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 <[email protected]> Signed-off-by: Ming Lei <[email protected]> --- 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
