Re: [PATCH v2] net/9p/trans_virtio.c: add null terminal for mount tag

piaojun
2018-08-02T02:01:14Z

Hi Dominique,

On 2018/8/2 9:54, Dominique Martinet wrote:
> piaojun wrote on Thu, Aug 02, 2018:
>> chan->tag is Non-null terminated which will result in printing messy code
>> when debugging code. So we should add '\0' for tag to make the code more
>> convenient and robust. In addition, I drop char->tag_len to simplify the
>> code.
>
> Some new lines in commit message would be appreciated.
>
> That aside, I have a couple of nitpicks, but it looks good to me - thanks
>
>>
>> Signed-off-by: Jun Piao <piaojun@huawei.com>
>> ---
>> net/9p/trans_virtio.c | 15 +++++----------
>> 1 file changed, 5 insertions(+), 10 deletions(-)
>>
>> diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c
>> index d422bfc..0fe9c37 100644
>> --- a/net/9p/trans_virtio.c
>> +++ b/net/9p/trans_virtio.c
>> @@ -89,10 +89,8 @@ struct virtio_chan {
>> unsigned long p9_max_pages;
>> /* Scatterlist: can be too big for stack. */
>> struct scatterlist sg[VIRTQUEUE_NUM];
>> -
>> - int tag_len;
>> /*
>> - * tag name to identify a mount Non-null terminated
>> + * tag name to identify a mount null terminated
>> */
>> char *tag;
>>
>> @@ -529,10 +527,9 @@ static ssize_t p9_mount_tag_show(struct device *dev,
>> vdev = dev_to_virtio(dev);
>> chan = vdev->priv;
>>
>> - memcpy(buf, chan->tag, chan->tag_len);
>> - buf[chan->tag_len] = 0;
>> + memcpy(buf, chan->tag, strlen(chan->tag) + 1);
>>
>> - return chan->tag_len + 1;
>> + return strlen(chan->tag) + 1;
>
> Use a local variable for strlen(chan->tag)?
>
Yes, local variable looks better.

>> }
>>
>> static DEVICE_ATTR(mount_tag, 0444, p9_mount_tag_show, NULL);
>> @@ -585,7 +582,7 @@ static int p9_virtio_probe(struct virtio_device *vdev)
>> err = -EINVAL;
>> goto out_free_vq;
>> }
>> - tag = kmalloc(tag_len, GFP_KERNEL);
>> + tag = kzalloc(tag_len + 1, GFP_KERNEL);
>> if (!tag) {
>> err = -ENOMEM;
>> goto out_free_vq;
>> @@ -594,7 +591,6 @@ static int p9_virtio_probe(struct virtio_device *vdev)
>> virtio_cread_bytes(vdev, offsetof(struct virtio_9p_config, tag),
>> tag, tag_len);
>> chan->tag = tag;
>> - chan->tag_len = tag_len;
>> err = sysfs_create_file(&(vdev->dev.kobj), &dev_attr_mount_tag.attr);
>> if (err) {
>> goto out_free_tag;
>> @@ -654,8 +650,7 @@ static int p9_virtio_probe(struct virtio_device *vdev)
>>
>> mutex_lock(&virtio_9p_lock);
>> list_for_each_entry(chan, &virtio_chan_list, chan_list) {
>> - if (!strncmp(devname, chan->tag, chan->tag_len) &&
>> - strlen(devname) == chan->tag_len) {
>> + if (!strncmp(devname, chan->tag, strlen(chan->tag) + 1)) {
>
> strncmp(x, y, strlen(y)+1) is precisely what strcmp does so let's use
> the simpler version
>
strcmp looks simpler, and I will wait for a while to hear more
suggestions, and then post another patch for these fixes.

Thanks,
Jun