elevator switch can be done just between register_disk() and
blk_register_queue(), then we can't change elevator during this period
because FLAG_REGISTERED isn't set at that time.
One typical use case is that elevator is changed via udev by the following
rule, and the KOBJ_ADD uevent is just emited at the end of register_disk()
and before running blk_register_queue().
ACTION=="add|change", SUBSYSTEM=="block" , KERNEL=="sda", RUN+="/bin/sh -c 'echo none > /sys/block/sda/queue/scheduler'"
This patch fixes the elevator switch failure issue.
Fixes: e9a823fb34a8b0(block: fix warning when I/O elevator is changed as request_queue is being removed)
Cc: David Jeffery <djeffery@xxxxxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
block/blk-sysfs.c | 7 ++++++-
block/elevator.c | 13 +++++++++----
2 files changed, 15 insertions(+), 5 deletions(-)
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index b8362c0df51d..480959c5b036 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -927,12 +927,17 @@ int blk_register_queue(struct gendisk *disk)
void blk_unregister_queue(struct gendisk *disk)
{
struct request_queue *q = disk->queue;
+ bool elv_registered;
if (WARN_ON(!q))
return;
mutex_lock(&q->sysfs_lock);
queue_flag_clear_unlocked(QUEUE_FLAG_REGISTERED, q);
+ if (q->request_fn || (q->mq_ops && q->elevator))
+ elv_registered = q->elevator->registered;
+ else
+ elv_registered = false;
mutex_unlock(&q->sysfs_lock);
wbt_exit(q);
@@ -941,7 +946,7 @@ void blk_unregister_queue(struct gendisk *disk)
if (q->mq_ops)
blk_mq_unregister_dev(disk_to_dev(disk), q);
- if (q->request_fn || (q->mq_ops && q->elevator))
+ if (elv_registered)
elv_unregister_queue(q);
kobject_uevent(&q->kobj, KOBJ_REMOVE);
diff --git a/block/elevator.c b/block/elevator.c
index 7ae50eb2732b..0e2a5140111f 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -852,6 +852,15 @@ int elv_register_queue(struct request_queue *q)
struct elevator_queue *e = q->elevator;
int error;
+ /*
+ * When queue isn't registerd to gendisk, the elevator queue
+ * will be added after it is registered to gendisk; When queue
+ * is being unregistered, not necessary to add elevator queue
+ * any more.
+ */
+ if (!test_bit(QUEUE_FLAG_REGISTERED, &q->queue_flags))
+ return 0;
+
error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched");
if (!error) {
struct elv_fs_entry *attr = e->type->elevator_attrs;
@@ -1055,10 +1064,6 @@ static int __elevator_change(struct request_queue *q, const char *name)
char elevator_name[ELV_NAME_MAX];
struct elevator_type *e;
- /* Make sure queue is not in the middle of being removed */
- if (!test_bit(QUEUE_FLAG_REGISTERED, &q->queue_flags))
- return -ENOENT;
-
/*
* Special case for mq, turn off scheduling
*/
--
2.9.5
