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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 /fs
parentf349cf34731c3b3eddbcd63cb04489aee2c405bd (diff)
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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>
Diffstat (limited to 'fs')
-rw-r--r--fs/sysfs/dir.c8
-rw-r--r--fs/sysfs/sysfs.h13
2 files changed, 20 insertions, 1 deletions
diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index a63eb4ba7867..7e54bac8c4b0 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 93847d54c2e3..6a13105b5594 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];
};