[PATCH 1/3] block cleanups: Fix iosched module refcount leak

[PATCH 1/3] block cleanups: Fix iosched module refcount leak

[Nate Diller]

If the requested I/O scheduler is already in place, elevator_switch simply leaves the queue 
alone, and returns.  However, it forgets to call elevator_put, so

'echo [current_sched] > /sys/block/[dev]/queue/scheduler'

will leak a reference, causing the current_sched module to be permanently pinned in memory.

This patchset is against 2.6.14-rc2-mm1, but should apply to anything recent.

NATE

Signed-off-by: Nate Diller <nate@namesys.com>

--- a/drivers/block/elevator.c	2005-09-26 19:17:59.000000000 -0700
+++ b/drivers/block/elevator.c	2005-09-27 11:13:15.000000000 -0700
@@ -692,8 +692,10 @@ ssize_t elv_iosched_store(request_queue_
  		return -EINVAL;
  	}

-	if (!strcmp(elevator_name, q->elevator->elevator_type->elevator_name))
+	if (!strcmp(elevator_name, q->elevator->elevator_type->elevator_name)) {
+		elevator_put(e);
  		return count;
+	}

  	elevator_switch(q, e);
  	return count;

Re: [PATCH 1/3] block cleanups: Fix iosched module refcount leak

[Jens Axboe]

On Tue, Sep 27 2005, Nate Diller wrote:
> If the requested I/O scheduler is already in place, elevator_switch simply 
> leaves the queue alone, and returns.  However, it forgets to call 
> elevator_put, so
> 
> 'echo [current_sched] > /sys/block/[dev]/queue/scheduler'
> 
> will leak a reference, causing the current_sched module to be permanently 
> pinned in memory.
> 
> This patchset is against 2.6.14-rc2-mm1, but should apply to anything 
> recent.

Thanks, looks good.

Signed-off-by: Jens Axboe <axboe@suse.de>

-- 
Jens Axboe