Re: [PATCH v3 net-next 10/12] net: bonding: ensure .ndo_get_stats64 can sleep
From: Vladimir Oltean <olteanv@gmail.com>
Date: 2021-01-07 11:34:29
On Thu, Jan 07, 2021 at 12:18:28PM +0100, Eric Dumazet wrote:
What a mess really.
Thanks, that's at least _some_ feedback :)
You chose to keep the assumption that ndo_get_stats() would not fail, since we were providing the needed storage from callers. If ndo_get_stats() are now allowed to sleep, and presumably allocate memory, we need to make sure we report potential errors back to the user. I think your patch series is mostly good, but I would prefer not hiding errors and always report them to user space. And no, netdev_err() is not appropriate, we do not want tools to look at syslog to guess something went wrong.
Well, there are only 22 dev_get_stats callers in the kernel, so I assume that after the conversion to return void, I can do another conversion to return int, and then I can convert the ndo_get_stats64 method to return int too. I will keep the plain ndo_get_stats still void (no reason not to).
Last point about drivers having to go to slow path, talking to firmware : Make sure that malicious/innocent users reading /proc/net/dev from many threads in parallel wont brick these devices. Maybe they implicitly _relied_ on the fact that firmware was gently read every second and results were cached from a work queue or something.
How? I don't understand how I can make sure of that. There is an effort initiated by Jakub to standardize the ethtool statistics. My objection was that you can't expect that to happen unless dev_get_stats is sleepable just like ethtool -S is. So I think the same reasoning should apply to ethtool -S too, really.