On 11/10/21 10:14 AM, Christoph Hellwig wrote:

Hi Jens and Ming,

I've been looking into properly supporting queue freezing for bio based
drivers (that is only release q_usage_counter on bio completion for them).
And the deeper I look into the code the more I'm confused by us having
the blk_mq_quiesce* interface in addition to blk_freeze_queue.  What
is a good reason to do a quiesce separately from a freeze?

IIRC the 'quiesce' interface was an abstraction from the SCSI 'quiesce'
operation, where we had to stop all I/O except for TMFs and scanning.
And 'freeze' was designed fro stopping all I/O.

But I'm not sure if that ever was the distinction, or if it still
applies today.

And yeah, I've been wondering myself.

Probably we should just kill the 'quiesce' stuff and see where we end up :-)

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		           Kernel Storage Architect
hare@suse.de			                  +49 911 74053 688
SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), GF: Felix Imendörffer