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Commit be867b19 authored by Serge E. Hallyn's avatar Serge E. Hallyn Committed by Greg Kroah-Hartman
Browse files

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: default avatarSerge E. Hallyn <serue@us.ibm.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent f349cf34

fs/sysfs/dir.c

+8 −0
Original line number Diff line number Diff line
@@ -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;

fs/sysfs/sysfs.h

+12 −1
Original line number Diff line number Diff line
@@ -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];

};

include/linux/kobject.h

+11 −0
Original line number Diff line number Diff line
@@ -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);

include/linux/sysfs.h

+1 −0
Original line number Diff line number Diff line
@@ -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);

lib/kobject.c

+11 −0
Original line number Diff line number Diff line
@@ -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);