Re: [RFC V5 01/16] blk: make the whole blk_mq_submit_bio under q_usage_counter

[Christoph Hellwig]

On Thu, Feb 24, 2022 at 05:06:39PM +0800, Wang Jianchao (Kuaishou) wrote:
> This is to protect the rqos list against the rqos open/close. We
> need to drain all of the caller of blk_mq_submit_bio() before
> we can operate the rqos list.

This means ever I/O now has to d an extra refcount roundtrip.