Re: [PATCH 06/10] sd: don't use scsi_setup_blk_pc_cmnd for discard requests

[Douglas Gilbert <dgilbert@interlog.com>]

On 14-07-13 10:35 AM, Martin K. Petersen wrote:
>>>>>> "Christoph" == Christoph Hellwig <hch@lst.de> writes:
>
> Christoph> Simplify handling of discard requests by setting up the
> Christoph> command directly instead of initializing request fields and
> Christoph> then calling scsi_setup_blk_pc_cmnd to propagate the
> Christoph> information into the command.
>
> Would be nice to add a comment similar to the WRITE SAME one. Something
> like:
>
> /*
>   * Initially __data_len is set to the amount of data that needs to be
>   * transferred to the target. This amount depends on whether WRITE SAME
>   * or UNMAP is being used. After the scatterlist has been mapped by
>   * scsi_init_io() we set __data_len to the size of the area to be
>   * discarded on disk. This allows us to report completion on the full
>   * amount of blocks described by the request.
>   */
>
> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>

To make things clearer when referring to the WRITE SAME command
I would suggest "WRITE SAME(unmap)" for the case when its UNMAP
field is 1 (as I assume it is in this case).

Doug Gilbert