nvme: allow ANA support to be independent of native multipathing
Whether or not ANA is present is a choice of the target implementation;
the host (and whether it supports multipathing) has _zero_ influence on
this. If the target declares a path as 'inaccessible' the path _is_
inaccessible to the host. As such, ANA support should be functional
even if native multipathing is not.
Introduce ability to always re-read ANA log page as required due to ANA
error and make current ANA state available via sysfs -- even if native
multipathing is disabled on the host (e.g. nvme_core.multipath=N).
This affords userspace access to the current ANA state independent of
which layer might be doing multipathing. It also allows multipath-tools
to rely on the NVMe driver for ANA support while dm-multipath takes care
of multipathing.
While implementing these changes care was taken to preserve the exact
ANA functionality and code sequence native multipathing has provided.
This manifests as native multipathing's nvme_failover_req() being
tweaked to call __nvme_update_ana() which was factored out to allow
nvme_update_ana() to be called independent of nvme_failover_req().
And as always, if embedded NVMe users do not want any performance
overhead associated with ANA or native NVMe multipathing they can
disable CONFIG_NVME_MULTIPATH.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
3 files changed
