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Subject[PATCH] fs/configfs: allow to create groups on demand
This patch adds a function add a group to an existing one and its
counterart. The newly created group behaves as it would be created via
default_groups[] which means the user can't rmdir it.
This should be used by the upcomming USB gadget interface in order to
add the currently available UDCs as a child of the UDC node. The UDC
itself will appear once the hardware driver is loaded and can appear
later.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
fs/configfs/dir.c | 63 ++++++++++++++++++++++++++++++++++------------
include/linux/configfs.h | 4 +++
2 files changed, 51 insertions(+), 16 deletions(-)

diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
index 7414ae2..50ee2bd 100644
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -1663,19 +1663,13 @@ const struct file_operations configfs_dir_operations = {
.readdir = configfs_readdir,
};

-int configfs_register_subsystem(struct configfs_subsystem *subsys)
+static int __create_group(struct config_group *group, struct dentry *root)
{
int err;
- struct config_group *group = &subsys->su_group;
struct qstr name;
struct dentry *dentry;
- struct dentry *root;
struct configfs_dirent *sd;

- root = configfs_pin_fs();
- if (IS_ERR(root))
- return PTR_ERR(root);
-
if (!group->cg_item.ci_name)
group->cg_item.ci_name = group->cg_item.ci_namebuf;

@@ -1708,25 +1702,48 @@ int configfs_register_subsystem(struct configfs_subsystem *subsys)

mutex_unlock(&root->d_inode->i_mutex);

- if (err) {
+ if (err)
unlink_group(group);
- configfs_release_fs();
+
+ return err;
+}
+
+int configfs_create_group(struct config_group *parent, struct config_group *new)
+{
+ int ret;
+
+ ret = __create_group(new, parent->cg_item.ci_dentry);
+ if (!ret) {
+ struct configfs_dirent *sd = new->cg_item.ci_dentry->d_fsdata;
+
+ sd->s_type |= CONFIGFS_USET_DEFAULT;
}

+ return ret;
+}
+EXPORT_SYMBOL_GPL(configfs_create_group);
+
+int configfs_register_subsystem(struct configfs_subsystem *subsys)
+{
+ int err;
+ struct dentry *root;
+
+ root = configfs_pin_fs();
+ if (IS_ERR(root))
+ return PTR_ERR(root);
+
+ err = __create_group(&subsys->su_group, root);
+ if (err)
+ configfs_release_fs();
+
return err;
}

-void configfs_unregister_subsystem(struct configfs_subsystem *subsys)
+void configfs_remove_group(struct config_group *group)
{
- struct config_group *group = &subsys->su_group;
struct dentry *dentry = group->cg_item.ci_dentry;
struct dentry *root = dentry->d_sb->s_root;

- if (dentry->d_parent != root) {
- printk(KERN_ERR "configfs: Tried to unregister non-subsystem!\n");
- return;
- }
-
mutex_lock_nested(&root->d_inode->i_mutex,
I_MUTEX_PARENT);
mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_CHILD);
@@ -1749,6 +1766,20 @@ void configfs_unregister_subsystem(struct configfs_subsystem *subsys)
dput(dentry);

unlink_group(group);
+}
+EXPORT_SYMBOL_GPL(configfs_remove_group);
+
+void configfs_unregister_subsystem(struct configfs_subsystem *subsys)
+{
+ struct config_group *group = &subsys->su_group;
+ struct dentry *dentry = group->cg_item.ci_dentry;
+ struct dentry *root = dentry->d_sb->s_root;
+
+ if (dentry->d_parent != root) {
+ pr_err("configfs: Tried to unregister non-subsystem!\n");
+ return;
+ }
+ configfs_remove_group(group);
configfs_release_fs();
}

diff --git a/include/linux/configfs.h b/include/linux/configfs.h
index 34025df..660c25d 100644
--- a/include/linux/configfs.h
+++ b/include/linux/configfs.h
@@ -249,6 +249,10 @@ static inline struct configfs_subsystem *to_configfs_subsystem(struct config_gro
NULL;
}

+int configfs_create_group(struct config_group *parent,
+ struct config_group *new);
+void configfs_remove_group(struct config_group *group);
+
int configfs_register_subsystem(struct configfs_subsystem *subsys);
void configfs_unregister_subsystem(struct configfs_subsystem *subsys);

--
1.7.10.4


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