userfaultfd: non-cooperative: add madvise() event for MADV_FREE request

	struct mm_struct *mm = vma->vm_mm;

	struct mmu_gather tlb;

	if (vma->vm_flags & (VM_LOCKED|VM_HUGETLB|VM_PFNMAP))

		return -EINVAL;

	/* MADV_FREE works for only anon vma at the moment */

	if (!vma_is_anonymous(vma))

		return -EINVAL;

	return 0;

}

static long madvise_free(struct vm_area_struct *vma,

			     struct vm_area_struct **prev,

			     unsigned long start, unsigned long end)

{

	*prev = vma;

	return madvise_free_single_vma(vma, start, end);

}

/*

 * Application no longer needs these pages.  If the pages are dirty,

 * it's OK to just throw them away.  The app will be more careful about

 * An interface that causes the system to free clean pages and flush

 * dirty pages is already available as msync(MS_INVALIDATE).

 */

static long madvise_dontneed(struct vm_area_struct *vma,

			     struct vm_area_struct **prev,

static long madvise_dontneed_single_vma(struct vm_area_struct *vma,

					unsigned long start, unsigned long end)

{

	zap_page_range(vma, start, end - start);

	return 0;

}

static long madvise_dontneed_free(struct vm_area_struct *vma,

				  struct vm_area_struct **prev,

				  unsigned long start, unsigned long end,

				  int behavior)

{

	*prev = vma;

	if (!can_madv_dontneed_vma(vma))

			 * is also < vma->vm_end. If start <

			 * vma->vm_start it means an hole materialized

			 * in the user address space within the

			 * virtual range passed to MADV_DONTNEED.

			 * virtual range passed to MADV_DONTNEED

			 * or MADV_FREE.

			 */

			return -ENOMEM;

		}

			 * Don't fail if end > vma->vm_end. If the old

			 * vma was splitted while the mmap_sem was

			 * released the effect of the concurrent

			 * operation may not cause MADV_DONTNEED to

			 * operation may not cause madvise() to

			 * have an undefined result. There may be an

			 * adjacent next vma that we'll walk

			 * next. userfaultfd_remove() will generate an

		}

		VM_WARN_ON(start >= end);

	}

	zap_page_range(vma, start, end - start);

	return 0;

	if (behavior == MADV_DONTNEED)

		return madvise_dontneed_single_vma(vma, start, end);

	else if (behavior == MADV_FREE)

		return madvise_free_single_vma(vma, start, end);

	else

		return -EINVAL;

}

/*

	case MADV_WILLNEED:

		return madvise_willneed(vma, prev, start, end);

	case MADV_FREE:

		return madvise_free(vma, prev, start, end);

	case MADV_DONTNEED:

		return madvise_dontneed(vma, prev, start, end);

		return madvise_dontneed_free(vma, prev, start, end, behavior);

	default:

		return madvise_behavior(vma, prev, start, end, behavior);

	}