/* * 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; } 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. */ lru_add_drain_all(); if (!isolate_lru_page(page)) putback_lru_page(page); else if (PageUnevictable(page)) count_vm_event(UNEVICTABLE_PGSTRANDED); } } /* * 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)) { 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. * * 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)) { 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_SUCCESS || ret == SWAP_AGAIN) count_vm_event(UNEVICTABLE_PGMUNLOCKED); putback_lru_page(page); } else { /* * We lost the race. let try_to_unmap() deal * with it. At least we get the page state and * mlock stats right. However, page is still on * the noreclaim list. We'll fix that up when * the page is eventually freed or we scan the * noreclaim list. */ if (PageUnevictable(page)) count_vm_event(UNEVICTABLE_PGSTRANDED); else count_vm_event(UNEVICTABLE_PGMUNLOCKED); } } } /** * __mlock_vma_pages_range() - mlock/munlock a range of pages in the vma. * @vma: target vma * @start: start address * @end: end address * @mlock: 0 indicate munlock, otherwise mlock. * * If @mlock == 0, unlock an mlocked range; * else mlock the range of pages. This takes care of making the pages present , * too. * * return 0 on success, negative error code on error. * * vma->vm_mm->mmap_sem must be held for at least read. */ static long __mlock_vma_pages_range(struct vm_area_struct *vma, unsigned long start, unsigned long end, int mlock) { struct mm_struct *mm = vma->vm_mm; unsigned long addr = start; struct page *pages[16]; /* 16 gives a reasonable batch */ int nr_pages = (end - start) / PAGE_SIZE; int ret; int gup_flags = 0; 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)) && (atomic_read(&mm->mm_users) != 0)); /* * mlock: don't page populate if page has PROT_NONE permission. * munlock: the pages always do munlock althrough * its has PROT_NONE permission. */ if (!mlock) gup_flags |= GUP_FLAGS_IGNORE_VMA_PERMISSIONS; if (vma->vm_flags & VM_WRITE) gup_flags |= GUP_FLAGS_WRITE; 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)), gup_flags, 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) { if (mlock) mlock_vma_page(page); else munlock_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--; } ret = 0; } lru_add_drain_all(); /* to update stats */ return ret; /* count entire vma as locked_vm */ } /* * convert get_user_pages() return value to posix mlock() error */ static int __mlock_posix_error_return(long retval) { if (retval == -EFAULT) retval = -ENOMEM; else if (retval == -ENOMEM) retval = -EAGAIN; return retval; } #else /* CONFIG_UNEVICTABLE_LRU */ /* * Just make pages present if VM_LOCKED. No-op if unlocking. */ static long __mlock_vma_pages_range(struct vm_area_struct *vma, unsigned long start, unsigned long end, int mlock) { if (mlock && (vma->vm_flags & VM_LOCKED)) return make_pages_present(start, end); return 0; } static inline int __mlock_posix_error_return(long retval) { return 0; } #endif /* CONFIG_UNEVICTABLE_LRU */ /** * 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 * * 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. * * return negative error if vma spanning @start-@range disappears while * mmap semaphore is dropped. Unlikely? */ long 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))) { long error; downgrade_write(&mm->mmap_sem); error = __mlock_vma_pages_range(vma, start, end, 1); 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 -ENOMEM; return 0; /* hide other errors from mmap(), et al */ } /* * 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; /* error or pages NOT mlocked */ } /* * 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_range(struct vm_area_struct *vma, unsigned long start, unsigned long end) { vma->vm_flags &= ~VM_LOCKED; __mlock_vma_pages_range(vma, start, end, 0); } /* * 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, 1); /* * 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 = -ENOMEM; else if (ret > 0) { mm->locked_vm -= ret; ret = 0; } else ret = __mlock_posix_error_return(ret); /* translate if needed */ } 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 ? */ __mlock_vma_pages_range(vma, start, end, 0); } 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); }