nvme: export multipath failover count via sysfs

When an NVMe command completes with a path-specific error, the NVMe
driver may retry the command on an alternate controller or path if one
is available. These failover events indicate that I/O was redirected
away from the original path.

Currently, the number of times requests are failed over to another
available path is not visible to userspace. Exposing this information
can be useful for diagnosing path health and stability.

Export per-path sysfs attribute "multipath_failover_count" under diag
attribute group. This attribute is both readable and writable and thus
allowing user to reset the counter. This counter can be consumed by
monitoring tools such as nvme-top to help identify paths that
consistently trigger failovers under load.

Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>

0 files changed, 0 insertions, 0 deletions