Patch "net/sunrpc/xprt_sock: fix regression in connection error reporting." has been added to the 4.12-stable tree

This is a note to let you know that I've just added the patch titled

net/sunrpc/xprt_sock: fix regression in connection error reporting.

to the 4.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
net-sunrpc-xprt_sock-fix-regression-in-connection-error-reporting.patch
and it can be found in the queue-4.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: NeilBrown <[email protected]>
Date: Wed, 19 Jul 2017 14:05:01 +1000
Subject: net/sunrpc/xprt_sock: fix regression in connection error reporting.

From: NeilBrown <[email protected]>

commit 3ffbc1d65583394be12801655781dd2b079ce169 upstream.

Commit 3d4762639dd3 ("tcp: remove poll() flakes when receiving RST") in v4.12 changed the order in which ->sk_state_change() and ->sk_error_report() are called when a socket is shut down - sk_state_change() is now called first.

This causes xs_tcp_state_change() -> xs_sock_mark_closed() -> xprt_disconnect_done() to wake all pending tasked with -EAGAIN. When the ->sk_error_report() callback arrives, it is too late to pass the error on, and it is lost.

As easy way to demonstrate the problem caused is to try to start rpc.nfsd while rcpbind isn't running.
nfsd will attempt a tcp connection to rpcbind. A ECONNREFUSED error is returned, but sunrpc code loses the error and keeps retrying. If it saw the ECONNREFUSED, it would abort.

To fix this, handle the sk->sk_err in the TCP_CLOSE branch of xs_tcp_state_change().

---
 net/sunrpc/xprtsock.c |    2 ++
 1 file changed, 2 insertions(+)

@@ -1624,6 +1624,8 @@ static void xs_tcp_state_change(struct s
 		if (test_and_clear_bit(XPRT_SOCK_CONNECTING,
 					&transport->sock_state))
 			xprt_clear_connecting(xprt);
+		if (sk->sk_err)
+			xprt_wake_pending_tasks(xprt, -sk->sk_err);
 		xs_sock_mark_closed(xprt);
 	}
  out:

Patches currently in stable-queue which might be from [email protected] are

queue-4.12/nfs-only-invalidate-dentrys-that-are-clearly-invalid.patch queue-4.12/md-don-t-use-flush_signals-in-userspace-processes.patch queue-4.12/md-fix-deadlock-between-mddev_suspend-and-md_write_start.patch queue-4.12/net-sunrpc-xprt_sock-fix-regression-in-connection-error-reporting.patch