From: Chuck Lever Subject: Re: [PATCH 2/3] NFS: Add NFS_MOUNT_NONEGDE flag to avoid caching negative dentries Date: Tue, 15 Jan 2008 12:04:50 -0500 Message-ID: References: <20080115163013.GC18911@newbie.thebellsplace.net> <1200415972.7702.7.camel@heimdal.trondhjem.org> Mime-Version: 1.0 (Apple Message framework v753) Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed Cc: NFS list To: Bob Bell Return-path: Received: from agminet01.oracle.com ([141.146.126.228]:64558 "EHLO agminet01.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751315AbYAORFE (ORCPT ); Tue, 15 Jan 2008 12:05:04 -0500 In-Reply-To: <1200415972.7702.7.camel-rJ7iovZKK19ZJLDQqaL3InhyD016LWXt@public.gmane.org> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Jan 15, 2008, at 11:52 AM, Trond Myklebust wrote: > On Tue, 2008-01-15 at 11:30 -0500, Bob Bell wrote: >> From: Bob Bell >> >> Add NFS_MOUNT_NONEGDE mount flag. When this flag is set on a mounted >> NFS filesystem, negative dentries for that filesystem will not be >> cached. This can help address cache coherency when the NFS server >> does >> not provide sufficiently fine-grained timestamps to consistently >> distinguish when a directory has been modified, though performance >> when >> repeatedly accessing filenames for files that do not exist may be >> impacted. >> >> Signed-off-by: Bob Bell >> --- > > The patch itself looks OK. My only gripe is the two names 'negde' and > 'nonegde'. Can we find something that rolls a bit more smoothly off > the > tongue? Yeah, actually I thought it was spelled "non edge" until I looked closer. > How about something like 'cacheneglookup' 'nocacheneglookup'? Better > suggestions, anyone? I suspect system administrators have no idea what a "negative dentry" is, and it would probably be beyond the scope of nfs(5) to explain it. So I vote for something that describes the behavior as observed by a "lay person" rather than something that names the kernel mechanisms involved. You might consider tying this behavior to "noac" as well. In other words, make "noac" equivalent to "sync,actimeo=0,nonegde" . -- Chuck Lever chuck[dot]lever[at]oracle[dot]com