Re: [PATCH stable 4.18+] nvme: Treat discovery subsystems as unique subsystems

[Greg KH <greg@kroah.com>]

On Mon, Apr 13, 2020 at 01:13:49AM -0700, Sagi Grimberg wrote:
> From: James Smart <jsmart2021@gmail.com>
> 
> [ Upstream commit c26aa572027d438de9cc311aaebcbe972f698c24 ]
> 
> Current code matches subnqn and collapses all controllers to the
> same subnqn to a single subsystem structure. This is good for
> recognizing multiple controllers for the same subsystem. But with
> the well-known discovery subnqn, the subsystems aren't truly the
> same subsystem. As such, subsystem specific rules, such as no
> overlap of controller id, do not apply. With today's behavior, the
> check for overlap of controller id can fail, preventing the new
> discovery controller from being created.
> 
> When searching for like subsystem nqn, exclude the discovery nqn
> from matching. This will result in each discovery controller being
> attached to a unique subsystem structure.
> 
> Signed-off-by: James Smart <jsmart2021@gmail.com>
> Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Reviewed-by: Max Gurtovoy <maxg@mellanox.com>
> Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
> ---
>  drivers/nvme/host/core.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index fad04282148d..0545eb97d838 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -2374,6 +2374,17 @@ static struct nvme_subsystem *__nvme_find_get_subsystem(const char *subsysnqn)
>  
>  	lockdep_assert_held(&nvme_subsystems_lock);
>  
> +	/*
> +	 * Fail matches for discovery subsystems. This results
> +	 * in each discovery controller bound to a unique subsystem.
> +	 * This avoids issues with validating controller values
> +	 * that can only be true when there is a single unique subsystem.
> +	 * There may be multiple and completely independent entities
> +	 * that provide discovery controllers.
> +	 */
> +	if (!strcmp(subsysnqn, NVME_DISC_SUBSYS_NAME))
> +		return NULL;
> +
>  	list_for_each_entry(subsys, &nvme_subsystems, entry) {
>  		if (strcmp(subsys->subnqn, subsysnqn))
>  			continue;
> -- 
> 2.20.1
> 

Now queued up, thanks.

greg k-h