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authorSerge E. Hallyn <serue@us.ibm.com>2010-05-03 16:23:15 -0500
committerGreg Kroah-Hartman <gregkh@suse.de>2010-05-21 09:37:31 -0700
commitbe867b194a3ae3c680c29521287ae49b4d44d420 (patch)
tree1b3ad125d02603c6a9cc4bb8ae518695d7c6a66d
parentf349cf34731c3b3eddbcd63cb04489aee2c405bd (diff)
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>
-rw-r--r--fs/sysfs/dir.c8
-rw-r--r--fs/sysfs/sysfs.h13
-rw-r--r--include/linux/kobject.h11
-rw-r--r--include/linux/sysfs.h1
-rw-r--r--lib/kobject.c11
5 files changed, 43 insertions, 1 deletions
diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index a63eb4ba786..7e54bac8c4b 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -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;
diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
index 93847d54c2e..6a13105b559 100644
--- a/fs/sysfs/sysfs.h
+++ b/fs/sysfs/sysfs.h
@@ -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];
};
diff --git a/include/linux/kobject.h b/include/linux/kobject.h
index d9456f69904..b60d2dfe4e6 100644
--- a/include/linux/kobject.h
+++ b/include/linux/kobject.h
@@ -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);
diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
index 976c4664b21..47f1c95b529 100644
--- a/include/linux/sysfs.h
+++ b/include/linux/sysfs.h
@@ -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);
diff --git a/lib/kobject.c b/lib/kobject.c
index b2c6d1f56e6..f07c57252e8 100644
--- a/lib/kobject.c
+++ b/lib/kobject.c
@@ -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);