Re: [PATCH RFC 1/4] nfsd: fix a warning in __cld_pipe_upcall()

["J. Bruce Fields" <bfields@fieldses.org>]

This looks fine, applying now for 4.21.--b.

On Tue, Nov 06, 2018 at 01:35:08PM -0500, Scott Mayhew wrote:
> __cld_pipe_upcall() emits a "do not call blocking ops when
> !TASK_RUNNING" warning due to the dput() call in rpc_queue_upcall().
> Fix it by using a completion instead of hand coding the wait.
> 
> Signed-off-by: Scott Mayhew <smayhew@redhat.com>
> ---
>  fs/nfsd/nfs4recover.c | 17 ++++++-----------
>  1 file changed, 6 insertions(+), 11 deletions(-)
> 
> diff --git a/fs/nfsd/nfs4recover.c b/fs/nfsd/nfs4recover.c
> index 9c247fa1e959..5188f9f70c78 100644
> --- a/fs/nfsd/nfs4recover.c
> +++ b/fs/nfsd/nfs4recover.c
> @@ -662,7 +662,7 @@ struct cld_net {
>  struct cld_upcall {
>  	struct list_head	 cu_list;
>  	struct cld_net		*cu_net;
> -	struct task_struct	*cu_task;
> +	struct completion	 cu_done;
>  	struct cld_msg		 cu_msg;
>  };
>  
> @@ -671,23 +671,18 @@ __cld_pipe_upcall(struct rpc_pipe *pipe, struct cld_msg *cmsg)
>  {
>  	int ret;
>  	struct rpc_pipe_msg msg;
> +	struct cld_upcall *cup = container_of(cmsg, struct cld_upcall, cu_msg);
>  
>  	memset(&msg, 0, sizeof(msg));
>  	msg.data = cmsg;
>  	msg.len = sizeof(*cmsg);
>  
> -	/*
> -	 * Set task state before we queue the upcall. That prevents
> -	 * wake_up_process in the downcall from racing with schedule.
> -	 */
> -	set_current_state(TASK_UNINTERRUPTIBLE);
>  	ret = rpc_queue_upcall(pipe, &msg);
>  	if (ret < 0) {
> -		set_current_state(TASK_RUNNING);
>  		goto out;
>  	}
>  
> -	schedule();
> +	wait_for_completion(&cup->cu_done);
>  
>  	if (msg.errno < 0)
>  		ret = msg.errno;
> @@ -754,7 +749,7 @@ cld_pipe_downcall(struct file *filp, const char __user *src, size_t mlen)
>  	if (copy_from_user(&cup->cu_msg, src, mlen) != 0)
>  		return -EFAULT;
>  
> -	wake_up_process(cup->cu_task);
> +	complete(&cup->cu_done);
>  	return mlen;
>  }
>  
> @@ -769,7 +764,7 @@ cld_pipe_destroy_msg(struct rpc_pipe_msg *msg)
>  	if (msg->errno >= 0)
>  		return;
>  
> -	wake_up_process(cup->cu_task);
> +	complete(&cup->cu_done);
>  }
>  
>  static const struct rpc_pipe_ops cld_upcall_ops = {
> @@ -900,7 +895,7 @@ alloc_cld_upcall(struct cld_net *cn)
>  			goto restart_search;
>  		}
>  	}
> -	new->cu_task = current;
> +	init_completion(&new->cu_done);
>  	new->cu_msg.cm_vers = CLD_UPCALL_VERSION;
>  	put_unaligned(cn->cn_xid++, &new->cu_msg.cm_xid);
>  	new->cu_net = cn;
> -- 
> 2.17.1