Re: [PATCH] nvmet: handle rw's limited retry flag

[Guixin Liu <kanie@linux.alibaba.com>]

在 2024/11/22 20:09, Christoph Hellwig 写道:
> On Thu, Nov 21, 2024 at 06:24:54PM +0800, Guixin Liu wrote:
>> When the nvme target receive an rw command with limited retry flag,
>> handle it in block backend by setting the REQ_FAILFAST_DEV flag to
>> bio.
> Do you have a use case where this makes a difference?
>
> The code itself looks fine, but I doubt it's actually useful.

In our scenario, our multipath setup places the REQ_FAILFAST_DEV flag on 
I/O to prevent

retries and immediately switch to other paths for issuing I/O commands. 
This will reflect

on the NVMe read and write commands with the limited retry flag. 
However, the current

NVMe target side does not handle the limited retry flag, and the 
target's underlying

driver still retries the I/O. I believe this will result in the I/O not 
being quickly

switched to other paths, ultimately leading to increased I/O latency.

Best Regards,

Guixin Liu