[PATCH v3 1/3] fs: configfs: add helper to identify configfs paths

[Runyu Xiao]

Keep the configfs filesystem type check in configfs so callers can
classify resolved paths without comparing filesystem name strings or
using filesystem-specific magic numbers.

Export the helper for configfs users that need to reject paths into the
configuration filesystem while running from a configfs callback.

Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Sagi Grimberg <sagi@xxxxxxxxxxx>
Assisted-by: LLM Codex
Signed-off-by: Runyu Xiao <runyu.xiao@xxxxxxxxxx>
---
 fs/configfs/mount.c      | 6 ++++++
 include/linux/configfs.h | 2 ++
 2 files changed, 8 insertions(+)

diff --git a/fs/configfs/mount.c b/fs/configfs/mount.c
index d8cac1cbf..8abbe3afa 100644
--- a/fs/configfs/mount.c
+++ b/fs/configfs/mount.c
@@ -118,6 +118,12 @@ static struct file_system_type configfs_fs_type = {
 };
 MODULE_ALIAS_FS("configfs");
 
+bool configfs_path_is_configfs(const struct path *path)
+{
+	return path->dentry->d_sb->s_type == &configfs_fs_type;
+}
+EXPORT_SYMBOL_GPL(configfs_path_is_configfs);
+
 struct dentry *configfs_pin_fs(void)
 {
 	int err = simple_pin_fs(&configfs_fs_type, &configfs_mount,
diff --git a/include/linux/configfs.h b/include/linux/configfs.h
index ef65c75be..55df734da 100644
--- a/include/linux/configfs.h
+++ b/include/linux/configfs.h
@@ -34,6 +34,7 @@ struct configfs_group_operations;
 struct configfs_attribute;
 struct configfs_bin_attribute;
 struct configfs_subsystem;
+struct path;
 
 struct config_item {
 	char			*ci_name;
@@ -243,6 +244,7 @@ void configfs_unregister_subsystem(struct configfs_subsystem *subsys);
 int configfs_register_group(struct config_group *parent_group,
 			    struct config_group *group);
 void configfs_unregister_group(struct config_group *group);
+bool configfs_path_is_configfs(const struct path *path);
 
 void configfs_remove_default_groups(struct config_group *group);
 
-- 
2.34.1