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Re: [dm-devel] [RFC PATCH v2 2/2] init: boot to device-mapper targets without an initr*



On Fri, 14 May 2010 20:41:41 -0500 Will Drewry wrote:

> Add a dm= kernel parameter modeled after the md= parameter from
> do_mounts_md.  It allows for device-mapper targets to be configured at
> boot time for use early in the boot process (as the root device or
> otherwise).

dm=<blah>
documentation needs to be added to Documentation/kernel-parameters.txt and/or
Documentation/md.txt.


> The format is dm="name uuid ro,table line 1,table line 2,...".  The
> parser expects the comma to be safe to use as a newline substitute but,
> otherwise, uses the normal separator of space.  Some attempt has been
> made to make it forgiving of additional spaces (using skip_spaces()).

This "space in the arg string" has been tested, right?
It seems a bit odd to me.  Most kernel parameter strings that I am familiar with
use punctuation for separating parameter parts.


> A mapped device created during boot will be assigned a minor of 0 and
> may be access via /dev/dm-0.
> 
> An example dm-linear root with no uuid may look like:
> 
>   root=/dev/dm-0  dm="lroot none 0, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0"
> 
> Once udev is started, /dev/dm-0 will become /dev/mapper/lroot.
> 
> Signed-off-by: Will Drewry <wad chromium org>
> ---
>  init/Makefile       |    1 +
>  init/do_mounts.c    |    1 +
>  init/do_mounts.h    |   10 ++
>  init/do_mounts_dm.c |  353 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 365 insertions(+), 0 deletions(-)
>  create mode 100644 init/do_mounts_dm.c



---
~Randy
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