[PATCH] ide-io.c, kernel 2.4.22 Fix for IO stats in /proc/partitions, was Re: sard/iostat disk I/O statistics/accounting for 2.5.8-pre3

[Chad Talbott <ctalbott@google.com>]

I found the cause of ide disks' ios_in_flight going negative in
/proc/partitions.

It's due to unbalanced calls to up_ios and down_ios.  After an
explicit drive command, ide-io.c's ide_end_drive_cmd calls
end_that_request_last which eventually calls down_ios to decrement
ios_in_flight, however there is no corresponding call to up_ios when
the command is initiated.

My guess is that ios_in_flight goes negative when the drive is idle
because many people run hdparm in an init script, and this decrements
ios_in_flight early on.  It stays off center from there.

The following hack to ide_end_drive_cmd is a workaround, I would
rather call up_ios appropriately, so that explicit ide commands are
properly accounted.  However I'm having a hard time identifying all
the places that initiate a low-level drive command.  I'll look into a
proper fix, but someone else probably knows the ide layer better than
me.

Chad

--- linux-2.4.18-old/drivers/ide/ide-io.c	15 Sep 2003 17:41:32 -0000
+++ linux-2.4.18-new/drivers/ide/ide-io.c	15 Sep 2003 20:11:12 -0000
@@ -148,6 +148,7 @@
 	ide_hwif_t *hwif = HWIF(drive);
 	unsigned long flags;
 	struct request *rq;
+	struct completion *waiting;
 
 	spin_lock_irqsave(&io_request_lock, flags);
 	rq = HWGROUP(drive)->rq;
@@ -221,7 +222,13 @@
 	spin_lock_irqsave(&io_request_lock, flags);
 	blkdev_dequeue_request(rq);
 	HWGROUP(drive)->rq = NULL;
-	end_that_request_last(rq);
+
+	waiting = req->waiting;
+	req_finished_io(req);
+	blkdev_release_request(req);
+	if (waiting)
+		complete(waiting);
+
 	spin_unlock_irqrestore(&io_request_lock, flags);
 }