Re: [dm-devel] [RFC PATCH] init: boot to device-mapper targets without an initr*

[Alasdair G Kergon <agk redhat com>]

On Wed, May 12, 2010 at 03:30:54PM -0500, Will Drewry wrote:
> The format is dm=minor,rwmode,begin,length,target,target,params,with,commas

1. If we go down this route, pick a format that gives access to the full
set of allowed table formats (or which can be extended trivially to do
so in future).  So cope with multi-line tables e.g. with a marker (empty
field?) to start a new table line.

2. It would be wise to define a name and optional uuid too, so the device is
fully visible and accessible from userspace through existing mechanisms.
Originally the name+uuid were decoupled from the mapped device itself,
but that got changed, though the code layout (dm-ioctl.c vs. dm.c) still
makes them appear to be separate.
 
> +	char target[24];
> +	char target_params[256];

I'm never a fan of hard-coded restrictions, but at least make them
explicit as #defines, so people can see at a glance what to change
if they get errors for exceeding them.

> +static void __init dm_setup_drive(void)

Arguably most of this code could be a helper function exported from drivers/md.

Alasdair