linux-kernel - Re: [PATCH 1/2] md/raid5: avoid duplicate code

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Date:	Fri, 8 May 2015 13:34:35 +0800
From:	Yuanhan Liu <yuanhan.liu@...ux.intel.com>
To:	NeilBrown <neilb@...e.de>
Cc:	linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] md/raid5: avoid duplicate code

On Fri, May 08, 2015 at 03:28:00PM +1000, NeilBrown wrote:
> On Wed,  6 May 2015 17:45:49 +0800 Yuanhan Liu <yuanhan.liu@...ux.intel.com>
> wrote:
> 
> > Move the code that put one idle sh(hot in cache, but happens to be
> > zero referenced) back to active stage to __find_stripe(). Because
> > that's what need to do every time you invoke __find_stripe().
> > 
> > Moving it there avoids duplicate code, as well as makes a bit more
> > sense, IMO, as it tells a whole story now.
> 
> Thanks for this.  It is a good cleanup.
> 
> However I don't want to make any new changes to the RAID5 code until I find a
> couple of bugs that I'm hunting.  So I won't apply it just yet.
> Remind me in a couple of weeks if I seem to have forgotten.

Got it. Thanks.


	--yliu
> 
> > 
> > Signed-off-by: Yuanhan Liu <yuanhan.liu@...ux.intel.com>
> > ---
> >  drivers/md/raid5.c | 50 ++++++++++++++++++--------------------------------
> >  1 file changed, 18 insertions(+), 32 deletions(-)
> > 
> > diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> > index 77dfd72..e7fa818 100644
> > --- a/drivers/md/raid5.c
> > +++ b/drivers/md/raid5.c
> > @@ -567,8 +567,25 @@ static struct stripe_head *__find_stripe(struct r5conf *conf, sector_t sector,
> >  
> >  	pr_debug("__find_stripe, sector %llu\n", (unsigned long long)sector);
> >  	hlist_for_each_entry(sh, stripe_hash(conf, sector), hash)
> > -		if (sh->sector == sector && sh->generation == generation)
> > +		if (sh->sector == sector && sh->generation == generation) {
> > +			if (!atomic_inc_not_zero(&sh->count)) {
> > +				spin_lock(&conf->device_lock);
> > +				if (!atomic_read(&sh->count)) {
> > +					if (!test_bit(STRIPE_HANDLE, &sh->state))
> > +						atomic_inc(&conf->active_stripes);
> > +					BUG_ON(list_empty(&sh->lru) &&
> > +					       !test_bit(STRIPE_EXPANDING, &sh->state));
> > +					list_del_init(&sh->lru);
> > +					if (sh->group) {
> > +						sh->group->stripes_cnt--;
> > +						sh->group = NULL;
> > +					}
> > +				}
> > +				atomic_inc(&sh->count);
> > +				spin_unlock(&conf->device_lock);
> > +			}
> >  			return sh;
> > +		}
> >  	pr_debug("__stripe %llu not in cache\n", (unsigned long long)sector);
> >  	return NULL;
> >  }
> > @@ -698,21 +715,6 @@ get_active_stripe(struct r5conf *conf, sector_t sector,
> >  				init_stripe(sh, sector, previous);
> >  				atomic_inc(&sh->count);
> >  			}
> > -		} else if (!atomic_inc_not_zero(&sh->count)) {
> > -			spin_lock(&conf->device_lock);
> > -			if (!atomic_read(&sh->count)) {
> > -				if (!test_bit(STRIPE_HANDLE, &sh->state))
> > -					atomic_inc(&conf->active_stripes);
> > -				BUG_ON(list_empty(&sh->lru) &&
> > -				       !test_bit(STRIPE_EXPANDING, &sh->state));
> > -				list_del_init(&sh->lru);
> > -				if (sh->group) {
> > -					sh->group->stripes_cnt--;
> > -					sh->group = NULL;
> > -				}
> > -			}
> > -			atomic_inc(&sh->count);
> > -			spin_unlock(&conf->device_lock);
> >  		}
> >  	} while (sh == NULL);
> >  
> > @@ -771,22 +773,6 @@ static void stripe_add_to_batch_list(struct r5conf *conf, struct stripe_head *sh
> >  	hash = stripe_hash_locks_hash(head_sector);
> >  	spin_lock_irq(conf->hash_locks + hash);
> >  	head = __find_stripe(conf, head_sector, conf->generation);
> > -	if (head && !atomic_inc_not_zero(&head->count)) {
> > -		spin_lock(&conf->device_lock);
> > -		if (!atomic_read(&head->count)) {
> > -			if (!test_bit(STRIPE_HANDLE, &head->state))
> > -				atomic_inc(&conf->active_stripes);
> > -			BUG_ON(list_empty(&head->lru) &&
> > -			       !test_bit(STRIPE_EXPANDING, &head->state));
> > -			list_del_init(&head->lru);
> > -			if (head->group) {
> > -				head->group->stripes_cnt--;
> > -				head->group = NULL;
> > -			}
> > -		}
> > -		atomic_inc(&head->count);
> > -		spin_unlock(&conf->device_lock);
> > -	}
> >  	spin_unlock_irq(conf->hash_locks + hash);
> >  
> >  	if (!head)
> 


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