RE: 2.5.28 and partitions

Linus Torvalds
2002-07-25T05:23:10Z

On Wed, 24 Jul 2002 Matt_Domsch@Dell.com wrote:
>
> The promise of 64-bit block addresses eventually was a huge part of why I
> worked on the GPT code in the kernel, partx, parted, etc. I could really
> use it today, and it'll be a solid requirement less than a year from now.

Note that there is one place where 64 bits is simply _too_ expensive, and
that's the page cache. In particular, the "index" in "struct page". We
want to make "struct page" _smaller_, not larger.

Right now that means that 16TB really is a hard limit for at least some
device access on a 32-bit machine with a 4kB page-size (yes, you could
make a filesystem that is bigger, but you very fundamentally cannot make
individual files larger than 16TB).

The block device layer also cannot write to the 16TB+ region using the
page cache (but it should be possible to do it using raw device access
with a 64-bit sector_t, so you can initialize the filesystem).

Linus