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sysfs: Add support for permanently empty directories to serve as mount points. 

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.

Cc: stable@vger.kernel.org
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2015-05-13 16:31:40 -05:00
parent ea015218f2
commit 87d2846fcf
2 changed files with 49 additions and 0 deletions
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34
fs/sysfs/dir.c
View File

@ -121,3 +121,37 @@ int sysfs_move_dir_ns(struct kobject *kobj, struct kobject *new_parent_kobj,
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);

15
include/linux/sysfs.h
View File

@ -210,6 +210,10 @@ int __must_check sysfs_rename_dir_ns(struct kobject *kobj, const char *new_name,
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,
@ -298,6 +302,17 @@ static inline int sysfs_move_dir_ns(struct kobject *kobj,
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)