Re: [PATCH 2/9] block: add scatterlist-less DMA mapping helpers

[Daniel Gomez <da.gomez@xxxxxxxxxx>]

On 16/06/2025 07.02, Christoph Hellwig wrote:
> On Wed, Jun 11, 2025 at 03:43:07PM +0200, Daniel Gomez wrote:
>>> +struct blk_dma_iter {
>>> +	/* Output address range for this iteration */
>>> +	dma_addr_t			addr;
>>> +	u32				len;
>>> +
>>> +	/* Status code. Only valid when blk_rq_dma_map_iter_* returned false */
>>> +	blk_status_t			status;
>>
>> This comment does not match with blk_rq_dma_map_iter_start(). It returns false
>> and status is BLK_STS_INVAL.
> 
> I went over you comment a few times and still don't understand it.

The way I read the comment is that status is only valid when
blk_rq_dma_map_iter_* returns false.

But blk_rq_dma_map_iter_start() can return false and an invalid status (in the
default switch case).

Assuming the comment is the right thing, I'd expect a valid status for that
case:

--- a/block/blk-mq-dma.c
+++ b/block/blk-mq-dma.c
@@ -179,7 +179,6 @@ bool blk_rq_dma_map_iter_start(struct request *req, struct device *dma_dev,
                        req->cmd_flags &= ~REQ_P2PDMA;
                        break;
                default:
-                       iter->status = BLK_STS_INVAL;
                        return false;
                }
        }