[PATCHv7 RFC 1/3] nvme-multipath: Add visibility for round-robin io-policy

[Hannes Reinecke]

On 1/12/25 13:41, Nilay Shroff wrote:
> This patch helps add nvme native multipath visibility for round-robin
> io-policy. It creates a "multipath" sysfs directory under head gendisk
> device node directory and then from "multipath" directory it adds a link
> to each namespace path device the head node refers.
> 
> For instance, if we have a shared namespace accessible from two different
> controllers/paths then we create a soft link to each path device from head
> disk node as shown below:
> 
> $ ls -l /sys/block/nvme1n1/multipath/
> nvme1c1n1 -> ../../../../../pci052e:78/052e:78:00.0/nvme/nvme1/nvme1c1n1
> nvme1c3n1 -> ../../../../../pci058e:78/058e:78:00.0/nvme/nvme3/nvme1c3n1
> 
> In the above example, nvme1n1 is head gendisk node created for a shared
> namespace and the namespace is accessible from nvme1c1n1 and nvme1c3n1
> paths.
> 
> For round-robin I/O policy, we could easily infer from the above output
> that I/O workload targeted to nvme1n1 would toggle across paths nvme1c1n1
> and nvme1c3n1.
> 
> Signed-off-by: Nilay Shroff <nilay at linux.ibm.com>
> ---
>   drivers/nvme/host/core.c      |  3 ++
>   drivers/nvme/host/multipath.c | 99 +++++++++++++++++++++++++++++++++++
>   drivers/nvme/host/nvme.h      | 18 +++++--
>   drivers/nvme/host/sysfs.c     | 14 +++++
>   4 files changed, 130 insertions(+), 4 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare at suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
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