[RFC PATCHv4 3/6] nvme: add generic debugfs support
Nilay Shroff
nilay at linux.ibm.com
Tue Nov 4 02:45:18 PST 2025
Add generic infrastructure for creating and managing debugfs files in
the NVMe module. This introduces helper APIs that allow NVMe drivers to
register and unregister debugfs entries, along with a reusable attribute
structure for defining new debugfs files.
The implementation uses seq_file interfaces to safely expose per-NS and
per-NS-head statistics, while supporting both simple show callbacks and
full seq_operations.
Reviewed-by: Hannes Reinecke <hare at suse.de>
Signed-off-by: Nilay Shroff <nilay at linux.ibm.com>
---
drivers/nvme/host/Makefile | 2 +-
drivers/nvme/host/core.c | 3 +
drivers/nvme/host/debugfs.c | 138 ++++++++++++++++++++++++++++++++++
drivers/nvme/host/multipath.c | 2 +
drivers/nvme/host/nvme.h | 10 +++
5 files changed, 154 insertions(+), 1 deletion(-)
create mode 100644 drivers/nvme/host/debugfs.c
diff --git a/drivers/nvme/host/Makefile b/drivers/nvme/host/Makefile
index 6414ec968f99..7962dfc3b2ad 100644
--- a/drivers/nvme/host/Makefile
+++ b/drivers/nvme/host/Makefile
@@ -10,7 +10,7 @@ obj-$(CONFIG_NVME_FC) += nvme-fc.o
obj-$(CONFIG_NVME_TCP) += nvme-tcp.o
obj-$(CONFIG_NVME_APPLE) += nvme-apple.o
-nvme-core-y += core.o ioctl.o sysfs.o pr.o
+nvme-core-y += core.o ioctl.o sysfs.o pr.o debugfs.o
nvme-core-$(CONFIG_NVME_VERBOSE_ERRORS) += constants.o
nvme-core-$(CONFIG_TRACING) += trace.o
nvme-core-$(CONFIG_NVME_MULTIPATH) += multipath.o
diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 47f375c63d2d..c15dfcaf3de2 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -4187,6 +4187,8 @@ static void nvme_alloc_ns(struct nvme_ctrl *ctrl, struct nvme_ns_info *info)
if (device_add_disk(ctrl->device, ns->disk, nvme_ns_attr_groups))
goto out_cleanup_ns_from_list;
+ nvme_debugfs_register(ns->disk);
+
if (!nvme_ns_head_multipath(ns->head))
nvme_add_ns_cdev(ns);
@@ -4276,6 +4278,7 @@ static void nvme_ns_remove(struct nvme_ns *ns)
nvme_mpath_remove_sysfs_link(ns);
+ nvme_debugfs_unregister(ns->disk);
del_gendisk(ns->disk);
mutex_lock(&ns->ctrl->namespaces_lock);
diff --git a/drivers/nvme/host/debugfs.c b/drivers/nvme/host/debugfs.c
new file mode 100644
index 000000000000..6bb57c4b5c3b
--- /dev/null
+++ b/drivers/nvme/host/debugfs.c
@@ -0,0 +1,138 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2025 IBM Corporation
+ * Nilay Shroff <nilay at linux.ibm.com>
+ */
+
+#include <linux/debugfs.h>
+#include <linux/seq_file.h>
+
+#include "nvme.h"
+
+struct nvme_debugfs_attr {
+ const char *name;
+ umode_t mode;
+ int (*show)(void *data, struct seq_file *m);
+ ssize_t (*write)(void *data, const char __user *buf, size_t count,
+ loff_t *ppos);
+ const struct seq_operations *seq_ops;
+};
+
+struct nvme_debugfs_ctx {
+ void *data;
+ struct nvme_debugfs_attr *attr;
+ int srcu_idx;
+};
+
+static int nvme_debugfs_show(struct seq_file *m, void *v)
+{
+ struct nvme_debugfs_ctx *ctx = m->private;
+ void *data = ctx->data;
+ struct nvme_debugfs_attr *attr = ctx->attr;
+
+ return attr->show(data, m);
+}
+
+static int nvme_debugfs_open(struct inode *inode, struct file *file)
+{
+ void *data = inode->i_private;
+ struct nvme_debugfs_attr *attr = debugfs_get_aux(file);
+ struct nvme_debugfs_ctx *ctx;
+ struct seq_file *m;
+ int ret;
+
+ ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
+ if (WARN_ON_ONCE(!ctx))
+ return -ENOMEM;
+
+ ctx->data = data;
+ ctx->attr = attr;
+
+ if (attr->seq_ops) {
+ ret = seq_open(file, attr->seq_ops);
+ if (ret) {
+ kfree(ctx);
+ return ret;
+ }
+ m = file->private_data;
+ m->private = ctx;
+ return ret;
+ }
+
+ if (WARN_ON_ONCE(!attr->show)) {
+ kfree(ctx);
+ return -EPERM;
+ }
+
+ return single_open(file, nvme_debugfs_show, ctx);
+}
+
+static ssize_t nvme_debugfs_write(struct file *file, const char __user *buf,
+ size_t count, loff_t *ppos)
+{
+ struct seq_file *m = file->private_data;
+ struct nvme_debugfs_ctx *ctx = m->private;
+ struct nvme_debugfs_attr *attr = ctx->attr;
+
+ if (!attr->write)
+ return -EPERM;
+
+ return attr->write(ctx->data, buf, count, ppos);
+}
+
+static int nvme_debugfs_release(struct inode *inode, struct file *file)
+{
+ struct seq_file *m = file->private_data;
+ struct nvme_debugfs_ctx *ctx = m->private;
+ struct nvme_debugfs_attr *attr = ctx->attr;
+ int ret;
+
+ if (attr->seq_ops)
+ ret = seq_release(inode, file);
+ else
+ ret = single_release(inode, file);
+
+ kfree(ctx);
+ return ret;
+}
+
+static const struct file_operations nvme_debugfs_fops = {
+ .owner = THIS_MODULE,
+ .open = nvme_debugfs_open,
+ .read = seq_read,
+ .write = nvme_debugfs_write,
+ .llseek = seq_lseek,
+ .release = nvme_debugfs_release,
+};
+
+
+static const struct nvme_debugfs_attr nvme_mpath_debugfs_attrs[] = {
+ {},
+};
+
+static const struct nvme_debugfs_attr nvme_ns_debugfs_attrs[] = {
+ {},
+};
+
+static void nvme_debugfs_create_files(struct request_queue *q,
+ const struct nvme_debugfs_attr *attr, void *data)
+{
+ if (WARN_ON_ONCE(!q->debugfs_dir))
+ return;
+
+ for (; attr->name; attr++)
+ debugfs_create_file_aux(attr->name, attr->mode, q->debugfs_dir,
+ data, (void *)attr, &nvme_debugfs_fops);
+}
+
+void nvme_debugfs_register(struct gendisk *disk)
+{
+ const struct nvme_debugfs_attr *attr;
+
+ if (nvme_disk_is_ns_head(disk))
+ attr = nvme_mpath_debugfs_attrs;
+ else
+ attr = nvme_ns_debugfs_attrs;
+
+ nvme_debugfs_create_files(disk->queue, attr, disk->private_data);
+}
diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index 55dc28375662..047dd9da9cbf 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -1086,6 +1086,7 @@ static void nvme_remove_head(struct nvme_ns_head *head)
nvme_cdev_del(&head->cdev, &head->cdev_device);
synchronize_srcu(&head->srcu);
+ nvme_debugfs_unregister(head->disk);
del_gendisk(head->disk);
}
nvme_put_ns_head(head);
@@ -1192,6 +1193,7 @@ static void nvme_mpath_set_live(struct nvme_ns *ns)
}
nvme_add_ns_head_cdev(head);
kblockd_schedule_work(&head->partition_scan_work);
+ nvme_debugfs_register(head->disk);
}
nvme_mpath_add_sysfs_link(ns->head);
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 715c7053054c..1c1ec2a7f9ad 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -1000,6 +1000,16 @@ static inline int nvme_data_dir(const enum req_op op)
return NVME_STAT_OTHER;
}
+void nvme_debugfs_register(struct gendisk *disk);
+static inline void nvme_debugfs_unregister(struct gendisk *disk)
+{
+ /*
+ * Nothing to do for now. When the request queue is unregistered,
+ * all files under q->debugfs_dir are recursively deleted.
+ * This is just a placeholder; the compiler will optimize it out.
+ */
+}
+
#ifdef CONFIG_NVME_MULTIPATH
static inline bool nvme_ctrl_use_ana(struct nvme_ctrl *ctrl)
{
--
2.51.0
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