Re: [PATCH updated] net: add ability to clear per-interface network statistics via procfs
From: Ben Hutchings
Date: Sat May 17 2008 - 20:32:09 EST
James Cammarata wrote:
> >This version has a bug, please check again.
>
> Gah, you're right, fixed below.
>
> ---
>
> --- linux-2.6.25.4/net/core/dev.c 2008-05-15 10:00:12.000000000 -0500
> +++ linux-2.6.25.4-jcammara/net/core/dev.c 2008-05-17
> 17:45:57.000000000 -0500
> @@ -2455,2 +2455,80 @@
>
> +/**
> + * proc_net_dev_write - handle writes to /proc/net/dev
> + * @file: not used
> + * @buf: buffer to write
> + * @length: length of buf, at most PAGE_SIZE
> + * @ppos: not used
> + *
> + * Description: this provides a mechanism to clear statistics on a
> + * per-interface basis
> + * "echo 'net clear-stats ifdev' >/proc/net/dev"
> + * with "ifdev" replaced by the device name you wish to clear.
> + *
> + */
> +static ssize_t proc_net_dev_write(struct file *file, const char __user
> *buf,
You need to stop your mail client word-wrapping patches. It looks like
something has converted tabs to spaces, too.
[...]
> + /*
> + * Usage: echo "net clear-stats ifdev" >/proc/net/dev
> + * with "ifdev" replaced by the device name you wish to clear.
> + */
This is redundant with the kernel-doc comment.
> + if (!strncmp("net clear-stats",buffer,15)) {
This doesn't check for a space after, which you rely on later on. (What if
length == 15?) Also, explicitly writing the length of a literal string is
error-prone. Seems like it would be better to do something like:
static const char command[] = "net clear-stats ";
...
if (!strncmp(command, buffer, sizeof(command) - 1)) {
> + p = buffer + 16;
> + if(sscanf(p,"%16s",devname)>0) {
> + dev = dev_get_by_name(net,devname);
> + if (dev) {
> + if (dev->get_stats) {
> + struct net_device_stats *stats =
> + dev->get_stats(dev);
> + memset(stats,0,
> + sizeof(struct
> net_device_stats));
> + }
> + dev_put(dev);
> + }
Shouldn't this return an error if the device doesn't exist?
> + }
> + }
> +
> + /*
> + * convert success returns so that we return the
> + * number of bytes consumed.
> + */
> + if (!err)
> + err = length;
This won't work; the function updates err unconditionally further up!
> +
> + put_net(net);
> +
> + out:
> + free_page((unsigned long)buffer);
> + return err;
> +}
> +
> static void *softnet_seq_start(struct seq_file *seq, loff_t *pos)
> @@ -2498,2 +2576,3 @@
> .read = seq_read,
> + .write = proc_net_dev_write,
> .llseek = seq_lseek,
The context for this chunk seems to be too short.
There are a few formatting oddities; checkpatch.pl will point them out.
Ben.
--
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
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