diff options
authorTejun Heo <tj@kernel.org>2011-03-02 13:48:06 (GMT)
committerJens Axboe <jaxboe@fusionio.com>2011-03-02 13:48:06 (GMT)
commit255bb490c8c27eed484d538efe6ef6a7473bd3f6 (patch)
parent1654e7411a1ad4999fe7890ef51d2a2bbb1fcf76 (diff)
block: blk-flush shouldn't call directly into q->request_fn() __blk_run_queue()
blk-flush decomposes a flush into sequence of multiple requests. On completion of a request, the next one is queued; however, block layer must not implicitly call into q->request_fn() directly from completion path. This makes the queue behave unexpectedly when seen from the drivers and violates the assumption that q->request_fn() is called with process context + queue_lock. This patch makes blk-flush the following two changes to make sure q->request_fn() is not called directly from request completion path. - blk_flush_complete_seq_end_io() now asks __blk_run_queue() to always use kblockd instead of calling directly into q->request_fn(). - queue_next_fseq() uses ELEVATOR_INSERT_REQUEUE instead of ELEVATOR_INSERT_FRONT so that elv_insert() doesn't try to unplug the request queue directly. Reported by Jan in the following threads. http://thread.gmane.org/gmane.linux.ide/48778 http://thread.gmane.org/gmane.linux.ide/48786 stable: applicable to v2.6.37. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Jan Beulich <JBeulich@novell.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: stable@kernel.org Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
1 files changed, 5 insertions, 3 deletions
diff --git a/block/blk-flush.c b/block/blk-flush.c
index 56adaa8..b27d020 100644
--- a/block/blk-flush.c
+++ b/block/blk-flush.c
@@ -66,10 +66,12 @@ static void blk_flush_complete_seq_end_io(struct request_queue *q,
* Moving a request silently to empty queue_head may stall the
- * queue. Kick the queue in those cases.
+ * queue. Kick the queue in those cases. This function is called
+ * from request completion path and calling directly into
+ * request_fn may confuse the driver. Always use kblockd.
if (was_empty && next_rq)
- __blk_run_queue(q, false);
+ __blk_run_queue(q, true);
static void pre_flush_end_io(struct request *rq, int error)
@@ -130,7 +132,7 @@ static struct request *queue_next_fseq(struct request_queue *q)
- elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
+ elv_insert(q, rq, ELEVATOR_INSERT_REQUEUE);
return rq;

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