sysfs: make sysfs_dirent->s_element a union

Make sd->s_element a union of sysfs_elem_{dir|symlink|attr|bin_attr}
and rename it to s_elem.  This is to achieve...

* some level of type checking : changing symlink to point to
  sysfs_dirent instead of kobject is much safer and less painful now.
* easier / standardized dereferencing
* allow sysfs_elem_* to contain more than one entry

Where possible, pointer is obtained by directly deferencing from sd
instead of going through other entities.  This reduces dependencies to
dentry, inode and kobject.  to_attr() and to_bin_attr() are unused now
and removed.

This is in preparation of object reference simplification.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 31 insertions, 25 deletions

diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
index d34b008537d5..39ab0481379c 100644
--- a/fs/sysfs/sysfs.h
+++ b/fs/sysfs/sysfs.h
@@ -1,10 +1,33 @@
+struct sysfs_elem_dir {
+        struct kobject          * kobj;
+};
+
+struct sysfs_elem_symlink {
+        struct kobject          * target_kobj;
+};
+
+struct sysfs_elem_attr {
+        struct attribute        * attr;
+};
+
+struct sysfs_elem_bin_attr {
+        struct bin_attribute    * bin_attr;
+};
+
 struct sysfs_dirent {
         atomic_t                s_count;
         struct sysfs_dirent     * s_parent;
         struct list_head        s_sibling;
         struct list_head        s_children;
         const char              * s_name;
-        void                    * s_element;
+
+        union {
+                struct sysfs_elem_dir           dir;
+                struct sysfs_elem_symlink       symlink;
+                struct sysfs_elem_attr          attr;
+                struct sysfs_elem_bin_attr      bin_attr;
+        }                       s_elem;
+
         int                     s_type;
         umode_t                 s_mode;
         ino_t                   s_ino;
@@ -22,8 +45,8 @@ extern int sysfs_create(struct dentry *, int mode, int (*init)(struct inode *));
 
 extern void release_sysfs_dirent(struct sysfs_dirent * sd);
 extern int sysfs_dirent_exist(struct sysfs_dirent *, const unsigned char *);
-extern struct sysfs_dirent *sysfs_new_dirent(const char *name, void *element,
-                                             umode_t mode, int type);
+extern struct sysfs_dirent *sysfs_new_dirent(const char *name, umode_t mode,
+                                             int type);
 extern void sysfs_attach_dirent(struct sysfs_dirent *sd,
                                 struct sysfs_dirent *parent_sd,
                                 struct dentry *dentry);
@@ -47,10 +70,6 @@ extern const struct file_operations bin_fops;
 extern const struct inode_operations sysfs_dir_inode_operations;
 extern const struct inode_operations sysfs_symlink_inode_operations;
 
-struct sysfs_symlink {
-        struct kobject * target_kobj;
-};
-
 struct sysfs_buffer {
         struct list_head                associates;
         size_t                          count;
@@ -70,19 +89,7 @@ struct sysfs_buffer_collection {
 static inline struct kobject * to_kobj(struct dentry * dentry)
 {
         struct sysfs_dirent * sd = dentry->d_fsdata;
-        return ((struct kobject *) sd->s_element);
-}
-
-static inline struct attribute * to_attr(struct dentry * dentry)
-{
-        struct sysfs_dirent * sd = dentry->d_fsdata;
-        return ((struct attribute *) sd->s_element);
-}
-
-static inline struct bin_attribute * to_bin_attr(struct dentry * dentry)
-{
-        struct sysfs_dirent * sd = dentry->d_fsdata;
-        return ((struct bin_attribute *) sd->s_element);
+        return sd->s_elem.dir.kobj;
 }
 
 static inline struct kobject *sysfs_get_kobject(struct dentry *dentry)
@@ -92,11 +99,10 @@ static inline struct kobject *sysfs_get_kobject(struct dentry *dentry)
         spin_lock(&dcache_lock);
         if (!d_unhashed(dentry)) {
                 struct sysfs_dirent * sd = dentry->d_fsdata;
-                if (sd->s_type & SYSFS_KOBJ_LINK) {
-                        struct sysfs_symlink * sl = sd->s_element;
-                        kobj = kobject_get(sl->target_kobj);
-                } else
-                        kobj = kobject_get(sd->s_element);
+                if (sd->s_type & SYSFS_KOBJ_LINK)
+                        kobj = kobject_get(sd->s_elem.symlink.target_kobj);
+                else
+                        kobj = kobject_get(sd->s_elem.dir.kobj);
         }
         spin_unlock(&dcache_lock);