Re: [PATCH V2] nvme: Add module reference counting for multipath devices

[Nares Bannoth <nbannoth@linux.ibm.com>]

On 13/08/26 4:02 am, wenxiong@linux.ibm.com wrote:
> From: Wen Xiong <wenxiong@linux.ibm.com>
>
> Add proper module reference counting to prevent premature unloading of
> NVMe transport modules while multipath namespaces are still active.
>
> When a namespace is added to a multipath device via nvme_mpath_add_disk(),
> the underlying transport module (PCIe, FC, RDMA, TCP, etc.) must remain
> loaded as long as the multipath device references that namespace. Without
> proper reference counting, the transport module could be unloaded while
> the multipath device is still using resources from that module, leading
> to the potential system crashes.
>
> This ensures the transport module remains loaded for the entire lifetime
> of the multipath namespace association.
>
> Signed-off-by: Wen Xiong <wenxiong@linux.ibm.com>
> ---

Hi Wen,

I tested this patch and it is working as expected.

Patch Validation Results
--------------------------------
# lsmod | grep -i nvme
nvme_tcp              262144  0
nvme                  262144  9
nvme_fabrics          262144  1 nvme_tcp
nvme_core             458752  8 nvme_tcp,nvme,nvme_fabrics
nvme_keyring          262144  3 nvme_tcp,nvme_core,nvme_fabrics
nvme_auth             262144  1 nvme_core
# rmmod nvme
rmmod: ERROR: Module nvme is in use.
#
# rmmod nvme_tcp
#
# lsmod | grep -i nvme
nvme                  262144  9
nvme_fabrics          262144  0
nvme_core             458752  7 nvme,nvme_fabrics
nvme_keyring          262144  2 nvme_core,nvme_fabrics
nvme_auth             262144  1 nvme_core
# rmmod nvme_core
rmmod: ERROR: Module nvme_core is in use by: nvme nvme_fabrics
#
# rmmod nvme_fabrics
#
# rmmod nvme_core
rmmod: ERROR: Module nvme_core is in use by: nvme
#
# lsmod | grep -i nvme
nvme                  262144  9
nvme_core             458752  6 nvme
nvme_keyring          262144  1 nvme_core
nvme_auth             262144  1 nvme_core
#

Please add below tag :

Tested-by: Naresh Bannoth <nbannoth@linux.ibm.com>


Thanks and Regards,

Naresh.

>   drivers/nvme/host/multipath.c | 5 +++++
>   1 file changed, 5 insertions(+)
>
> diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
> index 9b9a657fa330..707b8f95727d 100644
> --- a/drivers/nvme/host/multipath.c
> +++ b/drivers/nvme/host/multipath.c
> @@ -1348,6 +1348,8 @@ void nvme_mpath_remove_sysfs_link(struct nvme_ns *ns)
>   	sysfs_remove_link_from_group(kobj, nvme_ns_mpath_attr_group.name,
>   			dev_name(target));
>   	clear_bit(NVME_NS_SYSFS_ATTR_LINK, &ns->flags);
> +
> +	module_put(ns->ctrl->ops->module);
>   }
>   
>   void nvme_mpath_add_disk(struct nvme_ns *ns, __le32 anagrpid)
> @@ -1379,6 +1381,9 @@ void nvme_mpath_add_disk(struct nvme_ns *ns, __le32 anagrpid)
>   	if (blk_queue_is_zoned(ns->queue) && ns->head->disk)
>   		ns->head->disk->nr_zones = ns->disk->nr_zones;
>   #endif
> +	if (!try_module_get(ns->ctrl->ops->module))
> +		dev_err(disk_to_dev(ns->disk),
> +				"Failed to get module reference\n");
>   }
>   
>   void nvme_mpath_remove_disk(struct nvme_ns_head *head)