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

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

[Sagi Grimberg]

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

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

[Greg KH]

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