From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg Banks Subject: Re: [PATCH 1/5] NFS: Update help text for CONFIG_NFS_FS Date: Tue, 05 Feb 2008 11:40:25 +1100 Message-ID: <47A7B079.8010903@melbourne.sgi.com> References: <20080205000421.18602.44285.stgit@manray.1015granger.net> <1202170682.28484.55.camel@heimdal.trondhjem.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Cc: Chuck Lever , bfields@citi.umich.edu, linux-nfs@vger.kernel.org To: Trond Myklebust Return-path: Received: from netops-testserver-3-out.sgi.com ([192.48.171.28]:59078 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755831AbYBEAdz (ORCPT ); Mon, 4 Feb 2008 19:33:55 -0500 In-Reply-To: <1202170682.28484.55.camel-rJ7iovZKK19ZJLDQqaL3InhyD016LWXt@public.gmane.org> Sender: linux-nfs-owner@vger.kernel.org List-ID: Trond Myklebust wrote: > On Mon, 2008-02-04 at 19:04 -0500, Chuck Lever wrote: > >> Refresh the help text for Kconfig items related to the NFS client. Remove >> obsolete URLs, and make the language consistent among the options. >> >> >> config NFS_DIRECTIO >> bool "Allow direct I/O on NFS files" >> depends on NFS_FS >> + default N >> > > Why? Isn't O_DIRECT pretty much a standard feature that is enabled in > most distros at this time? > IMO we should rather be aiming to phase out NFS_DIRECTIO. > Agreed. > >> help >> - This option enables applications to perform uncached I/O on files >> - in NFS file systems using the O_DIRECT open() flag. When O_DIRECT >> - is set for a file, its data is not cached in the system's page >> - cache. Data is moved to and from user-level application buffers >> - directly. Unlike local disk-based file systems, NFS O_DIRECT has >> - no alignment restrictions. >> + This option enables support for uncached I/O on files accessed >> + via an NFS mount point. Applications request direct I/O by >> + setting the O_DIRECT flag when opening a file. >> + >> + When direct I/O is requested, the NFS client moves data to and >> + from user-level application buffers directly to NFS servers. >> + Direct I/O on NFS files does not suffer from any I/O or buffer >> + alignment restrictions, as does direct I/O on files that reside >> + in local file systems. >> It might be an idea to mention that direct IO does *not* bypass the server's page cache, an unobvious semantic which escapes many people. >> + >> + For details, see the open(2) man page. >> FYI, I recently posted an update to the O_DIRECT documentation in open(2). http://marc.info/?l=linux-man&m=120107005026531&w=2 -- Greg Banks, R&D Software Engineer, SGI Australian Software Group. The cake is *not* a lie. I don't speak for SGI.