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Subject[PATCH 4.0 05/58] sysfs: Add support for permanently empty directories to serve as mount points.
Date
4.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: "Eric W. Biederman" <ebiederm@xmission.com>

commit 87d2846fcf88113fae2341da1ca9a71f0d916f2c upstream.

Add two functions sysfs_create_mount_point and
sysfs_remove_mount_point that hang a permanently empty directory off
of a kobject or remove a permanently emptpy directory hanging from a
kobject. Export these new functions so modular filesystems can use
them.

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/sysfs/dir.c | 34 ++++++++++++++++++++++++++++++++++
include/linux/sysfs.h | 15 +++++++++++++++
2 files changed, 49 insertions(+)

--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -121,3 +121,37 @@ int sysfs_move_dir_ns(struct kobject *ko

return kernfs_rename_ns(kn, new_parent, kn->name, new_ns);
}
+
+/**
+ * sysfs_create_mount_point - create an always empty directory
+ * @parent_kobj: kobject that will contain this always empty directory
+ * @name: The name of the always empty directory to add
+ */
+int sysfs_create_mount_point(struct kobject *parent_kobj, const char *name)
+{
+ struct kernfs_node *kn, *parent = parent_kobj->sd;
+
+ kn = kernfs_create_empty_dir(parent, name);
+ if (IS_ERR(kn)) {
+ if (PTR_ERR(kn) == -EEXIST)
+ sysfs_warn_dup(parent, name);
+ return PTR_ERR(kn);
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(sysfs_create_mount_point);
+
+/**
+ * sysfs_remove_mount_point - remove an always empty directory.
+ * @parent_kobj: kobject that will contain this always empty directory
+ * @name: The name of the always empty directory to remove
+ *
+ */
+void sysfs_remove_mount_point(struct kobject *parent_kobj, const char *name)
+{
+ struct kernfs_node *parent = parent_kobj->sd;
+
+ kernfs_remove_by_name_ns(parent, name, NULL);
+}
+EXPORT_SYMBOL_GPL(sysfs_remove_mount_point);
--- a/include/linux/sysfs.h
+++ b/include/linux/sysfs.h
@@ -195,6 +195,10 @@ int __must_check sysfs_rename_dir_ns(str
int __must_check sysfs_move_dir_ns(struct kobject *kobj,
struct kobject *new_parent_kobj,
const void *new_ns);
+int __must_check sysfs_create_mount_point(struct kobject *parent_kobj,
+ const char *name);
+void sysfs_remove_mount_point(struct kobject *parent_kobj,
+ const char *name);

int __must_check sysfs_create_file_ns(struct kobject *kobj,
const struct attribute *attr,
@@ -283,6 +287,17 @@ static inline int sysfs_move_dir_ns(stru
return 0;
}

+static inline int sysfs_create_mount_point(struct kobject *parent_kobj,
+ const char *name)
+{
+ return 0;
+}
+
+static inline void sysfs_remove_mount_point(struct kobject *parent_kobj,
+ const char *name)
+{
+}
+
static inline int sysfs_create_file_ns(struct kobject *kobj,
const struct attribute *attr,
const void *ns)



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