path: root/block
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authorDamien Le Moal <damien.lemoal@wdc.com>2019-09-05 18:51:33 +0900
committerJens Axboe <axboe@kernel.dk>2019-09-05 19:52:34 -0600
commit737eb78e82d52d35df166d29af32bf61992de71d (patch)
tree88571fe3b3a82b62192a895d1e81b71af99bfa74 /block
parenta0958ba7fcdc316e3900f8d2afda519850d60985 (diff)
block: Delay default elevator initialization
When elevator_init_mq() is called from blk_mq_init_allocated_queue(), the only information known about the device is the number of hardware queues as the block device scan by the device driver is not completed yet for most drivers. The device type and elevator required features are not set yet, preventing to correctly select the default elevator most suitable for the device. This currently affects all multi-queue zoned block devices which default to the "none" elevator instead of the required "mq-deadline" elevator. These drives currently include host-managed SMR disks connected to a smartpqi HBA and null_blk block devices with zoned mode enabled. Upcoming NVMe Zoned Namespace devices will also be affected. Fix this by adding the boolean elevator_init argument to blk_mq_init_allocated_queue() to control the execution of elevator_init_mq(). Two cases exist: 1) elevator_init = false is used for calls to blk_mq_init_allocated_queue() within blk_mq_init_queue(). In this case, a call to elevator_init_mq() is added to __device_add_disk(), resulting in the delayed initialization of the queue elevator after the device driver finished probing the device information. This effectively allows elevator_init_mq() access to more information about the device. 2) elevator_init = true preserves the current behavior of initializing the elevator directly from blk_mq_init_allocated_queue(). This case is used for the special request based DM devices where the device gendisk is created before the queue initialization and device information (e.g. queue limits) is already known when the queue initialization is executed. Additionally, to make sure that the elevator initialization is never done while requests are in-flight (there should be none when the device driver calls device_add_disk()), freeze and quiesce the device request queue before calling blk_mq_init_sched() in elevator_init_mq(). Reviewed-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block')
3 files changed, 25 insertions, 3 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c
index d10a7ab4207a..3647776a0f6e 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2695,7 +2695,11 @@ struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set)
if (!uninit_q)
return ERR_PTR(-ENOMEM);
- q = blk_mq_init_allocated_queue(set, uninit_q);
+ /*
+ * Initialize the queue without an elevator. device_add_disk() will do
+ * the initialization.
+ */
+ q = blk_mq_init_allocated_queue(set, uninit_q, false);
if (IS_ERR(q))
@@ -2846,7 +2850,8 @@ static unsigned int nr_hw_queues(struct blk_mq_tag_set *set)
struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
- struct request_queue *q)
+ struct request_queue *q,
+ bool elevator_init)
/* mark the queue as mq asap */
q->mq_ops = set->ops;
@@ -2908,7 +2913,8 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
blk_mq_add_queue_tag_set(set, q);
- elevator_init_mq(q);
+ if (elevator_init)
+ elevator_init_mq(q);
return q;
diff --git a/block/elevator.c b/block/elevator.c
index 520d6b224b74..096a670d22d7 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -712,7 +712,14 @@ void elevator_init_mq(struct request_queue *q)
if (!e)
+ blk_mq_freeze_queue(q);
+ blk_mq_quiesce_queue(q);
err = blk_mq_init_sched(q, e);
+ blk_mq_unquiesce_queue(q);
+ blk_mq_unfreeze_queue(q);
if (err) {
pr_warn("\"%s\" elevator initialization failed, "
"falling back to \"none\"\n", e->elevator_name);
diff --git a/block/genhd.c b/block/genhd.c
index 54f1f0d381f4..26b31fcae217 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -695,6 +695,15 @@ static void __device_add_disk(struct device *parent, struct gendisk *disk,
dev_t devt;
int retval;
+ /*
+ * The disk queue should now be all set with enough information about
+ * the device for the elevator code to pick an adequate default
+ * elevator if one is needed, that is, for devices requesting queue
+ * registration.
+ */
+ if (register_queue)
+ elevator_init_mq(disk->queue);
/* minors == 0 indicates to use ext devt from part0 and should
* be accompanied with EXT_DEVT flag. Make sure all
* parameters make sense.

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