart
, tmp
, newflags
);
403 if (nstart
< prev
->vm_end
)
404 nstart
= prev
->vm_end
;
409 if (!vma
|| vma
->vm_start
!= nstart
) {
417 static int do_mlock_pages(unsigned long start
, size_t len
, int ignore_errors
)
419 struct mm_struct
*mm
= current
->mm
;
420 unsigned long end
, nstart
, nend
;
421 struct vm_area_struct
*vma
= NULL
;
425 VM_BUG_ON(start
& ~PAGE_MASK
);
426 VM_BUG_ON(len
!= PAGE_ALIGN(len
));
429 for (nstart
= start
; nstart
< end
; nstart
= nend
) {
431 * We want to fault in pages for [nstart; end) address range.
432 * Find first corresponding VMA.
436 down_read(&mm
->mmap_sem
);
437 vma
= find_vma(mm
, nstart
);
438 } else if (nstart
>= vma
->vm_end
)
440 if (!vma
|| vma
->vm_start
>= end
)
443 * Set [nstart; nend) to intersection of desired address
444 * range with the first VMA. Also, skip undesirable VMA types.
446 nend
= min(end
, vma
->vm_end
);
447 if (vma
->vm_flags
& (VM_IO
| VM_PFNMAP
))
449 if (nstart
< vma
->vm_start
)
450 nstart
= vma
->vm_start
;
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.
456 ret
= __mlock_vma_pages_range(vma
, nstart
, nend
, &locked
);
460 continue; /* continue at next VMA */
462 ret
= __mlock_posix_error_return(ret
);
465 nend
= nstart
+ ret
* PAGE_SIZE
;
469 up_read(&mm
->mmap_sem
);
470 return ret
; /* 0 or negative error code */
473 SYSCALL_DEFINE2(mlock
, unsigned long, start
, size_t, len
)
475 unsigned long locked
;
476 unsigned long lock_limit
;
482 lru_add_drain_all(); /* flush pagevec */
484 down_write(¤t
->mm
->mmap_sem
);
485 len
= PAGE_ALIGN(len
+ (start
& ~PAGE_MASK
));
488 locked
= len
>> PAGE_SHIFT
;
489 locked
+= current
->mm
->locked_vm
;
491 lock_limit
= rlimit(RLIMIT_MEMLOCK
);
492 lock_limit
>>= PAGE_SHIFT
;
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
);
499 error
= do_mlock_pages(start
, len
, 0);
503 SYSCALL_DEFINE2(munlock
, unsigned long, start
, size_t, len
)
507 down_write(¤t
->mm
->mmap_sem
);
508 len
= PAGE_ALIGN(len
+ (start
& ~PAGE_MASK
));
510 ret
= do_mlock(start
, len
, 0);
511 up_write(¤t
->mm
->mmap_sem
);
515 static int do_mlockall(int flags
)
517 struct vm_area_struct
* vma
, * prev
= NULL
;
518 unsigned int def_flags
= 0;
520 if (flags
& MCL_FUTURE
)
521 def_flags
= VM_LOCKED
;
522 current
->mm
->def_flags
= def_flags
;
523 if (flags
== MCL_FUTURE
)
526 for (vma
= current
->mm
->mmap
; vma
; vma
= prev
->vm_next
) {
529 newflags
= vma
->vm_flags
| VM_LOCKED
;
530 if (!(flags
& MCL_CURRENT
))
531 newflags
&= ~VM_LOCKED
;
534 mlock_fixup(vma
, &prev
, vma
->vm_start
, vma
->vm_end
, newflags
);
540 SYSCALL_DEFINE1(mlockall
, int, flags
)
542 unsigned long lock_limit
;
545 if (!flags
|| (flags
& ~(MCL_CURRENT
| MCL_FUTURE
)))
552 lru_add_drain_all(); /* flush pagevec */
554 down_write(¤t
->mm
->mmap_sem
);
556 lock_limit
= rlimit(RLIMIT_MEMLOCK
);
557 lock_limit
>>= PAGE_SHIFT
;
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
)) {
566 do_mlock_pages(0, TASK_SIZE
, 1);
572 SYSCALL_DEFINE0(munlockall
)
576 down_write(¤t
->mm
->mmap_sem
);
577 ret
= do_mlockall(0);
578 up_write(¤t
->mm
->mmap_sem
);
583 * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
584 * shm segments) get accounted against the user_struct instead.
586 static DEFINE_SPINLOCK(shmlock_user_lock
);
588 int user_shm_lock(size_t size
, struct user_struct
*user
)
590 unsigned long lock_limit
, locked
;
593 locked
= (size
+ PAGE_SIZE
- 1) >> PAGE_SHIFT
;
594 lock_limit
= rlimit(RLIMIT_MEMLOCK
);
595 if (lock_limit
== RLIM_INFINITY
)
597 lock_limit
>>= PAGE_SHIFT
;
598 spin_lock(&shmlock_user_lock
);
600 locked
+ user
->locked_shm
> lock_limit
&& !capable(CAP_IPC_LOCK
))
603 user
->locked_shm
+= locked
;
606 spin_unlock(&shmlock_user_lock
);
610 void user_shm_unlock(size_t size
, struct user_struct
*user
)
612 spin_lock(&shmlock_user_lock
);
613 user
->locked_shm
-= (size
+ PAGE_SIZE
- 1) >> PAGE_SHIFT
;
614 spin_unlock(&shmlock_user_lock
);
This page took 0.044663 seconds and 5 git commands to generate.