[media] gspca_main: Locking fixes 1
[linux-2.6.git] / mm / mlock.c
blob13e81ee8be9d9b6a8d93b793c2dd837960b68a13
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 (rlimit(RLIMIT_MEMLOCK) != 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);
138 static inline int stack_guard_page(struct vm_area_struct *vma, unsigned long addr)
140 return (vma->vm_flags & VM_GROWSDOWN) &&
141 (vma->vm_start == addr) &&
142 !vma_stack_continue(vma->vm_prev, addr);
146 * __mlock_vma_pages_range() - mlock a range of pages in the vma.
147 * @vma: target vma
148 * @start: start address
149 * @end: end address
151 * This takes care of making the pages present too.
153 * return 0 on success, negative error code on error.
155 * vma->vm_mm->mmap_sem must be held for at least read.
157 static long __mlock_vma_pages_range(struct vm_area_struct *vma,
158 unsigned long start, unsigned long end,
159 int *nonblocking)
161 struct mm_struct *mm = vma->vm_mm;
162 unsigned long addr = start;
163 int nr_pages = (end - start) / PAGE_SIZE;
164 int gup_flags;
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;
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;
181 if (vma->vm_flags & VM_LOCKED)
182 gup_flags |= FOLL_MLOCK;
184 /* We don't try to access the guard page of a stack vma */
185 if (stack_guard_page(vma, start)) {
186 addr += PAGE_SIZE;
187 nr_pages--;
190 return __get_user_pages(current, mm, addr, nr_pages, gup_flags,
191 NULL, NULL, nonblocking);
195 * convert get_user_pages() return value to posix mlock() error
197 static int __mlock_posix_error_return(long retval)
199 if (retval == -EFAULT)
200 retval = -ENOMEM;
201 else if (retval == -ENOMEM)
202 retval = -EAGAIN;
203 return retval;
207 * mlock_vma_pages_range() - mlock pages in specified vma range.
208 * @vma - the vma containing the specfied address range
209 * @start - starting address in @vma to mlock
210 * @end - end address [+1] in @vma to mlock
212 * For mmap()/mremap()/expansion of mlocked vma.
214 * return 0 on success for "normal" vmas.
216 * return number of pages [> 0] to be removed from locked_vm on success
217 * of "special" vmas.
219 long mlock_vma_pages_range(struct vm_area_struct *vma,
220 unsigned long start, unsigned long end)
222 int nr_pages = (end - start) / PAGE_SIZE;
223 BUG_ON(!(vma->vm_flags & VM_LOCKED));
226 * filter unlockable vmas
228 if (vma->vm_flags & (VM_IO | VM_PFNMAP))
229 goto no_mlock;
231 if (!((vma->vm_flags & (VM_DONTEXPAND | VM_RESERVED)) ||
232 is_vm_hugetlb_page(vma) ||
233 vma == get_gate_vma(current))) {
235 __mlock_vma_pages_range(vma, start, end, NULL);
237 /* Hide errors from mmap() and other callers */
238 return 0;
242 * User mapped kernel pages or huge pages:
243 * make these pages present to populate the ptes, but
244 * fall thru' to reset VM_LOCKED--no need to unlock, and
245 * return nr_pages so these don't get counted against task's
246 * locked limit. huge pages are already counted against
247 * locked vm limit.
249 make_pages_present(start, end);
251 no_mlock:
252 vma->vm_flags &= ~VM_LOCKED; /* and don't come back! */
253 return nr_pages; /* error or pages NOT mlocked */
257 * munlock_vma_pages_range() - munlock all pages in the vma range.'
258 * @vma - vma containing range to be munlock()ed.
259 * @start - start address in @vma of the range
260 * @end - end of range in @vma.
262 * For mremap(), munmap() and exit().
264 * Called with @vma VM_LOCKED.
266 * Returns with VM_LOCKED cleared. Callers must be prepared to
267 * deal with this.
269 * We don't save and restore VM_LOCKED here because pages are
270 * still on lru. In unmap path, pages might be scanned by reclaim
271 * and re-mlocked by try_to_{munlock|unmap} before we unmap and
272 * free them. This will result in freeing mlocked pages.
274 void munlock_vma_pages_range(struct vm_area_struct *vma,
275 unsigned long start, unsigned long end)
277 unsigned long addr;
279 lru_add_drain();
280 vma->vm_flags &= ~VM_LOCKED;
282 for (addr = start; addr < end; addr += PAGE_SIZE) {
283 struct page *page;
285 * Although FOLL_DUMP is intended for get_dump_page(),
286 * it just so happens that its special treatment of the
287 * ZERO_PAGE (returning an error instead of doing get_page)
288 * suits munlock very well (and if somehow an abnormal page
289 * has sneaked into the range, we won't oops here: great).
291 page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP);
292 if (page && !IS_ERR(page)) {
293 lock_page(page);
295 * Like in __mlock_vma_pages_range(),
296 * because we lock page here and migration is
297 * blocked by the elevated reference, we need
298 * only check for file-cache page truncation.
300 if (page->mapping)
301 munlock_vma_page(page);
302 unlock_page(page);
303 put_page(page);
305 cond_resched();
310 * mlock_fixup - handle mlock[all]/munlock[all] requests.
312 * Filters out "special" vmas -- VM_LOCKED never gets set for these, and
313 * munlock is a no-op. However, for some special vmas, we go ahead and
314 * populate the ptes via make_pages_present().
316 * For vmas that pass the filters, merge/split as appropriate.
318 static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
319 unsigned long start, unsigned long end, unsigned int newflags)
321 struct mm_struct *mm = vma->vm_mm;
322 pgoff_t pgoff;
323 int nr_pages;
324 int ret = 0;
325 int lock = newflags & VM_LOCKED;
327 if (newflags == vma->vm_flags || (vma->vm_flags & VM_SPECIAL) ||
328 is_vm_hugetlb_page(vma) || vma == get_gate_vma(current))
329 goto out; /* don't set VM_LOCKED, don't count */
331 pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
332 *prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma,
333 vma->vm_file, pgoff, vma_policy(vma));
334 if (*prev) {
335 vma = *prev;
336 goto success;
339 if (start != vma->vm_start) {
340 ret = split_vma(mm, vma, start, 1);
341 if (ret)
342 goto out;
345 if (end != vma->vm_end) {
346 ret = split_vma(mm, vma, end, 0);
347 if (ret)
348 goto out;
351 success:
353 * Keep track of amount of locked VM.
355 nr_pages = (end - start) >> PAGE_SHIFT;
356 if (!lock)
357 nr_pages = -nr_pages;
358 mm->locked_vm += nr_pages;
361 * vm_flags is protected by the mmap_sem held in write mode.
362 * It's okay if try_to_unmap_one unmaps a page just after we
363 * set VM_LOCKED, __mlock_vma_pages_range will bring it back.
366 if (lock)
367 vma->vm_flags = newflags;
368 else
369 munlock_vma_pages_range(vma, start, end);
371 out:
372 *prev = vma;
373 return ret;
376 static int do_mlock(unsigned long start, size_t len, int on)
378 unsigned long nstart, end, tmp;
379 struct vm_area_struct * vma, * prev;
380 int error;
382 VM_BUG_ON(start & ~PAGE_MASK);
383 VM_BUG_ON(len != PAGE_ALIGN(len));
384 end = start + len;
385 if (end < start)
386 return -EINVAL;
387 if (end == start)
388 return 0;
389 vma = find_vma_prev(current->mm, start, &prev);
390 if (!vma || vma->vm_start > start)
391 return -ENOMEM;
393 if (start > vma->vm_start)
394 prev = vma;
396 for (nstart = start ; ; ) {
397 unsigned int newflags;
399 /* Here we know that vma->vm_start <= nstart < vma->vm_end. */
401 newflags = vma->vm_flags | VM_LOCKED;
402 if (!on)
403 newflags &= ~VM_LOCKED;
405 tmp = vma->vm_end;
406 if (tmp > end)
407 tmp = end;
408 error = mlock_fixup(vma, &prev, nstart, tmp, newflags);
409 if (error)
410 break;
411 nstart = tmp;
412 if (nstart < prev->vm_end)
413 nstart = prev->vm_end;
414 if (nstart >= end)
415 break;
417 vma = prev->vm_next;
418 if (!vma || vma->vm_start != nstart) {
419 error = -ENOMEM;
420 break;
423 return error;
426 static int do_mlock_pages(unsigned long start, size_t len, int ignore_errors)
428 struct mm_struct *mm = current->mm;
429 unsigned long end, nstart, nend;
430 struct vm_area_struct *vma = NULL;
431 int locked = 0;
432 int ret = 0;
434 VM_BUG_ON(start & ~PAGE_MASK);
435 VM_BUG_ON(len != PAGE_ALIGN(len));
436 end = start + len;
438 for (nstart = start; nstart < end; nstart = nend) {
440 * We want to fault in pages for [nstart; end) address range.
441 * Find first corresponding VMA.
443 if (!locked) {
444 locked = 1;
445 down_read(&mm->mmap_sem);
446 vma = find_vma(mm, nstart);
447 } else if (nstart >= vma->vm_end)
448 vma = vma->vm_next;
449 if (!vma || vma->vm_start >= end)
450 break;
452 * Set [nstart; nend) to intersection of desired address
453 * range with the first VMA. Also, skip undesirable VMA types.
455 nend = min(end, vma->vm_end);
456 if (vma->vm_flags & (VM_IO | VM_PFNMAP))
457 continue;
458 if (nstart < vma->vm_start)
459 nstart = vma->vm_start;
461 * Now fault in a range of pages. __mlock_vma_pages_range()
462 * double checks the vma flags, so that it won't mlock pages
463 * if the vma was already munlocked.
465 ret = __mlock_vma_pages_range(vma, nstart, nend, &locked);
466 if (ret < 0) {
467 if (ignore_errors) {
468 ret = 0;
469 continue; /* continue at next VMA */
471 ret = __mlock_posix_error_return(ret);
472 break;
474 nend = nstart + ret * PAGE_SIZE;
475 ret = 0;
477 if (locked)
478 up_read(&mm->mmap_sem);
479 return ret; /* 0 or negative error code */
482 SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
484 unsigned long locked;
485 unsigned long lock_limit;
486 int error = -ENOMEM;
488 if (!can_do_mlock())
489 return -EPERM;
491 lru_add_drain_all(); /* flush pagevec */
493 down_write(&current->mm->mmap_sem);
494 len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
495 start &= PAGE_MASK;
497 locked = len >> PAGE_SHIFT;
498 locked += current->mm->locked_vm;
500 lock_limit = rlimit(RLIMIT_MEMLOCK);
501 lock_limit >>= PAGE_SHIFT;
503 /* check against resource limits */
504 if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
505 error = do_mlock(start, len, 1);
506 up_write(&current->mm->mmap_sem);
507 if (!error)
508 error = do_mlock_pages(start, len, 0);
509 return error;
512 SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
514 int ret;
516 down_write(&current->mm->mmap_sem);
517 len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
518 start &= PAGE_MASK;
519 ret = do_mlock(start, len, 0);
520 up_write(&current->mm->mmap_sem);
521 return ret;
524 static int do_mlockall(int flags)
526 struct vm_area_struct * vma, * prev = NULL;
527 unsigned int def_flags = 0;
529 if (flags & MCL_FUTURE)
530 def_flags = VM_LOCKED;
531 current->mm->def_flags = def_flags;
532 if (flags == MCL_FUTURE)
533 goto out;
535 for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
536 unsigned int newflags;
538 newflags = vma->vm_flags | VM_LOCKED;
539 if (!(flags & MCL_CURRENT))
540 newflags &= ~VM_LOCKED;
542 /* Ignore errors */
543 mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
545 out:
546 return 0;
549 SYSCALL_DEFINE1(mlockall, int, flags)
551 unsigned long lock_limit;
552 int ret = -EINVAL;
554 if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE)))
555 goto out;
557 ret = -EPERM;
558 if (!can_do_mlock())
559 goto out;
561 lru_add_drain_all(); /* flush pagevec */
563 down_write(&current->mm->mmap_sem);
565 lock_limit = rlimit(RLIMIT_MEMLOCK);
566 lock_limit >>= PAGE_SHIFT;
568 ret = -ENOMEM;
569 if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
570 capable(CAP_IPC_LOCK))
571 ret = do_mlockall(flags);
572 up_write(&current->mm->mmap_sem);
573 if (!ret && (flags & MCL_CURRENT)) {
574 /* Ignore errors */
575 do_mlock_pages(0, TASK_SIZE, 1);
577 out:
578 return ret;
581 SYSCALL_DEFINE0(munlockall)
583 int ret;
585 down_write(&current->mm->mmap_sem);
586 ret = do_mlockall(0);
587 up_write(&current->mm->mmap_sem);
588 return ret;
592 * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
593 * shm segments) get accounted against the user_struct instead.
595 static DEFINE_SPINLOCK(shmlock_user_lock);
597 int user_shm_lock(size_t size, struct user_struct *user)
599 unsigned long lock_limit, locked;
600 int allowed = 0;
602 locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
603 lock_limit = rlimit(RLIMIT_MEMLOCK);
604 if (lock_limit == RLIM_INFINITY)
605 allowed = 1;
606 lock_limit >>= PAGE_SHIFT;
607 spin_lock(&shmlock_user_lock);
608 if (!allowed &&
609 locked + user->locked_shm > lock_limit && !capable(CAP_IPC_LOCK))
610 goto out;
611 get_uid(user);
612 user->locked_shm += locked;
613 allowed = 1;
614 out:
615 spin_unlock(&shmlock_user_lock);
616 return allowed;
619 void user_shm_unlock(size_t size, struct user_struct *user)
621 spin_lock(&shmlock_user_lock);
622 user->locked_shm -= (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
623 spin_unlock(&shmlock_user_lock);
624 free_uid(user);