[PATCH] nvmet: fix nvme status code when namespace is disabled

[Keith Busch]

On Sun, Apr 28, 2024 at 12:25:40PM +0300, Sagi Grimberg wrote:
> If the user disabled a nvmet namesapce, it is removed from
> the subsystem namespaces list. When nvmet processes a command
> directed to an nsid that was disabled, it cannot differentiate
> between a nsid that is disabled vs. a non-existent namespace,
> and resorts to return NVME_SC_INVALID_NS with the dnr bit set.
> 
> This translates to a non-retryable status for the host, which
> translates to a user error. We should expect disabled namespaces
> to not cause an I/O error in a multipath environment.
> 
> Address this by searching a configfs item for the namespace nvmet
> failed to find, and if we found one, conclude that the namespace
> is disabled (perhaps temporarily). Return NVME_SC_INTERNAL_PATH_ERROR
> in this case and keep DNR bit cleared.
> 
> Reported-by: Jirong Feng <jirong.feng at easystack.cn>
> Signed-off-by: Sagi Grimberg <sagi at grimberg.me>

Applied with Jirong's "Tested-by" and Christoph's suggestions (spelling,
word wrap, and unnecessary 'else') to nvme-6.9.