Re: CPU stall, eventual host hang with BTRFS + NFS under heavy load

[Trond Myklebust <trondmy@hammerspace.com>]

On Tue, 2021-10-12 at 08:57 +1100, NeilBrown wrote:
> On Tue, 12 Oct 2021, Chuck Lever III wrote:
> > 
> > Scott seems well positioned to identify a reproducer. Maybe we
> > can give him some likely candidates for possible bugs to explore
> > first.
> 
> Has this patch been tried?
> 
> NeilBrown
> 
> 
> diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
> index c045f63d11fa..308f5961cb78 100644
> --- a/net/sunrpc/sched.c
> +++ b/net/sunrpc/sched.c
> @@ -814,6 +814,7 @@ rpc_reset_task_statistics(struct rpc_task *task)
>  {
>         task->tk_timeouts = 0;
>         task->tk_flags &= ~(RPC_CALL_MAJORSEEN|RPC_TASK_SENT);
> +       clear_bit(RPC_TASK_SIGNALLED, &task->tk_runstate);
>         rpc_init_task_st

We shouldn't automatically "unsignal" a task once it has been told to
die. The correct thing to do here should rather be to change
rpc_restart_call() to exit early if the task was signalled.

> atistics(task);
>  }
>  

-- 
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@hammerspace.com