Re: [PATCH] libata: initialize qc->dma_dir to DMA_NONE

[Brian King <brking@us.ibm.com>]

ACK

Tejun Heo wrote:
> libata didn't used to init qc->dma_dir to any specific value on qc
> initialization and command translation path didn't set qc->dma_dir if
> the command doesn't need data transfer.  This made non-data commands
> to have random qc->dma_dir.
> 
> This usually doesn't cause problem because LLDs usually check
> qc->protocol first and look at qc->dma_dir iff the command needs data
> transfer but this doesn't hold for all LLDs.
> 
> It might be worthwhile to rename qc->dma_dir to qc->data_dir as we use
> the field to tag data direction for both PIO and DMA protocols.
> 
> This problem has been spotted by James Bottomley.
> 
> Signed-off-by: Tejun Heo <htejun@gmail.com>
> Cc: James Bottomley <James.Bottomley@SteelEye.com>
> 
> diff --git a/include/linux/libata.h b/include/linux/libata.h
> index 7cfc18f..925ad7f 100644
> --- a/include/linux/libata.h
> +++ b/include/linux/libata.h
> @@ -1139,6 +1139,7 @@ static inline void ata_tf_init(struct ata_device *dev, struct ata_taskfile *tf)
> 
>  static inline void ata_qc_reinit(struct ata_queued_cmd *qc)
>  {
> +	qc->dma_dir = DMA_NONE;
>  	qc->__sg = NULL;
>  	qc->flags = 0;
>  	qc->cursect = qc->cursg = qc->cursg_ofs = 0;
> -
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-- 
Brian King
eServer Storage I/O
IBM Linux Technology Center