Root/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
24int 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}
32EXPORT_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 */
54void __clear_page_mlock(struct page *page)
55{
56    VM_BUG_ON(!PageLocked(page));
57
58    if (!page->mapping) { /* truncated ? */
59        return;
60    }
61
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 {
67        /*
68         * We lost the race. the page already moved to evictable list.
69         */
70        if (PageUnevictable(page))
71            count_vm_event(UNEVICTABLE_PGSTRANDED);
72    }
73}
74
75/*
76 * Mark page as mlocked if not already.
77 * If page on LRU, isolate and putback to move to unevictable list.
78 */
79void mlock_vma_page(struct page *page)
80{
81    BUG_ON(!PageLocked(page));
82
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);
88    }
89}
90
91/**
92 * munlock_vma_page - munlock a vma page
93 * @page - page to be unlocked
94 *
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.
105 */
106void munlock_vma_page(struct page *page)
107{
108    BUG_ON(!PageLocked(page));
109
110    if (TestClearPageMlocked(page)) {
111        dec_zone_page_state(page, NR_MLOCK);
112        if (!isolate_lru_page(page)) {
113            int ret = SWAP_AGAIN;
114
115            /*
116             * Optimization: if the page was mapped just once,
117             * that's our mapping and we don't need to check all the
118             * other vmas.
119             */
120            if (page_mapcount(page) > 1)
121                ret = try_to_munlock(page);
122            /*
123             * did try_to_unlock() succeed or punt?
124             */
125            if (ret != SWAP_MLOCK)
126                count_vm_event(UNEVICTABLE_PGMUNLOCKED);
127
128            putback_lru_page(page);
129        } else {
130            /*
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
136             * mlocked.
137             */
138            if (PageUnevictable(page))
139                count_vm_event(UNEVICTABLE_PGSTRANDED);
140            else
141                count_vm_event(UNEVICTABLE_PGMUNLOCKED);
142        }
143    }
144}
145
146/**
147 * __mlock_vma_pages_range() - mlock a range of pages in the vma.
148 * @vma: target vma
149 * @start: start address
150 * @end: end address
151 *
152 * This takes care of making the pages present too.
153 *
154 * return 0 on success, negative error code on error.
155 *
156 * vma->vm_mm->mmap_sem must be held for at least read.
157 */
158static long __mlock_vma_pages_range(struct vm_area_struct *vma,
159                    unsigned long start, unsigned long end,
160                    int *nonblocking)
161{
162    struct mm_struct *mm = vma->vm_mm;
163    unsigned long addr = start;
164    int nr_pages = (end - start) / PAGE_SIZE;
165    int gup_flags;
166
167    VM_BUG_ON(start & ~PAGE_MASK);
168    VM_BUG_ON(end & ~PAGE_MASK);
169    VM_BUG_ON(start < vma->vm_start);
170    VM_BUG_ON(end > vma->vm_end);
171    VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem));
172
173    gup_flags = FOLL_TOUCH | FOLL_MLOCK;
174    /*
175     * We want to touch writable mappings with a write fault in order
176     * to break COW, except for shared mappings because these don't COW
177     * and we would not want to dirty them for nothing.
178     */
179    if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
180        gup_flags |= FOLL_WRITE;
181
182    /*
183     * We want mlock to succeed for regions that have any permissions
184     * other than PROT_NONE.
185     */
186    if (vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))
187        gup_flags |= FOLL_FORCE;
188
189    return __get_user_pages(current, mm, addr, nr_pages, gup_flags,
190                NULL, NULL, nonblocking);
191}
192
193/*
194 * convert get_user_pages() return value to posix mlock() error
195 */
196static int __mlock_posix_error_return(long retval)
197{
198    if (retval == -EFAULT)
199        retval = -ENOMEM;
200    else if (retval == -ENOMEM)
201        retval = -EAGAIN;
202    return retval;
203}
204
205/**
206 * mlock_vma_pages_range() - mlock pages in specified vma range.
207 * @vma - the vma containing the specfied address range
208 * @start - starting address in @vma to mlock
209 * @end - end address [+1] in @vma to mlock
210 *
211 * For mmap()/mremap()/expansion of mlocked vma.
212 *
213 * return 0 on success for "normal" vmas.
214 *
215 * return number of pages [> 0] to be removed from locked_vm on success
216 * of "special" vmas.
217 */
218long mlock_vma_pages_range(struct vm_area_struct *vma,
219            unsigned long start, unsigned long end)
220{
221    int nr_pages = (end - start) / PAGE_SIZE;
222    BUG_ON(!(vma->vm_flags & VM_LOCKED));
223
224    /*
225     * filter unlockable vmas
226     */
227    if (vma->vm_flags & (VM_IO | VM_PFNMAP))
228        goto no_mlock;
229
230    if (!((vma->vm_flags & (VM_DONTEXPAND | VM_RESERVED)) ||
231            is_vm_hugetlb_page(vma) ||
232            vma == get_gate_vma(current->mm))) {
233
234        __mlock_vma_pages_range(vma, start, end, NULL);
235
236        /* Hide errors from mmap() and other callers */
237        return 0;
238    }
239
240    /*
241     * User mapped kernel pages or huge pages:
242     * make these pages present to populate the ptes, but
243     * fall thru' to reset VM_LOCKED--no need to unlock, and
244     * return nr_pages so these don't get counted against task's
245     * locked limit. huge pages are already counted against
246     * locked vm limit.
247     */
248    make_pages_present(start, end);
249
250no_mlock:
251    vma->vm_flags &= ~VM_LOCKED; /* and don't come back! */
252    return nr_pages; /* error or pages NOT mlocked */
253}
254
255/*
256 * munlock_vma_pages_range() - munlock all pages in the vma range.'
257 * @vma - vma containing range to be munlock()ed.
258 * @start - start address in @vma of the range
259 * @end - end of range in @vma.
260 *
261 * For mremap(), munmap() and exit().
262 *
263 * Called with @vma VM_LOCKED.
264 *
265 * Returns with VM_LOCKED cleared. Callers must be prepared to
266 * deal with this.
267 *
268 * We don't save and restore VM_LOCKED here because pages are
269 * still on lru. In unmap path, pages might be scanned by reclaim
270 * and re-mlocked by try_to_{munlock|unmap} before we unmap and
271 * free them. This will result in freeing mlocked pages.
272 */
273void munlock_vma_pages_range(struct vm_area_struct *vma,
274                 unsigned long start, unsigned long end)
275{
276    unsigned long addr;
277
278    lru_add_drain();
279    vma->vm_flags &= ~VM_LOCKED;
280
281    for (addr = start; addr < end; addr += PAGE_SIZE) {
282        struct page *page;
283        /*
284         * Although FOLL_DUMP is intended for get_dump_page(),
285         * it just so happens that its special treatment of the
286         * ZERO_PAGE (returning an error instead of doing get_page)
287         * suits munlock very well (and if somehow an abnormal page
288         * has sneaked into the range, we won't oops here: great).
289         */
290        page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP);
291        if (page && !IS_ERR(page)) {
292            lock_page(page);
293            /*
294             * Like in __mlock_vma_pages_range(),
295             * because we lock page here and migration is
296             * blocked by the elevated reference, we need
297             * only check for file-cache page truncation.
298             */
299            if (page->mapping)
300                munlock_vma_page(page);
301            unlock_page(page);
302            put_page(page);
303        }
304        cond_resched();
305    }
306}
307
308/*
309 * mlock_fixup - handle mlock[all]/munlock[all] requests.
310 *
311 * Filters out "special" vmas -- VM_LOCKED never gets set for these, and
312 * munlock is a no-op. However, for some special vmas, we go ahead and
313 * populate the ptes via make_pages_present().
314 *
315 * For vmas that pass the filters, merge/split as appropriate.
316 */
317static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
318    unsigned long start, unsigned long end, vm_flags_t newflags)
319{
320    struct mm_struct *mm = vma->vm_mm;
321    pgoff_t pgoff;
322    int nr_pages;
323    int ret = 0;
324    int lock = !!(newflags & VM_LOCKED);
325
326    if (newflags == vma->vm_flags || (vma->vm_flags & VM_SPECIAL) ||
327        is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm))
328        goto out; /* don't set VM_LOCKED, don't count */
329
330    pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
331    *prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma,
332              vma->vm_file, pgoff, vma_policy(vma));
333    if (*prev) {
334        vma = *prev;
335        goto success;
336    }
337
338    if (start != vma->vm_start) {
339        ret = split_vma(mm, vma, start, 1);
340        if (ret)
341            goto out;
342    }
343
344    if (end != vma->vm_end) {
345        ret = split_vma(mm, vma, end, 0);
346        if (ret)
347            goto out;
348    }
349
350success:
351    /*
352     * Keep track of amount of locked VM.
353     */
354    nr_pages = (end - start) >> PAGE_SHIFT;
355    if (!lock)
356        nr_pages = -nr_pages;
357    mm->locked_vm += nr_pages;
358
359    /*
360     * vm_flags is protected by the mmap_sem held in write mode.
361     * It's okay if try_to_unmap_one unmaps a page just after we
362     * set VM_LOCKED, __mlock_vma_pages_range will bring it back.
363     */
364
365    if (lock)
366        vma->vm_flags = newflags;
367    else
368        munlock_vma_pages_range(vma, start, end);
369
370out:
371    *prev = vma;
372    return ret;
373}
374
375static int do_mlock(unsigned long start, size_t len, int on)
376{
377    unsigned long nstart, end, tmp;
378    struct vm_area_struct * vma, * prev;
379    int error;
380
381    VM_BUG_ON(start & ~PAGE_MASK);
382    VM_BUG_ON(len != PAGE_ALIGN(len));
383    end = start + len;
384    if (end < start)
385        return -EINVAL;
386    if (end == start)
387        return 0;
388    vma = find_vma(current->mm, start);
389    if (!vma || vma->vm_start > start)
390        return -ENOMEM;
391
392    prev = vma->vm_prev;
393    if (start > vma->vm_start)
394        prev = vma;
395
396    for (nstart = start ; ; ) {
397        vm_flags_t newflags;
398
399        /* Here we know that vma->vm_start <= nstart < vma->vm_end. */
400
401        newflags = vma->vm_flags | VM_LOCKED;
402        if (!on)
403            newflags &= ~VM_LOCKED;
404
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;
416
417        vma = prev->vm_next;
418        if (!vma || vma->vm_start != nstart) {
419            error = -ENOMEM;
420            break;
421        }
422    }
423    return error;
424}
425
426static int do_mlock_pages(unsigned long start, size_t len, int ignore_errors)
427{
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;
433
434    VM_BUG_ON(start & ~PAGE_MASK);
435    VM_BUG_ON(len != PAGE_ALIGN(len));
436    end = start + len;
437
438    for (nstart = start; nstart < end; nstart = nend) {
439        /*
440         * We want to fault in pages for [nstart; end) address range.
441         * Find first corresponding VMA.
442         */
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;
451        /*
452         * Set [nstart; nend) to intersection of desired address
453         * range with the first VMA. Also, skip undesirable VMA types.
454         */
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;
460        /*
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.
464         */
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 */
470            }
471            ret = __mlock_posix_error_return(ret);
472            break;
473        }
474        nend = nstart + ret * PAGE_SIZE;
475        ret = 0;
476    }
477    if (locked)
478        up_read(&mm->mmap_sem);
479    return ret; /* 0 or negative error code */
480}
481
482SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
483{
484    unsigned long locked;
485    unsigned long lock_limit;
486    int error = -ENOMEM;
487
488    if (!can_do_mlock())
489        return -EPERM;
490
491    lru_add_drain_all(); /* flush pagevec */
492
493    down_write(&current->mm->mmap_sem);
494    len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
495    start &= PAGE_MASK;
496
497    locked = len >> PAGE_SHIFT;
498    locked += current->mm->locked_vm;
499
500    lock_limit = rlimit(RLIMIT_MEMLOCK);
501    lock_limit >>= PAGE_SHIFT;
502
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;
510}
511
512SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
513{
514    int ret;
515
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;
522}
523
524static int do_mlockall(int flags)
525{
526    struct vm_area_struct * vma, * prev = NULL;
527    unsigned int def_flags = 0;
528
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;
534
535    for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
536        vm_flags_t newflags;
537
538        newflags = vma->vm_flags | VM_LOCKED;
539        if (!(flags & MCL_CURRENT))
540            newflags &= ~VM_LOCKED;
541
542        /* Ignore errors */
543        mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
544    }
545out:
546    return 0;
547}
548
549SYSCALL_DEFINE1(mlockall, int, flags)
550{
551    unsigned long lock_limit;
552    int ret = -EINVAL;
553
554    if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE)))
555        goto out;
556
557    ret = -EPERM;
558    if (!can_do_mlock())
559        goto out;
560
561    if (flags & MCL_CURRENT)
562        lru_add_drain_all(); /* flush pagevec */
563
564    down_write(&current->mm->mmap_sem);
565
566    lock_limit = rlimit(RLIMIT_MEMLOCK);
567    lock_limit >>= PAGE_SHIFT;
568
569    ret = -ENOMEM;
570    if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
571        capable(CAP_IPC_LOCK))
572        ret = do_mlockall(flags);
573    up_write(&current->mm->mmap_sem);
574    if (!ret && (flags & MCL_CURRENT)) {
575        /* Ignore errors */
576        do_mlock_pages(0, TASK_SIZE, 1);
577    }
578out:
579    return ret;
580}
581
582SYSCALL_DEFINE0(munlockall)
583{
584    int ret;
585
586    down_write(&current->mm->mmap_sem);
587    ret = do_mlockall(0);
588    up_write(&current->mm->mmap_sem);
589    return ret;
590}
591
592/*
593 * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
594 * shm segments) get accounted against the user_struct instead.
595 */
596static DEFINE_SPINLOCK(shmlock_user_lock);
597
598int user_shm_lock(size_t size, struct user_struct *user)
599{
600    unsigned long lock_limit, locked;
601    int allowed = 0;
602
603    locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
604    lock_limit = rlimit(RLIMIT_MEMLOCK);
605    if (lock_limit == RLIM_INFINITY)
606        allowed = 1;
607    lock_limit >>= PAGE_SHIFT;
608    spin_lock(&shmlock_user_lock);
609    if (!allowed &&
610        locked + user->locked_shm > lock_limit && !capable(CAP_IPC_LOCK))
611        goto out;
612    get_uid(user);
613    user->locked_shm += locked;
614    allowed = 1;
615out:
616    spin_unlock(&shmlock_user_lock);
617    return allowed;
618}
619
620void user_shm_unlock(size_t size, struct user_struct *user)
621{
622    spin_lock(&shmlock_user_lock);
623    user->locked_shm -= (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
624    spin_unlock(&shmlock_user_lock);
625    free_uid(user);
626}
627

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jz-3.12
jz-3.13
jz-3.15
jz-3.16
jz-3.18-dt
jz-3.2
jz-3.3
jz-3.4
jz-3.5
jz-3.6
jz-3.6-rc2-pwm
jz-3.9
jz-3.9-clk
jz-3.9-rc8
jz47xx
jz47xx-2.6.38
master

Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9



interactive