From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from bronze.cs.yorku.ca ([130.63.90.34]:55211 "EHLO bronze.cs.yorku.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932320Ab0HDNrq (ORCPT ); Wed, 4 Aug 2010 09:47:46 -0400 Message-ID: <4C596F81.6010409@cse.yorku.ca> Date: Wed, 04 Aug 2010 09:47:45 -0400 From: Jason Keltz To: Neil Brown CC: linux-nfs@vger.kernel.org Subject: Re: exporting to a list of IPs References: <4C583B63.4050903@cse.yorku.ca> <20100804134527.146397ff@notabene> In-Reply-To: <20100804134527.146397ff@notabene> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Sender: linux-nfs-owner@vger.kernel.org List-ID: MIME-Version: 1.0 Neil Brown wrote: > On Tue, 03 Aug 2010 11:53:07 -0400 > Jason Keltz wrote: > >> Hi. >> >> Why is it that you cannot NFS export to a list of IPs and have exportfs >> leave the list of IPs in etab without converting over to FQDN? > > My memory is that if you only list IP addresses in /etc/exports then it will > do just want you want. But if you list any host names or net groups then it > has to do a DNS lookup on everything to see if either of those matches. Hi Neil. Thanks for your response! Actually, if I list ONLY IPs in /etc/exports, and nothing else, then etab gets converted over to using hostnames: For example: # cat /etc/exports /test 130.63.92.24(ro,sync) # cat /var/lib/nfs/etab (it's empty) # exportfs -a # cat /var/lib/nfs/etab /test gold.cs.yorku.ca(ro,sync,wdelay,hide,nocrossmnt,secure,root_squash,no_all_squash,subtree_check,secure_locks,mapping=identity,anonuid=-2,anongid=-2) In fact, I see two problems here. First, exportfs shouldn't convert etab over to using FQDN. Second, if it does do this, I don't see why rpc.mountd needs to RE-resolve each hostname in etab. During this time (right after exportfs exits), all of my NFS shares hang, and an strace of rpc.mountd shows that it is re-resolving all the hostnames from etab. When it finishes, all activity continues. On one system with a total of 30,000 hostnames listed, this ends up in a 30 second hang time for all NFS exports! I was able to shrink this time slightly by putting a caching name server on the NFS server, so that the NFS server wasn't killing the DNS, but this didn't help enough. If exportfs truly has to convert IPs over to hostname, I can live with that, but then rpc.mountd shouldn't re-resolve the names. If both can live with IPs, I'm good with that as well. Now, albeit, I'm using an older nfs-utils that comes with RHEL4 installation. Compiling a later version is a bit tricky because some libraries have changed. That being said, reviewing the source (given that I don't really know it that well) for the newest nfs-utils, I don't see how this behavior would really be any different. For example, in client_lookup in support/export/client.c, adding some printfs, I can see that the IPs always get into the ... if (htype == MCL_FQDN && !canonical) { ... where there's a call to gethostbyname. This is the same in nfs-utils-1.0.6 as it is in 1.2.2. >> Why does mountd need to repeat the gethostbyname() lookup on every host >> even though exportfs already converted over to using hostname? > > exportfs doesn't convert over host hostnames. It essentially > copies /etc/exports to /var/lib/nfs/etab with minor formatting changes. > > What do you actually put in /etc/exports, what do you find > in /var/lib/nfs/etab, and what exactly is the problem? > > NeilBrown See above.. thanks :) Jason.