Re: [RFC v2] mkfs.xfs: add mkfs.xfs.conf parse support using libini_config

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Fri, Mar 02, 2018 at 11:01:40PM -0600, Eric Sandeen wrote:
> On 3/2/18 2:32 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.
> > 
> > Although mkfs.xfs already uses sensible defaults this adds a configuration
> > option for parsing defaults settings for mkfs.xfs parsed prior to processing
> > input arguments from the command line.
> > 
> > We define an XFS configuration directory, /etc/mkfs.xfs.d/ and allow for
> > different types of configuration files, if none is specified we look for
> > the default type, /etc/mkfs.xfs.d/default, and you can override with -t.
> > For instance if you specify:
> > 
> > 	mkfs.xfs -t 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 enviornment variable.
> > 
> > To use /etc/ be sure to configure xfsprogs with:
> > 
> >  ./configure --sysconfdir=/etc/
> > 
> > To verify what configuration file is used on a system use the typical:
> > 
> >   mkfs.xfs -N
> > 
> > There is only a subset of options allowed to be set on the conifiguration
> > file, and currently only 1 or 0 are acceptable values. They are:
> > 
> > [data]
> > noalign=
> > 
> > [inode]
> > align=
> > attr=
> > projid32bit=
> > sparse=
> 
> Hey, can I ask a maybe ridiculous question ...
> 
> What's the advantage of haggling over ini file parsers and file formats, vs. just:
> 
> # echo "-m crc=0 -n ftype=0" > /etc/mkfs.xfs.d/default
> 
> and parse that into defaults exactly as if it had been on the commandline?

Except for having to break that up into individual argv-like strings,
I too was wondering if that would be the simplest answer.  Same syntax,
same parsing of number-with-units, etc.

Should we run getopt ahead of time to pick out the -T arg so that we
always load the settings file before we start processing the rest of the
cli options?  So that:

# mkfs.xfs -m crc=1 -T default /dev/sda

actually formats a v5 fs?

--D

> 
> -Eric
> --
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