Re: [PATCH] nvme-core: fix io interrupt when work with dm-multipah

From: Chao Leng <lengchao@huawei.com>
To: Christoph Hellwig <hch@lst.de>
Cc: kbusch@kernel.org, axboe@fb.com, sagi@grimberg.me,
	linux-nvme@lists.infradead.org
Subject: Re: [PATCH] nvme-core: fix io interrupt when work with dm-multipah
Date: Wed, 29 Jul 2020 10:54:29 +0800	[thread overview]
Message-ID: <6df01884-5498-0809-b358-0c9f7d775a73@huawei.com> (raw)
In-Reply-To: <20200728111956.GA31546@lst.de>



On 2020/7/28 19:19, Christoph Hellwig wrote:
> On Mon, Jul 27, 2020 at 01:58:18PM +0800, Chao Leng wrote:
>> The protocol NVM-Express-1.4 define:
>> Command Interrupted: Command processing was interrupted and the
>> controller is unable to successfully complete the command. The host
>> should retry the command. If this status code is returned, then
>> the controller shall clear the Do Not Retry bit to ‘0’ in the Status
>> field of the CQE (refer to Figure 124). The controller shall not return
>> this status code unless the host has set the Advanced Command Retry
>> Enable (ACRE) field to 1h in the Host Behavior Support feature(refer to
>> section 5.21.1.22).
>>
>> According the protocol define, NVME_SC_CMD_INTERRUPTED need retry.
>> The error code NVME_SC_CMD_INTERRUPTED should not translate to
>> BLK_STS_TARGET, because if the error code translate to BLK_STS_TARGET,
>> dm-multipah will return error to application. So if target return error
>> code NVME_SC_CMD_INTERRUPTED, io will interrupt. NVME_SC_CMD_INTERRUPTED
>> should translate to BLK_STS_IOERR by default, dm-multipath will fail
>> over to other path retry the io.
> 
> IOERR still seems wrong, though.
> .

BLK_STS_TARGET means target has critical error. NVME_SC_CMD_INTERRUPTED
just means target need retry io. It is not suitable to translate
NVME_SC_CMD_INTERRUPTED to BLK_STS_TARGET. Maybe translate to
BLK_STS_IOERR is also not suitable, we should translate
NVME_SC_CMD_INTERRUPTED to BLK_STS_AGAIN.
We can do like this:
---
  drivers/nvme/host/core.c | 3 ++-
  1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index c2c5bc4fb702..359ce471df1d 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -211,7 +211,6 @@ static blk_status_t nvme_error_status(u16 status)
  	case NVME_SC_CAP_EXCEEDED:
  		return BLK_STS_NOSPC;
  	case NVME_SC_LBA_RANGE:
-	case NVME_SC_CMD_INTERRUPTED:
  	case NVME_SC_NS_NOT_READY:
  		return BLK_STS_TARGET;
  	case NVME_SC_BAD_ATTRIBUTES:
@@ -236,6 +235,8 @@ static blk_status_t nvme_error_status(u16 status)
  		return BLK_STS_NEXUS;
  	case NVME_SC_HOST_PATH_ERROR:
  		return BLK_STS_TRANSPORT;
+	case NVME_SC_CMD_INTERRUPTED:
+		return BLK_STS_AGAIN;
  	default:
  		return BLK_STS_IOERR;
  	}
-- 
2.16.4

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