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block: don't allow to switch elevator if updating nr_hw_queues is in-progress 

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.

Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/linux-block/aAWv3NPtNIKKvJZc@fedora/ [1]
Reported-by: Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Closes: https://lore.kernel.org/linux-block/mz4t4tlwiqjijw3zvqnjb7ovvvaegkqganegmmlc567tt5xj67@xal5ro544cnc/
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20250505141805.2751237-10-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Ming Lei 2025-05-05 22:17:47 +08:00 committed by Jens Axboe
parent 98e68f6702
commit b126d9d747
1 changed files with 3 additions and 0 deletions
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3
block/elevator.c
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@ -723,6 +723,7 @@ ssize_t elv_iosched_store(struct gendisk *disk, const char *buf,
int ret;
unsigned int memflags;
struct request_queue *q = disk->queue;
struct blk_mq_tag_set *set = q->tag_set;
/*
* If the attribute needs to load a module, do it before freezing the
@ -734,6 +735,7 @@ ssize_t elv_iosched_store(struct gendisk *disk, const char *buf,
elv_iosched_load_module(name);
down_read(&set->update_nr_hwq_lock);
memflags = blk_mq_freeze_queue(q);
mutex_lock(&q->elevator_lock);
ret = elevator_change(q, name);
@ -741,6 +743,7 @@ ssize_t elv_iosched_store(struct gendisk *disk, const char *buf,
ret = count;
mutex_unlock(&q->elevator_lock);
blk_mq_unfreeze_queue(q, memflags);
up_read(&set->update_nr_hwq_lock);
return ret;
}