/* *	linux/mm/msync.c * * Copyright (C) 1994-1999  Linus Torvalds *//* * The msync() system call. */#include <linux/fs.h>#include <linux/mm.h>#include <linux/mman.h>#include <linux/file.h>#include <linux/syscalls.h>#include <linux/sched.h>/* * MS_SYNC syncs the entire file - including mappings. * * MS_ASYNC does not start I/O (it used to, up to 2.5.67). * Nor does it marks the relevant pages dirty (it used to up to 2.6.17). * Now it doesn't do anything, since dirty pages are properly tracked. * * The application may now run fsync() to * write out the dirty pages and wait on the writeout and check the result. * Or the application may run fadvise(FADV_DONTNEED) against the fd to start * async writeout immediately. * So by _not_ starting I/O in MS_ASYNC we provide complete flexibility to * applications. */SYSCALL_DEFINE3(msync, unsigned long, start, size_t, len, int, flags){	unsigned long end;	struct mm_struct *mm = current->mm;	struct vm_area_struct *vma;	int unmapped_error = 0;	int error = -EINVAL;	if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC))		goto out;	if (start & ~PAGE_MASK)		goto out;	if ((flags & MS_ASYNC) && (flags & MS_SYNC))		goto out;	error = -ENOMEM;	len = (len + ~PAGE_MASK) & PAGE_MASK;	end = start + len;	if (end < start)		goto out;	error = 0;	if (end == start)		goto out;	/*	 * If the interval [start,end) covers some unmapped address ranges,	 * just ignore them, but return -ENOMEM at the end.	 */	down_read(&mm->mmap_sem);	vma = find_vma(mm, start);	for (;;) {		struct file *file;		/* Still start < end. */		error = -ENOMEM;		if (!vma)			goto out_unlock;		/* Here start < vma->vm_end. */		if (start < vma->vm_start) {			start = vma->vm_start;			if (start >= end)				goto out_unlock;			unmapped_error = -ENOMEM;		}		/* Here vma->vm_start <= start < vma->vm_end. */		if ((flags & MS_INVALIDATE) &&				(vma->vm_flags & VM_LOCKED)) {			error = -EBUSY;			goto out_unlock;		}		file = vma->vm_file;		start = vma->vm_end;		if ((flags & MS_SYNC) && file &&				(vma->vm_flags & VM_SHARED)) {			get_file(file);			up_read(&mm->mmap_sem);			error = vfs_fsync(file, file->f_path.dentry, 0);			fput(file);			if (error || start >= end)				goto out;			down_read(&mm->mmap_sem);			vma = find_vma(mm, start);		} else {			if (start >= end) {				error = 0;				goto out_unlock;			}			vma = vma->vm_next;		}	}out_unlock:	up_read(&mm->mmap_sem);out:	return error ? : unmapped_error;}