Re: [PATCH Linux 2.6.12-rc5-mm1 00/06] blk: barrier flushing reimplementation

[Tejun Heo <htejun@gmail.com>]

Jens Axboe wrote:
> On Sun, May 29 2005, Jens Axboe wrote:
> 
>>On Sun, May 29 2005, Tejun Heo wrote:
>>
>>> Hello, guys.
>>>
>>> This patchset is reimplementation of QUEUE_ORDERED_FLUSH feature.  It
>>>doens't update API docs yet.  If it's determined that this patchset
>>>can go in, I'll regenerate this patchset with doc updates (sans the
>>>last debug message patch of course).
>>
>>Awesome work, that's really the last step in getting the barrier code
>>fully unified and working with tags. I'll review your patchset tomorrow.
> 
> 
> Patches look nice, this is a good step forward. If you feel like doing a
> little more work in this area, I would very much like to add
> QUEUE_ORDERED_FUA as a third method for implementing barriers. Basically
> it would use the FUA commands to put data safely on disk, instead of
> using the post flushes.
> 
> For NCQ, we have a FUA bit in the FPDMA commands. For non-ncq, we have
> the various WRITE_DMA_EXT_FUA (and similar). It would be identical to
> ORDERED_FLUSH in that we let the queue drain, issue a pre-flush, and
> then a write with FUA set. It would eliminate the need to issue an extra
> flush at the end, cutting down the required commands for writing a
> barrier from 3 to 2.
> 

  Hi, Jens.

  I'm on it.

  Thanks.

-- 
tejun