nvme reservation commands during controller reset

[Engel, Amit]

In nvme,
cmd_flags is set with REQ_FAILFAST_DRIVER as part of nvme_alloc_request
while in scsi,
sd_pr_command is called with flags = 0

-----Original Message-----
From: Sagi Grimberg <sagi at grimberg.me> 
Sent: Tuesday, August 11, 2020 11:48 PM
To: Keith Busch; Engel, Amit
Cc: Christoph Hellwig; Anner, Ran; linux-nvme at lists.infradead.org
Subject: Re: nvme reservation commands during controller reset


[EXTERNAL EMAIL] 


>> We saw that in case of path error, nvme reservation cmds does not get error handling.
>> This is true via the blk layer as well as nvme-cli.
>>
>> We are working on implementing nvmeof stack and this current behavior 
>> is blocking our host from running nvme reservation cmds during path error.
> 
> What's blocking you from retrying this command in your host software?
> 
> If we truly want to provide a way to hide intermittent errors on 
> passthrough commands via automatic retry, it may be a little longer 
> before such an interface hits a released kernel.

I think we need to keep the passthru commands as they are, but reservations coming from the pr_ops maybe we can failover these in nvme_pr_command?

What is the semantics in scsi btw? Didn't see any failover functionality for pr_ops...