Re: [dm-devel] [PATCHSET block#for-2.6.36-post] block: replace barrier with sequenced flush

[Tejun Heo <tj kernel org>]

Hello,

On 08/18/2010 11:46 AM, Christoph Hellwig wrote:
> FYI: One issue with this series is that make_request based drivers
> not have to access all REQ_FLUSH and REQ_FUA requests.  We'll either
> need to add handling to empty REQ_FLUSH requests to all of them or
> figure out a way to prevent them getting sent.  That is assuming they'll
> simply ignore REQ_FLUSH/REQ_FUA on normal writes.

Can you be a bit more specific?  In most cases, request based drivers
should be fine.  They sit behind the front most request_queue which
would discompose REQ_FLUSH/FUAs into appropriate command sequence.
For the request based drivers, it's not different from the original
REQ_HARDBARRIER mechanism, it'll just see flushes and optionally FUA
writes.

Thanks.

-- 
tejun