[PATCH RFC v3 02/12] fs/configfs: dynamically allocate super_info
From: Hannes Reinecke
Date: Tue Jun 23 2026 - 05:20:19 EST
Define 'struct configfs_super_info' to hold all required structures
and allocate the filesystem contents dynamically.
Signed-off-by: Hannes Reinecke <hare@xxxxxxxxxx>
---
fs/configfs/configfs_internal.h | 13 ++++
fs/configfs/dir.c | 44 +++++++-----
fs/configfs/mount.c | 148 ++++++++++++++++++++++++++++++----------
include/linux/configfs.h | 1 +
4 files changed, 154 insertions(+), 52 deletions(-)
diff --git a/fs/configfs/configfs_internal.h b/fs/configfs/configfs_internal.h
index 6261e1f3ec201a58a5d46b08dfbced8c2a44d82b..94b9e306709150e7a123c46bb359077c6dc917ad 100644
--- a/fs/configfs/configfs_internal.h
+++ b/fs/configfs/configfs_internal.h
@@ -44,6 +44,17 @@ struct configfs_dirent {
struct configfs_fragment *s_frag;
};
+struct configfs_super_info {
+ struct configfs_dirent root;
+ struct config_group group;
+ struct list_head subsys_list;
+ struct mutex subsys_mutex;
+ struct vfsmount *mnt;
+ int mnt_count;
+ struct net *net_ns;
+ refcount_t ref;
+};
+
#define CONFIGFS_ROOT 0x0001
#define CONFIGFS_DIR 0x0002
#define CONFIGFS_ITEM_ATTR 0x0004
@@ -81,6 +92,8 @@ extern int configfs_setattr(struct mnt_idmap *idmap,
extern struct dentry *configfs_pin_fs(void);
extern void configfs_release_fs(void);
+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 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 3c88f13f1ca2e9f0ee61ab5003356c070f2c05be..1e9c82e02741798930b08c96fb59a2767c7e00fc 100644
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -34,14 +34,6 @@
*/
DEFINE_SPINLOCK(configfs_dirent_lock);
-/*
- * All of link_obj/unlink_obj/link_group/unlink_group require that
- * subsys->su_mutex is held.
- * But parent configfs_subsystem is NULL when config_item is root.
- * Use this mutex when config_item is root.
- */
-static DEFINE_MUTEX(configfs_subsystem_mutex);
-
static void configfs_d_iput(struct dentry * dentry,
struct inode * inode)
{
@@ -1871,20 +1863,28 @@ EXPORT_SYMBOL(configfs_unregister_default_group);
int configfs_register_subsystem(struct configfs_subsystem *subsys)
{
- int err;
+ struct configfs_super_info *info;
struct config_group *group = &subsys->su_group;
struct dentry *dentry;
struct dentry *root;
struct configfs_dirent *sd;
struct configfs_fragment *frag;
+ int err;
+
+ info = configfs_get_super_info(&init_net);
+ if (IS_ERR(info))
+ return PTR_ERR(info);
frag = new_fragment();
- if (!frag)
+ if (!frag) {
+ configfs_put_super_info(info);
return -ENOMEM;
+ }
root = configfs_pin_fs();
if (IS_ERR(root)) {
put_fragment(frag);
+ configfs_put_super_info(info);
return PTR_ERR(root);
}
@@ -1892,9 +1892,9 @@ int configfs_register_subsystem(struct configfs_subsystem *subsys)
group->cg_item.ci_name = group->cg_item.ci_namebuf;
sd = root->d_fsdata;
- mutex_lock(&configfs_subsystem_mutex);
+ mutex_lock(&info->subsys_mutex);
link_group(to_config_group(sd->s_element), group);
- mutex_unlock(&configfs_subsystem_mutex);
+ mutex_unlock(&info->subsys_mutex);
inode_lock_nested(d_inode(root), I_MUTEX_PARENT);
@@ -1921,26 +1921,35 @@ int configfs_register_subsystem(struct configfs_subsystem *subsys)
inode_unlock(d_inode(root));
if (err) {
- mutex_lock(&configfs_subsystem_mutex);
+ mutex_lock(&info->subsys_mutex);
unlink_group(group);
- mutex_unlock(&configfs_subsystem_mutex);
+ mutex_unlock(&info->subsys_mutex);
configfs_release_fs();
}
put_fragment(frag);
-
+ configfs_put_super_info(info);
return err;
}
void configfs_unregister_subsystem(struct configfs_subsystem *subsys)
{
+ struct configfs_super_info *info;
struct config_group *group = &subsys->su_group;
struct dentry *dentry = dget(group->cg_item.ci_dentry);
struct dentry *root = dentry->d_sb->s_root;
struct configfs_dirent *sd = dentry->d_fsdata;
struct configfs_fragment *frag = sd->s_frag;
+ info = configfs_get_super_info(&init_net);
+ if (WARN_ON(IS_ERR(info))) {
+ dput(dentry);
+ return;
+ }
+
if (dentry->d_parent != root) {
pr_err("Tried to unregister non-subsystem!\n");
+ dput(dentry);
+ configfs_put_super_info(info);
return;
}
@@ -1970,10 +1979,11 @@ void configfs_unregister_subsystem(struct configfs_subsystem *subsys)
dput(dentry);
- mutex_lock(&configfs_subsystem_mutex);
+ mutex_lock(&info->subsys_mutex);
unlink_group(group);
- mutex_unlock(&configfs_subsystem_mutex);
+ mutex_unlock(&info->subsys_mutex);
configfs_release_fs();
+ configfs_put_super_info(info);
}
EXPORT_SYMBOL(configfs_register_subsystem);
diff --git a/fs/configfs/mount.c b/fs/configfs/mount.c
index 88da7b428e52f2f4ab139ad3907101f685d617b1..067bb1099a52ca2216d1b2881429a3fd1811c706 100644
--- a/fs/configfs/mount.c
+++ b/fs/configfs/mount.c
@@ -22,10 +22,18 @@
/* Random magic number */
#define CONFIGFS_MAGIC 0x62656570
-static struct vfsmount *configfs_mount = NULL;
struct kmem_cache *configfs_dir_cachep;
-static int configfs_mnt_count = 0;
+static DEFINE_XARRAY(configfs_super_xa);
+static struct configfs_super_info *configfs_root;
+static u64 configfs_ns_id(struct net *net_ns)
+{
+ struct ns_common *ns = net_ns ? to_ns_common(net_ns) : NULL;
+
+ if (!ns || net_ns == &init_net)
+ return 0;
+ return ns->ns_id;
+}
static void configfs_free_inode(struct inode *inode)
{
@@ -40,13 +48,6 @@ static const struct super_operations configfs_ops = {
.free_inode = configfs_free_inode,
};
-static struct config_group configfs_root_group = {
- .cg_item = {
- .ci_namebuf = "root",
- .ci_name = configfs_root_group.cg_item.ci_namebuf,
- },
-};
-
bool configfs_is_root(struct config_item *item)
{
struct configfs_dirent *sd;
@@ -57,19 +58,76 @@ bool configfs_is_root(struct config_item *item)
return !!(sd->s_type & CONFIGFS_ROOT);
}
-static struct configfs_dirent configfs_root = {
- .s_sibling = LIST_HEAD_INIT(configfs_root.s_sibling),
- .s_children = LIST_HEAD_INIT(configfs_root.s_children),
- .s_element = &configfs_root_group.cg_item,
- .s_type = CONFIGFS_ROOT,
- .s_iattr = NULL,
-};
+static void configfs_fill_super_info(struct configfs_super_info *info)
+{
+ INIT_LIST_HEAD(&info->root.s_sibling);
+ INIT_LIST_HEAD(&info->root.s_children);
+ info->root.s_type = CONFIGFS_ROOT;
+ info->root.s_element = &info->group.cg_item;
+ strscpy(info->group.cg_item.ci_namebuf, "root", 4);
+ info->group.cg_item.ci_name = info->group.cg_item.ci_namebuf;
+ config_group_init(&info->group);
+ INIT_LIST_HEAD(&info->subsys_list);
+ mutex_init(&info->subsys_mutex);
+ refcount_set(&info->ref, 1);
+ info->mnt_count = 0;
+}
+
+struct configfs_super_info *configfs_get_super_info(struct net *net_ns)
+{
+ struct configfs_super_info *info;
+ u64 ns_id = configfs_ns_id(net_ns);
+ int err;
+
+ xa_lock(&configfs_super_xa);
+ info = xa_load(&configfs_super_xa, ns_id);
+ if (info) {
+ if (!refcount_inc_not_zero((&info->ref)))
+ info = ERR_PTR(-EBUSY);
+ xa_unlock(&configfs_super_xa);
+ return info;
+ }
+ info = kzalloc_obj(*info);
+ if (!info) {
+ xa_unlock(&configfs_super_xa);
+ return ERR_PTR(-ENOMEM);
+ }
+
+ info->net_ns = get_net(net_ns);
+ configfs_fill_super_info(info);
+ err = __xa_insert(&configfs_super_xa, ns_id,
+ info, GFP_KERNEL);
+ xa_unlock(&configfs_super_xa);
+ if (err < 0) {
+ put_net(info->net_ns);
+ kfree(info);
+ return ERR_PTR(err);
+ }
+ return info;
+}
+
+void configfs_put_super_info(struct configfs_super_info *info)
+{
+ u64 ns_id = configfs_ns_id(info->net_ns);
+
+ xa_lock(&configfs_super_xa);
+ if (!refcount_dec_and_test(&info->ref)) {
+ xa_unlock(&configfs_super_xa);
+ return;
+ }
+ __xa_erase(&configfs_super_xa, ns_id);
+ xa_unlock(&configfs_super_xa);
+ put_net(info->net_ns);
+ kfree(info);
+}
static int configfs_fill_super(struct super_block *sb, struct fs_context *fc)
{
+ struct configfs_super_info *info = configfs_get_super_info(&init_net);
struct inode *inode;
struct dentry *root;
+ sb->s_fs_info = info;
sb->s_blocksize = PAGE_SIZE;
sb->s_blocksize_bits = PAGE_SHIFT;
sb->s_magic = CONFIGFS_MAGIC;
@@ -77,25 +135,25 @@ static int configfs_fill_super(struct super_block *sb, struct fs_context *fc)
sb->s_time_gran = 1;
inode = configfs_new_inode(S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
- &configfs_root, sb);
- if (inode) {
- inode->i_op = &configfs_root_inode_operations;
- inode->i_fop = &configfs_dir_operations;
- /* directory inodes start off with i_nlink == 2 (for "." entry) */
- inc_nlink(inode);
- } else {
+ &info->root, sb);
+ if (IS_ERR(inode)) {
pr_debug("could not get root inode\n");
- return -ENOMEM;
+ configfs_put_super_info(info);
+ return PTR_ERR(inode);
}
+ inode->i_op = &configfs_root_inode_operations;
+ inode->i_fop = &configfs_dir_operations;
+ /* directory inodes start off with i_nlink == 2 (for "." entry) */
+ inc_nlink(inode);
root = d_make_root(inode);
if (!root) {
pr_debug("%s: could not get root dentry!\n",__func__);
+ configfs_put_super_info(info);
return -ENOMEM;
}
- config_group_init(&configfs_root_group);
- configfs_root_group.cg_item.ci_dentry = root;
- root->d_fsdata = &configfs_root;
+ info->group.cg_item.ci_dentry = root;
+ root->d_fsdata = &info->root;
sb->s_root = root;
set_default_d_op(sb, &configfs_dentry_ops); /* the rest get that */
sb->s_d_flags |= DCACHE_DONTCACHE;
@@ -117,24 +175,33 @@ static int configfs_init_fs_context(struct fs_context *fc)
return 0;
}
+static void configfs_kill_sb(struct super_block *sb)
+{
+ struct configfs_super_info *info = sb->s_fs_info;
+
+ kill_anon_super(sb);
+ configfs_put_super_info(info);
+ sb->s_fs_info = NULL;
+}
+
static struct file_system_type configfs_fs_type = {
.owner = THIS_MODULE,
.name = "configfs",
.init_fs_context = configfs_init_fs_context,
- .kill_sb = kill_anon_super,
+ .kill_sb = configfs_kill_sb,
};
MODULE_ALIAS_FS("configfs");
struct dentry *configfs_pin_fs(void)
{
- int err = simple_pin_fs(&configfs_fs_type, &configfs_mount,
- &configfs_mnt_count);
- return err ? ERR_PTR(err) : configfs_mount->mnt_root;
+ int err = simple_pin_fs(&configfs_fs_type, &configfs_root->mnt,
+ &configfs_root->mnt_count);
+ return err ? ERR_PTR(err) : configfs_root->mnt->mnt_root;
}
void configfs_release_fs(void)
{
- simple_release_fs(&configfs_mount, &configfs_mnt_count);
+ simple_release_fs(&configfs_root->mnt, &configfs_root->mnt_count);
}
@@ -148,18 +215,27 @@ static int __init configfs_init(void)
if (!configfs_dir_cachep)
goto out;
+ configfs_root = configfs_get_super_info(&init_net);
+ if (IS_ERR(configfs_root)) {
+ err = PTR_ERR(configfs_root);
+ goto out2;
+ }
+
err = sysfs_create_mount_point(kernel_kobj, "config");
if (err)
- goto out2;
+ goto out3;
err = register_filesystem(&configfs_fs_type);
if (err)
- goto out3;
+ goto out4;
return 0;
-out3:
+out4:
pr_err("Unable to register filesystem!\n");
sysfs_remove_mount_point(kernel_kobj, "config");
+out3:
+ configfs_put_super_info(configfs_root);
+ configfs_root = NULL;
out2:
kmem_cache_destroy(configfs_dir_cachep);
configfs_dir_cachep = NULL;
@@ -171,6 +247,8 @@ static void __exit configfs_exit(void)
{
unregister_filesystem(&configfs_fs_type);
sysfs_remove_mount_point(kernel_kobj, "config");
+ configfs_put_super_info(configfs_root);
+ configfs_root = NULL;
kmem_cache_destroy(configfs_dir_cachep);
configfs_dir_cachep = NULL;
}
diff --git a/include/linux/configfs.h b/include/linux/configfs.h
index ef65c75beeaad87d33a18e86ac47bf2994705f2e..19165e36da810c75500bb584702ae3a594c3510d 100644
--- a/include/linux/configfs.h
+++ b/include/linux/configfs.h
@@ -24,6 +24,7 @@
#include <linux/list.h> /* struct list_head */
#include <linux/kref.h> /* struct kref */
#include <linux/mutex.h> /* struct mutex */
+#include <net/net_namespace.h> /* struct net */
#define CONFIGFS_ITEM_NAME_LEN 20
--
2.51.0