netdev - Re: [PATCHv3] net: usbnet: support 64bit stats in qmi

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Message-ID: <24368A4E-6CB6-4646-B5EE-84831CC7F4BD@mork.no>
Date:   Fri, 31 Mar 2017 15:35:46 +0200
From:   Bjørn Mork <bjorn@...k.no>
To:     Greg Ungerer <gerg@...ux-m68k.org>
CC:     oneukum@...e.com, eric.dumazet@...il.com,
        stephen@...workplumber.org, netdev@...r.kernel.org,
        linux-usb@...r.kernel.org
Subject: Re: [PATCHv3] net: usbnet: support 64bit stats in qmi_wwan driver



On March 31, 2017 3:27:59 PM CEST, Greg Ungerer <gerg@...ux-m68k.org> wrote:
>On 31/03/17 18:48, Bjørn Mork wrote:
>
>>> +void usbnet_get_stats64(struct net_device *net, struct
>rtnl_link_stats64 *stats)
>>> +{
>>> +	struct usbnet *dev = netdev_priv(net);
>>> +	unsigned int start;
>>> +	int cpu;
>>> +
>>> +	netdev_stats_to_stats64(stats, &net->stats);
>>> +
>>> +	for_each_possible_cpu(cpu) {
>>> +		struct pcpu_sw_netstats *stats64;
>>> +		u64 rx_packets, rx_bytes;
>>> +		u64 tx_packets, tx_bytes;
>>> +
>>> +		stats64 = per_cpu_ptr(dev->stats64, cpu);
>>> +
>>> +		do {
>>> +			start = u64_stats_fetch_begin_irq(&stats64->syncp);
>>> +			rx_packets = stats64->rx_packets;
>>> +			rx_bytes = stats64->rx_bytes;
>>> +			tx_packets = stats64->tx_packets;
>>> +			tx_bytes = stats64->tx_bytes;
>>> +		} while (u64_stats_fetch_retry_irq(&stats64->syncp, start));
>>> +
>>> +		stats->rx_packets += rx_packets;
>>> +		stats->rx_bytes += rx_bytes;
>>> +		stats->tx_packets += tx_packets;
>>> +		stats->tx_bytes += tx_bytes;
>>> +	}
>>> +}
>>
>> So we only count packets and bytes.  No errors.  Why?
>
>All stats are counted. That call to netdev_stats_to_stats64() transfers
>all other stats struct fields (errors, etc) to the stats64 struct.
>No error counts are lost (though they are only stored as 32bits values
>on 32bit machines).


Ah, right. Thanks for explaining and sorry for being so slow. Then I have no objection to the patch as it is.


Bjørn