nvmet: add debugfs support

Add a debugfs hierarchy to display the configured subsystems
and the controllers attached to the subsystems.

Suggested-by: Redouane BOUFENGHOUR <redouane.boufenghour@shadow.tech>
Signed-off-by: Hannes Reinecke <hare@kernel.org>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Signed-off-by: Daniel Wagner <dwagner@suse.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>

drivers/nvme/target/Kconfig

@@ -17,6 +17,15 @@ config NVME_TARGET
 	  To configure the NVMe target you probably want to use the nvmetcli
 	  tool from http://git.infradead.org/users/hch/nvmetcli.git.
 
+config NVME_TARGET_DEBUGFS
+        bool "NVMe Target debugfs support"
+	depends on NVME_TARGET
+	help
+	  This enables debugfs support to display the connected controllers
+	  to each subsystem
+
+	  If unsure, say N.
+
 config NVME_TARGET_PASSTHRU
 	bool "NVMe Target Passthrough support"
 	depends on NVME_TARGET

drivers/nvme/target/Makefile

@@ -11,6 +11,7 @@ obj-$(CONFIG_NVME_TARGET_TCP)		+= nvmet-tcp.o
 
 nvmet-y		+= core.o configfs.o admin-cmd.o fabrics-cmd.o \
 			discovery.o io-cmd-file.o io-cmd-bdev.o
+nvmet-$(CONFIG_NVME_TARGET_DEBUGFS)	+= debugfs.o
 nvmet-$(CONFIG_NVME_TARGET_PASSTHRU)	+= passthru.o
 nvmet-$(CONFIG_BLK_DEV_ZONED)		+= zns.o
 nvmet-$(CONFIG_NVME_TARGET_AUTH)	+= fabrics-cmd-auth.o auth.o

drivers/nvme/target/core.c

@@ -16,6 +16,7 @@
 #include "trace.h"
 
 #include "nvmet.h"
+#include "debugfs.h"
 
 struct kmem_cache *nvmet_bvec_cache;
 struct workqueue_struct *buffered_io_wq;
@@ -1478,6 +1479,7 @@ u16 nvmet_alloc_ctrl(const char *subsysnqn, const char *hostnqn,
 	mutex_lock(&subsys->lock);
 	list_add_tail(&ctrl->subsys_entry, &subsys->ctrls);
 	nvmet_setup_p2p_ns_map(ctrl, req);
+	nvmet_debugfs_ctrl_setup(ctrl);
 	mutex_unlock(&subsys->lock);
 
 	*ctrlp = ctrl;
@@ -1512,6 +1514,8 @@ static void nvmet_ctrl_free(struct kref *ref)
 
 	nvmet_destroy_auth(ctrl);
 
+	nvmet_debugfs_ctrl_free(ctrl);
+
 	ida_free(&cntlid_ida, ctrl->cntlid);
 
 	nvmet_async_events_free(ctrl);
@@ -1632,8 +1636,14 @@ struct nvmet_subsys *nvmet_subsys_alloc(const char *subsysnqn,
 	INIT_LIST_HEAD(&subsys->ctrls);
 	INIT_LIST_HEAD(&subsys->hosts);
 
+	ret = nvmet_debugfs_subsys_setup(subsys);
+	if (ret)
+		goto free_subsysnqn;
+
 	return subsys;
 
+free_subsysnqn:
+	kfree(subsys->subsysnqn);
 free_fr:
 	kfree(subsys->firmware_rev);
 free_mn:
@@ -1650,6 +1660,8 @@ static void nvmet_subsys_free(struct kref *ref)
 
 	WARN_ON_ONCE(!xa_empty(&subsys->namespaces));
 
+	nvmet_debugfs_subsys_free(subsys);
+
 	xa_destroy(&subsys->namespaces);
 	nvmet_passthru_subsys_free(subsys);
 
@@ -1704,11 +1716,18 @@ static int __init nvmet_init(void)
 	if (error)
 		goto out_free_nvmet_work_queue;
 
-	error = nvmet_init_configfs();
+	error = nvmet_init_debugfs();
 	if (error)
 		goto out_exit_discovery;
+
+	error = nvmet_init_configfs();
+	if (error)
+		goto out_exit_debugfs;
+
 	return 0;
 
+out_exit_debugfs:
+	nvmet_exit_debugfs();
 out_exit_discovery:
 	nvmet_exit_discovery();
 out_free_nvmet_work_queue:
@@ -1725,6 +1744,7 @@ out_destroy_bvec_cache:
 static void __exit nvmet_exit(void)
 {
 	nvmet_exit_configfs();
+	nvmet_exit_debugfs();
 	nvmet_exit_discovery();
 	ida_destroy(&cntlid_ida);
 	destroy_workqueue(nvmet_wq);

drivers/nvme/target/debugfs.c

@@ -0,0 +1,183 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * DebugFS interface for the NVMe target.
+ * Copyright (c) 2022-2024 Shadow
+ * Copyright (c) 2024 SUSE LLC
+ */
+
+#include <linux/debugfs.h>
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+
+#include "nvmet.h"
+#include "debugfs.h"
+
+struct dentry *nvmet_debugfs;
+
+#define NVMET_DEBUGFS_ATTR(field) \
+	static int field##_open(struct inode *inode, struct file *file) \
+	{ return single_open(file, field##_show, inode->i_private); } \
+	\
+	static const struct file_operations field##_fops = { \
+		.open = field##_open, \
+		.read = seq_read, \
+		.release = single_release, \
+	}
+
+#define NVMET_DEBUGFS_RW_ATTR(field) \
+	static int field##_open(struct inode *inode, struct file *file) \
+	{ return single_open(file, field##_show, inode->i_private); } \
+	\
+	static const struct file_operations field##_fops = { \
+		.open = field##_open, \
+		.read = seq_read, \
+		.write = field##_write, \
+		.release = single_release, \
+	}
+
+static int nvmet_ctrl_hostnqn_show(struct seq_file *m, void *p)
+{
+	struct nvmet_ctrl *ctrl = m->private;
+
+	seq_puts(m, ctrl->hostnqn);
+	return 0;
+}
+NVMET_DEBUGFS_ATTR(nvmet_ctrl_hostnqn);
+
+static int nvmet_ctrl_kato_show(struct seq_file *m, void *p)
+{
+	struct nvmet_ctrl *ctrl = m->private;
+
+	seq_printf(m, "%d\n", ctrl->kato);
+	return 0;
+}
+NVMET_DEBUGFS_ATTR(nvmet_ctrl_kato);
+
+static int nvmet_ctrl_port_show(struct seq_file *m, void *p)
+{
+	struct nvmet_ctrl *ctrl = m->private;
+
+	seq_printf(m, "%d\n", le16_to_cpu(ctrl->port->disc_addr.portid));
+	return 0;
+}
+NVMET_DEBUGFS_ATTR(nvmet_ctrl_port);
+
+static const char *const csts_state_names[] = {
+	[NVME_CSTS_RDY]		= "ready",
+	[NVME_CSTS_CFS]		= "fatal",
+	[NVME_CSTS_NSSRO]	= "reset",
+	[NVME_CSTS_SHST_OCCUR]	= "shutdown",
+	[NVME_CSTS_SHST_CMPLT]	= "completed",
+	[NVME_CSTS_PP]		= "paused",
+};
+
+static int nvmet_ctrl_state_show(struct seq_file *m, void *p)
+{
+	struct nvmet_ctrl *ctrl = m->private;
+	bool sep = false;
+	int i;
+
+	for (i = 0; i < 7; i++) {
+		int state = BIT(i);
+
+		if (!(ctrl->csts & state))
+			continue;
+		if (sep)
+			seq_puts(m, "|");
+		sep = true;
+		if (csts_state_names[state])
+			seq_puts(m, csts_state_names[state]);
+		else
+			seq_printf(m, "%d", state);
+	}
+	if (sep)
+		seq_printf(m, "\n");
+	return 0;
+}
+
+static ssize_t nvmet_ctrl_state_write(struct file *file, const char __user *buf,
+				      size_t count, loff_t *ppos)
+{
+	struct seq_file *m = file->private_data;
+	struct nvmet_ctrl *ctrl = m->private;
+	char reset[16];
+
+	if (count >= sizeof(reset))
+		return -EINVAL;
+	if (copy_from_user(reset, buf, count))
+		return -EFAULT;
+	if (!memcmp(reset, "fatal", 5))
+		nvmet_ctrl_fatal_error(ctrl);
+	else
+		return -EINVAL;
+	return count;
+}
+NVMET_DEBUGFS_RW_ATTR(nvmet_ctrl_state);
+
+int nvmet_debugfs_ctrl_setup(struct nvmet_ctrl *ctrl)
+{
+	char name[32];
+	struct dentry *parent = ctrl->subsys->debugfs_dir;
+	int ret;
+
+	if (!parent)
+		return -ENODEV;
+	snprintf(name, sizeof(name), "ctrl%d", ctrl->cntlid);
+	ctrl->debugfs_dir = debugfs_create_dir(name, parent);
+	if (IS_ERR(ctrl->debugfs_dir)) {
+		ret = PTR_ERR(ctrl->debugfs_dir);
+		ctrl->debugfs_dir = NULL;
+		return ret;
+	}
+	debugfs_create_file("port", S_IRUSR, ctrl->debugfs_dir, ctrl,
+			    &nvmet_ctrl_port_fops);
+	debugfs_create_file("hostnqn", S_IRUSR, ctrl->debugfs_dir, ctrl,
+			    &nvmet_ctrl_hostnqn_fops);
+	debugfs_create_file("kato", S_IRUSR, ctrl->debugfs_dir, ctrl,
+			    &nvmet_ctrl_kato_fops);
+	debugfs_create_file("state", S_IRUSR | S_IWUSR, ctrl->debugfs_dir, ctrl,
+			    &nvmet_ctrl_state_fops);
+	return 0;
+}
+
+void nvmet_debugfs_ctrl_free(struct nvmet_ctrl *ctrl)
+{
+	debugfs_remove_recursive(ctrl->debugfs_dir);
+}
+
+int nvmet_debugfs_subsys_setup(struct nvmet_subsys *subsys)
+{
+	int ret = 0;
+
+	subsys->debugfs_dir = debugfs_create_dir(subsys->subsysnqn,
+						 nvmet_debugfs);
+	if (IS_ERR(subsys->debugfs_dir)) {
+		ret = PTR_ERR(subsys->debugfs_dir);
+		subsys->debugfs_dir = NULL;
+	}
+	return ret;
+}
+
+void nvmet_debugfs_subsys_free(struct nvmet_subsys *subsys)
+{
+	debugfs_remove_recursive(subsys->debugfs_dir);
+}
+
+int __init nvmet_init_debugfs(void)
+{
+	struct dentry *parent;
+
+	parent = debugfs_create_dir("nvmet", NULL);
+	if (IS_ERR(parent)) {
+		pr_warn("%s: failed to create debugfs directory\n", "nvmet");
+		return PTR_ERR(parent);
+	}
+	nvmet_debugfs = parent;
+	return 0;
+}
+
+void nvmet_exit_debugfs(void)
+{
+	debugfs_remove_recursive(nvmet_debugfs);
+}

drivers/nvme/target/debugfs.h

@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * DebugFS interface for the NVMe target.
+ * Copyright (c) 2022-2024 Shadow
+ * Copyright (c) 2024 SUSE LLC
+ */
+#ifndef NVMET_DEBUGFS_H
+#define NVMET_DEBUGFS_H
+
+#include <linux/types.h>
+
+#ifdef CONFIG_NVME_TARGET_DEBUGFS
+int nvmet_debugfs_subsys_setup(struct nvmet_subsys *subsys);
+void nvmet_debugfs_subsys_free(struct nvmet_subsys *subsys);
+int nvmet_debugfs_ctrl_setup(struct nvmet_ctrl *ctrl);
+void nvmet_debugfs_ctrl_free(struct nvmet_ctrl *ctrl);
+
+int __init nvmet_init_debugfs(void);
+void nvmet_exit_debugfs(void);
+#else
+static inline int nvmet_debugfs_subsys_setup(struct nvmet_subsys *subsys)
+{
+	return 0;
+}
+static inline void nvmet_debugfs_subsys_free(struct nvmet_subsys *subsys){}
+
+static inline int nvmet_debugfs_ctrl_setup(struct nvmet_ctrl *ctrl)
+{
+	return 0;
+}
+static inline void nvmet_debugfs_ctrl_free(struct nvmet_ctrl *ctrl) {}
+
+static inline int __init nvmet_init_debugfs(void)
+{
+    return 0;
+}
+
+static inline void nvmet_exit_debugfs(void) {}
+
+#endif
+
+#endif /* NVMET_DEBUGFS_H */

drivers/nvme/target/nvmet.h

@@ -230,7 +230,9 @@ struct nvmet_ctrl {
 
 	struct device		*p2p_client;
 	struct radix_tree_root	p2p_ns_map;
-
+#ifdef CONFIG_NVME_TARGET_DEBUGFS
+	struct dentry		*debugfs_dir;
+#endif
 	spinlock_t		error_lock;
 	u64			err_counter;
 	struct nvme_error_slot	slots[NVMET_ERROR_LOG_SLOTS];
@@ -262,7 +264,9 @@ struct nvmet_subsys {
 
 	struct list_head	hosts;
 	bool			allow_any_host;
-
+#ifdef CONFIG_NVME_TARGET_DEBUGFS
+	struct dentry		*debugfs_dir;
+#endif
 	u16			max_qid;
 
 	u64			ver;