When the deadline scheduler is used with a zoned block device, writes to a zone will be dispatched one at a time. This causes the warning message:

deadline: forced dispatching is broken (nr_sorted=X), please report this

to be displayed when switching to another elevator with the legacy I/O path while write requests to a zone are being retained in the scheduler queue.

Prevent this message from being displayed when executing elv_drain_elevator() for a zoned block device. __blk_drain_queue() will loop until all writes are dispatched and completed, resulting in the desired elevator queue drain without extensive modifications to the deadline code itself to handle forced-dispatch calls.

Signed-off-by: Damien Le Moal damien.lemoal@wdc.com Fixes: 8dc8146f9c92 ("deadline-iosched: Introduce zone locking support") Cc: stable@vger.kernel.org ---

Changes from v2: * Move zoned block device test before 'printed' increment as suggested by Bart * Added "Fixes" tag and cc stable

Changes from v1: * Fixed typo in commit message

block/elevator.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/elevator.c b/block/elevator.c index 6a06b5d040e5..fae58b2f906f 100644 --- a/block/elevator.c +++ b/block/elevator.c @@ -609,7 +609,7 @@ void elv_drain_elevator(struct request_queue *q)

while (e->type->ops.sq.elevator_dispatch_fn(q, 1)) ; - if (q->nr_sorted && printed++ < 10) { + if (q->nr_sorted && !blk_queue_is_zoned(q) && printed++ < 10 ) { printk(KERN_ERR "%s: forced dispatching is broken " "(nr_sorted=%u), please report this\n", q->elevator->type->elevator_name, q->nr_sorted);