Hi Chengguang, On 2018/3/30 8:50, cgxu519@xxxxxxx wrote: > 在 2018年3月29日，下午7:26，Marian Marinov <kernel@xxxxxxxx> 写道： >> >> On 03/27/2018 06:20 PM, Chengguang Xu wrote: >>>> Sent: Tuesday, March 27, 2018 at 9:58 PM >>>> From: "Tejun Heo" <tj@xxxxxxxxxx> >>>> To: "Chengguang Xu" <cgxu519@xxxxxxx> >>>> Cc: lizefan@xxxxxxxxxx, cgroups@xxxxxxxxxxxxxxx >>>> Subject: Re: [PATCH RFC] cpuset: change error code to -EPERM from -ENOSPC >>>> >>>> On Tue, Mar 27, 2018 at 06:02:24PM +0800, Chengguang Xu wrote: >>>>> When adding task to cpuset with empty cpus_allowed or empty mems_allowed, >>>>> there is an error with code -ENOSPC, it is a little bit confusing, >>>>> so change error code to -EPERM for better understanding. >>>>> >>>>> Signed-off-by: Chengguang Xu <cgxu519@xxxxxxx> >>>> >>>> I don't see why we'd change this or how EPERM is necessarily more >>>> intuitive here. >>> >>> After changing the error code, error message showed to user will change >>> from >>> >>> $ echo $$ > /sys/fs/cgroup/cpuset/2/tasks >>> -bash: echo: write error: No space left on device >>> >>> to >>> >>> $ echo $$ > /sys/fs/cgroup/cpuset/2/tasks >>> -bash: echo: write error: Operation not permitted >>> >>> Isn't it more understandable? IIUC, the logic here is for prohibiting attaching or >>> changing operations. >> >> I somewhat agree that "Operation not permitted" is a bit more meaningful. >> However this is something that has been in the kernel for a lot of years and changing it to another error message, that is also not the actual cause is not solving anyone's problems with this ;( > > Actually, the motivation of this patch is from my experience. > I encountered -ENOSPC when I try to manipulate cpuset, then I had no idea about the reason > at all, so I had to dive into the code to analyze the root cause, but I think there are also > many sysadmins do not understand the code, so meaningful error message is much helpful to > them. > > IMHO, it’s a trivial change and it will not bring side effect so the change would not be so > difficult though the -ENOSPC has been in kernel for a long time. > You don't have to dive into cpuset internal implmentation. There's document you can refer to. http://man7.org/linux/man-pages/man7/cpuset.7.html ENOSPC Attempted to write(2) the process ID (PID) of a process to a cpuset tasks file when the cpuset had an empty cpuset.cpus or empty cpuset.mems setting. > >> >> The other thing is, that "Operation not permitted" may push the sysadmins in completely different search, like is it a SELinux related problem. > > I also propose to add additional warning message here to give some hints to sysadmins, > but I guess mismatched warning/error messages will also cause users’ confusing. > > > Thanks, > Chengguang. > > . > -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
