I/O Errors due to keepalive timeouts with NVMf RDMA

[Johannes Thumshirn]

On Mon, Jul 10, 2017 at 11:46:47AM +0300, Max Gurtovoy wrote:
> >>- What kato is required to not stumble on this?

Tried up to 120 now, still broken.

> >Well, this sounds identically to the path_checker problem we're having
> >in multipathing (and hch complained about several times).
> >There's a rather easy solution to it: don't send keepalives if I/O is
> >running, but rather tack it on the most current I/O packet.
> >In the end, you only want to know if the link is alive; you don't have
> >to transfer any data as such.
> >So if you just add a flag (maybe on the RDMA layer) to the next command
> >to be sent you could easily simulate keepalive without having to send
> >additional commands.
> 
> Hannes,
> This is a good solution and actually the way we work in iSCSI/iSER with
> nopin/nopout.
> Don't you think it should be a ctrl attribute ?

Let me see if I can come up with something.

-- 
Johannes Thumshirn                                          Storage
jthumshirn at suse.de                                +49 911 74053 689
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Felix Imendörffer, Jane Smithard, Graham Norton
HRB 21284 (AG Nürnberg)
Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850