Re: [00/17] Large Blocksize Support V3

Nick Piggin
2007-04-26T06:53:51Z

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
>>>pages.
>>
>>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.