Re: [syzbot] [netfs?] INFO: task hung in netfs_unbuffered_write_iter

[Oleg Nesterov]

Damn, sorry for the noise please ignore ;)

On 03/26, Oleg Nesterov wrote:
>
> On 03/26, Oleg Nesterov wrote:
> >
> > Hmm... I don't understand why the 2nd vfs_poll(ts->wr) depends on the
> > ret from vfs_poll(ts->rd), but I assume this is correct.
>
> I meant, if pt != NULL and ts->rd != ts->wr we need both
> vfs_poll(ts->rd) and vfs_poll(ts->wr) ?

I am stupid. After the lot of reading I can't distinguish "|" and "||".

Oleg.

> and the reproducer writes to the pipe before it mounts 9p...
> 
> Prateek, this is just a shot in the dark but since you can reproduce,
> can you check if the patch below makes any difference?
> 
> Oleg.
> 
> --- x/net/9p/trans_fd.c
> +++ x/net/9p/trans_fd.c
> @@ -234,8 +234,10 @@ p9_fd_poll(struct p9_client *client, str
>  	}
>  
>  	ret = vfs_poll(ts->rd, pt);
> -	if (ts->rd != ts->wr)
> +	if (ts->rd != ts->wr) {
> +		if (pt != NULL) vfs_poll(ts->wr, pt);
>  		ret = (ret & ~EPOLLOUT) | (vfs_poll(ts->wr, pt) & ~EPOLLIN);
> +	}
>  	return ret;
>  }
>