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 int 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;
188 return __get_user_pages(current, mm, addr, nr_pages, gup_flags,
189 NULL, NULL, nonblocking);
193 * convert get_user_pages() return value to posix mlock() error
195 static int __mlock_posix_error_return(long retval)
197 if (retval == -EFAULT)
199 else if (retval == -ENOMEM)
205 * munlock_vma_pages_range() - munlock all pages in the vma range.'
206 * @vma - vma containing range to be munlock()ed.
207 * @start - start address in @vma of the range
208 * @end - end of range in @vma.
210 * For mremap(), munmap() and exit().
212 * Called with @vma VM_LOCKED.
214 * Returns with VM_LOCKED cleared. Callers must be prepared to
217 * We don't save and restore VM_LOCKED here because pages are
218 * still on lru. In unmap path, pages might be scanned by reclaim
219 * and re-mlocked by try_to_{munlock|unmap} before we unmap and
220 * free them. This will result in freeing mlocked pages.
222 void munlock_vma_pages_range(struct vm_area_struct *vma,
223 unsigned long start, unsigned long end)
228 vma->vm_flags &= ~VM_LOCKED;
230 for (addr = start; addr < end; addr += PAGE_SIZE) {
233 * Although FOLL_DUMP is intended for get_dump_page(),
234 * it just so happens that its special treatment of the
235 * ZERO_PAGE (returning an error instead of doing get_page)
236 * suits munlock very well (and if somehow an abnormal page
237 * has sneaked into the range, we won't oops here: great).
239 page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP);
240 if (page && !IS_ERR(page)) {
242 munlock_vma_page(page);
251 * mlock_fixup - handle mlock[all]/munlock[all] requests.
253 * Filters out "special" vmas -- VM_LOCKED never gets set for these, and
254 * munlock is a no-op. However, for some special vmas, we go ahead and
257 * For vmas that pass the filters, merge/split as appropriate.
259 static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
260 unsigned long start, unsigned long end, vm_flags_t newflags)
262 struct mm_struct *mm = vma->vm_mm;
266 int lock = !!(newflags & VM_LOCKED);
268 if (newflags == vma->vm_flags || (vma->vm_flags & VM_SPECIAL) ||
269 is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm))
270 goto out; /* don't set VM_LOCKED, don't count */
272 pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
273 *prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma,
274 vma->vm_file, pgoff, vma_policy(vma));
280 if (start != vma->vm_start) {
281 ret = split_vma(mm, vma, start, 1);
286 if (end != vma->vm_end) {
287 ret = split_vma(mm, vma, end, 0);
294 * Keep track of amount of locked VM.
296 nr_pages = (end - start) >> PAGE_SHIFT;
298 nr_pages = -nr_pages;
299 mm->locked_vm += nr_pages;
302 * vm_flags is protected by the mmap_sem held in write mode.
303 * It's okay if try_to_unmap_one unmaps a page just after we
304 * set VM_LOCKED, __mlock_vma_pages_range will bring it back.
308 vma->vm_flags = newflags;
310 munlock_vma_pages_range(vma, start, end);
317 static int do_mlock(unsigned long start, size_t len, int on)
319 unsigned long nstart, end, tmp;
320 struct vm_area_struct * vma, * prev;
323 VM_BUG_ON(start & ~PAGE_MASK);
324 VM_BUG_ON(len != PAGE_ALIGN(len));
330 vma = find_vma(current->mm, start);
331 if (!vma || vma->vm_start > start)
335 if (start > vma->vm_start)
338 for (nstart = start ; ; ) {
341 /* Here we know that vma->vm_start <= nstart < vma->vm_end. */
343 newflags = vma->vm_flags & ~VM_LOCKED;
345 newflags |= VM_LOCKED | VM_POPULATE;
350 error = mlock_fixup(vma, &prev, nstart, tmp, newflags);
354 if (nstart < prev->vm_end)
355 nstart = prev->vm_end;
360 if (!vma || vma->vm_start != nstart) {
369 * __mm_populate - populate and/or mlock pages within a range of address space.
371 * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
372 * flags. VMAs must be already marked with the desired vm_flags, and
373 * mmap_sem must not be held.
375 int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
377 struct mm_struct *mm = current->mm;
378 unsigned long end, nstart, nend;
379 struct vm_area_struct *vma = NULL;
383 VM_BUG_ON(start & ~PAGE_MASK);
384 VM_BUG_ON(len != PAGE_ALIGN(len));
387 for (nstart = start; nstart < end; nstart = nend) {
389 * We want to fault in pages for [nstart; end) address range.
390 * Find first corresponding VMA.
394 down_read(&mm->mmap_sem);
395 vma = find_vma(mm, nstart);
396 } else if (nstart >= vma->vm_end)
398 if (!vma || vma->vm_start >= end)
401 * Set [nstart; nend) to intersection of desired address
402 * range with the first VMA. Also, skip undesirable VMA types.
404 nend = min(end, vma->vm_end);
405 if ((vma->vm_flags & (VM_IO | VM_PFNMAP | VM_POPULATE)) !=
408 if (nstart < vma->vm_start)
409 nstart = vma->vm_start;
411 * Now fault in a range of pages. __mlock_vma_pages_range()
412 * double checks the vma flags, so that it won't mlock pages
413 * if the vma was already munlocked.
415 ret = __mlock_vma_pages_range(vma, nstart, nend, &locked);
419 continue; /* continue at next VMA */
421 ret = __mlock_posix_error_return(ret);
424 nend = nstart + ret * PAGE_SIZE;
428 up_read(&mm->mmap_sem);
429 return ret; /* 0 or negative error code */
432 SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
434 unsigned long locked;
435 unsigned long lock_limit;
441 lru_add_drain_all(); /* flush pagevec */
443 down_write(¤t->mm->mmap_sem);
444 len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
447 locked = len >> PAGE_SHIFT;
448 locked += current->mm->locked_vm;
450 lock_limit = rlimit(RLIMIT_MEMLOCK);
451 lock_limit >>= PAGE_SHIFT;
453 /* check against resource limits */
454 if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
455 error = do_mlock(start, len, 1);
456 up_write(¤t->mm->mmap_sem);
458 error = __mm_populate(start, len, 0);
462 SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
466 down_write(¤t->mm->mmap_sem);
467 len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
469 ret = do_mlock(start, len, 0);
470 up_write(¤t->mm->mmap_sem);
474 static int do_mlockall(int flags)
476 struct vm_area_struct * vma, * prev = NULL;
478 if (flags & MCL_FUTURE)
479 current->mm->def_flags |= VM_LOCKED | VM_POPULATE;
481 current->mm->def_flags &= ~(VM_LOCKED | VM_POPULATE);
482 if (flags == MCL_FUTURE)
485 for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
488 newflags = vma->vm_flags & ~VM_LOCKED;
489 if (flags & MCL_CURRENT)
490 newflags |= VM_LOCKED | VM_POPULATE;
493 mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
499 SYSCALL_DEFINE1(mlockall, int, flags)
501 unsigned long lock_limit;
504 if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE)))
511 if (flags & MCL_CURRENT)
512 lru_add_drain_all(); /* flush pagevec */
514 down_write(¤t->mm->mmap_sem);
516 lock_limit = rlimit(RLIMIT_MEMLOCK);
517 lock_limit >>= PAGE_SHIFT;
520 if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
521 capable(CAP_IPC_LOCK))
522 ret = do_mlockall(flags);
523 up_write(¤t->mm->mmap_sem);
524 if (!ret && (flags & MCL_CURRENT))
525 mm_populate(0, TASK_SIZE);
530 SYSCALL_DEFINE0(munlockall)
534 down_write(¤t->mm->mmap_sem);
535 ret = do_mlockall(0);
536 up_write(¤t->mm->mmap_sem);
541 * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
542 * shm segments) get accounted against the user_struct instead.
544 static DEFINE_SPINLOCK(shmlock_user_lock);
546 int user_shm_lock(size_t size, struct user_struct *user)
548 unsigned long lock_limit, locked;
551 locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
552 lock_limit = rlimit(RLIMIT_MEMLOCK);
553 if (lock_limit == RLIM_INFINITY)
555 lock_limit >>= PAGE_SHIFT;
556 spin_lock(&shmlock_user_lock);
558 locked + user->locked_shm > lock_limit && !capable(CAP_IPC_LOCK))
561 user->locked_shm += locked;
564 spin_unlock(&shmlock_user_lock);
568 void user_shm_unlock(size_t size, struct user_struct *user)
570 spin_lock(&shmlock_user_lock);
571 user->locked_shm -= (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
572 spin_unlock(&shmlock_user_lock);