Re: [PATCH] memcg: skip cgroup_file_notify if spinning is not allowed

[Peilin Ye <yepeilin@google.com>]

On Fri, Sep 05, 2025 at 02:33:16PM -0700, Shakeel Butt wrote:
> On Fri, Sep 05, 2025 at 08:48:46PM +0000, Peilin Ye wrote:
> > On Fri, Sep 05, 2025 at 01:16:06PM -0700, Shakeel Butt wrote:
> > > Generally memcg charging is allowed from all the contexts including NMI
> > > where even spinning on spinlock can cause locking issues. However one
> > > call chain was missed during the addition of memcg charging from any
> > > context support. That is try_charge_memcg() -> memcg_memory_event() ->
> > > cgroup_file_notify().
> > > 
> > > The possible function call tree under cgroup_file_notify() can acquire
> > > many different spin locks in spinning mode. Some of them are
> > > cgroup_file_kn_lock, kernfs_notify_lock, pool_workqeue's lock. So, let's
> > > just skip cgroup_file_notify() from memcg charging if the context does
> > > not allow spinning.
> > > 
> > > Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
> > 
> > Tested-by: Peilin Ye <yepeilin@google.com>
> 
> Thanks Peilin. When you post the official patch for __GFP_HIGH in
> __bpf_async_init(), please add a comment on why __GFP_HIGH is used
> instead of GFP_ATOMIC.

Got it!  I'll schedule to have that done today.

Thanks,
Peilin Ye