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sysfs: Comment sysfs directory tagging logic

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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
committed by Greg Kroah-Hartman
parent f349cf3473
commit be867b194a
5 changed files with 43 additions and 1 deletions
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8
fs/sysfs/dir.c
View File

@@ -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;

13
fs/sysfs/sysfs.h
View File

@@ -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];
};