[PATCH v2] nvme: Treat discovery subsystems as unique subsystems

[PATCH v2] nvme: Treat discovery subsystems as unique subsystems

[James Smart]

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>

---
v2: add comment
---
 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 4660505eded9..6960781a514e 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -2358,6 +2358,17 @@ 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;
-- 
2.13.7


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Re: [PATCH v2] nvme: Treat discovery subsystems as unique subsystems

[Christoph Hellwig]

On Tue, Sep 03, 2019 at 02:20:37PM -0700, James Smart wrote:
> 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.

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

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Re: [PATCH v2] nvme: Treat discovery subsystems as unique subsystems

[Max Gurtovoy]

On 9/4/2019 12:20 AM, James Smart wrote:
> 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>
>
> ---
> v2: add comment
> ---
>   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 4660505eded9..6960781a514e 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -2358,6 +2358,17 @@ 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;


Looks good,

Reviewed-by: Max Gurtovoy <maxg@mellanox.com>



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