mm: munlock: remove unnecessary call to lru_add_drain()
[platform/adaptation/renesas_rcar/renesas_kernel.git] / mm / mlock.c
1 /*
2  *      linux/mm/mlock.c
3  *
4  *  (C) Copyright 1995 Linus Torvalds
5  *  (C) Copyright 2002 Christoph Hellwig
6  */
7
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/export.h>
18 #include <linux/rmap.h>
19 #include <linux/mmzone.h>
20 #include <linux/hugetlb.h>
21
22 #include "internal.h"
23
24 int can_do_mlock(void)
25 {
26         if (capable(CAP_IPC_LOCK))
27                 return 1;
28         if (rlimit(RLIMIT_MEMLOCK) != 0)
29                 return 1;
30         return 0;
31 }
32 EXPORT_SYMBOL(can_do_mlock);
33
34 /*
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.
38  *
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.
43  *
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).
49  */
50
51 /*
52  *  LRU accounting for clear_page_mlock()
53  */
54 void clear_page_mlock(struct page *page)
55 {
56         if (!TestClearPageMlocked(page))
57                 return;
58
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);
64         } else {
65                 /*
66                  * We lost the race. the page already moved to evictable list.
67                  */
68                 if (PageUnevictable(page))
69                         count_vm_event(UNEVICTABLE_PGSTRANDED);
70         }
71 }
72
73 /*
74  * Mark page as mlocked if not already.
75  * If page on LRU, isolate and putback to move to unevictable list.
76  */
77 void mlock_vma_page(struct page *page)
78 {
79         BUG_ON(!PageLocked(page));
80
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);
87         }
88 }
89
90 /**
91  * munlock_vma_page - munlock a vma page
92  * @page - page to be unlocked
93  *
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.
104  */
105 unsigned int munlock_vma_page(struct page *page)
106 {
107         unsigned int page_mask = 0;
108
109         BUG_ON(!PageLocked(page));
110
111         if (TestClearPageMlocked(page)) {
112                 unsigned int nr_pages = hpage_nr_pages(page);
113                 mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages);
114                 page_mask = nr_pages - 1;
115                 if (!isolate_lru_page(page)) {
116                         int ret = SWAP_AGAIN;
117
118                         /*
119                          * Optimization: if the page was mapped just once,
120                          * that's our mapping and we don't need to check all the
121                          * other vmas.
122                          */
123                         if (page_mapcount(page) > 1)
124                                 ret = try_to_munlock(page);
125                         /*
126                          * did try_to_unlock() succeed or punt?
127                          */
128                         if (ret != SWAP_MLOCK)
129                                 count_vm_event(UNEVICTABLE_PGMUNLOCKED);
130
131                         putback_lru_page(page);
132                 } else {
133                         /*
134                          * Some other task has removed the page from the LRU.
135                          * putback_lru_page() will take care of removing the
136                          * page from the unevictable list, if necessary.
137                          * vmscan [page_referenced()] will move the page back
138                          * to the unevictable list if some other vma has it
139                          * mlocked.
140                          */
141                         if (PageUnevictable(page))
142                                 count_vm_event(UNEVICTABLE_PGSTRANDED);
143                         else
144                                 count_vm_event(UNEVICTABLE_PGMUNLOCKED);
145                 }
146         }
147
148         return page_mask;
149 }
150
151 /**
152  * __mlock_vma_pages_range() -  mlock a range of pages in the vma.
153  * @vma:   target vma
154  * @start: start address
155  * @end:   end address
156  *
157  * This takes care of making the pages present too.
158  *
159  * return 0 on success, negative error code on error.
160  *
161  * vma->vm_mm->mmap_sem must be held for at least read.
162  */
163 long __mlock_vma_pages_range(struct vm_area_struct *vma,
164                 unsigned long start, unsigned long end, int *nonblocking)
165 {
166         struct mm_struct *mm = vma->vm_mm;
167         unsigned long nr_pages = (end - start) / PAGE_SIZE;
168         int gup_flags;
169
170         VM_BUG_ON(start & ~PAGE_MASK);
171         VM_BUG_ON(end   & ~PAGE_MASK);
172         VM_BUG_ON(start < vma->vm_start);
173         VM_BUG_ON(end   > vma->vm_end);
174         VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem));
175
176         gup_flags = FOLL_TOUCH | FOLL_MLOCK;
177         /*
178          * We want to touch writable mappings with a write fault in order
179          * to break COW, except for shared mappings because these don't COW
180          * and we would not want to dirty them for nothing.
181          */
182         if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
183                 gup_flags |= FOLL_WRITE;
184
185         /*
186          * We want mlock to succeed for regions that have any permissions
187          * other than PROT_NONE.
188          */
189         if (vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))
190                 gup_flags |= FOLL_FORCE;
191
192         /*
193          * We made sure addr is within a VMA, so the following will
194          * not result in a stack expansion that recurses back here.
195          */
196         return __get_user_pages(current, mm, start, nr_pages, gup_flags,
197                                 NULL, NULL, nonblocking);
198 }
199
200 /*
201  * convert get_user_pages() return value to posix mlock() error
202  */
203 static int __mlock_posix_error_return(long retval)
204 {
205         if (retval == -EFAULT)
206                 retval = -ENOMEM;
207         else if (retval == -ENOMEM)
208                 retval = -EAGAIN;
209         return retval;
210 }
211
212 /*
213  * munlock_vma_pages_range() - munlock all pages in the vma range.'
214  * @vma - vma containing range to be munlock()ed.
215  * @start - start address in @vma of the range
216  * @end - end of range in @vma.
217  *
218  *  For mremap(), munmap() and exit().
219  *
220  * Called with @vma VM_LOCKED.
221  *
222  * Returns with VM_LOCKED cleared.  Callers must be prepared to
223  * deal with this.
224  *
225  * We don't save and restore VM_LOCKED here because pages are
226  * still on lru.  In unmap path, pages might be scanned by reclaim
227  * and re-mlocked by try_to_{munlock|unmap} before we unmap and
228  * free them.  This will result in freeing mlocked pages.
229  */
230 void munlock_vma_pages_range(struct vm_area_struct *vma,
231                              unsigned long start, unsigned long end)
232 {
233         vma->vm_flags &= ~VM_LOCKED;
234
235         while (start < end) {
236                 struct page *page;
237                 unsigned int page_mask, page_increm;
238
239                 /*
240                  * Although FOLL_DUMP is intended for get_dump_page(),
241                  * it just so happens that its special treatment of the
242                  * ZERO_PAGE (returning an error instead of doing get_page)
243                  * suits munlock very well (and if somehow an abnormal page
244                  * has sneaked into the range, we won't oops here: great).
245                  */
246                 page = follow_page_mask(vma, start, FOLL_GET | FOLL_DUMP,
247                                         &page_mask);
248                 if (page && !IS_ERR(page)) {
249                         lock_page(page);
250                         /*
251                          * Any THP page found by follow_page_mask() may have
252                          * gotten split before reaching munlock_vma_page(),
253                          * so we need to recompute the page_mask here.
254                          */
255                         page_mask = munlock_vma_page(page);
256                         unlock_page(page);
257                         put_page(page);
258                 }
259                 page_increm = 1 + (~(start >> PAGE_SHIFT) & page_mask);
260                 start += page_increm * PAGE_SIZE;
261                 cond_resched();
262         }
263 }
264
265 /*
266  * mlock_fixup  - handle mlock[all]/munlock[all] requests.
267  *
268  * Filters out "special" vmas -- VM_LOCKED never gets set for these, and
269  * munlock is a no-op.  However, for some special vmas, we go ahead and
270  * populate the ptes.
271  *
272  * For vmas that pass the filters, merge/split as appropriate.
273  */
274 static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
275         unsigned long start, unsigned long end, vm_flags_t newflags)
276 {
277         struct mm_struct *mm = vma->vm_mm;
278         pgoff_t pgoff;
279         int nr_pages;
280         int ret = 0;
281         int lock = !!(newflags & VM_LOCKED);
282
283         if (newflags == vma->vm_flags || (vma->vm_flags & VM_SPECIAL) ||
284             is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm))
285                 goto out;       /* don't set VM_LOCKED,  don't count */
286
287         pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
288         *prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma,
289                           vma->vm_file, pgoff, vma_policy(vma));
290         if (*prev) {
291                 vma = *prev;
292                 goto success;
293         }
294
295         if (start != vma->vm_start) {
296                 ret = split_vma(mm, vma, start, 1);
297                 if (ret)
298                         goto out;
299         }
300
301         if (end != vma->vm_end) {
302                 ret = split_vma(mm, vma, end, 0);
303                 if (ret)
304                         goto out;
305         }
306
307 success:
308         /*
309          * Keep track of amount of locked VM.
310          */
311         nr_pages = (end - start) >> PAGE_SHIFT;
312         if (!lock)
313                 nr_pages = -nr_pages;
314         mm->locked_vm += nr_pages;
315
316         /*
317          * vm_flags is protected by the mmap_sem held in write mode.
318          * It's okay if try_to_unmap_one unmaps a page just after we
319          * set VM_LOCKED, __mlock_vma_pages_range will bring it back.
320          */
321
322         if (lock)
323                 vma->vm_flags = newflags;
324         else
325                 munlock_vma_pages_range(vma, start, end);
326
327 out:
328         *prev = vma;
329         return ret;
330 }
331
332 static int do_mlock(unsigned long start, size_t len, int on)
333 {
334         unsigned long nstart, end, tmp;
335         struct vm_area_struct * vma, * prev;
336         int error;
337
338         VM_BUG_ON(start & ~PAGE_MASK);
339         VM_BUG_ON(len != PAGE_ALIGN(len));
340         end = start + len;
341         if (end < start)
342                 return -EINVAL;
343         if (end == start)
344                 return 0;
345         vma = find_vma(current->mm, start);
346         if (!vma || vma->vm_start > start)
347                 return -ENOMEM;
348
349         prev = vma->vm_prev;
350         if (start > vma->vm_start)
351                 prev = vma;
352
353         for (nstart = start ; ; ) {
354                 vm_flags_t newflags;
355
356                 /* Here we know that  vma->vm_start <= nstart < vma->vm_end. */
357
358                 newflags = vma->vm_flags & ~VM_LOCKED;
359                 if (on)
360                         newflags |= VM_LOCKED;
361
362                 tmp = vma->vm_end;
363                 if (tmp > end)
364                         tmp = end;
365                 error = mlock_fixup(vma, &prev, nstart, tmp, newflags);
366                 if (error)
367                         break;
368                 nstart = tmp;
369                 if (nstart < prev->vm_end)
370                         nstart = prev->vm_end;
371                 if (nstart >= end)
372                         break;
373
374                 vma = prev->vm_next;
375                 if (!vma || vma->vm_start != nstart) {
376                         error = -ENOMEM;
377                         break;
378                 }
379         }
380         return error;
381 }
382
383 /*
384  * __mm_populate - populate and/or mlock pages within a range of address space.
385  *
386  * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
387  * flags. VMAs must be already marked with the desired vm_flags, and
388  * mmap_sem must not be held.
389  */
390 int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
391 {
392         struct mm_struct *mm = current->mm;
393         unsigned long end, nstart, nend;
394         struct vm_area_struct *vma = NULL;
395         int locked = 0;
396         long ret = 0;
397
398         VM_BUG_ON(start & ~PAGE_MASK);
399         VM_BUG_ON(len != PAGE_ALIGN(len));
400         end = start + len;
401
402         for (nstart = start; nstart < end; nstart = nend) {
403                 /*
404                  * We want to fault in pages for [nstart; end) address range.
405                  * Find first corresponding VMA.
406                  */
407                 if (!locked) {
408                         locked = 1;
409                         down_read(&mm->mmap_sem);
410                         vma = find_vma(mm, nstart);
411                 } else if (nstart >= vma->vm_end)
412                         vma = vma->vm_next;
413                 if (!vma || vma->vm_start >= end)
414                         break;
415                 /*
416                  * Set [nstart; nend) to intersection of desired address
417                  * range with the first VMA. Also, skip undesirable VMA types.
418                  */
419                 nend = min(end, vma->vm_end);
420                 if (vma->vm_flags & (VM_IO | VM_PFNMAP))
421                         continue;
422                 if (nstart < vma->vm_start)
423                         nstart = vma->vm_start;
424                 /*
425                  * Now fault in a range of pages. __mlock_vma_pages_range()
426                  * double checks the vma flags, so that it won't mlock pages
427                  * if the vma was already munlocked.
428                  */
429                 ret = __mlock_vma_pages_range(vma, nstart, nend, &locked);
430                 if (ret < 0) {
431                         if (ignore_errors) {
432                                 ret = 0;
433                                 continue;       /* continue at next VMA */
434                         }
435                         ret = __mlock_posix_error_return(ret);
436                         break;
437                 }
438                 nend = nstart + ret * PAGE_SIZE;
439                 ret = 0;
440         }
441         if (locked)
442                 up_read(&mm->mmap_sem);
443         return ret;     /* 0 or negative error code */
444 }
445
446 SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
447 {
448         unsigned long locked;
449         unsigned long lock_limit;
450         int error = -ENOMEM;
451
452         if (!can_do_mlock())
453                 return -EPERM;
454
455         lru_add_drain_all();    /* flush pagevec */
456
457         down_write(&current->mm->mmap_sem);
458         len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
459         start &= PAGE_MASK;
460
461         locked = len >> PAGE_SHIFT;
462         locked += current->mm->locked_vm;
463
464         lock_limit = rlimit(RLIMIT_MEMLOCK);
465         lock_limit >>= PAGE_SHIFT;
466
467         /* check against resource limits */
468         if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
469                 error = do_mlock(start, len, 1);
470         up_write(&current->mm->mmap_sem);
471         if (!error)
472                 error = __mm_populate(start, len, 0);
473         return error;
474 }
475
476 SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
477 {
478         int ret;
479
480         down_write(&current->mm->mmap_sem);
481         len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
482         start &= PAGE_MASK;
483         ret = do_mlock(start, len, 0);
484         up_write(&current->mm->mmap_sem);
485         return ret;
486 }
487
488 static int do_mlockall(int flags)
489 {
490         struct vm_area_struct * vma, * prev = NULL;
491
492         if (flags & MCL_FUTURE)
493                 current->mm->def_flags |= VM_LOCKED;
494         else
495                 current->mm->def_flags &= ~VM_LOCKED;
496         if (flags == MCL_FUTURE)
497                 goto out;
498
499         for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
500                 vm_flags_t newflags;
501
502                 newflags = vma->vm_flags & ~VM_LOCKED;
503                 if (flags & MCL_CURRENT)
504                         newflags |= VM_LOCKED;
505
506                 /* Ignore errors */
507                 mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
508         }
509 out:
510         return 0;
511 }
512
513 SYSCALL_DEFINE1(mlockall, int, flags)
514 {
515         unsigned long lock_limit;
516         int ret = -EINVAL;
517
518         if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE)))
519                 goto out;
520
521         ret = -EPERM;
522         if (!can_do_mlock())
523                 goto out;
524
525         if (flags & MCL_CURRENT)
526                 lru_add_drain_all();    /* flush pagevec */
527
528         down_write(&current->mm->mmap_sem);
529
530         lock_limit = rlimit(RLIMIT_MEMLOCK);
531         lock_limit >>= PAGE_SHIFT;
532
533         ret = -ENOMEM;
534         if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
535             capable(CAP_IPC_LOCK))
536                 ret = do_mlockall(flags);
537         up_write(&current->mm->mmap_sem);
538         if (!ret && (flags & MCL_CURRENT))
539                 mm_populate(0, TASK_SIZE);
540 out:
541         return ret;
542 }
543
544 SYSCALL_DEFINE0(munlockall)
545 {
546         int ret;
547
548         down_write(&current->mm->mmap_sem);
549         ret = do_mlockall(0);
550         up_write(&current->mm->mmap_sem);
551         return ret;
552 }
553
554 /*
555  * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
556  * shm segments) get accounted against the user_struct instead.
557  */
558 static DEFINE_SPINLOCK(shmlock_user_lock);
559
560 int user_shm_lock(size_t size, struct user_struct *user)
561 {
562         unsigned long lock_limit, locked;
563         int allowed = 0;
564
565         locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
566         lock_limit = rlimit(RLIMIT_MEMLOCK);
567         if (lock_limit == RLIM_INFINITY)
568                 allowed = 1;
569         lock_limit >>= PAGE_SHIFT;
570         spin_lock(&shmlock_user_lock);
571         if (!allowed &&
572             locked + user->locked_shm > lock_limit && !capable(CAP_IPC_LOCK))
573                 goto out;
574         get_uid(user);
575         user->locked_shm += locked;
576         allowed = 1;
577 out:
578         spin_unlock(&shmlock_user_lock);
579         return allowed;
580 }
581
582 void user_shm_unlock(size_t size, struct user_struct *user)
583 {
584         spin_lock(&shmlock_user_lock);
585         user->locked_shm -= (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
586         spin_unlock(&shmlock_user_lock);
587         free_uid(user);
588 }