Re: [PATCH V2 10/20] blk-mq-sched: introduce helpers for query, change busy state

Ming Lei
2017-08-24T06:56:11Z

On Wed, Aug 23, 2017 at 02:02:20PM -0600, Jens Axboe wrote:
> On Tue, Aug 22 2017, Bart Van Assche wrote:
> > On Sat, 2017-08-05 at 14:56 +0800, Ming Lei wrote:
> > > +static inline bool blk_mq_hctx_is_dispatch_busy(struct blk_mq_hw_ctx *hctx)
> > > +{
> > > + return test_bit(BLK_MQ_S_DISPATCH_BUSY, &hctx->state);
> > > +}
> > > +
> > > +static inline void blk_mq_hctx_set_dispatch_busy(struct blk_mq_hw_ctx *hctx)
> > > +{
> > > + set_bit(BLK_MQ_S_DISPATCH_BUSY, &hctx->state);
> > > +}
> > > +
> > > +static inline void blk_mq_hctx_clear_dispatch_busy(struct blk_mq_hw_ctx *hctx)
> > > +{
> > > + clear_bit(BLK_MQ_S_DISPATCH_BUSY, &hctx->state);
> > > +}
> >
> > Hello Ming,
> >
> > Are these helper functions modified in a later patch? If not, please drop
> > this patch. One line helper functions are not useful and do not improve
> > readability of source code.
>
> Agree, they just obfuscate the code. Only reason to do this is to do
> things like:

If you look at the following patch, these introduced functions are
modified a lot.

>
> static inline void blk_mq_hctx_clear_dispatch_busy(struct blk_mq_hw_ctx *hctx)
> {
> if (test_bit(BLK_MQ_S_DISPATCH_BUSY, &hctx->state))
> clear_bit(BLK_MQ_S_DISPATCH_BUSY, &hctx->state);
> }
>
> to avoid unecessary RMW (and locked instruction). At least then you can
> add a single comment as to why it's done that way. Apart from that, I
> prefer to open-code it so people don't have to grep to figure out wtf
> blk_mq_hctx_clear_dispatch_busy() does.

Ok, will do that in this way.

--
Ming