[dm-devel] [PATCH] multipath-tools: check sysfs path state for NVMe/NVMf

[Christophe Varoqui]

Merged.
Thanks.

On Fri, Jul 28, 2017 at 8:54 AM, Guan Junxiong <guanjunxiong at huawei.com>
wrote:

> Hi Hannes,
>
> On 2017/7/28 14:12, Hannes Reinecke wrote:
> > On 07/28/2017 03:28 AM, Guan Junxiong wrote:
> >> The previous code of path_offline checking was only valid for SCSI
> >> device. It returned PATH_UP for other devices and throwed path check-
> >> ing to chekers. This patch supplements checking sysfs path state for
> >> NVMe/NVMf devices. For example, if NVMe/NVMf path is reconnectting or
> >> resetting, we return PATH_PENDING in order to skip current path check-
> >> ing and reschedule path checking in the next tick as soon as possible.
> >>
> >> Signed-off-by: Guan Junxiong <guanjunxiong at huawei.com>
> >> ---
> >>  libmultipath/discovery.c | 45 ++++++++++++++++++++++++++++++
> +++++----------
> >>  1 file changed, 35 insertions(+), 10 deletions(-)
> >>
> > Thanks for doing this.
> >
> >>
> > Patch looks good.
> >
> > Reviewed-by: Hannes Reinecke <hare at suse.com>
> >
> Nice to have any review. Thanks.
>
> > However, I do wonder if we really need a path checker for NVMf once we
> > have this. After all, the sysfs attribute reflects that KATO status,
> > which pretty much determines if we can send I/O _at all_.
> >
> > Cheers,
> >
> > Hannes
>
> IMO, I think Keep Alive feature is in controller granularity , _not_
> namespace
> granularity. A namespace can be detached ( or disabled with nvmetcli tools)
> from controller which has many namespaces attached, but the controller
> sysfs
> state attribute is still "live". Therefor, we do need further path checker
> after we know controller is live.
>
> Refer to the following quoted from NVMe Spec 1.3:
> "The Keep Alive feature is used by the host to determine that the
> controller
> is operational and by the controller to determine that the host is
> operational.
> The host and controller are operational when each is accessible and able to
> issue or execute commands."
>
>
> Regards
> Guan
>
>
> .
>
>
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