[PATCH 2/2] Block: use round_jiffies_up()

[PATCH 2/2] Block: use round_jiffies_up()

[Alan Stern]

This patch (as1159) changes the timeout routines in the block core to
use round_jiffies_up().  There's no point in rounding the timer
deadline down, since if it expires too early we will have to restart
it.

The patch also removes a redundant test of q->rq_timed_out_fn, and it
sets req->deadline back to 0 when req is removed from the timer list
(to indicate the req is no longer being timed).

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>

---

Index: usb-2.6/block/blk-timeout.c
===================================================================
--- usb-2.6.orig/block/blk-timeout.c
+++ usb-2.6/block/blk-timeout.c
@@ -78,13 +78,14 @@ void blk_delete_timer(struct request *re
 	/*
 	 * Nothing to detach
 	 */
-	if (!q->rq_timed_out_fn || !req->deadline)
+	if (!req->deadline)
 		return;
 
 	list_del_init(&req->timeout_list);
 
 	if (list_empty(&q->timeout_list))
 		del_timer(&q->timeout);
+	req->deadline = 0;
 }
 
 static void blk_rq_timed_out(struct request *req)
@@ -142,7 +143,7 @@ void blk_rq_timed_out_timer(unsigned lon
 	}
 
 	if (next_set && !list_empty(&q->timeout_list))
-		mod_timer(&q->timeout, round_jiffies(next));
+		mod_timer(&q->timeout, round_jiffies_up(next));
 
 	spin_unlock_irqrestore(q->queue_lock, flags);
 }
@@ -201,7 +202,7 @@ void blk_add_timer(struct request *req)
 	 * than an existing one, modify the timer. Round to next nearest
 	 * second.
 	 */
-	expiry = round_jiffies(req->deadline);
+	expiry = round_jiffies_up(req->deadline);
 
 	/*
 	 * We use ->deadline == 0 to detect whether a timer was added or

Re: [PATCH 2/2] Block: use round_jiffies_up()

[Tejun Heo]

Hello,

Alan Stern wrote:
> @@ -78,13 +78,14 @@ void blk_delete_timer(struct request *re
>  	/*
>  	 * Nothing to detach
>  	 */
> -	if (!q->rq_timed_out_fn || !req->deadline)
> +	if (!req->deadline)
>  		return;
>  
>  	list_del_init(&req->timeout_list);
>  
>  	if (list_empty(&q->timeout_list))
>  		del_timer(&q->timeout);
> +	req->deadline = 0;
>  }

Actually, this can just be

blk_delete_timer()
{
	list_del_init(&req->timeout_list);
	if (list_empty(&q->timeout_list))
		del_timer(&q->timeout);
}

and none of req->deadline trick is necessary.

Thanks.

-- 
tejun

Re: [PATCH 2/2] Block: use round_jiffies_up()

[Alan Stern]

On Wed, 5 Nov 2008, Tejun Heo wrote:

> Hello,
> 
> Alan Stern wrote:
> > @@ -78,13 +78,14 @@ void blk_delete_timer(struct request *re
> >  	/*
> >  	 * Nothing to detach
> >  	 */
> > -	if (!q->rq_timed_out_fn || !req->deadline)
> > +	if (!req->deadline)
> >  		return;
> >  
> >  	list_del_init(&req->timeout_list);
> >  
> >  	if (list_empty(&q->timeout_list))
> >  		del_timer(&q->timeout);
> > +	req->deadline = 0;
> >  }
> 
> Actually, this can just be
> 
> blk_delete_timer()
> {
> 	list_del_init(&req->timeout_list);
> 	if (list_empty(&q->timeout_list))
> 		del_timer(&q->timeout);
> }
> 
> and none of req->deadline trick is necessary.

True.  And if we do this, then there's no need to test and increment
req->deadline in blk_add_timer().

Alan Stern

Re: [PATCH 2/2] Block: use round_jiffies_up()

[Jens Axboe]

On Wed, Nov 05 2008, Alan Stern wrote:
> On Wed, 5 Nov 2008, Tejun Heo wrote:
> 
> > Hello,
> > 
> > Alan Stern wrote:
> > > @@ -78,13 +78,14 @@ void blk_delete_timer(struct request *re
> > >  	/*
> > >  	 * Nothing to detach
> > >  	 */
> > > -	if (!q->rq_timed_out_fn || !req->deadline)
> > > +	if (!req->deadline)
> > >  		return;
> > >  
> > >  	list_del_init(&req->timeout_list);
> > >  
> > >  	if (list_empty(&q->timeout_list))
> > >  		del_timer(&q->timeout);
> > > +	req->deadline = 0;
> > >  }
> > 
> > Actually, this can just be
> > 
> > blk_delete_timer()
> > {
> > 	list_del_init(&req->timeout_list);
> > 	if (list_empty(&q->timeout_list))
> > 		del_timer(&q->timeout);
> > }
> > 
> > and none of req->deadline trick is necessary.
> 
> True.  And if we do this, then there's no need to test and increment
> req->deadline in blk_add_timer().

It was an optimization for drivers that don't use block layer timers,
but we can get rid of it.

-- 
Jens Axboe

[PATCH 2/2 ver 2] Block: use round_jiffies_up()

[Alan Stern]

This patch (as1159b) changes the timeout routines in the block core to
use round_jiffies_up().  There's no point in rounding the timer
deadline down, since if it expires too early we will have to restart
it.

The patch also removes some unnecessary tests when a request is
removed from the queue's timer list.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>

---

Index: usb-2.6/block/blk-timeout.c
===================================================================
--- usb-2.6.orig/block/blk-timeout.c
+++ usb-2.6/block/blk-timeout.c
@@ -75,14 +75,7 @@ void blk_delete_timer(struct request *re
 {
 	struct request_queue *q = req->q;
 
-	/*
-	 * Nothing to detach
-	 */
-	if (!q->rq_timed_out_fn || !req->deadline)
-		return;
-
 	list_del_init(&req->timeout_list);
-
 	if (list_empty(&q->timeout_list))
 		del_timer(&q->timeout);
 }
@@ -142,7 +135,7 @@ void blk_rq_timed_out_timer(unsigned lon
 	}
 
 	if (next_set && !list_empty(&q->timeout_list))
-		mod_timer(&q->timeout, round_jiffies(next));
+		mod_timer(&q->timeout, round_jiffies_up(next));
 
 	spin_unlock_irqrestore(q->queue_lock, flags);
 }
@@ -198,17 +191,10 @@ void blk_add_timer(struct request *req)
 
 	/*
 	 * If the timer isn't already pending or this timeout is earlier
-	 * than an existing one, modify the timer. Round to next nearest
+	 * than an existing one, modify the timer. Round up to next nearest
 	 * second.
 	 */
-	expiry = round_jiffies(req->deadline);
-
-	/*
-	 * We use ->deadline == 0 to detect whether a timer was added or
-	 * not, so just increase to next jiffy for that specific case
-	 */
-	if (unlikely(!req->deadline))
-		req->deadline = 1;
+	expiry = round_jiffies_up(req->deadline);
 
 	if (!timer_pending(&q->timeout) ||
 	    time_before(expiry, q->timeout.expires))