[PATCH 0/2] nvme: missed AENs during scanning

[Hannes Reinecke <hare@kernel.org>]

Hi all,

I have been tracking down a long-standing issue from one of our partners
which had a test where namespaces have been remapped in quick succession.
The operation was to remove a namespace and add a new namespace at the same
NSID with a different UUID and different ANA group ID.
And that repeated in quick succession.
There had been several attempts to fix this ([1], [2], and the patch from
Keith in 1f021341eef4 ("nvme-multipath: defer partition scanning")), but
the test case continued to fail ending up with all paths in ANA Inaccessible.

Eventually it turned out that we're skipping NS Changed AENs; if namescan
scanning is active when we receive a NS Changed AEN we'll simply ignore it,
and do not re-read the namespace list as we should.
Additionally the NVMe base spec states (NVMe Base Specification v2.1, Figure
151 'Asynchonous Event Information - Notice': Asymmetric Namespace Access Change):

  A controller shall not send this even if an Attached Namespace Attribute Changed
  asynchronous event [ .. ] is sent for the same event.

so we need to re-read the ANA log page after we rescanned the namespace list to
update the ANA states of the new namespaces.

As usual, comments and reviews are welcome.

[1] https://lore.kernel.org/linux-nvme/20240902111548.41430-1-hare@kernel.org/
[2] https://lore.kernel.org/linux-nvme/20241007100134.21104-1-hare@kernel.org/

Hannes Reinecke (2):
  nvme: requeue namespace scan on missed AENs
  nvme: re-read ANA log page after ns scan completes

 drivers/nvme/host/core.c | 9 +++++++++
 1 file changed, 9 insertions(+)

-- 
2.35.3