Re: [PATCH v3 1/8] blk-mq-dma: restore BLK_STS_TARGET for unsupported P2P transfers

> Unsupported P2P transfers used to fail with BLK_STS_TARGET, chosen
> by commit 91fb2b6052f7 ("nvme-pci: convert to using
> dma_map_sgtable()") for dma_map_sgtable()'s -EREMOTEIO: an I/O that
> can never succeed on this device must not be retried.  The
> blk_rq_dma_map conversion changed it to BLK_STS_INVAL, which
> blk_path_error() treats as retryable and md deliberately ignores
> for member failures -- a P2P write to a member the peer cannot
> reach is counted as written and the mirrors silently diverge.
> 
> Restore BLK_STS_TARGET.  Hit e.g. with CMB memory of one NVMe
> device used as the data buffer for I/O to a second one behind a
> different host bridge.
> 
> Fixes: 858299dc6160 ("block: add scatterlist-less DMA mapping helpers")
> Fixes: 7ce3c1dd78fc ("nvme-pci: convert the data mapping to blk_rq_dma_map")
> Cc: [email protected] # v6.17
> Assisted-by: Claude:claude-opus-4-8
> Signed-off-by: Mykola Marzhan <[email protected]>

Sashiko has reviewed this patch and found no issues. It looks great!

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