I can get done what I need for ship of the full NWFS (with mirroring) if
I can get an async interface to the disks that isn't tied into the
buffer cache from a memory consumption viewpoint. At present, the
interface still requires that I call getblk() for any buffer heads I
want to pass to the drivers. I need a way not to have to do this, so I
could simply pass my own buffer_head elements into ll_rw_block or
make_request(). I've found that when I do, all the drivers
malfunction. I want very much to work within a "Linux" framework, but I
realize that what's there just aint gonna' work without a sledge hammer
approach. Can you help?
Please advise,
Jeff
Linus Torvalds wrote:
>
> In article <381DC5A0.CABB7735@timpanogas.com>,
> Jeff V. Merkey <jmerkey@timpanogas.com> wrote:
> >
> >What everyone is side-stepping is that the interface between the drivers
> >and the buffer cache is incestuous -- this prevents folks from building
> >async I/O based FS's on Linux. The solution is not a simple one -- the
> >drivers and buffer cache interface needs to be changed to elimnate these
> >dependencies so.
>
> Actually, not at all.
>
> The way to fix what you call "incestuous" is to just marry the two off
> for good. They aren't incestuous, they're just living in sin..
>
> The buffer cache is closely related to the drivers, and will become only
> _MORE_ closely related to the drivers. That's because the buffer cache
> is quite consciously being evolved into just a driver interface for IO:
> the "buffer cache" is transforming away from a "cache", and into a pure
> "block IO interface".
>
> So no, the buffer cache doesn't support the kind of mirroring you want,
> and almost certainly never will. But the page cache may eventually
> evolve into the direction you're looking for.
>
> Linus
>
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