[PATCH V3 1/3] nvmet: make ctrl-id configurable

[Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>]

This patch adds a new target subsys attribute which allows user to
optionally specify target controller IDs which then used in the
nvmet_execute_identify_ctrl() to fill up the nvme_id_ctrl structure.

For example, when using a cluster setup with two nodes, with a dual
ported NVMe drive and exporting the drive from both the nodes,
The connection to the host fails due to the same controller ID and
results in the following error message:-

"nvme nvmeX: Duplicate cntlid XXX with nvmeX, rejecting"

With this patch now user can partition the controller IDs for each
subsystem by setting up the cntlid_min and cntlid_max. These values
will be used at the time of the controller ID creation. By partitioning
the ctrl-ids for each subsystem results in the unique ctrl-id space
which avoids the collision.

When new attribute is not specified target will fall back to original
cntlid calculation method.

Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
---
Changes from V2:-

1. Reduce the size of the lock for sscanf for cntlid_min and cntlid_max.
2. Remove the common show and store function for cntlid.
3. Move cntlid_min and cntlid_max check into the store function. 
4. Update the patch description.
5. Move check for valid cntlid_[min|max] parameter into configfs
   respective store function.

Changes from V1:-

1. Add cntlid max and min configfs attributes.
2. Use simple if .. else statements instead of ternary operators.
---
 drivers/nvme/target/configfs.c | 72 ++++++++++++++++++++++++++++++++++
 drivers/nvme/target/core.c     |  5 ++-
 drivers/nvme/target/nvmet.h    |  2 +
 3 files changed, 77 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c
index 98613a45bd3b..772a74a7d969 100644
--- a/drivers/nvme/target/configfs.c
+++ b/drivers/nvme/target/configfs.c
@@ -862,10 +862,82 @@ static ssize_t nvmet_subsys_attr_serial_store(struct config_item *item,
 }
 CONFIGFS_ATTR(nvmet_subsys_, attr_serial);
 
+static ssize_t nvmet_subsys_attr_cntlid_min_show(struct config_item *item,
+						 char *page)
+{
+	return snprintf(page, PAGE_SIZE, "%u\n", to_subsys(item)->cntlid_min);
+}
+
+static ssize_t nvmet_subsys_attr_cntlid_min_store(struct config_item *item,
+						  const char *page, size_t cnt)
+{
+	int ret = -EINVAL;
+	u16 cntlid_min;
+
+	if (sscanf(page, "%hu\n", &cntlid_min) != 1)
+		return ret;
+
+	if (cntlid_min == 0) {
+		pr_info("specified cntlid_min = 0 is not allowed\n");
+		return ret;
+	}
+
+	down_write(&nvmet_config_sem);
+	if (cntlid_min >= to_subsys(item)->cntlid_max) {
+		pr_info("specified cntlid_min is >= current cntlid_max\n");
+		goto out;
+	}
+
+	ret = 0;
+	to_subsys(item)->cntlid_min = cntlid_min;
+out:
+	up_write(&nvmet_config_sem);
+
+	return ret ? ret : cnt;
+}
+CONFIGFS_ATTR(nvmet_subsys_, attr_cntlid_min);
+
+static ssize_t nvmet_subsys_attr_cntlid_max_show(struct config_item *item,
+						 char *page)
+{
+	return snprintf(page, PAGE_SIZE, "%u\n", to_subsys(item)->cntlid_max);
+}
+
+static ssize_t nvmet_subsys_attr_cntlid_max_store(struct config_item *item,
+						  const char *page, size_t cnt)
+{
+	int ret = -EINVAL;
+	u16 cntlid_max;
+
+	if (sscanf(page, "%hu\n", &cntlid_max) != 1)
+		return ret;
+
+	if (cntlid_max == 0) {
+		pr_info("specified cntlid_max = 0 is not allowed\n");
+		return ret;
+	}
+
+	down_write(&nvmet_config_sem);
+	if (cntlid_max <= to_subsys(item)->cntlid_min) {
+		pr_info("specified cntlid_max is <= current cntlid_min\n");
+		goto out;
+	}
+
+	ret = 0;
+	to_subsys(item)->cntlid_max = cntlid_max;
+out:
+	up_write(&nvmet_config_sem);
+
+	return ret ? ret : cnt;
+}
+CONFIGFS_ATTR(nvmet_subsys_, attr_cntlid_max);
+
 static struct configfs_attribute *nvmet_subsys_attrs[] = {
 	&nvmet_subsys_attr_attr_allow_any_host,
 	&nvmet_subsys_attr_attr_version,
 	&nvmet_subsys_attr_attr_serial,
+	&nvmet_subsys_attr_attr_cntlid_min,
+	&nvmet_subsys_attr_attr_cntlid_max,
 	NULL,
 };
 
diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c
index 28438b833c1b..387628ec7e37 100644
--- a/drivers/nvme/target/core.c
+++ b/drivers/nvme/target/core.c
@@ -1268,7 +1268,7 @@ u16 nvmet_alloc_ctrl(const char *subsysnqn, const char *hostnqn,
 		goto out_free_cqs;
 
 	ret = ida_simple_get(&cntlid_ida,
-			     NVME_CNTLID_MIN, NVME_CNTLID_MAX,
+			     subsys->cntlid_min, subsys->cntlid_max,
 			     GFP_KERNEL);
 	if (ret < 0) {
 		status = NVME_SC_CONNECT_CTRL_BUSY | NVME_SC_DNR;
@@ -1416,7 +1416,8 @@ struct nvmet_subsys *nvmet_subsys_alloc(const char *subsysnqn,
 		kfree(subsys);
 		return ERR_PTR(-ENOMEM);
 	}
-
+	subsys->cntlid_min = NVME_CNTLID_MIN;
+	subsys->cntlid_max = NVME_CNTLID_MAX;
 	kref_init(&subsys->ref);
 
 	mutex_init(&subsys->lock);
diff --git a/drivers/nvme/target/nvmet.h b/drivers/nvme/target/nvmet.h
index 46df45e837c9..6492d12e626a 100644
--- a/drivers/nvme/target/nvmet.h
+++ b/drivers/nvme/target/nvmet.h
@@ -211,6 +211,8 @@ struct nvmet_subsys {
 	struct list_head	namespaces;
 	unsigned int		nr_namespaces;
 	unsigned int		max_nsid;
+	u16			cntlid_min;
+	u16			cntlid_max;
 
 	struct list_head	ctrls;
 
-- 
2.22.1


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