block: internal dequeue shouldn't start timer

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>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 2 insertions, 5 deletions

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index a135256..9cc7cc5 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -786,6 +786,8 @@ static inline void blk_run_address_space(struct address_space *mapping)
 		blk_run_backing_dev(mapping->backing_dev_info, NULL);
 }
 
+extern void blkdev_dequeue_request(struct request *req);
+
 /*
  * blk_end_request() and friends.
  * __blk_end_request() and end_request() must be called with
@@ -820,11 +822,6 @@ extern void blk_update_request(struct request *rq, int error,
 extern unsigned int blk_rq_bytes(struct request *rq);
 extern unsigned int blk_rq_cur_bytes(struct request *rq);
 
-static inline void blkdev_dequeue_request(struct request *req)
-{
-	elv_dequeue_request(req->q, req);
-}
-
 /*
  * Access functions for manipulating queue properties
  */