Re: [PATCH v2 00/13] libmultipath: a generic multipath lib for block drivers

[Mike Snitzer <snitzer@kernel.org>]

On Tue, Apr 28, 2026 at 11:10:52AM +0000, John Garry wrote:
> libmultipath: a generic multipath lib for block drivers
> 
> This series introduces libmultipath. It is essentially a refactoring of
> NVME multipath support, so we can have a common library to also support
> native SCSI multipath.
> 
> Much of the code is taken directly from the NVMe multipath code. However,
> NVMe specifics are removed. A template structure is provided so the driver
> may provide callbacks for driver specifics, like ANA support for NVMe.
> 
> Important new structures introduced include:
> 
> - mpath_head
> These contain much of the multipath-specific functionality from
> nvme_ns_head, including a pointer to the gendisk structure and
> a path SRCU-based array.
> 
> - mpath_device
> This is the per-path structure, and contains much the same
> multipath-specific functionality in nvme_ns
> 
> libmultipath provides functionality for path management, path selection,
> data path, and failover handling.
> 
> Since the NVMe driver has some code in the sysfs and ioctl handling
> which iterate all multipath NSes, functions like mpath_call_for_device()
> are added to do the same per-path iteration.

To get upstream this library needs an in-tree consumer. So at the end
of the series, it'd makes sense to include the NVMe and/or SCSI
changes that uses it.

Mike