On Tue, May 10, 2022 at 3:07 PM Tejun Heo <tj@xxxxxxxxxx> wrote: > > Hello, > > On Tue, May 10, 2022 at 02:12:16PM -0700, Hao Luo wrote: > > > Is there a reason why this can't be a proper iterator which supports > > > lseek64() to locate a specific cgroup? > > > > > > > There are two reasons: > > > > - Bpf_iter assumes no_llseek. I haven't looked closely on why this is > > so and whether we can add its support. > > > > - Second, the name 'iter' in this patch is misleading. What this patch > > really does is reusing the functionality of dumping in bpf_iter. > > 'Dumper' is a better name. We want to create one file in bpffs for > > each cgroup. We are essentially just iterating a set of one single > > element. > > I see. I'm just shooting in the dark without context but at least in > principle there's no reason why cgroups wouldn't be iterable, so it might be > something worth at least thinking about before baking in the interface. > Yep. Conceptually there should be no problem to iterate cgroups in the system. It may be better to have two independent bpf objects: bpf_iter and bpf_dumper. In our use case, we want bpf_dumper, which just exports data out through fs interface. Hao
