Re: [PATCH 6/9] target: Allow sbc_ops->execute_rw() to accept SGLs +data_direction

From: Christoph Hellwig
Date: Wed Aug 21 2013 - 02:35:34 EST


On Tue, Aug 20, 2013 at 08:07:57PM +0000, Nicholas A. Bellinger wrote:
> From: Nicholas Bellinger <nab@xxxxxxxxxxxxx>
>
> COMPARE_AND_WRITE expects to be able to send down a DMA_FROM_DEVICE
> to obtain the necessary READ payload for comparision against the
> first half of the WRITE payload containing the verify user data.
>
> Currently virtual backends expect to internally reference SGLs,
> SGL nents, and data_direction, so change IBLOCK, FILEIO and RD
> sbc_ops->execute_rw() to accept this values as function parameters.
>
> Also add the sbc_execute_rw() wrapper to handle the special case
> for the initial COMPARE_AND_WRITE DMA_FROM_DEVICE -> READ I/O
> submission.

I don't like the way this is structured with the new method. It seems
like we should just pass the sgl and associated data to execute_cmd
and have the read vs write logic driven by command code, using generic
flags instead of specificly checking for compare and write.

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