sysfs: Comment sysfs directory tagging logic

Add some in-line comments to explain the new infrastructure, which
was introduced to support sysfs directory tagging with namespaces.
I think an overall description someplace might be good too, but it
didn't really seem to fit into Documentation/filesystems/sysfs.txt,
which appears more geared toward users, rather than maintainers, of
sysfs.

(Tejun, please let me know if I can make anything clearer or failed
altogether to comment something that should be commented.)

Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Serge E. Hallyn 2010-05-03 16:23:15 -05:00 коммит произвёл Greg Kroah-Hartman
Родитель f349cf3473
Коммит be867b194a
5 изменённых файлов: 43 добавлений и 1 удалений

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@ -614,6 +614,14 @@ int sysfs_create_subdir(struct kobject *kobj, const char *name,
KOBJ_NS_TYPE_NONE, NULL, name, p_sd);
}
/**
* sysfs_read_ns_type: return associated ns_type
* @kobj: the kobject being queried
*
* Each kobject can be tagged with exactly one namespace type
* (i.e. network or user). Return the ns_type associated with
* this object if any
*/
static enum kobj_ns_type sysfs_read_ns_type(struct kobject *kobj)
{
const struct kobj_ns_type_operations *ops;

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@ -58,7 +58,7 @@ struct sysfs_dirent {
struct sysfs_dirent *s_sibling;
const char *s_name;
const void *s_ns;
const void *s_ns; /* namespace tag */
union {
struct sysfs_elem_dir s_dir;
struct sysfs_elem_symlink s_symlink;
@ -82,6 +82,7 @@ struct sysfs_dirent {
#define SYSFS_COPY_NAME (SYSFS_DIR | SYSFS_KOBJ_LINK)
#define SYSFS_ACTIVE_REF (SYSFS_KOBJ_ATTR | SYSFS_KOBJ_BIN_ATTR)
/* identify any namespace tag on sysfs_dirents */
#define SYSFS_NS_TYPE_MASK 0xff00
#define SYSFS_NS_TYPE_SHIFT 8
@ -93,6 +94,10 @@ static inline unsigned int sysfs_type(struct sysfs_dirent *sd)
return sd->s_flags & SYSFS_TYPE_MASK;
}
/*
* Return any namespace tags on this dirent.
* enum kobj_ns_type is defined in linux/kobject.h
*/
static inline enum kobj_ns_type sysfs_ns_type(struct sysfs_dirent *sd)
{
return (sd->s_flags & SYSFS_NS_TYPE_MASK) >> SYSFS_NS_TYPE_SHIFT;
@ -123,6 +128,12 @@ struct sysfs_addrm_cxt {
/*
* mount.c
*/
/*
* Each sb is associated with a set of namespace tags (i.e.
* the network namespace of the task which mounted this sysfs
* instance).
*/
struct sysfs_super_info {
const void *ns[KOBJ_NS_TYPES];
};

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@ -136,12 +136,23 @@ struct kobj_attribute {
extern const struct sysfs_ops kobj_sysfs_ops;
/*
* Namespace types which are used to tag kobjects and sysfs entries.
* Network namespace will likely be the first.
*/
enum kobj_ns_type {
KOBJ_NS_TYPE_NONE = 0,
KOBJ_NS_TYPES
};
struct sock;
/*
* Callbacks so sysfs can determine namespaces
* @current_ns: return calling task's namespace
* @netlink_ns: return namespace to which a sock belongs (right?)
* @initial_ns: return the initial namespace (i.e. init_net_ns)
*/
struct kobj_ns_type_operations {
enum kobj_ns_type type;
const void *(*current_ns)(void);

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@ -178,6 +178,7 @@ struct sysfs_dirent *sysfs_get(struct sysfs_dirent *sd);
void sysfs_put(struct sysfs_dirent *sd);
void sysfs_printk_last_file(void);
/* Called to clear a ns tag when it is no longer valid */
void sysfs_exit_ns(enum kobj_ns_type type, const void *tag);
int __must_check sysfs_init(void);

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@ -948,6 +948,17 @@ const void *kobj_ns_initial(enum kobj_ns_type type)
return ns;
}
/*
* kobj_ns_exit - invalidate a namespace tag
*
* @type: the namespace type (i.e. KOBJ_NS_TYPE_NET)
* @ns: the actual namespace being invalidated
*
* This is called when a tag is no longer valid. For instance,
* when a network namespace exits, it uses this helper to
* make sure no sb's sysfs_info points to the now-invalidated
* netns.
*/
void kobj_ns_exit(enum kobj_ns_type type, const void *ns)
{
sysfs_exit_ns(type, ns);