| /* |
| * linux/mm/mlock.c |
| * |
| * (C) Copyright 1995 Linus Torvalds |
| * (C) Copyright 2002 Christoph Hellwig |
| */ |
| |
| #include <linux/capability.h> |
| #include <linux/mman.h> |
| #include <linux/mm.h> |
| #include <linux/swap.h> |
| #include <linux/swapops.h> |
| #include <linux/pagemap.h> |
| #include <linux/mempolicy.h> |
| #include <linux/syscalls.h> |
| #include <linux/sched.h> |
| #include <linux/module.h> |
| #include <linux/rmap.h> |
| #include <linux/mmzone.h> |
| #include <linux/hugetlb.h> |
| |
| #include "internal.h" |
| |
| int can_do_mlock(void) |
| { |
| if (capable(CAP_IPC_LOCK)) |
| return 1; |
| if (current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur != 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 |
| * statistics. |
| * |
| * An mlocked page [PageMlocked(page)] is unevictable. As such, it will |
| * be placed on the LRU "unevictable" list, rather than the [in]active lists. |
| * The unevictable list is an LRU sibling list to the [in]active lists. |
| * PageUnevictable is set to indicate the unevictable state. |
| * |
| * When lazy mlocking via vmscan, it is important to ensure that the |
| * vma's VM_LOCKED status is not concurrently being modified, otherwise we |
| * may have mlocked a page that is being munlocked. So lazy mlock must take |
| * the mmap_sem for read, and verify that the vma really is locked |
| * (see mm/rmap.c). |
| */ |
| |
| /* |
| * LRU accounting for clear_page_mlock() |
| */ |
| void __clear_page_mlock(struct page *page) |
| { |
| VM_BUG_ON(!PageLocked(page)); |
| |
| if (!page->mapping) { /* truncated ? */ |
| return; |
| } |
| |
| if (!isolate_lru_page(page)) { |
| putback_lru_page(page); |
| } else { |
| /* |
| * Page not on the LRU yet. Flush all pagevecs and retry. |
| */ |
| lru_add_drain_all(); |
| if (!isolate_lru_page(page)) |
| putback_lru_page(page); |
| } |
| } |
| |
| /* |
| * Mark page as mlocked if not already. |
| * If page on LRU, isolate and putback to move to unevictable list. |
| */ |
| void mlock_vma_page(struct page *page) |
| { |
| BUG_ON(!PageLocked(page)); |
| |
| if (!TestSetPageMlocked(page) && !isolate_lru_page(page)) |
| putback_lru_page(page); |
| } |
| |
| /* |
| * called from munlock()/munmap() path with page supposedly on the LRU. |
| * |
| * 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. |
| */ |
| static 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); |
| } |
| } |
| |
| /* |
| * mlock a range of pages in the vma. |
| * |
| * This takes care of making the pages present too. |
| * |
| * vma->vm_mm->mmap_sem must be held for write. |
| */ |
| static int __mlock_vma_pages_range(struct vm_area_struct *vma, |
| unsigned long start, unsigned long end) |
| { |
| 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; |
| } |
| |
| 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; |
| |
| retry: |
| pte = *ptep; |
| /* |
| * If it's a swap pte, we might be racing with page migration. |
| */ |
| 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; |
| } |
| |
| 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); |
| |
| out: |
| return 0; |
| } |
| |
| /* |
| * Save pmd for pte handler for waiting on migration entries |
| */ |
| static int __munlock_pmd_handler(pmd_t *pmd, unsigned long addr, |
| unsigned long end, struct mm_walk *walk) |
| { |
| struct munlock_page_walk *mpw = walk->private; |
| |
| mpw->pmd = pmd; |
| return 0; |
| } |
| |
| |
| /* |
| * munlock a range of pages in the vma using standard page table walk. |
| * |
| * 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()/... |
| */ |
| int mlock_vma_pages_range(struct vm_area_struct *vma, |
| unsigned long start, unsigned long end) |
| { |
| struct mm_struct *mm = vma->vm_mm; |
| int nr_pages = (end - start) / PAGE_SIZE; |
| BUG_ON(!(vma->vm_flags & VM_LOCKED)); |
| |
| /* |
| * filter unlockable vmas |
| */ |
| if (vma->vm_flags & (VM_IO | VM_PFNMAP)) |
| goto no_mlock; |
| |
| if (!((vma->vm_flags & (VM_DONTEXPAND | VM_RESERVED)) || |
| is_vm_hugetlb_page(vma) || |
| vma == get_gate_vma(current))) { |
| downgrade_write(&mm->mmap_sem); |
| nr_pages = __mlock_vma_pages_range(vma, start, end); |
| |
| up_read(&mm->mmap_sem); |
| /* vma can change or disappear */ |
| down_write(&mm->mmap_sem); |
| vma = find_vma(mm, start); |
| /* non-NULL vma must contain @start, but need to check @end */ |
| if (!vma || end > vma->vm_end) |
| return -EAGAIN; |
| return nr_pages; |
| } |
| |
| /* |
| * User mapped kernel pages or huge pages: |
| * make these pages present to populate the ptes, but |
| * fall thru' to reset VM_LOCKED--no need to unlock, and |
| * return nr_pages so these don't get counted against task's |
| * locked limit. huge pages are already counted against |
| * locked vm limit. |
| */ |
| make_pages_present(start, end); |
| |
| no_mlock: |
| vma->vm_flags &= ~VM_LOCKED; /* and don't come back! */ |
| return nr_pages; /* pages NOT mlocked */ |
| } |
| |
| |
| /* |
| * munlock all pages in vma. For munmap() and exit(). |
| */ |
| void munlock_vma_pages_all(struct vm_area_struct *vma) |
| { |
| vma->vm_flags &= ~VM_LOCKED; |
| __munlock_vma_pages_range(vma, vma->vm_start, vma->vm_end); |
| } |
| |
| /* |
| * mlock_fixup - handle mlock[all]/munlock[all] requests. |
| * |
| * Filters out "special" vmas -- VM_LOCKED never gets set for these, and |
| * munlock is a no-op. However, for some special vmas, we go ahead and |
| * populate the ptes via make_pages_present(). |
| * |
| * 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) |
| { |
| struct mm_struct *mm = vma->vm_mm; |
| pgoff_t pgoff; |
| int nr_pages; |
| int ret = 0; |
| int lock = newflags & VM_LOCKED; |
| |
| if (newflags == vma->vm_flags || |
| (vma->vm_flags & (VM_IO | VM_PFNMAP))) |
| 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)); |
| if (*prev) { |
| vma = *prev; |
| goto success; |
| } |
| |
| if (start != vma->vm_start) { |
| ret = split_vma(mm, vma, start, 1); |
| if (ret) |
| goto out; |
| } |
| |
| if (end != vma->vm_end) { |
| ret = split_vma(mm, vma, end, 0); |
| if (ret) |
| goto out; |
| } |
| |
| success: |
| /* |
| * Keep track of amount of locked VM. |
| */ |
| nr_pages = (end - start) >> PAGE_SHIFT; |
| if (!lock) |
| nr_pages = -nr_pages; |
| mm->locked_vm += nr_pages; |
| |
| /* |
| * vm_flags is protected by the mmap_sem held in write mode. |
| * 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) { |
| /* |
| * mmap_sem is currently held for write. Downgrade the write |
| * lock to a read lock so that other faults, mmap scans, ... |
| * while we fault in all pages. |
| */ |
| downgrade_write(&mm->mmap_sem); |
| |
| ret = __mlock_vma_pages_range(vma, start, end); |
| if (ret > 0) { |
| mm->locked_vm -= ret; |
| ret = 0; |
| } |
| /* |
| * Need to reacquire mmap sem in write mode, as our callers |
| * expect this. We have no support for atomically upgrading |
| * a sem to write, so we need to check for ranges while sem |
| * is unlocked. |
| */ |
| up_read(&mm->mmap_sem); |
| /* vma can change or disappear */ |
| down_write(&mm->mmap_sem); |
| *prev = find_vma(mm, start); |
| /* non-NULL *prev must contain @start, but need to check @end */ |
| if (!(*prev) || end > (*prev)->vm_end) |
| ret = -EAGAIN; |
| } else { |
| /* |
| * TODO: for unlocking, pages will already be resident, so |
| * we don't need to wait for allocations/reclaim/pagein, ... |
| * However, unlocking a very large region can still take a |
| * while. Should we downgrade the semaphore for both lock |
| * AND unlock ? |
| */ |
| __munlock_vma_pages_range(vma, start, end); |
| } |
| |
| out: |
| *prev = vma; |
| return ret; |
| } |
| |
| static int do_mlock(unsigned long start, size_t len, int on) |
| { |
| unsigned long nstart, end, tmp; |
| struct vm_area_struct * vma, * prev; |
| int error; |
| |
| len = PAGE_ALIGN(len); |
| end = start + len; |
| if (end < start) |
| return -EINVAL; |
| if (end == start) |
| return 0; |
| vma = find_vma_prev(current->mm, start, &prev); |
| if (!vma || vma->vm_start > start) |
| return -ENOMEM; |
| |
| if (start > vma->vm_start) |
| prev = vma; |
| |
| for (nstart = start ; ; ) { |
| unsigned int newflags; |
| |
| /* Here we know that vma->vm_start <= nstart < vma->vm_end. */ |
| |
| newflags = vma->vm_flags | VM_LOCKED; |
| if (!on) |
| newflags &= ~VM_LOCKED; |
| |
| tmp = vma->vm_end; |
| if (tmp > end) |
| tmp = end; |
| error = mlock_fixup(vma, &prev, nstart, tmp, newflags); |
| if (error) |
| break; |
| nstart = tmp; |
| if (nstart < prev->vm_end) |
| nstart = prev->vm_end; |
| if (nstart >= end) |
| break; |
| |
| vma = prev->vm_next; |
| if (!vma || vma->vm_start != nstart) { |
| error = -ENOMEM; |
| break; |
| } |
| } |
| return error; |
| } |
| |
| asmlinkage long sys_mlock(unsigned long start, size_t len) |
| { |
| unsigned long locked; |
| unsigned long lock_limit; |
| int error = -ENOMEM; |
| |
| if (!can_do_mlock()) |
| return -EPERM; |
| |
| down_write(¤t->mm->mmap_sem); |
| len = PAGE_ALIGN(len + (start & ~PAGE_MASK)); |
| start &= PAGE_MASK; |
| |
| locked = len >> PAGE_SHIFT; |
| locked += current->mm->locked_vm; |
| |
| lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur; |
| lock_limit >>= PAGE_SHIFT; |
| |
| /* check against resource limits */ |
| if ((locked <= lock_limit) || capable(CAP_IPC_LOCK)) |
| error = do_mlock(start, len, 1); |
| up_write(¤t->mm->mmap_sem); |
| return error; |
| } |
| |
| asmlinkage long sys_munlock(unsigned long start, size_t len) |
| { |
| int ret; |
| |
| down_write(¤t->mm->mmap_sem); |
| len = PAGE_ALIGN(len + (start & ~PAGE_MASK)); |
| start &= PAGE_MASK; |
| ret = do_mlock(start, len, 0); |
| up_write(¤t->mm->mmap_sem); |
| return ret; |
| } |
| |
| static int do_mlockall(int flags) |
| { |
| struct vm_area_struct * vma, * prev = NULL; |
| unsigned int def_flags = 0; |
| |
| if (flags & MCL_FUTURE) |
| def_flags = VM_LOCKED; |
| current->mm->def_flags = def_flags; |
| if (flags == MCL_FUTURE) |
| goto out; |
| |
| for (vma = current->mm->mmap; vma ; vma = prev->vm_next) { |
| unsigned int newflags; |
| |
| newflags = vma->vm_flags | VM_LOCKED; |
| if (!(flags & MCL_CURRENT)) |
| newflags &= ~VM_LOCKED; |
| |
| /* Ignore errors */ |
| mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags); |
| } |
| out: |
| return 0; |
| } |
| |
| asmlinkage long sys_mlockall(int flags) |
| { |
| unsigned long lock_limit; |
| int ret = -EINVAL; |
| |
| if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE))) |
| goto out; |
| |
| ret = -EPERM; |
| if (!can_do_mlock()) |
| goto out; |
| |
| down_write(¤t->mm->mmap_sem); |
| |
| lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur; |
| lock_limit >>= PAGE_SHIFT; |
| |
| ret = -ENOMEM; |
| if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) || |
| capable(CAP_IPC_LOCK)) |
| ret = do_mlockall(flags); |
| up_write(¤t->mm->mmap_sem); |
| out: |
| return ret; |
| } |
| |
| asmlinkage long sys_munlockall(void) |
| { |
| int ret; |
| |
| down_write(¤t->mm->mmap_sem); |
| ret = do_mlockall(0); |
| up_write(¤t->mm->mmap_sem); |
| return ret; |
| } |
| |
| /* |
| * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB |
| * shm segments) get accounted against the user_struct instead. |
| */ |
| static DEFINE_SPINLOCK(shmlock_user_lock); |
| |
| int user_shm_lock(size_t size, struct user_struct *user) |
| { |
| unsigned long lock_limit, locked; |
| int allowed = 0; |
| |
| locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT; |
| lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur; |
| if (lock_limit == RLIM_INFINITY) |
| allowed = 1; |
| lock_limit >>= PAGE_SHIFT; |
| spin_lock(&shmlock_user_lock); |
| if (!allowed && |
| locked + user->locked_shm > lock_limit && !capable(CAP_IPC_LOCK)) |
| goto out; |
| get_uid(user); |
| user->locked_shm += locked; |
| allowed = 1; |
| out: |
| spin_unlock(&shmlock_user_lock); |
| return allowed; |
| } |
| |
| void user_shm_unlock(size_t size, struct user_struct *user) |
| { |
| spin_lock(&shmlock_user_lock); |
| user->locked_shm -= (size + PAGE_SIZE - 1) >> PAGE_SHIFT; |
| spin_unlock(&shmlock_user_lock); |
| free_uid(user); |
| } |