Re: [00/17] Large Blocksize Support V3

From: Nick Piggin
Date: Thu Apr 26 2007 - 02:54:09 EST

Christoph Lameter wrote:
On Thu, 26 Apr 2007, Nick Piggin wrote:

The page cache has no problems supporting things with a block
size larger then page size. Now the block device layer may not
have the code to do the scatter gather into small pages and it
may not handle buffer heads whose data is split between multiple

Yeah, this patch is not really large blocksize support (which we normally
think of as block size > page cache size).

No? It depends on how you define block size. This patch definitely allows
a set blocksize function call with a size larger than 4k.

Yeah because it is still <= page cache page size. Anyway, that's just
semantics, it doesn't matter.

I suspect what needs to be fixed is the page cache block device
interface so that we have helper functions that know how to stuff
a single block into several pages.

I am working now and again on some code to do this, it is a big job but
I think it is the right way to do it. But it would take a long time to
get stable and supported by filesystems...

Ummm... We already have a radix tree for this???? What more is needed? You just need to go through all filesystems and make them use extends.

I'm talking about block size > page size in the buffer layer.

SUSE Labs, Novell Inc.
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