[PATCH 4/7] sysfs: remove ktype->namespace() invocations in symlink code

Tejun Heo
2013-09-12T02:30:47Z

There's no reason for sysfs to be calling ktype->namespace(). It is
backwards, obfuscates what's going on and unnecessarily tangles two
separate layers.

There are two places where symlink code calls ktype->namespace().

* sysfs_do_create_link_sd() calls it to find out the namespace tag of
the target directory. Unless symlinking races with cross-namespace
renaming, this equals @target_sd->s_ns.

* sysfs_rename_link() uses it to find out the new namespace to rename
to and the new namespace can be different from the existing one.
The function is renamed to sysfs_rename_link_ns() with an explicit
@ns argument and the ktype->namespace() invocation is shifted to the
device layer.

While this patch replaces ktype->namespace() invocation with the
recorded result in @target_sd, this shouldn't result in any behvior
difference.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Kay Sievers <kay@vrfy.org>
---
drivers/base/core.c | 8 +++++---
fs/sysfs/symlink.c | 16 +++++++---------
include/linux/sysfs.h | 16 ++++++++++++----
3 files changed, 24 insertions(+), 16 deletions(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index c7cfadc..3335000 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -1881,6 +1881,7 @@ EXPORT_SYMBOL_GPL(device_destroy);
*/
int device_rename(struct device *dev, const char *new_name)
{
+ struct kobject *kobj = &dev->kobj;
char *old_device_name = NULL;
int error;

@@ -1898,13 +1899,14 @@ int device_rename(struct device *dev, const char *new_name)
}

if (dev->class) {
- error = sysfs_rename_link(&dev->class->p->subsys.kobj,
- &dev->kobj, old_device_name, new_name);
+ error = sysfs_rename_link_ns(&dev->class->p->subsys.kobj,
+ kobj, old_device_name,
+ new_name, kobject_namespace(kobj));
if (error)
goto out;
}

- error = kobject_rename(&dev->kobj, new_name);
+ error = kobject_rename(kobj, new_name);
if (error)
goto out;

diff --git a/fs/sysfs/symlink.c b/fs/sysfs/symlink.c
index 2dd4507..12d58ad 100644
--- a/fs/sysfs/symlink.c
+++ b/fs/sysfs/symlink.c
@@ -52,7 +52,7 @@ static int sysfs_do_create_link_sd(struct sysfs_dirent *parent_sd,

ns_type = sysfs_ns_type(parent_sd);
if (ns_type)
- sd->s_ns = target->ktype->namespace(target);
+ sd->s_ns = target_sd->s_ns;
sd->s_symlink.target_sd = target_sd;
target_sd = NULL; /* reference is now owned by the symlink */

@@ -181,19 +181,20 @@ void sysfs_remove_link(struct kobject *kobj, const char *name)
EXPORT_SYMBOL_GPL(sysfs_remove_link);

/**
- * sysfs_rename_link - rename symlink in object's directory.
+ * sysfs_rename_link_ns - rename symlink in object's directory.
* @kobj: object we're acting for.
* @targ: object we're pointing to.
* @old: previous name of the symlink.
* @new: new name of the symlink.
+ * @new_ns: new namespace of the symlink.
*
* A helper function for the common rename symlink idiom.
*/
-int sysfs_rename_link(struct kobject *kobj, struct kobject *targ,
- const char *old, const char *new)
+int sysfs_rename_link_ns(struct kobject *kobj, struct kobject *targ,
+ const char *old, const char *new, const void *new_ns)
{
struct sysfs_dirent *parent_sd, *sd = NULL;
- const void *old_ns = NULL, *new_ns = NULL;
+ const void *old_ns = NULL;
int result;

if (!kobj)
@@ -215,16 +216,13 @@ int sysfs_rename_link(struct kobject *kobj, struct kobject *targ,
if (sd->s_symlink.target_sd->s_dir.kobj != targ)
goto out;

- if (sysfs_ns_type(parent_sd))
- new_ns = targ->ktype->namespace(targ);
-
result = sysfs_rename(sd, parent_sd, new_ns, new);

out:
sysfs_put(sd);
return result;
}
-EXPORT_SYMBOL_GPL(sysfs_rename_link);
+EXPORT_SYMBOL_GPL(sysfs_rename_link_ns);

static int sysfs_get_target_path(struct sysfs_dirent *parent_sd,
struct sysfs_dirent *target_sd, char *path)
diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
index 7f56bad..c792f73 100644
--- a/include/linux/sysfs.h
+++ b/include/linux/sysfs.h
@@ -213,8 +213,9 @@ int __must_check sysfs_create_link_nowarn(struct kobject *kobj,
const char *name);
void sysfs_remove_link(struct kobject *kobj, const char *name);

-int sysfs_rename_link(struct kobject *kobj, struct kobject *target,
- const char *old_name, const char *new_name);
+int sysfs_rename_link_ns(struct kobject *kobj, struct kobject *target,
+ const char *old_name, const char *new_name,
+ const void *new_ns);

void sysfs_delete_link(struct kobject *dir, struct kobject *targ,
const char *name);
@@ -340,8 +341,9 @@ static inline void sysfs_remove_link(struct kobject *kobj, const char *name)
{
}

-static inline int sysfs_rename_link(struct kobject *k, struct kobject *t,
- const char *old_name, const char *new_name)
+static inline int sysfs_rename_link_ns(struct kobject *k, struct kobject *t,
+ const char *old_name,
+ const char *new_name, const void *ns)
{
return 0;
}
@@ -454,4 +456,10 @@ static inline void sysfs_remove_file(struct kobject *kobj,
return sysfs_remove_file_ns(kobj, attr, NULL);
}

+static inline int sysfs_rename_link(struct kobject *kobj, struct kobject *target,
+ const char *old_name, const char *new_name)
+{
+ return sysfs_rename_link_ns(kobj, target, old_name, new_name, NULL);
+}
+
#endif /* _SYSFS_H_ */
--
1.8.3.1