On Wed, 2008-04-23 at 23:47 -0700, Matt Helsley wrote:
<snip>
> +static ssize_t freezer_write(struct cgroup *cgroup,
> + struct cftype *cft,
> + struct file *file,
> + const char __user *userbuf,
> + size_t nbytes, loff_t *unused_ppos)
> +{
> + char *buffer;
> + int retval = 0;
> + enum freezer_state goal_state;
> +
> + if (nbytes >= PATH_MAX)
> + return -E2BIG;
> +
> + /* +1 for nul-terminator */
> + buffer = kmalloc(nbytes + 1, GFP_KERNEL);
> + if (buffer == NULL)
> + return -ENOMEM;
> +
> + if (copy_from_user(buffer, userbuf, nbytes)) {
> + retval = -EFAULT;
> + goto free_buffer;
> + }
> + buffer[nbytes] = 0; /* nul-terminate */
> + strstrip(buffer);
> + if (strcmp(buffer, "RUNNING") == 0)
> + goal_state = STATE_RUNNING;
> + else if (strcmp(buffer, "FROZEN") == 0)
> + goal_state = STATE_FROZEN;
> + else {
> + retval = -EIO;
> + goto free_buffer;
> + }
> +
> + cgroup_lock();
> +
> + if (cgroup_is_removed(cgroup)) {
> + retval = -ENODEV;
> + goto unlock;
> + }
I think this was copy/paste'd from cgroup_common_file_write() which
modifies the cgroup hierarchy. However this function does not modify the
cgroup hierarchy and we're not getting the cgroup from the task. So I
don't think cgroup_lock()/unlock() are needed here. Paul, do you agree?
> + retval = freezer_freeze(cgroup, goal_state);
> + if (retval == 0)
> + retval = nbytes;
> +unlock:
> + cgroup_unlock();
> +free_buffer:
> + kfree(buffer);
> + return retval;
> +}
Cheers,
-Matt Helsley
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