On Fri, Mar 29, 2024 at 2:39 PM Tejun Heo <tj@xxxxxxxxxx> wrote: > > Hello, > > On Fri, Mar 29, 2024 at 02:22:28PM +0100, Djalal Harouni wrote: > > It would be easy at least for me if I just start with cgroupv2 and > > ensure that it has same available filenames as if we go through kernfs. > > Not a root cgroup node and maybe only freeze and kill for now that are > > part of cgroup_base_files. > > > > So if I get it right, somehow like what I did but we endup with: > > > > In bpf, cgroup was already acquired. > > > > bpf_cgroup_knob_write(cgroup, "freeze", buf) > > |_ parse params -> lock cgroup_mutex -> cgroup_freeze() -> unlock > > > > > > cgroup_freeze_write(struct kernfs_open_file *of, char *buf,...) > > |_ parse params -> cgroup_ref++ -> krnfs_active_ref-- -> > > -> lock cgroup_mutex -> cgroup_freeze() -> unlock + krnfs++ ... > > > > Please let me know if I missed something. > > I've thought about it a bit and I wonder whether a better way to do this is > implementing this at the kernfs layer. Something like (hopefully with a > better name): > > s32 bpf_kernfs_knob_write(struct kernfs_node *dir, const char *knob, char *buf); > > So, about the same, but takes kernfs_node directory instead of cgroup. This > would make the interface useful for accessing sysfs knobs too which use > similar conventions. For cgroup, @dir is just cgrp->kn and for sysfs it'd be > kobj->sd. This way we can avoid the internal object -> path -> internal > object ping-poinging while keeping the interface a lot more generic. What do > you think? And helpers like cgroup_freeze_write() will be refactored to take kernfs_node directly instead of kernfs_open_file? Makes sense to me. Sounds like a minimal amount of changes and flexible enough.
