sysfs: Implement sysfs_rename_link

Because of rename ordering problems we occassionally give false
warnings about invalid sysfs operations.  So using sysfs_rename
create a sysfs_rename_link function that doesn't need strange
workarounds.

Cc: Benjamin Thery <benjamin.thery@bull.net>
Cc: Daniel Lezcano <dlezcano@fr.ibm.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Eric W. Biederman <ebiederm@aristanetworks.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

2 files changed, 47 insertions, 0 deletions

diff --git a/fs/sysfs/symlink.c b/fs/sysfs/symlink.c
index c5eff49fa41b..1b9a3a1e8a17 100644
--- a/fs/sysfs/symlink.c
+++ b/fs/sysfs/symlink.c
@@ -123,6 +123,44 @@ 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)
+{
+        struct sysfs_dirent *parent_sd, *sd = NULL;
+        int result;
+
+        if (!kobj)
+                parent_sd = &sysfs_root;
+        else
+                parent_sd = kobj->sd;
+
+        result = -ENOENT;
+        sd = sysfs_get_dirent(parent_sd, old);
+        if (!sd)
+                goto out;
+
+        result = -EINVAL;
+        if (sysfs_type(sd) != SYSFS_KOBJ_LINK)
+                goto out;
+        if (sd->s_symlink.target_sd->s_dir.kobj != targ)
+                goto out;
+
+        result = sysfs_rename(sd, parent_sd, new);
+
+out:
+        sysfs_put(sd);
+        return result;
+}
+
 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 5b8f80f5aca6..d77cde6d0498 100644
--- a/include/linux/sysfs.h
+++ b/include/linux/sysfs.h
@@ -151,6 +151,9 @@ 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,
@@ -255,6 +258,12 @@ 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)
 {