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

[Oleg Nesterov <oleg@redhat.com>]

On 03/28, syzbot wrote:
>
> Hello,
>
> syzbot has tested the proposed patch but the reproducer is still triggering an issue:
> unregister_netdevice: waiting for DEV to become free
>
> unregister_netdevice: waiting for batadv0 to become free. Usage count = 3

Looks "obviously unrelated", but I'm not sure about anything anymore.

In any case I leave this to 9p maintainers.

Okay, just out of curiosity:

#syz test: upstream aaec5a95d59615523db03dd53c2052f0a87beea7


diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c
index 56e62978e502..aa9cd248a243 100644
--- a/net/9p/trans_fd.c
+++ b/net/9p/trans_fd.c
@@ -669,7 +669,6 @@ static void p9_poll_mux(struct p9_conn *m)
 
 static int p9_fd_request(struct p9_client *client, struct p9_req_t *req)
 {
-	__poll_t n;
 	struct p9_trans_fd *ts = client->trans;
 	struct p9_conn *m = &ts->conn;
 
@@ -687,13 +686,7 @@ static int p9_fd_request(struct p9_client *client, struct p9_req_t *req)
 	list_add_tail(&req->req_list, &m->unsent_req_list);
 	spin_unlock(&m->req_lock);
 
-	if (test_and_clear_bit(Wpending, &m->wsched))
-		n = EPOLLOUT;
-	else
-		n = p9_fd_poll(m->client, NULL, NULL);
-
-	if (n & EPOLLOUT && !test_and_set_bit(Wworksched, &m->wsched))
-		schedule_work(&m->wq);
+	p9_poll_mux(m);
 
 	return 0;
 }