Re: [PATCH] block: eliminate ELEVATOR_INSERT_REQUEUE

[Vivek Goyal]

On Wed, Mar 30, 2011 at 10:02:03AM +0200, Tejun Heo wrote:
> Hello, Jens.
> 
> On Wed, Mar 30, 2011 at 09:59:09AM +0200, Jens Axboe wrote:
> > Pure front insert should be used for requeue and internal commands (like
> > spin up this drive, or get error information). Flush should append to
> > the dispatch list.
> 
> Yeah, right.  The reason I used REQUEUE/FRONT was because BACK
> insertion involves draining the elevator and then appending the
> request at the end of the dispatch queue, which is unnecessary and
> inefficient.  So, front insertion was a quick work around that.  If
> we're removing elv_insert(), we can just append directly to the
> dispatch queue from flush code.

Hi Tejun,

With ordering semantics gone, do we still need to drain the elevator before
queuing flush at the end of request queue.

Thanks
Vivek
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