On Thu, Nov 02 2017 at 2:30pm -0400, Christoph Hellwig <hch@xxxxxx> 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 > > diff --git a/drivers/nvme/host/Kconfig b/drivers/nvme/host/Kconfig > index 46d6cb1e03bd..45886800a1df 100644 > --- a/drivers/nvme/host/Kconfig > +++ b/drivers/nvme/host/Kconfig > @@ -13,6 +13,15 @@ config BLK_DEV_NVME > To compile this driver as a module, choose M here: the > module will be called nvme. > > +config NVME_MULTIPATH > + bool "NVMe multipath support" > + depends on NVME_CORE > + ---help--- > + This option enables support for multipath access to NVMe > + subsystems. If this option is enabled only a single > + /dev/nvneXnY device will show up for each NVMe namespaces, > + even if it is accessible through multiple controllers. > + > config NVME_FABRICS > tristate > Thanks for adding this, appreciate it.
