[PATCH 9/9] nvme: implement multipath access to nvme subsystems

[Johannes Thumshirn]

On Mon, Sep 18, 2017 at 04:14:53PM -0700, Christoph Hellwig wrote:
> This patch adds initial multipath support to the nvme driver.  For each
> namespace we create a new block device node, which can be used to access
> that namespace through any of the controllers that refer to it.
> 
> Currently we will always send I/O to the first available path, this will
> be changed once the NVMe Asynchronous Namespace Access (ANA) TP is
> ratified and implemented, at which point we will look at the ANA state
> for each namespace.  Another possibility that was prototyped is to
> use the path that is closes to the submitting NUMA code, which will be
> mostly interesting for PCI, but might also be useful for RDMA or FC
> transports in the future.  There is not plan to implement round robin
                                    no ^
> or I/O service time path selectors, as those are not scalable with
> the performance rates provided by NVMe.
> 
> The multipath device will go away once all paths to it disappear,
> any delay to keep it alive needs to be implemented at the controller
> level.

Sorry for the typo only mail, I'll be going around a real review soon but I
wanted to test the patchset in my nvme-rdma setup and just hit a panic in
ib_core with your branched merged into -rc1.

Byte,
	Johannes

-- 
Johannes Thumshirn                                          Storage
jthumshirn at suse.de                                +49 911 74053 689
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