For blk-mq disks with a single hardware queue, setting by default the
disk scheduler to mq-deadline early during the queue initialization
prevents properly setting zone write locking for zoned block device as
the fact that the disk is zoned is not yet known.
Fix this by simply not setting the default scheduler to mq-deadline for
single hardware queue disks. udev can be used to easily do the same
later in the system initialization sequence, when the device
characteristics are known.
Signed-off-by: Damien Le Moal <damien.lemoal@xxxxxxx>
---
block/elevator.c | 17 ++++++-----------
1 file changed, 6 insertions(+), 11 deletions(-)
diff --git a/block/elevator.c b/block/elevator.c
index 153926a90901..8b65a757f726 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -222,19 +222,14 @@ int elevator_init(struct request_queue *q, char *name)
if (!e) {
/*
- * For blk-mq devices, we default to using mq-deadline,
- * if available, for single queue devices. If deadline
- * isn't available OR we have multiple queues, default
- * to "none".
+ * For blk-mq devices, default to "none". udev can later set
+ * an appropriate default scheduler based on the disk
+ * characteristics which we do not yet have here.
*/
- if (q->mq_ops) {
- if (q->nr_hw_queues == 1)
- e = elevator_get("mq-deadline", false);
- if (!e)
- return 0;
- } else
- e = elevator_get(CONFIG_DEFAULT_IOSCHED, false);
+ if (q->mq_ops)
+ return 0;
+ e = elevator_get(CONFIG_DEFAULT_IOSCHED, false);
if (!e) {
printk(KERN_ERR
"Default I/O scheduler not found. " \
--
2.13.5
