On 4/30/25 06:35, Ming Lei wrote:
scheduler's ->exit() is called with queue frozen and elevator lock is held, and
wbt_enable_default() can't be called with queue frozen, otherwise the
following lockdep warning is triggered:
#6 (&q->rq_qos_mutex){+.+.}-{4:4}:
#5 (&eq->sysfs_lock){+.+.}-{4:4}:
#4 (&q->elevator_lock){+.+.}-{4:4}:
#3 (&q->q_usage_counter(io)#3){++++}-{0:0}:
#2 (fs_reclaim){+.+.}-{0:0}:
#1 (&sb->s_type->i_mutex_key#3){+.+.}-{4:4}:
#0 (&q->debugfs_mutex){+.+.}-{4:4}:
Fix the issue by moving wbt_enable_default() out of bfq's exit(), and
call it from elevator_change_done().
Meantime add disk->rqos_state_mutex for covering wbt state change, which
matches the purpose more than ->elevator_lock.
Reviewed-by: Nilay Shroff <nilay@xxxxxxxxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
block/bfq-iosched.c | 2 +-
block/blk-sysfs.c | 10 ++++------
block/blk-wbt.c | 6 ++++++
block/elevator.c | 5 +++++
block/elevator.h | 1 +
block/genhd.c | 1 +
include/linux/blkdev.h | 2 ++
7 files changed, 20 insertions(+), 7 deletions(-)
Reviewed-by: Hannes Reinecke <hare@xxxxxxx>
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@xxxxxxx +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
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