Re: [Kiobuf-io-devel] RFC: Kernel mechanism: Compound event wait

Stephen C. Tweedie
2001-02-07T00:41:22Z

Hi,

On Tue, Feb 06, 2001 at 07:25:19PM -0500, Ingo Molnar wrote:
>
> On Wed, 7 Feb 2001, Stephen C. Tweedie wrote:
>
> > No, it is a problem of the ll_rw_block interface: buffer_heads need to
> > be aligned on disk at a multiple of their buffer size. Under the Unix
> > raw IO interface it is perfectly legal to begin a 128kB IO at offset
> > 512 bytes into a device.
>
> then we should either fix this limitation, or the raw IO code should split
> the request up into several, variable-size bhs, so that the range is
> filled out optimally with aligned bhs.

That gets us from 512-byte blocks to 4k, but no more (ll_rw_block
enforces a single blocksize on all requests but that relaxing that
requirement is no big deal). Buffer_heads can't deal with data which
spans more than a page right now.

--Stephen