On Wed, Nov 27, 2024 at 05:17:08PM +0900, Damien Le Moal wrote: > After all these fixes, the last remaining problem is the zone write > plug error recovery issuing a report zone which can block if a queue > freeze was initiated. > > That can prevent forward progress and hang the freeze caller. I do not > see any way to avoid that report zones. I think this could be fixed with > a magic BLK_MQ_REQ_INTERNAL flag passed to blk_mq_alloc_request() and > propagated to blk_queue_enter() to forcefully take a queue usage counter > reference even if a queue freeze was started. That would ensure forward > progress (i.e. scsi_execute_cmd() or the NVMe equivalent would not block > forever). Need to think more about that. You are talking about disk_zone_wplug_handle_error here, right? We should not issue a report zones to a frozen queue, as that would bypass the freezing protection. I suspect the right thing is to simply defer the error recovery action until after the queue is unfrozen. I wonder if the separate error work handler should go away, instead blk_zone_wplug_bio_work should always check for an error first and in that case do the report zones. And blk_zone_wplug_handle_write would always defer to the work queue if there was an error.
