Linux 2.6.33-rc2
[pohmelfs.git] / mm / mlock.c
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1 /*
2 * linux/mm/mlock.c
4 * (C) Copyright 1995 Linus Torvalds
5 * (C) Copyright 2002 Christoph Hellwig
6 */
8 #include <linux/capability.h>
9 #include <linux/mman.h>
10 #include <linux/mm.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>
22 #include "internal.h"
24 int can_do_mlock(void)
26 if (capable(CAP_IPC_LOCK))
27 return 1;
28 if (current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur != 0)
29 return 1;
30 return 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
37 * statistics.
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
48 * (see mm/rmap.c).
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 ? */
59 return;
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);
66 } else {
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);
91 /**
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);
121 } else {
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
128 * mlocked.
130 if (PageUnevictable(page))
131 count_vm_event(UNEVICTABLE_PGSTRANDED);
132 else
133 count_vm_event(UNEVICTABLE_PGMUNLOCKED);
139 * __mlock_vma_pages_range() - mlock a range of pages in the vma.
140 * @vma: target vma
141 * @start: start address
142 * @end: end 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)
153 struct mm_struct *mm = vma->vm_mm;
154 unsigned long addr = start;
155 struct page *pages[16]; /* 16 gives a reasonable batch */
156 int nr_pages = (end - start) / PAGE_SIZE;
157 int ret = 0;
158 int gup_flags;
160 VM_BUG_ON(start & ~PAGE_MASK);
161 VM_BUG_ON(end & ~PAGE_MASK);
162 VM_BUG_ON(start < vma->vm_start);
163 VM_BUG_ON(end > vma->vm_end);
164 VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem));
166 gup_flags = FOLL_TOUCH | FOLL_GET;
167 if (vma->vm_flags & VM_WRITE)
168 gup_flags |= FOLL_WRITE;
170 while (nr_pages > 0) {
171 int i;
173 cond_resched();
176 * get_user_pages makes pages present if we are
177 * setting mlock. and this extra reference count will
178 * disable migration of this page. However, page may
179 * still be truncated out from under us.
181 ret = __get_user_pages(current, mm, addr,
182 min_t(int, nr_pages, ARRAY_SIZE(pages)),
183 gup_flags, pages, NULL);
185 * This can happen for, e.g., VM_NONLINEAR regions before
186 * a page has been allocated and mapped at a given offset,
187 * or for addresses that map beyond end of a file.
188 * We'll mlock the pages if/when they get faulted in.
190 if (ret < 0)
191 break;
193 lru_add_drain(); /* push cached pages to LRU */
195 for (i = 0; i < ret; i++) {
196 struct page *page = pages[i];
198 if (page->mapping) {
200 * That preliminary check is mainly to avoid
201 * the pointless overhead of lock_page on the
202 * ZERO_PAGE: which might bounce very badly if
203 * there is contention. However, we're still
204 * dirtying its cacheline with get/put_page:
205 * we'll add another __get_user_pages flag to
206 * avoid it if that case turns out to matter.
208 lock_page(page);
210 * Because we lock page here and migration is
211 * blocked by the elevated reference, we need
212 * only check for file-cache page truncation.
214 if (page->mapping)
215 mlock_vma_page(page);
216 unlock_page(page);
218 put_page(page); /* ref from get_user_pages() */
221 addr += ret * PAGE_SIZE;
222 nr_pages -= ret;
223 ret = 0;
226 return ret; /* 0 or negative error code */
230 * convert get_user_pages() return value to posix mlock() error
232 static int __mlock_posix_error_return(long retval)
234 if (retval == -EFAULT)
235 retval = -ENOMEM;
236 else if (retval == -ENOMEM)
237 retval = -EAGAIN;
238 return retval;
242 * mlock_vma_pages_range() - mlock pages in specified vma range.
243 * @vma - the vma containing the specfied address range
244 * @start - starting address in @vma to mlock
245 * @end - end address [+1] in @vma to mlock
247 * For mmap()/mremap()/expansion of mlocked vma.
249 * return 0 on success for "normal" vmas.
251 * return number of pages [> 0] to be removed from locked_vm on success
252 * of "special" vmas.
254 long mlock_vma_pages_range(struct vm_area_struct *vma,
255 unsigned long start, unsigned long end)
257 int nr_pages = (end - start) / PAGE_SIZE;
258 BUG_ON(!(vma->vm_flags & VM_LOCKED));
261 * filter unlockable vmas
263 if (vma->vm_flags & (VM_IO | VM_PFNMAP))
264 goto no_mlock;
266 if (!((vma->vm_flags & (VM_DONTEXPAND | VM_RESERVED)) ||
267 is_vm_hugetlb_page(vma) ||
268 vma == get_gate_vma(current))) {
270 __mlock_vma_pages_range(vma, start, end);
272 /* Hide errors from mmap() and other callers */
273 return 0;
277 * User mapped kernel pages or huge pages:
278 * make these pages present to populate the ptes, but
279 * fall thru' to reset VM_LOCKED--no need to unlock, and
280 * return nr_pages so these don't get counted against task's
281 * locked limit. huge pages are already counted against
282 * locked vm limit.
284 make_pages_present(start, end);
286 no_mlock:
287 vma->vm_flags &= ~VM_LOCKED; /* and don't come back! */
288 return nr_pages; /* error or pages NOT mlocked */
292 * munlock_vma_pages_range() - munlock all pages in the vma range.'
293 * @vma - vma containing range to be munlock()ed.
294 * @start - start address in @vma of the range
295 * @end - end of range in @vma.
297 * For mremap(), munmap() and exit().
299 * Called with @vma VM_LOCKED.
301 * Returns with VM_LOCKED cleared. Callers must be prepared to
302 * deal with this.
304 * We don't save and restore VM_LOCKED here because pages are
305 * still on lru. In unmap path, pages might be scanned by reclaim
306 * and re-mlocked by try_to_{munlock|unmap} before we unmap and
307 * free them. This will result in freeing mlocked pages.
309 void munlock_vma_pages_range(struct vm_area_struct *vma,
310 unsigned long start, unsigned long end)
312 unsigned long addr;
314 lru_add_drain();
315 vma->vm_flags &= ~VM_LOCKED;
317 for (addr = start; addr < end; addr += PAGE_SIZE) {
318 struct page *page;
320 * Although FOLL_DUMP is intended for get_dump_page(),
321 * it just so happens that its special treatment of the
322 * ZERO_PAGE (returning an error instead of doing get_page)
323 * suits munlock very well (and if somehow an abnormal page
324 * has sneaked into the range, we won't oops here: great).
326 page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP);
327 if (page && !IS_ERR(page)) {
328 lock_page(page);
330 * Like in __mlock_vma_pages_range(),
331 * because we lock page here and migration is
332 * blocked by the elevated reference, we need
333 * only check for file-cache page truncation.
335 if (page->mapping)
336 munlock_vma_page(page);
337 unlock_page(page);
338 put_page(page);
340 cond_resched();
345 * mlock_fixup - handle mlock[all]/munlock[all] requests.
347 * Filters out "special" vmas -- VM_LOCKED never gets set for these, and
348 * munlock is a no-op. However, for some special vmas, we go ahead and
349 * populate the ptes via make_pages_present().
351 * For vmas that pass the filters, merge/split as appropriate.
353 static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
354 unsigned long start, unsigned long end, unsigned int newflags)
356 struct mm_struct *mm = vma->vm_mm;
357 pgoff_t pgoff;
358 int nr_pages;
359 int ret = 0;
360 int lock = newflags & VM_LOCKED;
362 if (newflags == vma->vm_flags ||
363 (vma->vm_flags & (VM_IO | VM_PFNMAP)))
364 goto out; /* don't set VM_LOCKED, don't count */
366 if ((vma->vm_flags & (VM_DONTEXPAND | VM_RESERVED)) ||
367 is_vm_hugetlb_page(vma) ||
368 vma == get_gate_vma(current)) {
369 if (lock)
370 make_pages_present(start, end);
371 goto out; /* don't set VM_LOCKED, don't count */
374 pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
375 *prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma,
376 vma->vm_file, pgoff, vma_policy(vma));
377 if (*prev) {
378 vma = *prev;
379 goto success;
382 if (start != vma->vm_start) {
383 ret = split_vma(mm, vma, start, 1);
384 if (ret)
385 goto out;
388 if (end != vma->vm_end) {
389 ret = split_vma(mm, vma, end, 0);
390 if (ret)
391 goto out;
394 success:
396 * Keep track of amount of locked VM.
398 nr_pages = (end - start) >> PAGE_SHIFT;
399 if (!lock)
400 nr_pages = -nr_pages;
401 mm->locked_vm += nr_pages;
404 * vm_flags is protected by the mmap_sem held in write mode.
405 * It's okay if try_to_unmap_one unmaps a page just after we
406 * set VM_LOCKED, __mlock_vma_pages_range will bring it back.
409 if (lock) {
410 vma->vm_flags = newflags;
411 ret = __mlock_vma_pages_range(vma, start, end);
412 if (ret < 0)
413 ret = __mlock_posix_error_return(ret);
414 } else {
415 munlock_vma_pages_range(vma, start, end);
418 out:
419 *prev = vma;
420 return ret;
423 static int do_mlock(unsigned long start, size_t len, int on)
425 unsigned long nstart, end, tmp;
426 struct vm_area_struct * vma, * prev;
427 int error;
429 len = PAGE_ALIGN(len);
430 end = start + len;
431 if (end < start)
432 return -EINVAL;
433 if (end == start)
434 return 0;
435 vma = find_vma_prev(current->mm, start, &prev);
436 if (!vma || vma->vm_start > start)
437 return -ENOMEM;
439 if (start > vma->vm_start)
440 prev = vma;
442 for (nstart = start ; ; ) {
443 unsigned int newflags;
445 /* Here we know that vma->vm_start <= nstart < vma->vm_end. */
447 newflags = vma->vm_flags | VM_LOCKED;
448 if (!on)
449 newflags &= ~VM_LOCKED;
451 tmp = vma->vm_end;
452 if (tmp > end)
453 tmp = end;
454 error = mlock_fixup(vma, &prev, nstart, tmp, newflags);
455 if (error)
456 break;
457 nstart = tmp;
458 if (nstart < prev->vm_end)
459 nstart = prev->vm_end;
460 if (nstart >= end)
461 break;
463 vma = prev->vm_next;
464 if (!vma || vma->vm_start != nstart) {
465 error = -ENOMEM;
466 break;
469 return error;
472 SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
474 unsigned long locked;
475 unsigned long lock_limit;
476 int error = -ENOMEM;
478 if (!can_do_mlock())
479 return -EPERM;
481 lru_add_drain_all(); /* flush pagevec */
483 down_write(&current->mm->mmap_sem);
484 len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
485 start &= PAGE_MASK;
487 locked = len >> PAGE_SHIFT;
488 locked += current->mm->locked_vm;
490 lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
491 lock_limit >>= PAGE_SHIFT;
493 /* check against resource limits */
494 if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
495 error = do_mlock(start, len, 1);
496 up_write(&current->mm->mmap_sem);
497 return error;
500 SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
502 int ret;
504 down_write(&current->mm->mmap_sem);
505 len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
506 start &= PAGE_MASK;
507 ret = do_mlock(start, len, 0);
508 up_write(&current->mm->mmap_sem);
509 return ret;
512 static int do_mlockall(int flags)
514 struct vm_area_struct * vma, * prev = NULL;
515 unsigned int def_flags = 0;
517 if (flags & MCL_FUTURE)
518 def_flags = VM_LOCKED;
519 current->mm->def_flags = def_flags;
520 if (flags == MCL_FUTURE)
521 goto out;
523 for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
524 unsigned int newflags;
526 newflags = vma->vm_flags | VM_LOCKED;
527 if (!(flags & MCL_CURRENT))
528 newflags &= ~VM_LOCKED;
530 /* Ignore errors */
531 mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
533 out:
534 return 0;
537 SYSCALL_DEFINE1(mlockall, int, flags)
539 unsigned long lock_limit;
540 int ret = -EINVAL;
542 if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE)))
543 goto out;
545 ret = -EPERM;
546 if (!can_do_mlock())
547 goto out;
549 lru_add_drain_all(); /* flush pagevec */
551 down_write(&current->mm->mmap_sem);
553 lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
554 lock_limit >>= PAGE_SHIFT;
556 ret = -ENOMEM;
557 if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
558 capable(CAP_IPC_LOCK))
559 ret = do_mlockall(flags);
560 up_write(&current->mm->mmap_sem);
561 out:
562 return ret;
565 SYSCALL_DEFINE0(munlockall)
567 int ret;
569 down_write(&current->mm->mmap_sem);
570 ret = do_mlockall(0);
571 up_write(&current->mm->mmap_sem);
572 return ret;
576 * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
577 * shm segments) get accounted against the user_struct instead.
579 static DEFINE_SPINLOCK(shmlock_user_lock);
581 int user_shm_lock(size_t size, struct user_struct *user)
583 unsigned long lock_limit, locked;
584 int allowed = 0;
586 locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
587 lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
588 if (lock_limit == RLIM_INFINITY)
589 allowed = 1;
590 lock_limit >>= PAGE_SHIFT;
591 spin_lock(&shmlock_user_lock);
592 if (!allowed &&
593 locked + user->locked_shm > lock_limit && !capable(CAP_IPC_LOCK))
594 goto out;
595 get_uid(user);
596 user->locked_shm += locked;
597 allowed = 1;
598 out:
599 spin_unlock(&shmlock_user_lock);
600 return allowed;
603 void user_shm_unlock(size_t size, struct user_struct *user)
605 spin_lock(&shmlock_user_lock);
606 user->locked_shm -= (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
607 spin_unlock(&shmlock_user_lock);
608 free_uid(user);
611 int account_locked_memory(struct mm_struct *mm, struct rlimit *rlim,
612 size_t size)
614 unsigned long lim, vm, pgsz;
615 int error = -ENOMEM;
617 pgsz = PAGE_ALIGN(size) >> PAGE_SHIFT;
619 down_write(&mm->mmap_sem);
621 lim = rlim[RLIMIT_AS].rlim_cur >> PAGE_SHIFT;
622 vm = mm->total_vm + pgsz;
623 if (lim < vm)
624 goto out;
626 lim = rlim[RLIMIT_MEMLOCK].rlim_cur >> PAGE_SHIFT;
627 vm = mm->locked_vm + pgsz;
628 if (lim < vm)
629 goto out;
631 mm->total_vm += pgsz;
632 mm->locked_vm += pgsz;
634 error = 0;
635 out:
636 up_write(&mm->mmap_sem);
637 return error;
640 void refund_locked_memory(struct mm_struct *mm, size_t size)
642 unsigned long pgsz = PAGE_ALIGN(size) >> PAGE_SHIFT;
644 down_write(&mm->mmap_sem);
646 mm->total_vm -= pgsz;
647 mm->locked_vm -= pgsz;
649 up_write(&mm->mmap_sem);