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

From: Jeff V. Merkey (
Date: Tue Feb 06 2001 - 21:00:50 EST

On Wed, Feb 07, 2001 at 02:02:21AM +0100, Jens Axboe wrote:
> On Tue, Feb 06 2001, Jeff V. Merkey wrote:
> > I remember Linus asking to try this variable buffer head chaining
> > thing 512-1024-512 kind of stuff several months back, and mixing them to
> > see what would happen -- result. About half the drivers break with it.
> > The interface allows you to do it, I've tried it, (works on Andre's
> > drivers, but a lot of SCSI drivers break) but a lot of drivers seem to
> > have assumptions about these things all being the same size in a
> > buffer head chain.
> I don't see anything that would break doing this, in fact you can
> do this as long as the buffers are all at least a multiple of the
> block size. All the drivers I've inspected handle this fine, noone
> assumes that rq->bh->b_size is the same in all the buffers attached
> to the request. This includes SCSI (scsi_lib.c builds sg tables),
> IDE, and the Compaq array + Mylex driver. This mostly leaves the
> "old-style" drivers using CURRENT etc, the kernel helpers for these
> handle it as well.
> So I would appreciate pointers to these devices that break so we
> can inspect them.
> --
> Jens Axboe

Adaptec drivers had an oops. Also, AIC7XXX also had some oops with it.


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