Re: [PATCH] nvme: Add support for ACRE Command Interrupted status

From: Hannes Reinecke <hare@suse.de>
To: Keith Busch <kbusch@kernel.org>
Cc: Jen Axboe <axboe@kernel.dk>, Sagi Grimberg <sagi@grimberg.me>,
	linux-nvme@lists.infradead.org, linux-block@vger.kernel.org,
	Christoph Hellwig <hch@lst.de>, John Meneghini <johnm@netapp.com>
Subject: Re: [PATCH] nvme: Add support for ACRE Command Interrupted status
Date: Tue, 26 Nov 2019 17:32:32 +0100	[thread overview]
Message-ID: <90bb47cc-8a4b-1ddb-be6c-d237bfbe88f8@suse.de> (raw)
In-Reply-To: <20191126160546.GA2906@redsun51.ssa.fujisawa.hgst.com>

On 11/26/19 5:05 PM, Keith Busch wrote:
> [cc'ing linux-block, Jens]
> 
> On Tue, Nov 26, 2019 at 02:36:50PM +0100, Hannes Reinecke wrote:
>> This patch fixes a bug in nvme_complete_rq logic introduced by
>> Enhanced Command Retry code. According to TP-4033 the controller
>> only sets CDR when the Command Interrupted status is returned.
>> The current code interprets Command Interrupted status as a
>> BLK_STS_IOERR, which results in a controller reset if
>> REQ_NVME_MPATH is set.
> 
> I see that Command Interrupted status requires ACRE enabled, but I don't
> see the TP saying that the CQE CRD fields are used only with that status
> code. I'm pretty sure I've seen it used for Namespace Not Ready status
> as well. That would also fail MPATH for the same reason as this new
> status...
> 
No, true, CRD is not directly related to 'command interrupted'.
According to the powers that be CRD evaluation is depending on the ACRE 
setting (and hence should be evaluated whenever a command needs to be 
retried), but 'command interrupted' will only be returned if ACRE is 
enabled.
Consequently, whenever you get a 'command interrupted' you need to check 
the CRD setting to figure out the delay.

>> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
>> index 108f60b46804..752a40daf2b3 100644
>> --- a/drivers/nvme/host/core.c
>> +++ b/drivers/nvme/host/core.c
>> @@ -201,6 +201,8 @@ static blk_status_t nvme_error_status(u16 status)
>>   	switch (status & 0x7ff) {
>>   	case NVME_SC_SUCCESS:
>>   		return BLK_STS_OK;
>> +	case NVME_SC_COMMAND_INTERRUPTED:
>> +		return BLK_STS_RESOURCE;
>>   	case NVME_SC_CAP_EXCEEDED:
>>   		return BLK_STS_NOSPC;
>>   	case NVME_SC_LBA_RANGE:
>> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
>> index d688b96d1d63..3a0d84528325 100644
>> --- a/include/linux/blk_types.h
>> +++ b/include/linux/blk_types.h
>> @@ -84,6 +84,7 @@ static inline bool blk_path_error(blk_status_t error)
>>   	case BLK_STS_NEXUS:
>>   	case BLK_STS_MEDIUM:
>>   	case BLK_STS_PROTECTION:
>> +	case BLK_STS_RESOURCE:
>>   		return false;
>>   	}
> 
> I agree we need to make this status a non-path error, but we at least
> need an Ack from Jens or have this patch go through linux-block if we're
> changing BLK_STS_RESOURCE to mean a non-path error.
> 
Alternatively we can define a new return value, if we shouldn't re-use 
existing ones. Either way I'm fine with.

>> diff --git a/include/linux/nvme.h b/include/linux/nvme.h
>> index f61d6906e59d..6b21f3888cad 100644
>> --- a/include/linux/nvme.h
>> +++ b/include/linux/nvme.h
>> @@ -1292,6 +1292,8 @@ enum {
>>   
>>   	NVME_SC_NS_WRITE_PROTECTED	= 0x20,
>>   
>> +	NVME_SC_COMMAND_INTERRUPTED	= 0x21,
> 
> This command status was actually already defined in commit
> 48c9e85b23464, though with a slightly different name.
> 
Ah. Will be modifying the patch then.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke            Teamlead Storage & Networking
hare@suse.de                              +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Felix Imendörffer, Mary Higgins, Sri Rasiah
HRB 21284 (AG Nürnberg)

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