Re: 2.1.108: file sizes > 2GB with ext2?

Jakub Jelinek (jj@sunsite.ms.mff.cuni.cz)
Fri, 31 Jul 1998 09:00:02 +0200 (MET DST)

>
> Date: Wed, 29 Jul 1998 14:09:37 -0800
> From: Steven Roberts <strobert@ata-sd.com>
>
> Seomthing just hit me on this, does this mean ext2 partitions made on a
> 64-bit arch aren't compatible with those made on a 32-bit arch (or is it
> just a in running kernel sizeof(long) limitation)?
>
> Am shuffling some servers around and was about to move a drive from an
> intel box to an alpha...
>
> When you create a file greater than 2GB on a 64-bit platform, it sets a
> read-only compatibility flag. This prevents you from mounting the file
> read/write on a 32-bit platform, but you can still mount the ext2
> partition read-only.

In fact, it is even more complicated: if the kernel on the 32bit platform is
recent enough (ie. 2.1.1xx - I don't remeber which kernel added it), then
the only read-only thing will be the large file (from which you'll be able
to see the initial portion), the whole filesystem may be read-write and
other files on it as well. Only if you have an old kernel, you'll be forced
to read-only mounting.
Ted, btw, I still see a problem: you removed bumping of GOOD_OLD_REV up, so
if the filesystem is GOOD_OLD_REV (I guess it is the default for mke2fs),
then the RO compatibility flag will be set, but nobody will care (except
fsck, I think). So, either we bump the revision, or we just disallow
creating large files in GOOD_OLD_REV and ask the user to tune2fs it to a
higher revision.

Cheers,
Jakub
___________________________________________________________________
Jakub Jelinek | jj@sunsite.mff.cuni.cz | http://sunsite.mff.cuni.cz
Administrator of SunSITE Czech Republic, MFF, Charles University
___________________________________________________________________
Ultralinux - first 64bit OS to take full power of the UltraSparc
Linux version 2.1.112 on a sparc64 machine (498.80 BogoMips).
___________________________________________________________________

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