/*
   *	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 {
  		/*

  		 * 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);
  	}

  }
  
  /*
   * 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 = 0;

  	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 vma has PROT_NONE permission.
  	 * munlock: always do munlock although the vma has PROT_NONE
  	 *          permission, or SIGKILL is pending.

  	 */
  	if (!mlock)

  		gup_flags |= GUP_FLAGS_IGNORE_VMA_PERMISSIONS |
  			     GUP_FLAGS_IGNORE_SIGKILL;

  	if (vma->vm_flags & VM_WRITE)
  		gup_flags |= GUP_FLAGS_WRITE;

  	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;

  	}

  	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;
  }

  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 = 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(&current->mm->mmap_sem);
  	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) {
  		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;
  }

  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 = 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(&current->mm->mmap_sem);
  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 = 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);
  }

  
  void *alloc_locked_buffer(size_t size)
  {
  	unsigned long rlim, vm, pgsz;
  	void *buffer = NULL;
  
  	pgsz = PAGE_ALIGN(size) >> PAGE_SHIFT;
  
  	down_write(&current->mm->mmap_sem);
  
  	rlim = current->signal->rlim[RLIMIT_AS].rlim_cur >> PAGE_SHIFT;
  	vm   = current->mm->total_vm + pgsz;
  	if (rlim < vm)
  		goto out;
  
  	rlim = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur >> PAGE_SHIFT;
  	vm   = current->mm->locked_vm + pgsz;
  	if (rlim < vm)
  		goto out;
  
  	buffer = kzalloc(size, GFP_KERNEL);
  	if (!buffer)
  		goto out;
  
  	current->mm->total_vm  += pgsz;
  	current->mm->locked_vm += pgsz;
  
   out:
  	up_write(&current->mm->mmap_sem);
  	return buffer;
  }
  
  void free_locked_buffer(void *buffer, size_t size)
  {
  	unsigned long pgsz = PAGE_ALIGN(size) >> PAGE_SHIFT;
  
  	down_write(&current->mm->mmap_sem);
  
  	current->mm->total_vm  -= pgsz;
  	current->mm->locked_vm -= pgsz;
  
  	up_write(&current->mm->mmap_sem);
  
  	kfree(buffer);
  }