Re: [PATCH v2 06/16] block: treat DMPG and SWAPIN requests as special

["S, Venkatraman" <svenkatr@ti.com>]

On Thu, May 3, 2012 at 8:08 PM, Jeff Moyer <jmoyer@redhat.com> wrote:
> Venkatraman S <svenkatr@ti.com> writes:
>
>> From: Ilan Smith <ilan.smith@sandisk.com>
>>
>> When exp_swapin and exp_dmpg are set, treat read requests
>> marked with DMPG and SWAPIN as high priority and move to
>> the front of the queue.
>>
> [...]
>> +     if (bio_swapin(bio) && blk_queue_exp_swapin(q)) {
>> +             spin_lock_irq(q->queue_lock);
>> +             where = ELEVATOR_INSERT_FLUSH;
>> +             goto get_rq;
>> +     }
>> +
>> +     if (bio_dmpg(bio) && blk_queue_exp_dmpg(q)) {
>> +             spin_lock_irq(q->queue_lock);
>> +             where = ELEVATOR_INSERT_FLUSH;
>> +             goto get_rq;
>
> Is ELEVATOR_INSERT_FRONT not good enough?  It seems wrong to use _FLUSH,
> here.  If the semantics of ELEVATOR_INSERT_FLUSH are really what is
> required, then perhaps we need to have another think about the naming of
> these flags.
>
Actually - yes, ELEVATOR_INSERT_FRONT would do as well. In the
previous version of MMC stack,
we needed the _FLUSH to trigger the write operation that was to be
preempted, to check that
it actually works.


> Cheers,
> Jeff
>
> --