[PATCH 01/20] sysfs: Implement sysfs_rename_link

[Eric W. Biederman]

From: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>

Because of rename ordering problems we occassionally give false
warnings about invalid sysfs operations, so implement a helper
function for this common sysfs idiom.

This is a stripped down version of an earlier patch that
also added sysfs_delete_link.

Cc: Benjamin Thery <benjamin.thery@xxxxxxxx>
Cc: Daniel Lezcano <dlezcano@xxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxxxxxxxx>
---
 fs/sysfs/symlink.c    |   16 ++++++++++++++++
 include/linux/sysfs.h |    9 +++++++++
 2 files changed, 25 insertions(+), 0 deletions(-)

diff --git a/fs/sysfs/symlink.c b/fs/sysfs/symlink.c
index a3ba217..11c4da5 100644
--- a/fs/sysfs/symlink.c
+++ b/fs/sysfs/symlink.c
@@ -122,6 +122,22 @@ void sysfs_remove_link(struct kobject * kobj, const char * name)
 	sysfs_hash_and_remove(parent_sd, name);
 }
 
+/**
+ *	sysfs_rename_link - 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.
+ *
+ *	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)
+{
+	sysfs_remove_link(kobj, old);
+	return sysfs_create_link(kobj, targ, new);
+}
+
 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 9d68fed..18c8e70 100644
--- a/include/linux/sysfs.h
+++ b/include/linux/sysfs.h
@@ -109,6 +109,9 @@ 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 __must_check sysfs_create_group(struct kobject *kobj,
 				    const struct attribute_group *grp);
 int sysfs_update_group(struct kobject *kobj,
@@ -202,6 +205,12 @@ 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)
+{
+	return 0;
+}
+
 static inline int sysfs_create_group(struct kobject *kobj,
 				     const struct attribute_group *grp)
 {
-- 
1.6.1.2.350.g88cc

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