[lustre-devel] [PATCH 08/30] lustre: mgc: Remove unnecessary checks for config_log_put()

[James Simmons]

> > From: Steve Guminski <stephenx.guminski at intel.com>
> >
> > Make config_log_put() check if its parameter is NULL, which makes
> > it is unnecessary to perform the check prior to calling it.
> > This patch removes the redundant checks.
> >
> > Signed-off-by: Steve Guminski <stephenx.guminski at intel.com>
> > WC-bug-id: https://jira.whamcloud.com/browse/LU-9152
> > Reviewed-on: https://review.whamcloud.com/25854
> > Reviewed-by: Bob Glossman <bob.glossman at intel.com>
> > Reviewed-by: Andreas Dilger <adilger at whamcloud.com>
> > Reviewed-by: James Simmons <uja.ornl at yahoo.com>
> > Signed-off-by: James Simmons <jsimmons at infradead.org>
> > ---
> >  drivers/staging/lustre/lustre/mgc/mgc_request.c | 36 +++++++++++--------------
> >  1 file changed, 16 insertions(+), 20 deletions(-)
> >
> > diff --git a/drivers/staging/lustre/lustre/mgc/mgc_request.c b/drivers/staging/lustre/lustre/mgc/mgc_request.c
> > index 4552cc5..e6f8d9e 100644
> > --- a/drivers/staging/lustre/lustre/mgc/mgc_request.c
> > +++ b/drivers/staging/lustre/lustre/mgc/mgc_request.c
> > @@ -131,6 +131,9 @@ static int config_log_get(struct config_llog_data *cld)
> >   */
> >  static void config_log_put(struct config_llog_data *cld)
> >  {
> > +	if (unlikely(!cld))
> > +		return;
> > +
> 
> I've removed the "unlikely()" call.
> 
> Partly because use of likely/unlikely is discouraged where the
> difference cannot be measured (or clearly justified some other way),
> and partly because .....

I kept it in since it was in the original patch. Personally I'm not a fan
either. The only time I would use it is in a case where code is executed
100k+ times a second and even then I question if you really get any boost
with modern processors. 
 
> > @@ -387,6 +387,9 @@ struct config_llog_data *do_config_log_add(struct obd_device *obd,
> >  
> >  static inline void config_mark_cld_stop(struct config_llog_data *cld)
> >  {
> > +	if (!cld)
> > +		return;
> > +
> 
> .... there is no "unlikely()" here, and I like consistency.
> 
> Thanks,
> NeilBrown
> 
> 
> >  	mutex_lock(&cld->cld_lock);
> >  	spin_lock(&config_list_lock);
> >  	cld->cld_stopping = 1;
> > @@ -436,18 +439,13 @@ static int config_log_end(char *logname, struct config_llog_instance *cfg)
> >  	cld->cld_sptlrpc = NULL;
> >  	mutex_unlock(&cld->cld_lock);
> >  
> > -	if (cld_recover) {
> > -		config_mark_cld_stop(cld_recover);
> > -		config_log_put(cld_recover);
> > -	}
> > +	config_mark_cld_stop(cld_recover);
> > +	config_log_put(cld_recover);
> >  
> > -	if (cld_params) {
> > -		config_mark_cld_stop(cld_params);
> > -		config_log_put(cld_params);
> > -	}
> > +	config_mark_cld_stop(cld_params);
> > +	config_log_put(cld_params);
> >  
> > -	if (cld_sptlrpc)
> > -		config_log_put(cld_sptlrpc);
> > +	config_log_put(cld_sptlrpc);
> >  
> >  	/* drop the ref from the find */
> >  	config_log_put(cld);
> > @@ -593,8 +591,7 @@ static int mgc_requeue_thread(void *data)
> >  			cld->cld_lostlock = 0;
> >  			spin_unlock(&config_list_lock);
> >  
> > -			if (cld_prev)
> > -				config_log_put(cld_prev);
> > +			config_log_put(cld_prev);
> >  			cld_prev = cld;
> >  
> >  			if (likely(!(rq_state & RQ_STOP))) {
> > @@ -606,8 +603,7 @@ static int mgc_requeue_thread(void *data)
> >  			}
> >  		}
> >  		spin_unlock(&config_list_lock);
> > -		if (cld_prev)
> > -			config_log_put(cld_prev);
> > +		config_log_put(cld_prev);
> >  
> >  		/* Wait a bit to see if anyone else needs a requeue */
> >  		wait_event_idle(rq_waitq, rq_state & (RQ_NOW | RQ_STOP));
> > -- 
> > 1.8.3.1
>