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Re: ext3 and raw devices



On 2002.07.23 12:02 Stephen C. Tweedie wrote:
Hi,

On Sat, Jul 06, 2002 at 10:18:37AM +0000, Ian Leonard wrote:

> I appears that the app writing to the raw partition had
> a bug that caused it to write to negative block numbers
> and that this wrote all over the disk.

Shouldn't be able to happen --- negative offsets are rejected
elsewhere in the kernel before raw devices can get to see them.  The
lseek/llseek syscalls return EINVAL if you try to set the offset to be
negative for normal read/write syscalls, and the pread and pwrite
syscalls also check for negative offsets before allowing things to
proceed.

I apolgise because this was a complete red herring. The app was behaving badly but the source of the corruption was due to the use of a 160Gb Maxtor disk.

However, FYI, the problem still exists. If you write constantly
to a partition (in this case I just wrote to the partition without
a filesystem), it will reach about 137GB (from memory), wrap
and destroy the first partition.

I note from the kernel archive that this problem should be fixed
in the next release. However 2.4.19-rc1 still does it. I need to
check further - maybe the fix is in the ac branch.

I also note that support for really, really large disks is due
for 2.6, but i think it needs to be sorted out before that.

--
Ian Leonard
eMail: ileonard ntlworld com
Phone: +44 (0)1865 765273

Please ignore spelling and punctuation - I did.





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