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 holding srcu lock & check set->updating_nr_hwq. 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 | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/block/elevator.c b/block/elevator.c index d25b9cc6c509..c23912652f96 100644 --- a/block/elevator.c +++ b/block/elevator.c @@ -720,9 +720,10 @@ ssize_t elv_iosched_store(struct gendisk *disk, const char *buf, { char elevator_name[ELV_NAME_MAX]; char *name; - int ret; + int ret, idx; 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 +735,12 @@ ssize_t elv_iosched_store(struct gendisk *disk, const char *buf, elv_iosched_load_module(name); + idx = srcu_read_lock(&set->update_nr_hwq_srcu); + if (set->updating_nr_hwq) { + ret = -EBUSY; + goto exit; + } + memflags = blk_mq_freeze_queue(q); mutex_lock(&q->elevator_lock); ret = elevator_change(q, name); @@ -741,6 +748,8 @@ ssize_t elv_iosched_store(struct gendisk *disk, const char *buf, ret = count; mutex_unlock(&q->elevator_lock); blk_mq_unfreeze_queue(q, memflags); +exit: + srcu_read_unlock(&set->update_nr_hwq_srcu, idx); return ret; } -- 2.47.0
