Re: transport_do_task_sg_chain() still needed?

["Nicholas A. Bellinger" <nab@xxxxxxxxxxxxxxx>]

On Wed, 2012-03-21 at 16:09 -0700, Roland Dreier wrote:
> Hi Nic,
> 
> I'm trying to understand how transport_do_task_sg_chain() is used in
> the current stack.  I'm not sure if I'm missing something, or if all
> this logic can be eliminated.  It looks like we always have an sg list
> in the se_cmd, and then when we split the command into tasks, we put a
> sublist of that sg list into each task.  Then all
> transport_do_task_sg_chain() does is chain those sublists back
> together into a new chained list that AFAICT is equivalent to the
> command's original sg list.
> 
> So does it make sense to get rid of this task_sg_chaining logic and
> just have the fabrics use commands' sg lists directly, or is there
> something deeper here that I'm not seeing?
> 

Hi Roland,

So for single task operation, the transport_do_task_sg_chain() logic is
not required because sg_chain() is never called with only a single
se_task->task_sg[] present per se_cmd.

For > 1 task operation in transport_allocate_data_tasks(), the
transport_do_task_sg_chain() is still required (along with an extra SGL
per se_task->task_sg[] for the link) in order for a se_cmd's SGLs to be
made into a single walkable list using scatterlist.h primitives.

So no, I don't think we can get rid of transport_do_task_sg_chain()
logic as it's still a hard requirement for > 1 task operation.

--nab

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