Re: Subject: [PATCH RFC] block: fix Amiga RDB partition support for disks >= 2 TB

Hi Michael,

On Fri, Jun 29, 2018 at 10:43 AM Michael Schmitz [off-list ref] wrote:

Am 28.06.18 um 21:25 schrieb Geert Uytterhoeven:

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Do we really need the warning?
Once the parsing is fixed doing 64-bit math, it does not matter for
Linux anymore.

Well, irony of this is: In my case the RDB has been created on a machine
with a native OS. So Linux warns me about something I already did so on
the native OS without any warning. In this case AmigaOS 4.0.

Exactly.

So moving a disk partitioned under AmigaOS 4.0 to a system running an
older version of AmigaOS can fail miserably. Not a Linux issue.
Linux also doesn't warn about disks with GPT failing to work on old MSDOS.

Would MSDOS recognize the GPT partition as 'probably FAT', and attempt
to use it?

No idea...

Probably some old Windows or MacOS versions will just suggest to
format your "new" disk ;-)

But it's up to the person (which is not Linux) formatting the disk to
not try to use
it on systems that cannot handle it, and may destroy it.

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Let me clarify: what exactly would the kernel option allow? When to use it?

Whether to use it if safe (on Linux). But whatever Linux does (after
this patch), access will go to the right area of the disk (as specified
by the RDB) so Linux won't any longer stomp on anything that would have
mattered to 32 bit disk drivers. So it really should be safe.

Personally, I see no reason to depend on a kernel option, if it is safe to use.
Just use it.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds