ide-scsi problems with multiple CD-Rs on same channel (2.2.14)

[Gadi Oxman]

On Wed, 26 Jan 2000, Tkil wrote:

> >>>>> "Gadi" == Gadi Oxman <gadio en netvision.net.il> writes:
> 
> Gadi> I'd recommend changing choose_drive() in drivers/block/ide.c
> Gadi> as follows -- replacing the "drive = hwgroup->drive;" line with
> Gadi> "drive = hwgroup->drive->next;" line, and commenting out the
> Gadi> part later which tests the best->nice1 flag (the second part
> Gadi> of the patch can alternatively be done by using "echo nice1:0 >
> Gadi> /proc/ide/hdx/settings for each IDE drive).
> 
> Gadi> This will select round-robin scheduling between the drives. This
> Gadi> is usually not the best for throughput, but might be more
> Gadi> appropriate when real-time constrains are involved.
> 
> Well, a few issues:
> 
> 1. Switching to hwgroup->drive->next causes serious problems at boot.
>    The four IDE devices are detected, but it stops at the "partition
>    check" for hda.
> 
>    So I reverted this portion of the patch.  It might still be usable,
>    but I suspect that we would need to fix the termination condition
>    there too.

Sorry, my bad (the end of the while block also has to check for
hwgroup->drive->next). Here is a corrected patch (against stock kernel).

Cheers,

Gadi

--- ide.c~	Wed Nov 17 08:15:22 1999
+++ ide.c	Thu Jan 27 02:14:55 2000
@@ -1079,19 +1079,20 @@
 
 repeat:	
 	best = NULL;
-	drive = hwgroup->drive;
+	drive = hwgroup->drive->next;
 	do {
 		if (drive->queue && (!drive->sleep || 0 <= (signed long)(jiffies - drive->sleep))) {
 			if (!best
 			 || (drive->sleep && (!best->sleep || 0 < (signed long)(best->sleep - drive->sleep)))
-			 || (!best->sleep && 0 < (signed long)(WAKEUP(best) - WAKEUP(drive))))
+			 || 0 /* (!best->sleep && 0 < (signed long)(WAKEUP(best) - WAKEUP(drive)))*/ )
 			{
 				struct blk_dev_struct *bdev = &blk_dev[HWIF(drive)->major];
 				if (bdev->current_request != &bdev->plug)
 					best = drive;
 			}
 		}
-	} while ((drive = drive->next) != hwgroup->drive);
+	} while ((drive = drive->next) != hwgroup->drive->next);
+#if 0
 	if (best && best->nice1 && !best->sleep && best != hwgroup->drive && best->service_time > WAIT_MIN_SLEEP) {
 		long t = (signed long)(WAKEUP(best) - jiffies);
 		if (t >= WAIT_MIN_SLEEP) {
@@ -1111,6 +1112,7 @@
 			} while ((drive = drive->next) != best);
 		}
 	}
+#endif
 	return best;
 }
 


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