nvme-multipath: fix possible io hang after ctrl reconnect
The following scenario results in an IO hang:
1) ctrl completes a request with NVME_SC_ANA_TRANSITION.
NVME_NS_ANA_PENDING bit in ns->flags is set and ana_work is triggered.
2) ana_work: nvme_read_ana_log() tries to get the ANA log page from the ctrl.
This fails because ctrl disconnects.
Therefore nvme_update_ns_ana_state() is not called
and NVME_NS_ANA_PENDING bit in ns->flags is not cleared.
3) ctrl reconnects: nvme_mpath_init(ctrl,...) calls
nvme_read_ana_log(ctrl, groups_only=true).
However, nvme_update_ana_state() does not update namespaces
because nr_nsids = 0 (due to groups_only mode).
4) scan_work calls nvme_validate_ns() finds the ns and re-validates OK.
Result:
The ctrl is now live but NVME_NS_ANA_PENDING bit in ns->flags is still set.
Consequently ctrl will never be considered a viable path by __nvme_find_path().
IO will hang if ctrl is the only or the last path to the namespace.
More generally, while ctrl is reconnecting, its ANA state may change.
And because nvme_mpath_init() requests ANA log in groups_only mode,
these changes are not propagated to the existing ctrl namespaces.
This may result in a mal-function or an IO hang.
Solution:
nvme_mpath_init() will nvme_read_ana_log() with groups_only set to false.
This will not harm the new ctrl case (no namespaces present),
and will make sure the ANA state of namespaces gets updated after reconnect.
Note: Another option would be for nvme_mpath_init() to invoke
nvme_parse_ana_log(..., nvme_set_ns_ana_state) for each existing namespace.
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Anton Eidelman <anton@lightbitslabs.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
1 file changed
