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 (current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur != 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 * called from munlock()/munmap() path with page supposedly on the LRU.
94 * Note: unlike mlock_vma_page(), we can't just clear the PageMlocked
95 * [in try_to_munlock()] and then attempt to isolate the page. We must
96 * isolate the page to keep others from messing with its unevictable
97 * and mlocked state while trying to munlock. However, we pre-clear the
98 * mlocked state anyway as we might lose the isolation race and we might
99 * not get another chance to clear PageMlocked. If we successfully
100 * isolate the page and try_to_munlock() detects other VM_LOCKED vmas
101 * mapping the page, it will restore the PageMlocked state, unless the page
102 * is mapped in a non-linear vma. So, we go ahead and ClearPageMlocked(),
103 * perhaps redundantly.
104 * If we lose the isolation race, and the page is mapped by other VM_LOCKED
105 * vmas, we'll detect this in vmscan--via try_to_munlock() or try_to_unmap()
106 * either of which will restore the PageMlocked state by calling
107 * mlock_vma_page() above, if it can grab the vma's mmap sem.
109 void munlock_vma_page(struct page *page)
111 BUG_ON(!PageLocked(page));
113 if (TestClearPageMlocked(page)) {
114 dec_zone_page_state(page, NR_MLOCK);
115 if (!isolate_lru_page(page)) {
116 int ret = try_to_munlock(page);
118 * did try_to_unlock() succeed or punt?
120 if (ret == SWAP_SUCCESS || ret == SWAP_AGAIN)
121 count_vm_event(UNEVICTABLE_PGMUNLOCKED);
123 putback_lru_page(page);
126 * We lost the race. let try_to_unmap() deal
127 * with it. At least we get the page state and
128 * mlock stats right. However, page is still on
129 * the noreclaim list. We'll fix that up when
130 * the page is eventually freed or we scan the
133 if (PageUnevictable(page))
134 count_vm_event(UNEVICTABLE_PGSTRANDED);
136 count_vm_event(UNEVICTABLE_PGMUNLOCKED);
141 /* Is the vma a continuation of the stack vma above it? */
142 static inline int vma_stack_continue(struct vm_area_struct *vma, unsigned long addr)
144 return vma && (vma->vm_end == addr) && (vma->vm_flags & VM_GROWSDOWN);
147 static inline int stack_guard_page(struct vm_area_struct *vma, unsigned long addr)
149 return (vma->vm_flags & VM_GROWSDOWN) &&
150 (vma->vm_start == addr) &&
151 !vma_stack_continue(vma->vm_prev, addr);
155 * __mlock_vma_pages_range() - mlock a range of pages in the vma.
157 * @start: start address
160 * This takes care of making the pages present too.
162 * return 0 on success, negative error code on error.
164 * vma->vm_mm->mmap_sem must be held for at least read.
166 static long __mlock_vma_pages_range(struct vm_area_struct *vma,
167 unsigned long start, unsigned long end)
169 struct mm_struct *mm = vma->vm_mm;
170 unsigned long addr = start;
171 struct page *pages[16]; /* 16 gives a reasonable batch */
172 int nr_pages = (end - start) / PAGE_SIZE;
176 VM_BUG_ON(start & ~PAGE_MASK);
177 VM_BUG_ON(end & ~PAGE_MASK);
178 VM_BUG_ON(start < vma->vm_start);
179 VM_BUG_ON(end > vma->vm_end);
180 VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem));
182 gup_flags = FOLL_TOUCH | FOLL_GET;
183 if (vma->vm_flags & VM_WRITE)
184 gup_flags |= FOLL_WRITE;
186 /* We don't try to access the guard page of a stack vma */
187 if (stack_guard_page(vma, start)) {
192 while (nr_pages > 0) {
198 * get_user_pages makes pages present if we are
199 * setting mlock. and this extra reference count will
200 * disable migration of this page. However, page may
201 * still be truncated out from under us.
203 ret = __get_user_pages(current, mm, addr,
204 min_t(int, nr_pages, ARRAY_SIZE(pages)),
205 gup_flags, pages, NULL);
207 * This can happen for, e.g., VM_NONLINEAR regions before
208 * a page has been allocated and mapped at a given offset,
209 * or for addresses that map beyond end of a file.
210 * We'll mlock the pages if/when they get faulted in.
215 lru_add_drain(); /* push cached pages to LRU */
217 for (i = 0; i < ret; i++) {
218 struct page *page = pages[i];
222 * That preliminary check is mainly to avoid
223 * the pointless overhead of lock_page on the
224 * ZERO_PAGE: which might bounce very badly if
225 * there is contention. However, we're still
226 * dirtying its cacheline with get/put_page:
227 * we'll add another __get_user_pages flag to
228 * avoid it if that case turns out to matter.
232 * Because we lock page here and migration is
233 * blocked by the elevated reference, we need
234 * only check for file-cache page truncation.
237 mlock_vma_page(page);
240 put_page(page); /* ref from get_user_pages() */
243 addr += ret * PAGE_SIZE;
248 return ret; /* 0 or negative error code */
252 * convert get_user_pages() return value to posix mlock() error
254 static int __mlock_posix_error_return(long retval)
256 if (retval == -EFAULT)
258 else if (retval == -ENOMEM)
264 * mlock_vma_pages_range() - mlock pages in specified vma range.
265 * @vma - the vma containing the specfied address range
266 * @start - starting address in @vma to mlock
267 * @end - end address [+1] in @vma to mlock
269 * For mmap()/mremap()/expansion of mlocked vma.
271 * return 0 on success for "normal" vmas.
273 * return number of pages [> 0] to be removed from locked_vm on success
276 long mlock_vma_pages_range(struct vm_area_struct *vma,
277 unsigned long start, unsigned long end)
279 int nr_pages = (end - start) / PAGE_SIZE;
280 BUG_ON(!(vma->vm_flags & VM_LOCKED));
283 * filter unlockable vmas
285 if (vma->vm_flags & (VM_IO | VM_PFNMAP))
288 if (!((vma->vm_flags & (VM_DONTEXPAND | VM_RESERVED)) ||
289 is_vm_hugetlb_page(vma) ||
290 vma == get_gate_vma(current))) {
292 __mlock_vma_pages_range(vma, start, end);
294 /* Hide errors from mmap() and other callers */
299 * User mapped kernel pages or huge pages:
300 * make these pages present to populate the ptes, but
301 * fall thru' to reset VM_LOCKED--no need to unlock, and
302 * return nr_pages so these don't get counted against task's
303 * locked limit. huge pages are already counted against
306 make_pages_present(start, end);
309 vma->vm_flags &= ~VM_LOCKED; /* and don't come back! */
310 return nr_pages; /* error or pages NOT mlocked */
314 * munlock_vma_pages_range() - munlock all pages in the vma range.'
315 * @vma - vma containing range to be munlock()ed.
316 * @start - start address in @vma of the range
317 * @end - end of range in @vma.
319 * For mremap(), munmap() and exit().
321 * Called with @vma VM_LOCKED.
323 * Returns with VM_LOCKED cleared. Callers must be prepared to
326 * We don't save and restore VM_LOCKED here because pages are
327 * still on lru. In unmap path, pages might be scanned by reclaim
328 * and re-mlocked by try_to_{munlock|unmap} before we unmap and
329 * free them. This will result in freeing mlocked pages.
331 void munlock_vma_pages_range(struct vm_area_struct *vma,
332 unsigned long start, unsigned long end)
337 vma->vm_flags &= ~VM_LOCKED;
339 for (addr = start; addr < end; addr += PAGE_SIZE) {
342 * Although FOLL_DUMP is intended for get_dump_page(),
343 * it just so happens that its special treatment of the
344 * ZERO_PAGE (returning an error instead of doing get_page)
345 * suits munlock very well (and if somehow an abnormal page
346 * has sneaked into the range, we won't oops here: great).
348 page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP);
349 if (page && !IS_ERR(page)) {
352 * Like in __mlock_vma_pages_range(),
353 * because we lock page here and migration is
354 * blocked by the elevated reference, we need
355 * only check for file-cache page truncation.
358 munlock_vma_page(page);
367 * mlock_fixup - handle mlock[all]/munlock[all] requests.
369 * Filters out "special" vmas -- VM_LOCKED never gets set for these, and
370 * munlock is a no-op. However, for some special vmas, we go ahead and
371 * populate the ptes via make_pages_present().
373 * For vmas that pass the filters, merge/split as appropriate.
375 static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
376 unsigned long start, unsigned long end, unsigned int newflags)
378 struct mm_struct *mm = vma->vm_mm;
382 int lock = newflags & VM_LOCKED;
384 if (newflags == vma->vm_flags ||
385 (vma->vm_flags & (VM_IO | VM_PFNMAP)))
386 goto out; /* don't set VM_LOCKED, don't count */
388 if ((vma->vm_flags & (VM_DONTEXPAND | VM_RESERVED)) ||
389 is_vm_hugetlb_page(vma) ||
390 vma == get_gate_vma(current)) {
392 make_pages_present(start, end);
393 goto out; /* don't set VM_LOCKED, don't count */
396 pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
397 *prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma,
398 vma->vm_file, pgoff, vma_policy(vma));
404 if (start != vma->vm_start) {
405 ret = split_vma(mm, vma, start, 1);
410 if (end != vma->vm_end) {
411 ret = split_vma(mm, vma, end, 0);
418 * Keep track of amount of locked VM.
420 nr_pages = (end - start) >> PAGE_SHIFT;
422 nr_pages = -nr_pages;
423 mm->locked_vm += nr_pages;
426 * vm_flags is protected by the mmap_sem held in write mode.
427 * It's okay if try_to_unmap_one unmaps a page just after we
428 * set VM_LOCKED, __mlock_vma_pages_range will bring it back.
432 vma->vm_flags = newflags;
433 ret = __mlock_vma_pages_range(vma, start, end);
435 ret = __mlock_posix_error_return(ret);
437 munlock_vma_pages_range(vma, start, end);
445 static int do_mlock(unsigned long start, size_t len, int on)
447 unsigned long nstart, end, tmp;
448 struct vm_area_struct * vma, * prev;
451 len = PAGE_ALIGN(len);
457 vma = find_vma_prev(current->mm, start, &prev);
458 if (!vma || vma->vm_start > start)
461 if (start > vma->vm_start)
464 for (nstart = start ; ; ) {
465 unsigned int newflags;
467 /* Here we know that vma->vm_start <= nstart < vma->vm_end. */
469 newflags = vma->vm_flags | VM_LOCKED;
471 newflags &= ~VM_LOCKED;
476 error = mlock_fixup(vma, &prev, nstart, tmp, newflags);
480 if (nstart < prev->vm_end)
481 nstart = prev->vm_end;
486 if (!vma || vma->vm_start != nstart) {
494 SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
496 unsigned long locked;
497 unsigned long lock_limit;
503 lru_add_drain_all(); /* flush pagevec */
505 down_write(¤t->mm->mmap_sem);
506 len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
509 locked = len >> PAGE_SHIFT;
510 locked += current->mm->locked_vm;
512 lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
513 lock_limit >>= PAGE_SHIFT;
515 /* check against resource limits */
516 if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
517 error = do_mlock(start, len, 1);
518 up_write(¤t->mm->mmap_sem);
522 SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
526 down_write(¤t->mm->mmap_sem);
527 len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
529 ret = do_mlock(start, len, 0);
530 up_write(¤t->mm->mmap_sem);
534 static int do_mlockall(int flags)
536 struct vm_area_struct * vma, * prev = NULL;
537 unsigned int def_flags = 0;
539 if (flags & MCL_FUTURE)
540 def_flags = VM_LOCKED;
541 current->mm->def_flags = def_flags;
542 if (flags == MCL_FUTURE)
545 for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
546 unsigned int newflags;
548 newflags = vma->vm_flags | VM_LOCKED;
549 if (!(flags & MCL_CURRENT))
550 newflags &= ~VM_LOCKED;
553 mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
559 SYSCALL_DEFINE1(mlockall, int, flags)
561 unsigned long lock_limit;
564 if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE)))
571 lru_add_drain_all(); /* flush pagevec */
573 down_write(¤t->mm->mmap_sem);
575 lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
576 lock_limit >>= PAGE_SHIFT;
579 if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
580 capable(CAP_IPC_LOCK))
581 ret = do_mlockall(flags);
582 up_write(¤t->mm->mmap_sem);
587 SYSCALL_DEFINE0(munlockall)
591 down_write(¤t->mm->mmap_sem);
592 ret = do_mlockall(0);
593 up_write(¤t->mm->mmap_sem);
598 * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
599 * shm segments) get accounted against the user_struct instead.
601 static DEFINE_SPINLOCK(shmlock_user_lock);
603 int user_shm_lock(size_t size, struct user_struct *user)
605 unsigned long lock_limit, locked;
608 locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
609 lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
610 if (lock_limit == RLIM_INFINITY)
612 lock_limit >>= PAGE_SHIFT;
613 spin_lock(&shmlock_user_lock);
615 locked + user->locked_shm > lock_limit && !capable(CAP_IPC_LOCK))
618 user->locked_shm += locked;
621 spin_unlock(&shmlock_user_lock);
625 void user_shm_unlock(size_t size, struct user_struct *user)
627 spin_lock(&shmlock_user_lock);
628 user->locked_shm -= (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
629 spin_unlock(&shmlock_user_lock);
633 int account_locked_memory(struct mm_struct *mm, struct rlimit *rlim,
636 unsigned long lim, vm, pgsz;
639 pgsz = PAGE_ALIGN(size) >> PAGE_SHIFT;
641 down_write(&mm->mmap_sem);
643 lim = rlim[RLIMIT_AS].rlim_cur >> PAGE_SHIFT;
644 vm = mm->total_vm + pgsz;
648 lim = rlim[RLIMIT_MEMLOCK].rlim_cur >> PAGE_SHIFT;
649 vm = mm->locked_vm + pgsz;
653 mm->total_vm += pgsz;
654 mm->locked_vm += pgsz;
658 up_write(&mm->mmap_sem);
662 void refund_locked_memory(struct mm_struct *mm, size_t size)
664 unsigned long pgsz = PAGE_ALIGN(size) >> PAGE_SHIFT;
666 down_write(&mm->mmap_sem);
668 mm->total_vm -= pgsz;
669 mm->locked_vm -= pgsz;
671 up_write(&mm->mmap_sem);