On 4/24/25 17:21, Ming Lei wrote:
Elevator switch code is another `nr_hw_queue` reader in non-fast-IO code
path, so it can't be done if updating `nr_hw_queues` is in-progress.
Take same approach with not allowing add/del disk when updating
nr_hw_queues is in-progress, by grabbing read lock of
set->update_nr_hwq_sema.
Take the nested variant for avoiding the following false positive
splat[1], and this way is correct because:
- the read lock in elv_iosched_store() is not overlapped with the read lock
in adding/deleting disk:
- kobject attribute is only available after the kobject is added and
before it is deleted
-> #4 (&q->q_usage_counter(queue){++++}-{0:0}:
-> #3 (&q->limits_lock){+.+.}-{4:4}:
-> #2 (&disk->open_mutex){+.+.}-{4:4}:
-> #1 (&set->update_nr_hwq_lock){.+.+}-{4:4}:
-> #0 (kn->active#103){++++}-{0:0}:
Link: https://lore.kernel.org/linux-block/aAWv3NPtNIKKvJZc@fedora/ [1]
Reported-by: Shinichiro Kawasaki <shinichiro.kawasaki@xxxxxxx>
Closes: https://lore.kernel.org/linux-block/mz4t4tlwiqjijw3zvqnjb7ovvvaegkqganegmmlc567tt5xj67@xal5ro544cnc/
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
block/elevator.c | 3 +++
1 file changed, 3 insertions(+)
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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