mm/mlock.c - kernel/msm - Gitiles

 /*
  *	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/export.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 (rlimit(RLIMIT_MEMLOCK) != 0)
 		return 1;
 	return 0;
 }
 EXPORT_SYMBOL(can_do_mlock);

 /*
  * 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 {
 		/*
 		 * We lost the race. the page already moved to evictable list.
 		 */
 		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);
 	}
 }

 /**
  * munlock_vma_page - munlock a vma page
  * @page - page to be unlocked
  *
  * 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.
  */
 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_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_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.
  *
  * 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 *nonblocking)
 {
 	struct mm_struct *mm = vma->vm_mm;
 	unsigned long addr = start;
 	int nr_pages = (end - start) / PAGE_SIZE;
 	int gup_flags;

 	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));

 	gup_flags = FOLL_TOUCH | FOLL_MLOCK;
 	/*
 	 * 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 ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
 		gup_flags |= FOLL_WRITE;

 	/*
 	 * 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;

 	return __get_user_pages(current, mm, addr, nr_pages, gup_flags,
 				NULL, NULL, nonblocking);
 }

 /*
  * 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;
 }

 /**
  * 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.
  */
 long mlock_vma_pages_range(struct vm_area_struct *vma,
 			unsigned long start, unsigned long end)
 {
 	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->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:
 	 * 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)
 {
 	unsigned long addr;

 	lru_add_drain();
 	vma->vm_flags &= ~VM_LOCKED;

 	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();
 	}
 }

 /*
  * 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, 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);

 	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 */

 	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.
 	 */

 	if (lock)
 		vma->vm_flags = newflags;
 	else
 		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;

 	VM_BUG_ON(start & ~PAGE_MASK);
 	VM_BUG_ON(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 ; ; ) {
 		vm_flags_t 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;
 }

 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;
 	int error = -ENOMEM;

 	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;

 	locked = len >> PAGE_SHIFT;
 	locked += current->mm->locked_vm;

 	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;
 }

 SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
 {
 	int ret;

 	down_write(&current->mm->mmap_sem);
 	len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
 	start &= PAGE_MASK;
 	ret = do_mlock(start, len, 0);
 	up_write(&current->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) {
 		vm_flags_t 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;
 }

 SYSCALL_DEFINE1(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;

 	lru_add_drain_all();	/* flush pagevec */

 	down_write(&current->mm->mmap_sem);

 	lock_limit = rlimit(RLIMIT_MEMLOCK);
 	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(&current->mm->mmap_sem);
 	if (!ret && (flags & MCL_CURRENT)) {
 		/* Ignore errors */
 		do_mlock_pages(0, TASK_SIZE, 1);
 	}
 out:
 	return ret;
 }

 SYSCALL_DEFINE0(munlockall)
 {
 	int ret;

 	down_write(&current->mm->mmap_sem);
 	ret = do_mlockall(0);
 	up_write(&current->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 = rlimit(RLIMIT_MEMLOCK);
 	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);
 }
	/*
	* 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/export.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 (rlimit(RLIMIT_MEMLOCK) != 0)
	return 1;
	return 0;
	}
	EXPORT_SYMBOL(can_do_mlock);

	/*
	* 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 {
	/*
	* We lost the race. the page already moved to evictable list.
	*/
	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);
	}
	}

	/**
	* munlock_vma_page - munlock a vma page
	* @page - page to be unlocked
	*
	* 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.
	*/
	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_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_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.
	*
	* 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 *nonblocking)
	{
	struct mm_struct *mm = vma->vm_mm;
	unsigned long addr = start;
	int nr_pages = (end - start) / PAGE_SIZE;
	int gup_flags;

	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));

	gup_flags = FOLL_TOUCH \| FOLL_MLOCK;
	/*
	* 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 ((vma->vm_flags & (VM_WRITE \| VM_SHARED)) == VM_WRITE)
	gup_flags \|= FOLL_WRITE;

	/*
	* 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;

	return __get_user_pages(current, mm, addr, nr_pages, gup_flags,
	NULL, NULL, nonblocking);
	}

	/*
	* 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;
	}

	/**
	* 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.
	*/
	long mlock_vma_pages_range(struct vm_area_struct *vma,
	unsigned long start, unsigned long end)
	{
	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->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:
	* 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)
	{
	unsigned long addr;

	lru_add_drain();
	vma->vm_flags &= ~VM_LOCKED;

	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();
	}
	}

	/*
	* 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, 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);

	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 */

	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.
	*/

	if (lock)
	vma->vm_flags = newflags;
	else
	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;

	VM_BUG_ON(start & ~PAGE_MASK);
	VM_BUG_ON(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 ; ; ) {
	vm_flags_t 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;
	}

	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;
	int error = -ENOMEM;

	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;

	locked = len >> PAGE_SHIFT;
	locked += current->mm->locked_vm;

	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;
	}

	SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
	{
	int ret;

	down_write(&current->mm->mmap_sem);
	len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
	start &= PAGE_MASK;
	ret = do_mlock(start, len, 0);
	up_write(&current->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) {
	vm_flags_t 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;
	}

	SYSCALL_DEFINE1(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;

	lru_add_drain_all(); /* flush pagevec */

	down_write(&current->mm->mmap_sem);

	lock_limit = rlimit(RLIMIT_MEMLOCK);
	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(&current->mm->mmap_sem);
	if (!ret && (flags & MCL_CURRENT)) {
	/* Ignore errors */
	do_mlock_pages(0, TASK_SIZE, 1);
	}
	out:
	return ret;
	}

	SYSCALL_DEFINE0(munlockall)
	{
	int ret;

	down_write(&current->mm->mmap_sem);
	ret = do_mlockall(0);
	up_write(&current->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 = rlimit(RLIMIT_MEMLOCK);
	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);
	}