Re: [Xen-devel] pygrub patch to allow explicit offset to fs

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2013-06-19 at 01:40 +0200, Kjetil Torgrim Homme wrote:
> I recently needed an old VM to work even though it was created on a SAN 
> LUN with no partition table, just LVM straight onto the raw device.
> 
> pygrub didn't like this, so I added a simple hack to allow the user to 
> override pygrub's probing when necessary.  please consider applying this 
> patch.  btw, I think most LVM will have first filesystem at offset 196608.
> 
> 
> commit 80a3f7b48da235695f8560deb41c19b23e7799e3
> Author: Kjetil Torgrim Homme <kjetil.homme@xxxxxxxxxxxxxxxxxx>
> Date:   Wed Jun 19 00:54:43 2013 +0200
> 
>      allow user to specify offset parameter which overrides partition 
> table parsing
> 
>      Signed-off-by: Kjetil Torgrim Homme <kjetil.homme@xxxxxxxxxxxxxxxxxx>

Looks good to me, thanks.

Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

although I've suggested a possible simplification below.

I think with the freeze being in force this, as a new feature, will have
to wait for the 4.4 dev cycle to be applied, although I will defer to
George's judgement.

> diff --git a/tools/pygrub/src/pygrub b/tools/pygrub/src/pygrub
> index eedfdb2..d46ee8c 100644
> --- a/tools/pygrub/src/pygrub
> +++ b/tools/pygrub/src/pygrub
> [...]
> @@ -765,6 +765,7 @@ if __name__ == "__main__":
>      interactive = True
>      list_entries = False
>      isconfig = False
> +    user_provided_offset = None

If you make this "part_offs = None"...

>      debug = False
>      not_really = False
>      output_format = "sxp"
> @@ -797,6 +798,8 @@ if __name__ == "__main__":
>              incfg["ramdisk"] = a
>          elif o in ("--args",):
>              incfg["args"] = a
> +        elif o in ("--offset",):
> +            user_provided_offset = a

... and this "part_offs = int(a)" ... (or [int(a)] if that's correct)

>          elif o in ("--entry",):
>              entry = a
>              # specifying the entry to boot implies non-interactive
> @@ -840,7 +843,10 @@ if __name__ == "__main__":
>          bootfsoptions = ""
>  
>      # get list of offsets into file which start partitions
> -    part_offs = get_partition_offsets(file)
> +    if user_provided_offset is None:
> +        part_offs = get_partition_offsets(file)
> +    else:
> +        part_offs = [ int(user_provided_offset) ]

Then this can become just:
     if part_offs = None:
         part_offs = get_partition_offsets(file)
> 
> Ian.


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