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Subject[PATCH linux-2.6.12-rc6-mm1] blk: elevator unplug thresh hanlding fix
 Hello, Jens.
Hello, Andrew.

This patch fixes q->unplug_thresh condition check in
__elv_add_request(). rq.count[READ] + rq.count[WRITE] can increase
more than one if another thread has allocated a request after the
current request is allocated or in_flight could have changed resulting
in larger-than-one change of nrq, thus breaking the threshold
mechanism.

Signed-off-by: Tejun Heo <htejun@gmail.com>

Index: blk-fixes/drivers/block/elevator.c
===================================================================
--- blk-fixes.orig/drivers/block/elevator.c 2005-06-16 12:16:59.000000000 +0900
+++ blk-fixes/drivers/block/elevator.c 2005-06-16 12:17:03.000000000 +0900
@@ -352,7 +352,7 @@ void __elv_add_request(request_queue_t *
int nrq = q->rq.count[READ] + q->rq.count[WRITE]
- q->in_flight;

- if (nrq == q->unplug_thresh)
+ if (nrq >= q->unplug_thresh)
__generic_unplug_device(q);
}
} else
-
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