From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Layton Subject: Re: stable page writes: wait_on_page_writeback and packet signing Date: Wed, 9 Mar 2011 18:54:27 -0500 Message-ID: <20110309185427.7858c29b@corrin.poochiereds.net> References: <20110309215148.GW15097@dastard> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Dave Chinner , linux-cifs@vger.kernel.org, linux-fsdevel , Mingming Cao To: Steve French Return-path: Received: from mx1.redhat.com ([209.132.183.28]:9563 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752390Ab1CIXy0 (ORCPT ); Wed, 9 Mar 2011 18:54:26 -0500 In-Reply-To: Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Wed, 9 Mar 2011 16:01:30 -0600 Steve French wrote: > > Except we don't need to wait that long with the page locked > ie for a response from the cifs server (such as Samba or Windows > or NetApp), just need to wait for it to get on the wire. > Waiting for us to get the server response would > take 10 or 100 times longer. In any case we can't resend > the same request to the server (the signature changes on the > resend since the sequence number is incremented on every > request/response so we have to recalc the checksum anyway) and > cifs requests can't get lost (as with nfs over udp). Keeping > a page locked for 10milliseconds seems like a bad idea - but > it is a little more complicated to implement (for the cifs case) > so that we end page writeback (for the non-WB_SYNC) > as quickly as reasonably possible so we don't kill perf. > The problem here is that the socket layer doesn't have a mechanism to notify us of a TCP ACK. So, we have to wait for the next-best thing -- a response from the server. -- Jeff Layton