Re: [PATCH net-next v4] xen-netback: Adding debugfs "io_ring_qX" files

[David Vrabel <david.vrabel@citrix.com>]

On 11/08/14 11:38, Wei Liu wrote:
> On Sun, Aug 10, 2014 at 10:57:51PM +0800, SeeChen Ng wrote:
>> Hi, I'm a noob to linux kernel, I tried to figure out the usage of the function
>> "simple_write_to_buffer", and I got confused about the code here.
>>
>>> +static ssize_t
>>> +xenvif_write_io_ring(struct file *filp, const char __user *buf, size_t count,
>>> +                    loff_t *ppos)
>>> +{
>>> +       struct xenvif_queue *queue =
>>> +               ((struct seq_file *)filp->private_data)->private;
>>> +       int len;
>>> +       char write[sizeof(XENVIF_KICK_STR)];
>>> +
>>> +       /* don't allow partial writes and check the length */
>>> +       if (*ppos != 0)
>>> +               return 0;
>>> +       if (count < sizeof(XENVIF_KICK_STR) - 1)
>>> +               return -ENOSPC;
>> The statement here is trying to verify the value of "count" is smaller
>> than the size of array "write", make sure that the array got
>> enough space for the write operation, right?
>>
> 
> Yes I think so.

Is anyone reading the comment?

/* don't allow partial writes and check the length */

The sense of the check is correct.

David