Re: [PATCH 0/4] Use of new scsi_allocate_command

[Boaz Harrosh <bharrosh-C4P08NqkoRlBDgjK7y7TUQ@public.gmane.org>]

On Thu, May 01 2008 at 20:33 +0300, James Bottomley <James.Bottomley-d9PhHud1JfjCXq6kfMZ53/egYHeGw8Jk@public.gmane.org> wrote:
> On Thu, 2008-05-01 at 20:06 +0300, Boaz Harrosh wrote:
>> On Thu, May 01 2008 at 19:38 +0300, James Bottomley <James.Bottomley-d9PhHud1JfjCXq6kfMZ53/egYHeGw8Jk@public.gmane.org> wrote:
>> <snip> 
>>> Er, but
>>>
>>>      1. struct cmdinfo is stack allocated; you can't dma to stack
>>>      2. even if you fix this, the structure is packed and will have the
>>>         original ppc coherence issues
>>>      3. Finally, even on the stack, it's not necessarily reachable with
>>>         the DMA mask
>>>
>> Ho, thanks for the catch. I really goofed here.
>>
>>> The whole point of managing sense buffer allocations centrally is to
>>> prevent driver writers from falling into all these traps.  I really
>>> don't think going back to hand rolled bounce buffering imporves the
>>> situation.
>>>
>> We don't have a choice Andi is removing all this. ISA is becoming
>> ISA's driver private problem.
> 
> No he's not .. not if it's going to cause this type of grief.
> 
> But I think you misread his patch set.  He still has a flag equivalent
> of unchecked_isa_dma  it's just called sense_buffer_isa instead.  The
> shift in his patch set is 
> 
>      1. it removes the need to allocate commands in dma'able memory
>      2. it removes the need for the ULD request path to allocate in
>         dma'able memory (it uses the block bounce path instead)
>      3. it *can't* remove the need to dma to the sense buffer, hence the
>         flag.
> 
> So it looks like the re-rolled patch set (when Andi gets around to
> posting it) will use one pool for the cmd buffer, but separate isa and
> non-isa pools for the sense buffer.  Thus it should just work for gdth
> with scsi_allocate_command predicated on sense_buffer_isa.
> 
> James
> 

I know all about Andi's patches, since I offered to help him as I
have some experience with scsi drivers. And it will be me that will
post the next round of ISA patches.

I have the complete body of work here:
http://git.open-osd.org/gitweb.cgi?p=open-osd.git;a=shortlog;h=boaz_sense_effort

I planed to first submit up to the Remove-ISA-dma tag and only then RFC and try
to push the rest of the work.

In the new ISA patchset we got rid of the sense_buffer_isa and converted all ISA
drivers to take care of their own sense problems. Which is much more simple then
one might think. This is because of 2 reasons. 1 - because to support it in Andi's
new mask allocation scheme was an hack, and 2 because I wanted to get rid of them
anyway.

I apologize in advance for any grief the all effort might cause, and I try to take
it upon myself to do all the work, I will very much appreciate any review, thanks
for your help already.

Boaz

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