Re: [syzbot] [netfs?] INFO: task hung in netfs_unbuffered_write_iter
From: Oleg Nesterov
Date: Tue Mar 25 2025 - 09:27:44 EST
On 03/25, K Prateek Nayak wrote:
>
> I chased this down to p9_client_rpc() net/9p/client.c specifically:
>
> err = c->trans_mod->request(c, req);
> if (err < 0) {
> /* write won't happen */
> p9_req_put(c, req);
> if (err != -ERESTARTSYS && err != -EFAULT)
> c->status = Disconnected;
> goto recalc_sigpending;
> }
>
> c->trans_mod->request() calls p9_fd_request() in net/9p/trans_fd.c
> which basically does a p9_fd_poll().
Again, I know nothing about 9p... but if p9_fd_request() returns
an err < 0, then it comes from p9_conn->err and p9_fd_request()
does nothing else.
> Previously, the above would fail with err as -EIO which would
> cause the client to "Disconnect" and the retry logic would make
> progress. Now however, the err returned is -ERESTARTSYS
OK... So p9_conn->err = -ERESTARTSYS was set by p9_conn_cancel()
called by p9_write_work() because pipe_write() returns ERESTARTSYS?
But I don't understand -EIO with the reverted commit aaec5a95d59615
Oleg.