Re: [PATCH v2 5/5] mkfs.xfs: add configuration file parsing support using our own parser

From: Dave Chinner <david@fromorbit.com>
To: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: Eric Sandeen <sandeen@sandeen.net>,
	"Luis R. Rodriguez" <mcgrof@kernel.org>,
	linux-xfs@vger.kernel.org, jack@suse.com, jeffm@suse.com,
	okurz@suse.com, lpechacek@suse.com, jtulak@redhat.com
Subject: Re: [PATCH v2 5/5] mkfs.xfs: add configuration file parsing support using our own parser
Date: Sun, 20 May 2018 10:16:48 +1000	[thread overview]
Message-ID: <20180520001648.GN23861@dastard> (raw)
In-Reply-To: <20180518034600.GW23858@magnolia>

On Thu, May 17, 2018 at 08:46:00PM -0700, Darrick J. Wong wrote:
> On Thu, May 17, 2018 at 10:24:13PM -0500, Eric Sandeen wrote:
> > On 5/17/18 2:27 PM, Luis R. Rodriguez wrote:
> > > You may want to stick to specific set of configuration options when
> > > creating filesystems with mkfs.xfs -- sometimes due to pure technical
> > > reasons, but some other times to ensure systems remain compatible as
> > > new features are introduced with older kernels, or if you always want
> > > to take advantage of some new feature which would otherwise typically
> > > be disruptive.
> > > 
> > > This adds support for parsing a configuration file to override defaults
> > > parameters to be used for mkfs.xfs.
> > > 
> > > We define an XFS configuration directory,/etc/mkfs.xfs.d/  and allow for
> > > different configuration files, if none is specified we look for the
> > > default configuration file, /etc/mkfs.xfs.d/default. You can override
> > > with -c.  For instance, if you specify:
> > > 
> > > 	mkfs.xfs -c experimental -f /dev/loop0
> > > 
> > > The file /etc/mkfs.xfs.d/experimental will be used as your configuration
> > > file. If you really need to override the full path of the configuration
> > > file you may use the MKFS_XFS_CONFIG environment variable.
> > 
> > I'm swamped under a deadline at work this week so just commenting at a
> > very high level for now, but I'm curious; why use an env var vs
> > providing a full path for -c ?  env vars always strike me as magic unexpected
> > behaviors.
> > 
> > # mkfs.xfs -c /my/fancy/path/to/config
> > 
> > seems much clearer than
> > 
> > # export MKFS_XFS_CONFIG=/my/fancy/path/to/
> > # mkfs.xfs -c config
> > 
> > i.e. if a full path is specified use it, else use the config directory.
> > 
> > Thoughts?
> 
> In this case your choices are:
> MKFS_XFS_CONFIG=/my/fancy/path/to/config mkfs.xfs
> 
> or:
> cp /my/fancy/path/to/config /etc/mkfs.xfs.d/hoogah
> mkfs.xfs -c hooga

Sorry, why do we need to copy it to /etc/mkfs.xfs.d/?

> <shrug> Bikeshedding more, what if either option accepted either an
> absolute path, or a file in $sysconfdir/etc/mkfs.xfs.d/ ? 

I kinda assumed that config files could be located anywhere, but we
only searched the sysconfig path if it didn't point at a local
file...

Cheers,

Dave.

-- 
Dave Chinner
david@fromorbit.com