Re: [PATCH] blk-mq: don't fail driver tag allocation because of inactive hctx

[John Garry <john.garry@huawei.com>]

On 05/06/2020 01:59, Ming Lei wrote:
>> 	hctx5: default 36 37 38 39
>> 	hctx6: default 40 41 42 43
>> 	hctx7: default 44 45 46 47
>> 	hctx8: default 48 49 50 51
>> 	hctx9: default 52 53 54 55
>> 	hctx10: default 56 57 58 59
>> 	hctx11: default 60 61 62 63
>> 	hctx12: default 0 1 2 3
>> 	hctx13: default 4 5 6 7
>> 	hctx14: default 8 9 10 11
>> 	hctx15: default 12 13 14 15
> OK, the queue mapping is correct.
> 
> As I mentioned in another thread, the real hw tag may be set as wrong.
> 

I doubt this.

And I think that you should also be able to add the same debug to 
blk_mq_hctx_notify_offline() to see that there may be still driver tags 
allocated to when all the scheduler tags are free'd for any test in your 
env.

> You have to double check your cooked tag allocation algorithm and see if it
> can work well when more requests than real hw queue depth are queued to hisi_sas,
> and the correct way is to return SCSI_MLQUEUE_HOST_BUSY from .queuecommand().

Yeah, the LLDD would just reject requests in that scenario and we would 
know about it from logs etc.

Anyway, I'll continue to check.

Thanks,
John