netdev - RE: [patch net-next v8 2/3] net: core: Add offload stats to if_stats

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Message-ID: <DB5PR05MB1895644891EFCDD8F9F619F9ACFF0@DB5PR05MB1895.eurprd05.prod.outlook.com>
Date:   Mon, 12 Sep 2016 11:29:20 +0000
From:   Nogah Frankel <nogahf@...lanox.com>
To:     Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
CC:     Jiri Pirko <jiri@...nulli.us>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        "Ido Schimmel" <idosch@...lanox.com>,
        Elad Raz <eladr@...lanox.com>,
        Yotam Gigi <yotamg@...lanox.com>,
        Or Gerlitz <ogerlitz@...lanox.com>,
        "roopa@...ulusnetworks.com" <roopa@...ulusnetworks.com>,
        "linville@...driver.com" <linville@...driver.com>,
        "tgraf@...g.ch" <tgraf@...g.ch>,
        "gospo@...ulusnetworks.com" <gospo@...ulusnetworks.com>,
        "sfeldma@...il.com" <sfeldma@...il.com>,
        "sd@...asysnail.net" <sd@...asysnail.net>,
        Eran Ben Elisha <eranbe@...lanox.com>,
        "ast@...mgrid.com" <ast@...mgrid.com>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "hannes@...essinduktion.org" <hannes@...essinduktion.org>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        "dsa@...ulusnetworks.com" <dsa@...ulusnetworks.com>
Subject: RE: [patch net-next v8 2/3] net: core: Add offload stats to
 if_stats_msg

> -----Original Message-----
> From: Nikolay Aleksandrov [mailto:nikolay@...ulusnetworks.com]
> Sent: Friday, September 09, 2016 4:39 PM
> To: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
> Cc: Jiri Pirko <jiri@...nulli.us>; Linux Kernel Network Developers <netdev@...r.kernel.org>; David S. Miller
> <davem@...emloft.net>; Nogah Frankel <nogahf@...lanox.com>; Ido Schimmel <idosch@...lanox.com>; Elad Raz
> <eladr@...lanox.com>; Yotam Gigi <yotamg@...lanox.com>; Or Gerlitz <ogerlitz@...lanox.com>; roopa@...ulusnetworks.com;
> linville@...driver.com; tgraf@...g.ch; gospo@...ulusnetworks.com; sfeldma@...il.com; sd@...asysnail.net; Eran Ben Elisha
> <eranbe@...lanox.com>; ast@...mgrid.com; edumazet@...gle.com; hannes@...essinduktion.org; f.fainelli@...il.com;
> dsa@...ulusnetworks.com
> Subject: Re: [patch net-next v8 2/3] net: core: Add offload stats to if_stats_msg
> 
> 
> > On Sep 9, 2016, at 4:36 PM, Nikolay Aleksandrov <nikolay@...ulusnetworks.com> wrote:
> >
> >>
> >> On Sep 8, 2016, at 9:19 AM, Jiri Pirko <jiri@...nulli.us> wrote:
> >>
> >> From: Nogah Frankel <nogahf@...lanox.com>
> >>
> >> Add a nested attribute of offload stats to if_stats_msg
> >> named IFLA_STATS_LINK_OFFLOAD_XSTATS.
> >> Under it, add SW stats, meaning stats only per packets that went via
> >> slowpath to the cpu, named IFLA_OFFLOAD_XSTATS_CPU_HIT.
> >>
> >> Signed-off-by: Nogah Frankel <nogahf@...lanox.com>
> >> Signed-off-by: Jiri Pirko <jiri@...lanox.com>
> >> ---
> >> include/uapi/linux/if_link.h |  9 ++++
> >> net/core/rtnetlink.c         | 97 ++++++++++++++++++++++++++++++++++++++++++--
> >> 2 files changed, 102 insertions(+), 4 deletions(-)
> >>
> > [snip]
> >> @@ -3655,6 +3725,22 @@ static int rtnl_fill_statsinfo(struct sk_buff *skb, struct net_device *dev,
> >> 		}
> >> 	}
> >>
> >> +	if (stats_attr_valid(filter_mask, IFLA_STATS_LINK_OFFLOAD_XSTATS,
> >> +			     *idxattr)) {
> >> +		attr = nla_nest_start(skb, IFLA_STATS_LINK_OFFLOAD_XSTATS);
> >> +		if (!attr)
> >> +			goto nla_put_failure;
> >> +
> >> +		err = rtnl_get_offload_stats(skb, dev);
> >> +		if (err == -ENODATA)
> >> +			nla_nest_cancel(skb, attr);
> >> +		else
> >> +			nla_nest_end(skb, attr);
> >> +
> >> +		if ((err) && (err != -ENODATA))
> >> +			goto nla_put_failure;
> >> +	}
> >> +
> >
> > Hmm, actually on a second read I think there’s a potential problem here. Since you don’t set *idxattr and if the space
> > isn’t enough the dump will get restarted and this will lead to an infinite loop.
> 
> Err, poor choice of words. I meant the loop will be for userspace since the dump will err out at the same spot all the time so it
> won’t be able to ever finish. :-)
> 
> > I.e. if the previous attributes filled the skb and there’s not enough room for this one, it will return an error
> > but *idxattr will be == 0 from the previous attribute thus the whole dump will be restarted (this is in case someone
> > requests this attribute with some of the others of course).
> >
> > Cheers,
> > Nik
> >
> >

I'll fix it. Thanks.

> >> 	nlmsg_end(skb, nlh);
> >>
> >> 	return 0;
> >> @@ -3712,6 +3798,9 @@ static size_t if_nlmsg_stats_size(const struct net_device *dev,
> >> 		}
> >> 	}
> >>
> >> +	if (stats_attr_valid(filter_mask, IFLA_STATS_LINK_OFFLOAD_XSTATS, 0))
> >> +		size += rtnl_get_offload_stats_size(dev);
> >> +
> >> 	return size;
> >> }
> >>
> >> --
> >> 2.5.5