Re: [00/17] Large Blocksize Support V3

[Nick Piggin]

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.
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