mm: Handle MADV_WILLNEED through vfs_fadvise()

#include <linux/userfaultfd_k.h>

#include <linux/hugetlb.h>

#include <linux/falloc.h>

#include <linux/fadvise.h>

#include <linux/sched.h>

#include <linux/ksm.h>

#include <linux/fs.h>

			     unsigned long start, unsigned long end)

{

	struct file *file = vma->vm_file;

	loff_t offset;

	*prev = vma;

#ifdef CONFIG_SWAP

		return 0;

	}

	start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;

	if (end > vma->vm_end)

		end = vma->vm_end;

	end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;

	force_page_cache_readahead(file->f_mapping, file, start, end - start);

	/*

	 * Filesystem's fadvise may need to take various locks.  We need to

	 * explicitly grab a reference because the vma (and hence the

	 * vma's reference to the file) can go away as soon as we drop

	 * mmap_sem.

	 */

	*prev = NULL;	/* tell sys_madvise we drop mmap_sem */

	get_file(file);

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

	offset = (loff_t)(start - vma->vm_start)

			+ ((loff_t)vma->vm_pgoff << PAGE_SHIFT);

	vfs_fadvise(file, offset, end - start, POSIX_FADV_WILLNEED);

	fput(file);

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

	return 0;

}