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Date: Fri, 21 May 2010 09:53:55 -0700
From: Greg Kroah-Hartman <gregkh@...e.de>
To: linux-kernel@...r.kernel.org
Cc: "Serge E. Hallyn" <serue@...ibm.com>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
Tejun Heo <tj@...nel.org>, Greg Kroah-Hartman <gregkh@...e.de>
Subject: [PATCH 25/38] sysfs: Comment sysfs directory tagging logic
From: Serge E. Hallyn <serue@...ibm.com>
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@...ibm.com>
Cc: Eric W. Biederman <ebiederm@...ssion.com>
Cc: Tejun Heo <tj@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
---
fs/sysfs/dir.c | 8 ++++++++
fs/sysfs/sysfs.h | 13 ++++++++++++-
include/linux/kobject.h | 11 +++++++++++
include/linux/sysfs.h | 1 +
lib/kobject.c | 11 +++++++++++
5 files changed, 43 insertions(+), 1 deletions(-)
diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index a63eb4b..7e54bac 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 93847d5..6a13105 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 d9456f6..b60d2df 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 976c466..47f1c95 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 b2c6d1f..f07c572 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);
--
1.7.0.3
--
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