mm: don't access vm_flags as 'int'
[linux-2.6.git] / mm / mlock.c
index 8746fe3..048260c 100644 (file)
@@ -25,13 +25,12 @@ int can_do_mlock(void)
 {
        if (capable(CAP_IPC_LOCK))
                return 1;
-       if (current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur != 0)
+       if (rlimit(RLIMIT_MEMLOCK) != 0)
                return 1;
        return 0;
 }
 EXPORT_SYMBOL(can_do_mlock);
 
-#ifdef CONFIG_UNEVICTABLE_LRU
 /*
  * Mlocked pages are marked with PageMlocked() flag for efficient testing
  * in vmscan and, possibly, the fault path; and to support semi-accurate
@@ -60,15 +59,16 @@ void __clear_page_mlock(struct page *page)
                return;
        }
 
+       dec_zone_page_state(page, NR_MLOCK);
+       count_vm_event(UNEVICTABLE_PGCLEARED);
        if (!isolate_lru_page(page)) {
                putback_lru_page(page);
        } else {
                /*
-                * Page not on the LRU yet.  Flush all pagevecs and retry.
+                * We lost the race. the page already moved to evictable list.
                 */
-               lru_add_drain_all();
-               if (!isolate_lru_page(page))
-                       putback_lru_page(page);
+               if (PageUnevictable(page))
+                       count_vm_event(UNEVICTABLE_PGSTRANDED);
        }
 }
 
@@ -80,242 +80,134 @@ void mlock_vma_page(struct page *page)
 {
        BUG_ON(!PageLocked(page));
 
-       if (!TestSetPageMlocked(page) && !isolate_lru_page(page))
-               putback_lru_page(page);
+       if (!TestSetPageMlocked(page)) {
+               inc_zone_page_state(page, NR_MLOCK);
+               count_vm_event(UNEVICTABLE_PGMLOCKED);
+               if (!isolate_lru_page(page))
+                       putback_lru_page(page);
+       }
 }
 
-/*
- * called from munlock()/munmap() path with page supposedly on the LRU.
+/**
+ * munlock_vma_page - munlock a vma page
+ * @page - page to be unlocked
  *
- * Note:  unlike mlock_vma_page(), we can't just clear the PageMlocked
- * [in try_to_munlock()] and then attempt to isolate the page.  We must
- * isolate the page to keep others from messing with its unevictable
- * and mlocked state while trying to munlock.  However, we pre-clear the
- * mlocked state anyway as we might lose the isolation race and we might
- * not get another chance to clear PageMlocked.  If we successfully
- * isolate the page and try_to_munlock() detects other VM_LOCKED vmas
- * mapping the page, it will restore the PageMlocked state, unless the page
- * is mapped in a non-linear vma.  So, we go ahead and SetPageMlocked(),
- * perhaps redundantly.
- * If we lose the isolation race, and the page is mapped by other VM_LOCKED
- * vmas, we'll detect this in vmscan--via try_to_munlock() or try_to_unmap()
- * either of which will restore the PageMlocked state by calling
- * mlock_vma_page() above, if it can grab the vma's mmap sem.
+ * called from munlock()/munmap() path with page supposedly on the LRU.
+ * When we munlock a page, because the vma where we found the page is being
+ * munlock()ed or munmap()ed, we want to check whether other vmas hold the
+ * page locked so that we can leave it on the unevictable lru list and not
+ * bother vmscan with it.  However, to walk the page's rmap list in
+ * try_to_munlock() we must isolate the page from the LRU.  If some other
+ * task has removed the page from the LRU, we won't be able to do that.
+ * So we clear the PageMlocked as we might not get another chance.  If we
+ * can't isolate the page, we leave it for putback_lru_page() and vmscan
+ * [page_referenced()/try_to_unmap()] to deal with.
  */
-static void munlock_vma_page(struct page *page)
+void munlock_vma_page(struct page *page)
 {
        BUG_ON(!PageLocked(page));
 
-       if (TestClearPageMlocked(page) && !isolate_lru_page(page)) {
-               try_to_munlock(page);
-               putback_lru_page(page);
+       if (TestClearPageMlocked(page)) {
+               dec_zone_page_state(page, NR_MLOCK);
+               if (!isolate_lru_page(page)) {
+                       int ret = try_to_munlock(page);
+                       /*
+                        * did try_to_unlock() succeed or punt?
+                        */
+                       if (ret != SWAP_MLOCK)
+                               count_vm_event(UNEVICTABLE_PGMUNLOCKED);
+
+                       putback_lru_page(page);
+               } else {
+                       /*
+                        * Some other task has removed the page from the LRU.
+                        * putback_lru_page() will take care of removing the
+                        * page from the unevictable list, if necessary.
+                        * vmscan [page_referenced()] will move the page back
+                        * to the unevictable list if some other vma has it
+                        * mlocked.
+                        */
+                       if (PageUnevictable(page))
+                               count_vm_event(UNEVICTABLE_PGSTRANDED);
+                       else
+                               count_vm_event(UNEVICTABLE_PGMUNLOCKED);
+               }
        }
 }
 
-/*
- * mlock a range of pages in the vma.
+/**
+ * __mlock_vma_pages_range() -  mlock a range of pages in the vma.
+ * @vma:   target vma
+ * @start: start address
+ * @end:   end address
  *
  * This takes care of making the pages present too.
  *
- * vma->vm_mm->mmap_sem must be held for write.
+ * return 0 on success, negative error code on error.
+ *
+ * vma->vm_mm->mmap_sem must be held for at least read.
  */
-static int __mlock_vma_pages_range(struct vm_area_struct *vma,
-                       unsigned long start, unsigned long end)
+static long __mlock_vma_pages_range(struct vm_area_struct *vma,
+                                   unsigned long start, unsigned long end,
+                                   int *nonblocking)
 {
        struct mm_struct *mm = vma->vm_mm;
        unsigned long addr = start;
-       struct page *pages[16]; /* 16 gives a reasonable batch */
-       int write = !!(vma->vm_flags & VM_WRITE);
        int nr_pages = (end - start) / PAGE_SIZE;
-       int ret;
-
-       VM_BUG_ON(start & ~PAGE_MASK || end & ~PAGE_MASK);
-       VM_BUG_ON(start < vma->vm_start || end > vma->vm_end);
-       VM_BUG_ON(!rwsem_is_locked(&vma->vm_mm->mmap_sem));
-
-       lru_add_drain_all();    /* push cached pages to LRU */
-
-       while (nr_pages > 0) {
-               int i;
-
-               cond_resched();
-
-               /*
-                * get_user_pages makes pages present if we are
-                * setting mlock. and this extra reference count will
-                * disable migration of this page.  However, page may
-                * still be truncated out from under us.
-                */
-               ret = get_user_pages(current, mm, addr,
-                               min_t(int, nr_pages, ARRAY_SIZE(pages)),
-                               write, 0, pages, NULL);
-               /*
-                * This can happen for, e.g., VM_NONLINEAR regions before
-                * a page has been allocated and mapped at a given offset,
-                * or for addresses that map beyond end of a file.
-                * We'll mlock the the pages if/when they get faulted in.
-                */
-               if (ret < 0)
-                       break;
-               if (ret == 0) {
-                       /*
-                        * We know the vma is there, so the only time
-                        * we cannot get a single page should be an
-                        * error (ret < 0) case.
-                        */
-                       WARN_ON(1);
-                       break;
-               }
+       int gup_flags;
 
-               lru_add_drain();        /* push cached pages to LRU */
-
-               for (i = 0; i < ret; i++) {
-                       struct page *page = pages[i];
-
-                       lock_page(page);
-                       /*
-                        * Because we lock page here and migration is blocked
-                        * by the elevated reference, we need only check for
-                        * page truncation (file-cache only).
-                        */
-                       if (page->mapping)
-                               mlock_vma_page(page);
-                       unlock_page(page);
-                       put_page(page);         /* ref from get_user_pages() */
-
-                       /*
-                        * here we assume that get_user_pages() has given us
-                        * a list of virtually contiguous pages.
-                        */
-                       addr += PAGE_SIZE;      /* for next get_user_pages() */
-                       nr_pages--;
-               }
-       }
-
-       lru_add_drain_all();    /* to update stats */
-
-       return 0;       /* count entire vma as locked_vm */
-}
-
-/*
- * private structure for munlock page table walk
- */
-struct munlock_page_walk {
-       struct vm_area_struct *vma;
-       pmd_t                 *pmd; /* for migration_entry_wait() */
-};
-
-/*
- * munlock normal pages for present ptes
- */
-static int __munlock_pte_handler(pte_t *ptep, unsigned long addr,
-                                  unsigned long end, struct mm_walk *walk)
-{
-       struct munlock_page_walk *mpw = walk->private;
-       swp_entry_t entry;
-       struct page *page;
-       pte_t pte;
+       VM_BUG_ON(start & ~PAGE_MASK);
+       VM_BUG_ON(end   & ~PAGE_MASK);
+       VM_BUG_ON(start < vma->vm_start);
+       VM_BUG_ON(end   > vma->vm_end);
+       VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem));
 
-retry:
-       pte = *ptep;
+       gup_flags = FOLL_TOUCH | FOLL_MLOCK;
        /*
-        * If it's a swap pte, we might be racing with page migration.
+        * We want to touch writable mappings with a write fault in order
+        * to break COW, except for shared mappings because these don't COW
+        * and we would not want to dirty them for nothing.
         */
-       if (unlikely(!pte_present(pte))) {
-               if (!is_swap_pte(pte))
-                       goto out;
-               entry = pte_to_swp_entry(pte);
-               if (is_migration_entry(entry)) {
-                       migration_entry_wait(mpw->vma->vm_mm, mpw->pmd, addr);
-                       goto retry;
-               }
-               goto out;
-       }
+       if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
+               gup_flags |= FOLL_WRITE;
 
-       page = vm_normal_page(mpw->vma, addr, pte);
-       if (!page)
-               goto out;
-
-       lock_page(page);
-       if (!page->mapping) {
-               unlock_page(page);
-               goto retry;
-       }
-       munlock_vma_page(page);
-       unlock_page(page);
+       /*
+        * We want mlock to succeed for regions that have any permissions
+        * other than PROT_NONE.
+        */
+       if (vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))
+               gup_flags |= FOLL_FORCE;
 
-out:
-       return 0;
+       return __get_user_pages(current, mm, addr, nr_pages, gup_flags,
+                               NULL, NULL, nonblocking);
 }
 
 /*
- * Save pmd for pte handler for waiting on migration entries
+ * convert get_user_pages() return value to posix mlock() error
  */
-static int __munlock_pmd_handler(pmd_t *pmd, unsigned long addr,
-                                unsigned long end, struct mm_walk *walk)
+static int __mlock_posix_error_return(long retval)
 {
-       struct munlock_page_walk *mpw = walk->private;
-
-       mpw->pmd = pmd;
-       return 0;
+       if (retval == -EFAULT)
+               retval = -ENOMEM;
+       else if (retval == -ENOMEM)
+               retval = -EAGAIN;
+       return retval;
 }
 
-
-/*
- * munlock a range of pages in the vma using standard page table walk.
+/**
+ * mlock_vma_pages_range() - mlock pages in specified vma range.
+ * @vma - the vma containing the specfied address range
+ * @start - starting address in @vma to mlock
+ * @end   - end address [+1] in @vma to mlock
  *
- * vma->vm_mm->mmap_sem must be held for write.
- */
-static void __munlock_vma_pages_range(struct vm_area_struct *vma,
-                             unsigned long start, unsigned long end)
-{
-       struct mm_struct *mm = vma->vm_mm;
-       struct munlock_page_walk mpw = {
-               .vma = vma,
-       };
-       struct mm_walk munlock_page_walk = {
-               .pmd_entry = __munlock_pmd_handler,
-               .pte_entry = __munlock_pte_handler,
-               .private = &mpw,
-               .mm = mm,
-       };
-
-       VM_BUG_ON(start & ~PAGE_MASK || end & ~PAGE_MASK);
-       VM_BUG_ON(!rwsem_is_locked(&vma->vm_mm->mmap_sem));
-       VM_BUG_ON(start < vma->vm_start);
-       VM_BUG_ON(end > vma->vm_end);
-
-       lru_add_drain_all();    /* push cached pages to LRU */
-       walk_page_range(start, end, &munlock_page_walk);
-       lru_add_drain_all();    /* to update stats */
-}
-
-#else /* CONFIG_UNEVICTABLE_LRU */
-
-/*
- * Just make pages present if VM_LOCKED.  No-op if unlocking.
- */
-static int __mlock_vma_pages_range(struct vm_area_struct *vma,
-                       unsigned long start, unsigned long end)
-{
-       if (vma->vm_flags & VM_LOCKED)
-               make_pages_present(start, end);
-       return 0;
-}
-
-/*
- * munlock a range of pages in the vma -- no-op.
- */
-static void __munlock_vma_pages_range(struct vm_area_struct *vma,
-                             unsigned long start, unsigned long end)
-{
-}
-#endif /* CONFIG_UNEVICTABLE_LRU */
-
-/*
- * mlock all pages in this vma range.  For mmap()/mremap()/...
+ * For mmap()/mremap()/expansion of mlocked vma.
+ *
+ * return 0 on success for "normal" vmas.
+ *
+ * return number of pages [> 0] to be removed from locked_vm on success
+ * of "special" vmas.
  */
-int mlock_vma_pages_range(struct vm_area_struct *vma,
+long mlock_vma_pages_range(struct vm_area_struct *vma,
                        unsigned long start, unsigned long end)
 {
        int nr_pages = (end - start) / PAGE_SIZE;
@@ -329,8 +221,13 @@ int mlock_vma_pages_range(struct vm_area_struct *vma,
 
        if (!((vma->vm_flags & (VM_DONTEXPAND | VM_RESERVED)) ||
                        is_vm_hugetlb_page(vma) ||
-                       vma == get_gate_vma(current)))
-               return __mlock_vma_pages_range(vma, start, end);
+                       vma == get_gate_vma(current->mm))) {
+
+               __mlock_vma_pages_range(vma, start, end, NULL);
+
+               /* Hide errors from mmap() and other callers */
+               return 0;
+       }
 
        /*
         * User mapped kernel pages or huge pages:
@@ -344,17 +241,60 @@ int mlock_vma_pages_range(struct vm_area_struct *vma,
 
 no_mlock:
        vma->vm_flags &= ~VM_LOCKED;    /* and don't come back! */
-       return nr_pages;                /* pages NOT mlocked */
+       return nr_pages;                /* error or pages NOT mlocked */
 }
 
-
 /*
- * munlock all pages in vma.   For munmap() and exit().
+ * munlock_vma_pages_range() - munlock all pages in the vma range.'
+ * @vma - vma containing range to be munlock()ed.
+ * @start - start address in @vma of the range
+ * @end - end of range in @vma.
+ *
+ *  For mremap(), munmap() and exit().
+ *
+ * Called with @vma VM_LOCKED.
+ *
+ * Returns with VM_LOCKED cleared.  Callers must be prepared to
+ * deal with this.
+ *
+ * We don't save and restore VM_LOCKED here because pages are
+ * still on lru.  In unmap path, pages might be scanned by reclaim
+ * and re-mlocked by try_to_{munlock|unmap} before we unmap and
+ * free them.  This will result in freeing mlocked pages.
  */
-void munlock_vma_pages_all(struct vm_area_struct *vma)
+void munlock_vma_pages_range(struct vm_area_struct *vma,
+                            unsigned long start, unsigned long end)
 {
+       unsigned long addr;
+
+       lru_add_drain();
        vma->vm_flags &= ~VM_LOCKED;
-       __munlock_vma_pages_range(vma, vma->vm_start, vma->vm_end);
+
+       for (addr = start; addr < end; addr += PAGE_SIZE) {
+               struct page *page;
+               /*
+                * Although FOLL_DUMP is intended for get_dump_page(),
+                * it just so happens that its special treatment of the
+                * ZERO_PAGE (returning an error instead of doing get_page)
+                * suits munlock very well (and if somehow an abnormal page
+                * has sneaked into the range, we won't oops here: great).
+                */
+               page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP);
+               if (page && !IS_ERR(page)) {
+                       lock_page(page);
+                       /*
+                        * Like in __mlock_vma_pages_range(),
+                        * because we lock page here and migration is
+                        * blocked by the elevated reference, we need
+                        * only check for file-cache page truncation.
+                        */
+                       if (page->mapping)
+                               munlock_vma_page(page);
+                       unlock_page(page);
+                       put_page(page);
+               }
+               cond_resched();
+       }
 }
 
 /*
@@ -367,26 +307,18 @@ void munlock_vma_pages_all(struct vm_area_struct *vma)
  * For vmas that pass the filters, merge/split as appropriate.
  */
 static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
-       unsigned long start, unsigned long end, unsigned int newflags)
+       unsigned long start, unsigned long end, vm_flags_t newflags)
 {
        struct mm_struct *mm = vma->vm_mm;
        pgoff_t pgoff;
        int nr_pages;
        int ret = 0;
-       int lock = newflags & VM_LOCKED;
+       int lock = !!(newflags & VM_LOCKED);
 
-       if (newflags == vma->vm_flags ||
-                       (vma->vm_flags & (VM_IO | VM_PFNMAP)))
+       if (newflags == vma->vm_flags || (vma->vm_flags & VM_SPECIAL) ||
+           is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm))
                goto out;       /* don't set VM_LOCKED,  don't count */
 
-       if ((vma->vm_flags & (VM_DONTEXPAND | VM_RESERVED)) ||
-                       is_vm_hugetlb_page(vma) ||
-                       vma == get_gate_vma(current)) {
-               if (lock)
-                       make_pages_present(start, end);
-               goto out;       /* don't set VM_LOCKED,  don't count */
-       }
-
        pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
        *prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma,
                          vma->vm_file, pgoff, vma_policy(vma));
@@ -421,16 +353,11 @@ success:
         * It's okay if try_to_unmap_one unmaps a page just after we
         * set VM_LOCKED, __mlock_vma_pages_range will bring it back.
         */
-       vma->vm_flags = newflags;
 
-       if (lock) {
-               ret = __mlock_vma_pages_range(vma, start, end);
-               if (ret > 0) {
-                       mm->locked_vm -= ret;
-                       ret = 0;
-               }
-       } else
-               __munlock_vma_pages_range(vma, start, end);
+       if (lock)
+               vma->vm_flags = newflags;
+       else
+               munlock_vma_pages_range(vma, start, end);
 
 out:
        *prev = vma;
@@ -443,7 +370,8 @@ static int do_mlock(unsigned long start, size_t len, int on)
        struct vm_area_struct * vma, * prev;
        int error;
 
-       len = PAGE_ALIGN(len);
+       VM_BUG_ON(start & ~PAGE_MASK);
+       VM_BUG_ON(len != PAGE_ALIGN(len));
        end = start + len;
        if (end < start)
                return -EINVAL;
@@ -457,7 +385,7 @@ static int do_mlock(unsigned long start, size_t len, int on)
                prev = vma;
 
        for (nstart = start ; ; ) {
-               unsigned int newflags;
+               vm_flags_t newflags;
 
                /* Here we know that  vma->vm_start <= nstart < vma->vm_end. */
 
@@ -486,7 +414,63 @@ static int do_mlock(unsigned long start, size_t len, int on)
        return error;
 }
 
-asmlinkage long sys_mlock(unsigned long start, size_t len)
+static int do_mlock_pages(unsigned long start, size_t len, int ignore_errors)
+{
+       struct mm_struct *mm = current->mm;
+       unsigned long end, nstart, nend;
+       struct vm_area_struct *vma = NULL;
+       int locked = 0;
+       int ret = 0;
+
+       VM_BUG_ON(start & ~PAGE_MASK);
+       VM_BUG_ON(len != PAGE_ALIGN(len));
+       end = start + len;
+
+       for (nstart = start; nstart < end; nstart = nend) {
+               /*
+                * We want to fault in pages for [nstart; end) address range.
+                * Find first corresponding VMA.
+                */
+               if (!locked) {
+                       locked = 1;
+                       down_read(&mm->mmap_sem);
+                       vma = find_vma(mm, nstart);
+               } else if (nstart >= vma->vm_end)
+                       vma = vma->vm_next;
+               if (!vma || vma->vm_start >= end)
+                       break;
+               /*
+                * Set [nstart; nend) to intersection of desired address
+                * range with the first VMA. Also, skip undesirable VMA types.
+                */
+               nend = min(end, vma->vm_end);
+               if (vma->vm_flags & (VM_IO | VM_PFNMAP))
+                       continue;
+               if (nstart < vma->vm_start)
+                       nstart = vma->vm_start;
+               /*
+                * Now fault in a range of pages. __mlock_vma_pages_range()
+                * double checks the vma flags, so that it won't mlock pages
+                * if the vma was already munlocked.
+                */
+               ret = __mlock_vma_pages_range(vma, nstart, nend, &locked);
+               if (ret < 0) {
+                       if (ignore_errors) {
+                               ret = 0;
+                               continue;       /* continue at next VMA */
+                       }
+                       ret = __mlock_posix_error_return(ret);
+                       break;
+               }
+               nend = nstart + ret * PAGE_SIZE;
+               ret = 0;
+       }
+       if (locked)
+               up_read(&mm->mmap_sem);
+       return ret;     /* 0 or negative error code */
+}
+
+SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
 {
        unsigned long locked;
        unsigned long lock_limit;
@@ -495,6 +479,8 @@ asmlinkage long sys_mlock(unsigned long start, size_t len)
        if (!can_do_mlock())
                return -EPERM;
 
+       lru_add_drain_all();    /* flush pagevec */
+
        down_write(&current->mm->mmap_sem);
        len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
        start &= PAGE_MASK;
@@ -502,17 +488,19 @@ asmlinkage long sys_mlock(unsigned long start, size_t len)
        locked = len >> PAGE_SHIFT;
        locked += current->mm->locked_vm;
 
-       lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
+       lock_limit = rlimit(RLIMIT_MEMLOCK);
        lock_limit >>= PAGE_SHIFT;
 
        /* check against resource limits */
        if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
                error = do_mlock(start, len, 1);
        up_write(&current->mm->mmap_sem);
+       if (!error)
+               error = do_mlock_pages(start, len, 0);
        return error;
 }
 
-asmlinkage long sys_munlock(unsigned long start, size_t len)
+SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
 {
        int ret;
 
@@ -536,7 +524,7 @@ static int do_mlockall(int flags)
                goto out;
 
        for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
-               unsigned int newflags;
+               vm_flags_t newflags;
 
                newflags = vma->vm_flags | VM_LOCKED;
                if (!(flags & MCL_CURRENT))
@@ -549,7 +537,7 @@ out:
        return 0;
 }
 
-asmlinkage long sys_mlockall(int flags)
+SYSCALL_DEFINE1(mlockall, int, flags)
 {
        unsigned long lock_limit;
        int ret = -EINVAL;
@@ -561,9 +549,11 @@ asmlinkage long sys_mlockall(int flags)
        if (!can_do_mlock())
                goto out;
 
+       lru_add_drain_all();    /* flush pagevec */
+
        down_write(&current->mm->mmap_sem);
 
-       lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
+       lock_limit = rlimit(RLIMIT_MEMLOCK);
        lock_limit >>= PAGE_SHIFT;
 
        ret = -ENOMEM;
@@ -571,11 +561,15 @@ asmlinkage long sys_mlockall(int flags)
            capable(CAP_IPC_LOCK))
                ret = do_mlockall(flags);
        up_write(&current->mm->mmap_sem);
+       if (!ret && (flags & MCL_CURRENT)) {
+               /* Ignore errors */
+               do_mlock_pages(0, TASK_SIZE, 1);
+       }
 out:
        return ret;
 }
 
-asmlinkage long sys_munlockall(void)
+SYSCALL_DEFINE0(munlockall)
 {
        int ret;
 
@@ -597,7 +591,7 @@ int user_shm_lock(size_t size, struct user_struct *user)
        int allowed = 0;
 
        locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
-       lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
+       lock_limit = rlimit(RLIMIT_MEMLOCK);
        if (lock_limit == RLIM_INFINITY)
                allowed = 1;
        lock_limit >>= PAGE_SHIFT;