On 7/1/25 10:19, Nilay Shroff wrote:
Move scheduler tags (sched_tags) allocation and deallocation outside both the ->elevator_lock and ->freeze_lock when updating nr_hw_queues. This change breaks the dependency chain from the percpu allocator lock to the elevator lock, helping to prevent potential deadlocks, as observed in the reported lockdep splat[1]. This commit introduces batch allocation and deallocation helpers for sched_tags, which are now used from within __blk_mq_update_nr_hw_queues routine while iterating through the tagset. With this change, all sched_tags memory management is handled entirely outside the ->elevator_lock and the ->freeze_lock context, thereby eliminating the lock dependency that could otherwise manifest during nr_hw_queues updates. [1] https://lore.kernel.org/all/0659ea8d-a463-47c8-9180-43c719e106eb@xxxxxxxxxxxxx/ Reported-by: Stefan Haberland <sth@xxxxxxxxxxxxx> Closes: https://lore.kernel.org/all/0659ea8d-a463-47c8-9180-43c719e106eb@xxxxxxxxxxxxx/ Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx> Reviewed-by: Christoph Hellwig <hch@xxxxxx> Signed-off-by: Nilay Shroff <nilay@xxxxxxxxxxxxx> --- block/blk-mq-sched.c | 65 ++++++++++++++++++++++++++++++++++++++++++++ block/blk-mq-sched.h | 4 +++ block/blk-mq.c | 16 +++++++++-- block/blk.h | 3 +- block/elevator.c | 6 ++-- 5 files changed, 88 insertions(+), 6 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 HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich
