[parted-devel] about msdos 2T partition issue

[xerces8]

Preventing creating a MSDOS labelin a low level tool is wrong IMHO.
A GUI can give a warning to the user, but parted should just do what 
the user tells him too.

You know:
 - no policy...
 - give enough rope ...

;)


Regards,
David

-----Original Message-----
From: Joel Granados <jgranado at redhat.com>
To: parted-devel <parted-devel at lists.alioth.debian.org>
Date: Fri, 14 Nov 2008 13:29:00 -0500 (EST)
Subject: [parted-devel] about msdos 2T partition issue

> Hi list:
> 
> The 71bbe2995371357c534dccf1eb3d436b399eaf32 commit patches parted so it stops users from
> creating partitions that are greater than 2T.  IMO this patch is in the wrong place.
> 
> 1. I think there is a misconception in the sense that the size is the one that is restricted. 
> This is not the case.  The size can actually be greater than 2T in msdos labels.  What is
> restricted is the sector count.  It is restricted to 2^32 (unsigned int).  And if you have 2^32-1
> 512 size sectors, you will have a partition of 2T.  Of course that can change if you change the
> sector size, and it will still be valid in the msdos label.  This does *not* mean we should not
> check and see how many sectors are in the disk and prevent the user from creating an msdos in a
> disk with more than 2^32 sectors.
> 
> 
> 2. can one have various partitions less then 2^32 sectors, but that all together sum up more than
> 2^32 sectors on an msdos label?  like if I had the 1st partition of size 1.8T and the second of
> 1.8T and a third partition of 1.8T (assuming 512 sector size).  IMO, no (pls correct me if I am
> wrong!!!!!)  As I understand it, the 32 bit restriction is on the drive and not the partitions
> because it not only contains the size but the start sector.  Now the 1.8T size can fit
> comfortably in the 32bit field, but the start sector cannot.  At least for the third partition it
> cant.
> 
> 3. IMO the place to put the label specific stuff is not the libparted/disk.c file.  IMO the best
> place to put these restrictions specific to labels are in the label files themselves.  This
> issue, for example, belongs in the libparted/lables/dos.c file.  Whenever a dos label is being
> created we should check for these kind of things.
> 
> 4.  Finally I propose replacing the current patch for this issue with something that prevents the
> user from creating a msdos label on a device that has more sectors than can be handled by the
> msdos label format.  (patch on the bottom).  IMO reverting the current patch and placing this one
> in its place would be the right thing to do because we wont get to the point of creating an msdos
> partition on a disk if we didn't create an msdos label to begin with :).  OTH we might come up to
> systems that have already made this mistake, in which case we simply need to tell the user that
> no partition can nor will be created.
> 
> If I am missing something please scream at me!!!!
> 
> New Patch:
> 
> -- 
> Joel Andres Granados
> Red Hat / Brno Czech Republic