[PATCH v2] driver/nvme/host: Support duplicated nsid for the private ns

[Sungup Moon]

When the multi-controller, managed by a special admin command, has private
namespace with same nsid, current linux driver raise "Duplicate unshared
namespace" error. But, NVMe Specification defines the NSID usage like this:

If Namespace Management, ANA Reporting, or NVM Sets are supported, the
NSIDs shall be unique within the NVM subsystem. If the Namespace
Management, ANA Reporting, and NVM Sets are not supported, then NSIDs:
a) for shared namespace shall be unique; and
b) for private namespace are not required to be unique.
(reference: 6.1.6 NSID and Namespace Usage; NVM Express 1.4c spec)

So, if a multi-controller, which is not managed by Namespace Management
function, creates some private namespaces without ANA and NVM Sets, the
duplicated NSID should be allowed because that is not a NVMe specification
violation.

But, current nvme driver checks only namespace is shared or not, so I
propose following patch:
1. nvme_ctrl has unique_nsid field to identify that controller should
   assign unique nsid.
2. nvme_init_ns_head function creates new nvme_ns_head instance not only
   head is null but controller's unique_nsid is false (no flagged
   attribute) and namespace is not shared.
3. for creating bdev device file, nvme_mpath_set_disk_name will return
   false when unique_nsid is false and namespace is not shared.
4. also, nvme_mpath_alloc_disk alto return 0 with same manner.

This patch has been modified the unique_nsid mechanism from flag based
to the checking function.
- v1: flag based initial patch
- v2: change from unique_nsid flag to nvme_check_unique_nsid

Signed-off-by: Sungup Moon <sungup.moon at samsung.com>
---
 drivers/nvme/host/core.c      |  9 ++++++++-
 drivers/nvme/host/multipath.c |  5 +++--
 drivers/nvme/host/nvme.h      | 16 ++++++++++++++++
 include/linux/nvme.h          |  1 +
 4 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 51c08f206cbf..5eedef9a781c 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -3816,7 +3816,14 @@ static int nvme_init_ns_head(struct nvme_ns *ns, unsigned nsid,
 
 	mutex_lock(&ctrl->subsys->lock);
 	head = nvme_find_ns_head(ctrl->subsys, nsid);
-	if (!head) {
+	if (!head || !(nvme_check_unique_nsid(ctrl, head) || is_shared)) {
+		/*
+		 * If the found ns head is null or both of ns are not shared
+		 * without the unique namespace condition (this means both
+		 * namespace are private namespaces and those can share the
+		 * same nsid), allocate the new head. Private namespace can
+		 * reuse nsid with the others.
+		 */
 		ret = nvme_subsys_check_duplicate_ids(ctrl->subsys, ids);
 		if (ret) {
 			dev_err(ctrl->device,
diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index ff775235534c..4671dc1b32da 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -88,7 +88,7 @@ void nvme_mpath_start_freeze(struct nvme_subsystem *subsys)
  */
 bool nvme_mpath_set_disk_name(struct nvme_ns *ns, char *disk_name, int *flags)
 {
-	if (!multipath)
+	if (!multipath || !nvme_check_unique_nsid(ns->ctrl, ns->head))
 		return false;
 	if (!ns->head->disk) {
 		sprintf(disk_name, "nvme%dn%d", ns->ctrl->subsys->instance,
@@ -507,7 +507,8 @@ int nvme_mpath_alloc_disk(struct nvme_ctrl *ctrl, struct nvme_ns_head *head)
 	 * We also do this for private namespaces as the namespace sharing data could
 	 * change after a rescan.
 	 */
-	if (!(ctrl->subsys->cmic & NVME_CTRL_CMIC_MULTI_CTRL) || !multipath)
+	if (!(ctrl->subsys->cmic & NVME_CTRL_CMIC_MULTI_CTRL) || !multipath ||
+	    !nvme_check_unique_nsid(ctrl, head))
 		return 0;
 
 	head->disk = blk_alloc_disk(ctrl->numa_node);
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index e7ccdb119ede..50091ed3713b 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -719,6 +719,22 @@ static inline bool nvme_check_ready(struct nvme_ctrl *ctrl, struct request *rq,
 		return queue_live;
 	return __nvme_check_ready(ctrl, rq, queue_live);
 }
+static inline bool nvme_check_unique_nsid(struct nvme_ctrl *ctrl,
+		struct nvme_ns_head *head)
+{
+	/*
+	 * NSID should be unique on the following condition
+	 * 1. Namespace Management support; or
+	 * 2. ANA Reporing support; or
+	 * 3. NVM Set support; or
+	 * 4. Namespace is shared
+	 * Other case, private namespace are not required to be unique.
+	 */
+	return (ctrl->oacs & NVME_CTRL_OACS_NS_MNGT_SUPP) ||
+		(ctrl->subsys->cmic & NVME_CTRL_CMIC_ANA) ||
+		(ctrl->ctratt & NVME_CTRL_CTRATT_NVM_SETS) ||
+		(head->shared);
+}
 int nvme_submit_sync_cmd(struct request_queue *q, struct nvme_command *cmd,
 		void *buf, unsigned bufflen);
 int __nvme_submit_sync_cmd(struct request_queue *q, struct nvme_command *cmd,
diff --git a/include/linux/nvme.h b/include/linux/nvme.h
index 4f44f83817a9..f626a445d1a8 100644
--- a/include/linux/nvme.h
+++ b/include/linux/nvme.h
@@ -346,6 +346,7 @@ enum {
 	NVME_CTRL_ONCS_TIMESTAMP		= 1 << 6,
 	NVME_CTRL_VWC_PRESENT			= 1 << 0,
 	NVME_CTRL_OACS_SEC_SUPP                 = 1 << 0,
+	NVME_CTRL_OACS_NS_MNGT_SUPP		= 1 << 3,
 	NVME_CTRL_OACS_DIRECTIVES		= 1 << 5,
 	NVME_CTRL_OACS_DBBUF_SUPP		= 1 << 8,
 	NVME_CTRL_LPA_CMD_EFFECTS_LOG		= 1 << 1,
-- 
2.25.1