Re: [PATCH] block: add a new flag BLK_MQ_POLL_HYBRID_INVALID for hybrid poll

[yuyufen <yuyufen@xxxxxxxxxx>]

On 2019/2/27 20:45, Damien Le Moal wrote:
> On 2019/02/27 5:38, yuyufen wrote:
> > On 2019/2/27 18:27, Marcos Paulo de Souza wrote:
> > > Hello Yufen,
> > >
> > > On 2/27/19 3:21 AM, Yufen Yu wrote:
> > > > For q->poll_nsec == -1, means using classic poll, not hybrid poll.
> > > > We introduce a new flag BLK_POLL_DELAY_INVALID to replace -1, which
> > > > may make code much easier to read.
> > > In the commit message you say BLK_POLL_DELAY_INVALID, but the code and
> > > the commit title use BLK_MQ_POLL_HYBRID_INVALID. Is this a typo?
> > Thanks a lot for pointing out this fault. What I want to
> > say is BLK_MQ_POLL_HYBRID_INVALID, not BLK_POLL_DELAY_INVALID.
> >
> > Yufen
> > Thanks
> >
> > > Thanks.
> > >
> > > > Signed-off-by: Yufen Yu <yuyufen@xxxxxxxxxx>
> > > > ---
> > > >    block/blk-mq.c         | 4 ++--
> > > >    block/blk-sysfs.c      | 4 ++--
> > > >    include/linux/blkdev.h | 3 +++
> > > >    3 files changed, 7 insertions(+), 4 deletions(-)
> > > >
> > > > diff --git a/block/blk-mq.c b/block/blk-mq.c
> > > > index 9437a5eb07cf..8df9f6e97d2e 100644
> > > > --- a/block/blk-mq.c
> > > > +++ b/block/blk-mq.c
> > > > @@ -2857,7 +2857,7 @@ struct request_queue
> > > > *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
> > > >        /*
> > > >         * Default to classic polling
> > > >         */
> > > > -    q->poll_nsec = -1;
> > > > +    q->poll_nsec = BLK_MQ_POLL_HYBRID_INVALID;
> > > >          blk_mq_init_cpu_queues(q, set->nr_hw_queues);
> > > >        blk_mq_add_queue_tag_set(set, q);
> > > > @@ -3389,7 +3389,7 @@ static bool blk_mq_poll_hybrid(struct
> > > > request_queue *q,
> > > >    {
> > > >        struct request *rq;
> > > >    -    if (q->poll_nsec == -1)
> > > > +    if (q->poll_nsec == BLK_MQ_POLL_HYBRID_INVALID)
> > > >            return false;
> > > >          if (!blk_qc_t_is_internal(cookie))
> > > > diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
> > > > index 590d1ef2f961..8775b898f96d 100644
> > > > --- a/block/blk-sysfs.c
> > > > +++ b/block/blk-sysfs.c
> > > > @@ -360,7 +360,7 @@ static ssize_t queue_poll_delay_show(struct
> > > > request_queue *q, char *page)
> > > >    {
> > > >        int val;
> > > >    -    if (q->poll_nsec == -1)
> > > > +    if (q->poll_nsec == BLK_MQ_POLL_HYBRID_INVALID)
> > > >            val = -1;
> > > >        else
> > > >            val = q->poll_nsec / 1000;
> > > > @@ -381,7 +381,7 @@ static ssize_t queue_poll_delay_store(struct
> > > > request_queue *q, const char *page,
> > > >            return err;
> > > >          if (val == -1)
> > > > -        q->poll_nsec = -1;
> > > > +        q->poll_nsec = BLK_MQ_POLL_HYBRID_INVALID;
> > > >        else
> > > >            q->poll_nsec = val * 1000;
> > > >    diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> > > > index 338604dff7d0..2102447b67d9 100644
> > > > --- a/include/linux/blkdev.h
> > > > +++ b/include/linux/blkdev.h
> > > > @@ -50,6 +50,9 @@ struct blk_stat_callback;
> > > >    /* Must be consistent with blk_mq_poll_stats_bkt() */
> > > >    #define BLK_MQ_POLL_STATS_BKTS 16
> > > >    +/* Using default classic polling */
> > > > +#define BLK_MQ_POLL_HYBRID_INVALID -1
> May be simply renaming this as BLK_MQ_POLL_CLASSIC would be even simpler ?
> That matches the comment and also the actual use of the macro, i.e.:
>
> if (q->poll_nsec == -1)
>
> means "do classic polling", which would nicely fits with:
>
> if (q->poll_nsec == BLK_MQ_POLL_CLASSIC)
>
> A lot easier to understand in my opinion. Using BLK_MQ_POLL_HYBRID_INVALID as a
> name is confusing with potential error cases where we actually want to do hybrid
> polling but the poll sleep time is invalid.

I think your suggestion is good. Thanks a lot.

Yufen
thanks



> > > > +
> > > >    /*
> > > >     * Maximum number of blkcg policies allowed to be registered
> > > > concurrently.
> > > >     * Defined here to simplify include dependency.
> > > .