Re: [PATCH 2.6.28-rc6] block: internal dequeue shouldn't start timer

[Mike Anderson <andmike@linux.vnet.ibm.com>]

Tejun Heo <tj@kernel.org> wrote:
> blkdev_dequeue_request() and elv_dequeue_request() are equivalent and
> both start the timeout timer.  Barrier code dequeues the original
> barrier request but doesn't passes the request itself to lower level
> driver, only broken down proxy requests; however, as the original
> barrier code goes through the same dequeue path and timeout timer is
> started on it.  If barrier sequence takes long enough, this timer
> expires but the low level driver has no idea about this request and
> oops follows.
> 
> Timeout timer shouldn't have been started on the original barrier
> request as it never goes through actual IO.  This patch unexports
> elv_dequeue_request(), which has no external user anyway, and makes it
> operate on elevator proper w/o adding the timer and make
> blkdev_dequeue_request() call elv_dequeue_request() and add timer.
> Internal users which don't pass the request to driver - barrier code
> and end_that_request_last() - are converted to use
> elv_dequeue_request().
> 
> Signed-off-by: Tejun Heo <tj@kernel.org>
> Cc: Mike Anderson <andmike@linux.vnet.ibm.com>
> ---
> Mike, this should fix the problem you were seeing (blk_add_timer on
> requests w/o REQ_STARTED set).
> 

Yes this fixed the "w/o REQ_STARTED" error I was seeing on a distro kernel
and a mainline system. 

Thanks,

-andmike
--
Michael Anderson
andmike@linux.vnet.ibm.com