From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH] net/ipv4: fix tcp_poll for SMC fallback Date: Thu, 18 Oct 2018 11:22:04 -0700 (PDT) Message-ID: <20181018.112204.1468321456234076481.davem@davemloft.net> References: <20181016144554.49660-1-kgraul@linux.ibm.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, ubraun@linux.ibm.com, hch@lst.de, linux-s390@vger.kernel.org To: kgraul@linux.ibm.com Return-path: Received: from shards.monkeyblade.net ([23.128.96.9]:38276 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726424AbeJSCYT (ORCPT ); Thu, 18 Oct 2018 22:24:19 -0400 In-Reply-To: <20181016144554.49660-1-kgraul@linux.ibm.com> Sender: netdev-owner@vger.kernel.org List-ID: From: Karsten Graul Date: Tue, 16 Oct 2018 16:45:54 +0200 > Commit dd979b4df817 ("net: simplify sock_poll_wait") breaks tcp_poll for > SMC fallback: An AF_SMC socket establishes an internal TCP socket for the > CLC handshake with the remote peer. Whenever the SMC connection can not be > established this CLC socket is used as a fallback. All socket operations on the > SMC socket are then forwarded to the CLC socket. In case of poll, the > file->private_data pointer references the SMC socket because the CLC socket has > no file assigned. This causes tcp_poll to wait on the wrong socket. > > This patch fixes the issue by (re)introducing a sock_poll_wait variant with > a socket parameter, and let tcp_poll use this variant. > > Fixes: dd979b4df817 ("net: simplify sock_poll_wait") > Signed-off-by: Karsten Graul Generally speaking, if the invariant of filp->private_data == sock does not actually hold true universally, I'd rather revert the simplifications and add a big comment to sock_poll_wait() explaining this. Thank you.