On Mon, Aug 25, 2025 at 11:48 AM Tejun Heo <tj@xxxxxxxxxx> wrote: > > Hello, > > On Fri, Aug 22, 2025 at 07:16:15PM +0100, Djalal Harouni wrote: > ... > > I do realize taking the same usual path with write is the obvious thing, > > but we don't have the corresponding open context, and faking it seems > > more trouble than calling directly cgroup backends... > > > > Allow me please to do it again directly on cgroup_base_file[] assuming > > it was Alexei suggestion and see how it looks. It's been 1.5 year since v1. It's safe to assume that all opinions have changed, including mine. > I'm probably missing something but what prevents you from getting a dentry > from kernfs_node and then calling vfs_open() on it and then do vfs_write() > on the returned file? Generic vfs ops from kfunc feels like a can of worms. It will require a lot more thinking and coordination with vfs folks. I'd rather keep things simple especially, since this thread might continue in 2026. > If there are some fundamental reasons that we can't do something like that, > let's go back to the simple approach where we just have bpf helpers for > freezing and unfreezing cgroups outside of fs interface. I'd just do whatever version of cgroup_lock*() is necessary from kfunc followed by cgroup_freeze(), and limit kfunc to sleepable progs, of course.
