cgroup: unify cgroup_write_X64() and cgroup_write_string()

/* A buffer size big enough for numbers or short strings */

#define CGROUP_LOCAL_BUFFER_SIZE 64

static ssize_t cgroup_write_X64(struct cgroup_subsys_state *css,

				struct cftype *cft, struct file *file,

				const char __user *userbuf, size_t nbytes,

				loff_t *unused_ppos)

{

	char buffer[CGROUP_LOCAL_BUFFER_SIZE];

	int retval = 0;

	char *end;

	if (!nbytes)

		return -EINVAL;

	if (nbytes >= sizeof(buffer))

		return -E2BIG;

	if (copy_from_user(buffer, userbuf, nbytes))

		return -EFAULT;

	buffer[nbytes] = 0;     /* nul-terminate */

	if (cft->write_u64) {

		u64 val = simple_strtoull(strstrip(buffer), &end, 0);

		if (*end)

			return -EINVAL;

		retval = cft->write_u64(css, cft, val);

	} else {

		s64 val = simple_strtoll(strstrip(buffer), &end, 0);

		if (*end)

			return -EINVAL;

		retval = cft->write_s64(css, cft, val);

	}

	if (!retval)

		retval = nbytes;

	return retval;

}

static ssize_t cgroup_write_string(struct cgroup_subsys_state *css,

				   struct cftype *cft, struct file *file,

				   const char __user *userbuf, size_t nbytes,

				   loff_t *unused_ppos)

static ssize_t cgroup_file_write(struct file *file, const char __user *userbuf,

				 size_t nbytes, loff_t *ppos)

{

	char local_buffer[CGROUP_LOCAL_BUFFER_SIZE];

	int retval = 0;

	size_t max_bytes = cft->max_write_len;

	char *buffer = local_buffer;

	struct cfent *cfe = __d_cfe(file->f_dentry);

	struct cftype *cft = __d_cft(file->f_dentry);

	struct cgroup_subsys_state *css = cfe->css;

	size_t max_bytes = cft->max_write_len ?: CGROUP_LOCAL_BUFFER_SIZE - 1;

	char *buf;

	int ret;

	if (!max_bytes)

		max_bytes = sizeof(local_buffer) - 1;

	if (nbytes >= max_bytes)

		return -E2BIG;

	/* Allocate a dynamic buffer if we need one */

	if (nbytes >= sizeof(local_buffer)) {

		buffer = kmalloc(nbytes + 1, GFP_KERNEL);

		if (buffer == NULL)

	buf = kmalloc(nbytes + 1, GFP_KERNEL);

	if (!buf)

		return -ENOMEM;

	}

	if (nbytes && copy_from_user(buffer, userbuf, nbytes)) {

		retval = -EFAULT;

		goto out;

	}

	buffer[nbytes] = 0;     /* nul-terminate */

	retval = cft->write_string(css, cft, strstrip(buffer));

	if (!retval)

		retval = nbytes;

out:

	if (buffer != local_buffer)

		kfree(buffer);

	return retval;

	if (copy_from_user(buf, userbuf, nbytes)) {

		ret = -EFAULT;

		goto out_free;

	}

static ssize_t cgroup_file_write(struct file *file, const char __user *buf,

				 size_t nbytes, loff_t *ppos)

{

	struct cfent *cfe = __d_cfe(file->f_dentry);

	struct cftype *cft = __d_cft(file->f_dentry);

	struct cgroup_subsys_state *css = cfe->css;

	if (cft->write_u64 || cft->write_s64)

		return cgroup_write_X64(css, cft, file, buf, nbytes, ppos);

	if (cft->write_string)

		return cgroup_write_string(css, cft, file, buf, nbytes, ppos);

	if (cft->trigger) {

		int ret = cft->trigger(css, (unsigned int)cft->private);

		return ret ? ret : nbytes;

	buf[nbytes] = '\0';

	if (cft->write_string) {

		ret = cft->write_string(css, cft, strstrip(buf));

	} else if (cft->write_u64) {

		unsigned long long v;

		ret = kstrtoull(buf, 0, &v);

		if (!ret)

			ret = cft->write_u64(css, cft, v);

	} else if (cft->write_s64) {

		long long v;

		ret = kstrtoll(buf, 0, &v);

		if (!ret)

			ret = cft->write_s64(css, cft, v);

	} else if (cft->trigger) {

		ret = cft->trigger(css, (unsigned int)cft->private);

	} else {

		ret = -EINVAL;

	}

	return -EINVAL;

out_free:

	kfree(buf);

	return ret ?: nbytes;

}

static ssize_t cgroup_read_u64(struct cgroup_subsys_state *css,