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Subject[PATCH 4.18 133/228] block: fix deadline elevator drain for zoned block devices
4.18-stable review patch.  If anyone has any objections, please let me know.


From: Damien Le Moal <>

commit 854f31ccdd7964c9c2e68da234a3a8aedb51cf6b upstream.

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

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

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 <>
Fixes: 8dc8146f9c92 ("deadline-iosched: Introduce zone locking support")
Signed-off-by: Jens Axboe <>
Signed-off-by: Greg Kroah-Hartman <>

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

--- a/block/elevator.c
+++ b/block/elevator.c
@@ -609,7 +609,7 @@ void elv_drain_elevator(struct request_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);

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