C++ (Cpp) read_zero_pagealigned Examples

Example #1

static ssize_t read_zero(struct file * file, char * buf, 
			 size_t count, loff_t *ppos)
{
	unsigned long left;

	if (!count)
		return 0;

	if (!access_ok(VERIFY_WRITE, buf, count))
		return -EFAULT;

	left = count;

#ifndef NO_MM
{
	unsigned long unwritten, written = 0;
	/* do we want to be clever? Arbitrary cut-off */
	if (count >= PAGE_SIZE*4) {
		unsigned long partial;

		/* How much left of the page? */
		partial = (PAGE_SIZE-1) & -(unsigned long) buf;
		unwritten = clear_user(buf, partial);
		written = partial - unwritten;
		if (unwritten)
			goto out;
		left -= partial;
		buf += partial;
		unwritten = read_zero_pagealigned(buf, left & PAGE_MASK);
		written += (left & PAGE_MASK) - unwritten;
		if (unwritten)
			goto out;
		buf += left & PAGE_MASK;
		left &= ~PAGE_MASK;
	}
	unwritten = clear_user(buf, left);
	written += left - unwritten;
out:
	return written ? written : -EFAULT;
}
#else
    for (left = count; left > 0; left--) {
        put_user(0,buf);
        buf++;
		if (current->need_resched)
			schedule();
    }
	return(count);
#endif
}

Example #2

File: mem.c Project: leonsh/eldk30ppc

static ssize_t read_zero(struct file * file, char * buf, 
			 size_t count, loff_t *ppos)
{
	unsigned long left, unwritten, written = 0;

	if (!count)
		return 0;

	if (!access_ok(VERIFY_WRITE, buf, count))
		return -EFAULT;

	left = count;

	/* do we want to be clever? Arbitrary cut-off */
	if (count >= PAGE_SIZE*4) {
		unsigned long partial;

		/* How much left of the page? */
		partial = (PAGE_SIZE-1) & -(unsigned long) buf;
		unwritten = clear_user(buf, partial);
		written = partial - unwritten;
		if (unwritten)
			goto out;
		left -= partial;
		buf += partial;
		unwritten = read_zero_pagealigned(buf, left & PAGE_MASK);
		written += (left & PAGE_MASK) - unwritten;
		if (unwritten)
			goto out;
		buf += left & PAGE_MASK;
		left &= ~PAGE_MASK;
	}
	unwritten = clear_user(buf, left);
	written += left - unwritten;
out:
	return written ? written : -EFAULT;
}