[PATCH RFC v3 05/12] fs/configfs: add 'fill_subsystem' and 'clear_subsystem' callbacks
From: Hannes Reinecke
Date: Tue Jun 23 2026 - 05:21:22 EST
When creating a new per-namespace filesystem static initialisation
doesn't work, so implement a 'fill_subsystem' and 'clear_subsystem'
callbacks to 'struct configfs_subsystem' to allow for every driver
to populate the subsystem structure dynamicall.
Signed-off-by: Hannes Reinecke <hare@xxxxxxxxxx>
---
fs/configfs/configfs_internal.h | 4 ++
fs/configfs/dir.c | 104 +++++++++++++++++++++++++++++++++++++++-
fs/configfs/mount.c | 4 ++
include/linux/configfs.h | 5 ++
4 files changed, 116 insertions(+), 1 deletion(-)
diff --git a/fs/configfs/configfs_internal.h b/fs/configfs/configfs_internal.h
index a4f10dd8ce0f46873d2053860a9fd25f3ee4c809..35eddc274b88796442c080fe4fe8a6ea68762185 100644
--- a/fs/configfs/configfs_internal.h
+++ b/fs/configfs/configfs_internal.h
@@ -94,6 +94,10 @@ extern struct dentry *configfs_pin_fs(struct super_block *sb);
extern void configfs_release_fs(struct super_block *sb);
extern struct configfs_super_info *configfs_get_super_info(struct net *net_ns);
extern void configfs_put_super_info(struct configfs_super_info *info);
+extern void configfs_link_subsystems(struct super_block *sb,
+ struct configfs_super_info *info);
+extern void configfs_unlink_subsystems(struct super_block *sb,
+ struct configfs_super_info *info);
extern const struct file_operations configfs_dir_operations;
extern const struct file_operations configfs_file_operations;
diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
index 64635c58c0f33ec2d722b0555d3a9153f28bb200..3d39a6c1a4163632c9acdc8cf831add40c9b430e 100644
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -1932,15 +1932,95 @@ int configfs_register_subsystem(struct configfs_subsystem *subsys)
goto out_put;
}
+ if (subsys->fill_subsystem) {
+ INIT_LIST_HEAD(&subsys->su_link);
+ mutex_init(&subsys->su_mutex);
+ config_group_init(&subsys->su_group);
+ err = subsys->fill_subsystem(subsys, info->net_ns);
+ if (err)
+ goto out_release;
+ }
+
err = configfs_link_root(info, subsys, root);
+ if (err) {
+ if (subsys->clear_subsystem)
+ subsys->clear_subsystem(subsys, info->net_ns);
+ goto out_release;
+ }
+
+ mutex_lock(&info->subsys_mutex);
+ list_add(&subsys->su_link, &info->subsys_list);
+ mutex_unlock(&info->subsys_mutex);
+
+out_release:
if (err)
configfs_release_fs(NULL);
-
out_put:
configfs_put_super_info(info);
return err;
}
+void configfs_link_subsystems(struct super_block *sb,
+ struct configfs_super_info *info)
+{
+ struct configfs_subsystem *s;
+ struct configfs_super_info *parent = configfs_get_super_info(&init_net);
+ LIST_HEAD(subsys_list);
+
+ if (WARN_ON(IS_ERR(parent)))
+ return;
+ if ((info->net_ns == &init_net) || WARN_ON(parent == info)) {
+ configfs_put_super_info(parent);
+ return;
+ }
+ mutex_lock(&parent->subsys_mutex);
+ list_splice_init(&parent->subsys_list, &subsys_list);
+ mutex_unlock(&parent->subsys_mutex);
+ list_for_each_entry(s, &subsys_list, su_link) {
+ struct configfs_subsystem *subsys;
+ struct dentry *root;
+ int err;
+
+ if (!s->fill_subsystem)
+ continue;
+ subsys = kzalloc_obj(*subsys);
+ if (!subsys)
+ continue;
+ subsys->fill_subsystem = s->fill_subsystem;
+ subsys->clear_subsystem = s->clear_subsystem;
+ INIT_LIST_HEAD(&subsys->su_link);
+ mutex_init(&subsys->su_mutex);
+ config_group_init(&subsys->su_group);
+ err = subsys->fill_subsystem(subsys, info->net_ns);
+ if (err) {
+ kfree(subsys);
+ continue;
+ }
+ root = configfs_pin_fs(sb);
+ if (IS_ERR(root)) {
+ if (subsys->clear_subsystem)
+ subsys->clear_subsystem(subsys, info->net_ns);
+ kfree(subsys);
+ continue;
+ }
+ err = configfs_link_root(info, subsys, root);
+ if (err) {
+ configfs_release_fs(sb);
+ if (subsys->clear_subsystem)
+ subsys->clear_subsystem(subsys, info->net_ns);
+ kfree(subsys);
+ continue;
+ }
+ mutex_lock(&info->subsys_mutex);
+ list_add(&subsys->su_link, &info->subsys_list);
+ mutex_unlock(&info->subsys_mutex);
+ }
+ mutex_lock(&parent->subsys_mutex);
+ list_splice(&subsys_list, &parent->subsys_list);
+ mutex_unlock(&parent->subsys_mutex);
+ configfs_put_super_info(parent);
+}
+
static bool configfs_unlink_root(struct configfs_subsystem *subsys)
{
struct config_group *group = &subsys->su_group;
@@ -1983,6 +2063,25 @@ static bool configfs_unlink_root(struct configfs_subsystem *subsys)
return true;
}
+void configfs_unlink_subsystems(struct super_block *sb,
+ struct configfs_super_info *info)
+{
+ struct configfs_subsystem *subsys, *s;
+
+ mutex_lock(&info->subsys_mutex);
+ list_for_each_entry_safe(subsys, s, &info->subsys_list, su_link) {
+ list_del_init(&subsys->su_link);
+ if (!configfs_unlink_root(subsys))
+ continue;
+ if (subsys->clear_subsystem)
+ subsys->clear_subsystem(subsys, info->net_ns);
+ unlink_group(&subsys->su_group);
+ configfs_release_fs(sb);
+ kfree(subsys);
+ }
+ mutex_unlock(&info->subsys_mutex);
+}
+
void configfs_unregister_subsystem(struct configfs_subsystem *subsys)
{
struct configfs_super_info *info;
@@ -1998,6 +2097,9 @@ void configfs_unregister_subsystem(struct configfs_subsystem *subsys)
}
mutex_lock(&info->subsys_mutex);
+ list_del_init(&subsys->su_link);
+ if (subsys->clear_subsystem)
+ subsys->clear_subsystem(subsys, info->net_ns);
unlink_group(group);
mutex_unlock(&info->subsys_mutex);
configfs_release_fs(NULL);
diff --git a/fs/configfs/mount.c b/fs/configfs/mount.c
index 8b26ceb7b0d4a03a17c251de42902aaabef5a652..d36fc4a6f6439bea645e62b8423b518a5d7d51c1 100644
--- a/fs/configfs/mount.c
+++ b/fs/configfs/mount.c
@@ -157,6 +157,9 @@ static int configfs_fill_super(struct super_block *sb, struct fs_context *fc)
sb->s_root = root;
set_default_d_op(sb, &configfs_dentry_ops); /* the rest get that */
sb->s_d_flags |= DCACHE_DONTCACHE;
+
+ configfs_link_subsystems(sb, info);
+
return 0;
}
@@ -179,6 +182,7 @@ static void configfs_kill_sb(struct super_block *sb)
{
struct configfs_super_info *info = sb->s_fs_info;
+ configfs_unlink_subsystems(sb, info);
kill_anon_super(sb);
configfs_put_super_info(info);
sb->s_fs_info = NULL;
diff --git a/include/linux/configfs.h b/include/linux/configfs.h
index 19165e36da810c75500bb584702ae3a594c3510d..893ae778585fb8be60026c661cb1ef63980ff0e3 100644
--- a/include/linux/configfs.h
+++ b/include/linux/configfs.h
@@ -227,8 +227,13 @@ struct configfs_group_operations {
};
struct configfs_subsystem {
+ struct list_head su_link;
struct config_group su_group;
struct mutex su_mutex;
+ int (*fill_subsystem)(struct configfs_subsystem *subsys,
+ struct net *net_ns);
+ void (*clear_subsystem)(struct configfs_subsystem *subsys,
+ struct net *net_ns);
};
static inline struct configfs_subsystem *to_configfs_subsystem(struct config_group *group)
--
2.51.0