[RFC PATCHv3 2/3] nvme: introduce multipath_always_on module param

[Hannes Reinecke]

On 5/4/25 19:50, Nilay Shroff wrote:
> Currently, a multipath head disk node is not created for single-ported
> NVMe adapters or private namespaces. However, creating a head node in
> these cases can help transparently handle transient PCIe link failures.
> Without a head node, features like delayed removal cannot be leveraged,
> making it difficult to tolerate such link failures. To address this,
> this commit introduces nvme_core module parameter multipath_always_on.
> 
> When this param is set to true, it forces the creation of a multipath
> head node regardless NVMe disk or namespace type. So this option allows
> the use of delayed removal of head node functionality even for single-
> ported NVMe disks and private namespaces and thus helps transparently
> handling transient PCIe link failures.
> 
> By default multipath_always_on is set to false, thus preserving the
> existing behavior. Setting it to true enables improved fault tolerance
> in PCIe setups. Moreover, please note that enabling this option would
> also implicitly enable nvme_core.multipath.
> 
> Signed-off-by: Nilay Shroff <nilay at linux.ibm.com>
> ---
>   drivers/nvme/host/multipath.c | 72 +++++++++++++++++++++++++++++++----
>   1 file changed, 65 insertions(+), 7 deletions(-)
> 

Reviewed-by: Hannes Reinecke <hare at suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare at suse.de                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich