On 11/09/2017 06:44 PM, Christoph Hellwig wrote: > This patch adds native multipath support to the nvme driver. For each > namespace we create only single block device node, which can be used > to access that namespace through any of the controllers that refer to it. > The gendisk for each controllers path to the name space still exists > inside the kernel, but is hidden from userspace. The character device > nodes are still available on a per-controller basis. A new link from > the sysfs directory for the subsystem allows to find all controllers > for a given subsystem. > > 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 > 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. > > Signed-off-by: Christoph Hellwig <hch@xxxxxx> > --- > drivers/nvme/host/Kconfig | 9 ++ > drivers/nvme/host/Makefile | 1 + > drivers/nvme/host/core.c | 133 +++++++++++++++++++--- > drivers/nvme/host/multipath.c | 255 ++++++++++++++++++++++++++++++++++++++++++ > drivers/nvme/host/nvme.h | 57 ++++++++++ > 5 files changed, 440 insertions(+), 15 deletions(-) > create mode 100644 drivers/nvme/host/multipath.c > After much discussion I'm finally fine with this. Reviewed-by: Hannes Reinecke <hare@xxxxxxxx> Cheers, Hannes -- Dr. Hannes Reinecke Teamlead Storage & Networking hare@xxxxxxx +49 911 74053 688 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton HRB 21284 (AG Nürnberg)
