Re: [PATCH v2] sg: add SG_FLAG_Q_AT_TAIL flag

[Ewan Milne <emilne@redhat.com>]

On Wed, 2014-06-04 at 10:58 -0400, Douglas Gilbert wrote:
> When the SG_IO ioctl was copied into the block layer and
> later into the bsg driver, subtle differences emerged.
> 
> One difference is the way injected commands are queued through
> the block layer (i.e. this is not SCSI device queueing nor SATA
> NCQ). Summarizing:
>    - SG_IO in the block layer: blk_exec*(at_head=false)
>    - sg SG_IO: at_head=true
>    - bsg SG_IO: at_head=true
> 
> Some time ago Boaz Harrosh introduced a sg v4 flag called
> BSG_FLAG_Q_AT_TAIL to override the bsg driver default.
> This patch does the equivalent for the sg driver.
> 
> 
> ChangeLog:
>      Introduce SG_FLAG_Q_AT_TAIL flag to cause commands
>      to be injected into the block layer with
>      at_head=false.
> 
> Changes since v1:
>      Make guard condition (only take sg v3 interface or later
>      invocations) clearer.
> 
> Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>

Looks good.

Reviewed-by: Ewan D. Milne <emilne@redhat.com>