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);