Re: [PATCH 1/1] block: rework flush sequencing for blk-mq

[Christoph Hellwig]

On Fri, Feb 07, 2014 at 09:18:27AM +0800, Shaohua Li wrote:
> Reusing the tag for flush request is considered before. The problem is driver
> need get a request from a tag, reusing tag breaks this. The possible solution
> is we provide a blk_mq_tag_to_request, and force driver uses it. And in this
> function, if tag equals to flush_rq tag, we return flush_request.

If we want to support tag to request reverse mapping we defintively
need to do this in the core, at which point special casing flush_rq
there is easy.

Which driver needs the reverse mapping? Neither virtio_blk nor null_blk
seem to and I've not seen any other conversions submitted except for the
scsi work.

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