A dm-multipath user reported[1] a problem when trying to boot
a kernel with commit 4853abaae7
(block: fix flush machinery for stacking drivers with differring
flush flags) applied. It turns out that an empty flush request
can be sent into blk_insert_flush. When the BUG_ON was fixed
to allow for this, I/O on the underlying device would stall. The
reason is that blk_insert_cloned_request does not kick the queue.
In the aforementioned commit, I had added a special case to
kick the queue if data was sent down but the queue flags did
not require a flush. A better solution is to push the queue
kick up into blk_insert_cloned_request.
This patch, along with a follow-on which fixes the BUG_ON, fixes
the issue reported.
[1] http://www.redhat.com/archives/dm-devel/2011-September/msg00154.html
Reported-by: Christophe Saout <christophe@saout.de>
Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
Stable note: 3.1
Cc: stable@vger.kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
e67b77c791