[PATCH 0/3] blk-mq/nvme-loop: use nvme-loop's lock class for addressing lockdep false positive warning

[Ming Lei]

On Thu, Nov 12, 2020 at 03:55:23PM +0800, Ming Lei wrote:
> Hi,
> 
> Qian reported there is hang during booting when shared host tagset is
> introduced on megaraid sas. Sumit reported the whole SCSI probe takes
> about ~45min in his test.
> 
> Turns out it is caused by nr_hw_queues increased, especially commit
> b3c6a5997541("block: Fix a lockdep complaint triggered by request queue flushing")
> adds synchronize_rcu() for each hctx's release handler.
> 
> Address the original lockdep false positive warning by simpler way, then
> long scsi probe can be avoided with lockdep enabled.
> 
> Ming Lei (3):
>   blk-mq: add new API of blk_mq_hctx_set_fq_lock_class
>   nvme-loop: use blk_mq_hctx_set_fq_lock_class to set loop's lock class
>   Revert "block: Fix a lockdep complaint triggered by request queue
>     flushing"
> 
>  block/blk-flush.c          | 30 +++++++++++++++++++++++++-----
>  block/blk.h                |  1 -
>  drivers/nvme/target/loop.c | 10 ++++++++++
>  include/linux/blk-mq.h     |  3 +++
>  4 files changed, 38 insertions(+), 6 deletions(-)
> 
> Cc: Qian Cai <cai at redhat.com>
> Cc: Sumit Saxena <sumit.saxena at broadcom.com>
> Cc: John Garry <john.garry at huawei.com>
> Cc: Kashyap Desai <kashyap.desai at broadcom.com>
> Cc: Bart Van Assche <bvanassche at acm.org>
> Cc: Hannes Reinecke <hare at suse.de>

Hello Jens,

Any chance to take a look? And this issue has been reported several
times in RH internal test.

Thanks,
Ming