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>

7 files changed, 71 insertions, 79 deletions

diff --git a/fs/sysfs/bin.c b/fs/sysfs/bin.c
index 606267a36275..67a0d5030c96 100644
--- a/fs/sysfs/bin.c
+++ b/fs/sysfs/bin.c
@@ -23,7 +23,8 @@
 static int
 fill_read(struct dentry *dentry, char *buffer, loff_t off, size_t count)
 {
-        struct bin_attribute * attr = to_bin_attr(dentry);
+        struct sysfs_dirent *attr_sd = dentry->d_fsdata;
+        struct bin_attribute *attr = attr_sd->s_elem.bin_attr.bin_attr;
         struct kobject * kobj = to_kobj(dentry->d_parent);
 
         if (!attr->read)
@@ -65,7 +66,8 @@ read(struct file *file, char __user *userbuf, size_t bytes, loff_t *off)
 static int
 flush_write(struct dentry *dentry, char *buffer, loff_t offset, size_t count)
 {
-        struct bin_attribute *attr = to_bin_attr(dentry);
+        struct sysfs_dirent *attr_sd = dentry->d_fsdata;
+        struct bin_attribute *attr = attr_sd->s_elem.bin_attr.bin_attr;
         struct kobject *kobj = to_kobj(dentry->d_parent);
 
         if (!attr->write)
@@ -101,9 +103,9 @@ static ssize_t write(struct file *file, const char __user *userbuf,
 
 static int mmap(struct file *file, struct vm_area_struct *vma)
 {
-        struct dentry *dentry = file->f_path.dentry;
-        struct bin_attribute *attr = to_bin_attr(dentry);
-        struct kobject *kobj = to_kobj(dentry->d_parent);
+        struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
+        struct bin_attribute *attr = attr_sd->s_elem.bin_attr.bin_attr;
+        struct kobject *kobj = to_kobj(file->f_path.dentry->d_parent);
 
         if (!attr->mmap)
                 return -EINVAL;
@@ -114,7 +116,8 @@ static int mmap(struct file *file, struct vm_area_struct *vma)
 static int open(struct inode * inode, struct file * file)
 {
         struct kobject *kobj = sysfs_get_kobject(file->f_path.dentry->d_parent);
-        struct bin_attribute * attr = to_bin_attr(file->f_path.dentry);
+        struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
+        struct bin_attribute *attr = attr_sd->s_elem.bin_attr.bin_attr;
         int error = -EINVAL;
 
         if (!kobj || !attr)
@@ -150,7 +153,8 @@ static int open(struct inode * inode, struct file * file)
 static int release(struct inode * inode, struct file * file)
 {
         struct kobject * kobj = to_kobj(file->f_path.dentry->d_parent);
-        struct bin_attribute * attr = to_bin_attr(file->f_path.dentry);
+        struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
+        struct bin_attribute *attr = attr_sd->s_elem.bin_attr.bin_attr;
         u8 * buffer = file->private_data;
 
         kobject_put(kobj);
diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index 6e8d6f54f082..079122695675 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -52,11 +52,8 @@ void release_sysfs_dirent(struct sysfs_dirent * sd)
  repeat:
         parent_sd = sd->s_parent;
 
-        if (sd->s_type & SYSFS_KOBJ_LINK) {
-                struct sysfs_symlink * sl = sd->s_element;
-                kobject_put(sl->target_kobj);
-                kfree(sl);
-        }
+        if (sd->s_type & SYSFS_KOBJ_LINK)
+                kobject_put(sd->s_elem.symlink.target_kobj);
         if (sd->s_type & SYSFS_COPY_NAME)
                 kfree(sd->s_name);
         kfree(sd->s_iattr);
@@ -95,8 +92,7 @@ static struct dentry_operations sysfs_dentry_ops = {
         .d_iput         = sysfs_d_iput,
 };
 
-struct sysfs_dirent *sysfs_new_dirent(const char *name, void *element,
-                                      umode_t mode, int type)
+struct sysfs_dirent *sysfs_new_dirent(const char *name, umode_t mode, int type)
 {
         char *dup_name = NULL;
         struct sysfs_dirent *sd = NULL;
@@ -120,7 +116,6 @@ struct sysfs_dirent *sysfs_new_dirent(const char *name, void *element,
         INIT_LIST_HEAD(&sd->s_sibling);
 
         sd->s_name = name;
-        sd->s_element = element;
         sd->s_mode = mode;
         sd->s_type = type;
 
@@ -160,7 +155,7 @@ int sysfs_dirent_exist(struct sysfs_dirent *parent_sd,
         struct sysfs_dirent * sd;
 
         list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
-                if (sd->s_element) {
+                if (sd->s_type) {
                         if (strcmp(sd->s_name, new))
                                 continue;
                         else
@@ -215,9 +210,10 @@ static int create_dir(struct kobject *kobj, struct dentry *parent,
                 goto out_dput;
 
         error = -ENOMEM;
-        sd = sysfs_new_dirent(name, kobj, mode, SYSFS_DIR);
+        sd = sysfs_new_dirent(name, mode, SYSFS_DIR);
         if (!sd)
                 goto out_drop;
+        sd->s_elem.dir.kobj = kobj;
         sysfs_attach_dirent(sd, parent->d_fsdata, dentry);
 
         error = sysfs_create(dentry, mode, init_dir);
@@ -290,10 +286,10 @@ static int sysfs_attach_attr(struct sysfs_dirent * sd, struct dentry * dentry)
         int error = 0;
 
         if (sd->s_type & SYSFS_KOBJ_BIN_ATTR) {
-                bin_attr = sd->s_element;
+                bin_attr = sd->s_elem.bin_attr.bin_attr;
                 attr = &bin_attr->attr;
         } else {
-                attr = sd->s_element;
+                attr = sd->s_elem.attr.attr;
                 init = init_file;
         }
 
@@ -404,7 +400,7 @@ static void __sysfs_remove_dir(struct dentry *dentry)
         mutex_lock(&dentry->d_inode->i_mutex);
         parent_sd = dentry->d_fsdata;
         list_for_each_entry_safe(sd, tmp, &parent_sd->s_children, s_sibling) {
-                if (!sd->s_element || !(sd->s_type & SYSFS_NOT_PINNED))
+                if (!sd->s_type || !(sd->s_type & SYSFS_NOT_PINNED))
                         continue;
                 list_del_init(&sd->s_sibling);
                 sysfs_drop_dentry(sd, dentry);
@@ -556,7 +552,7 @@ static int sysfs_dir_open(struct inode *inode, struct file *file)
         struct sysfs_dirent * sd;
 
         mutex_lock(&dentry->d_inode->i_mutex);
-        sd = sysfs_new_dirent("_DIR_", NULL, 0, 0);
+        sd = sysfs_new_dirent("_DIR_", 0, 0);
         if (sd)
                 sysfs_attach_dirent(sd, parent_sd, NULL);
         mutex_unlock(&dentry->d_inode->i_mutex);
@@ -623,7 +619,7 @@ static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir)
 
                                 next = list_entry(p, struct sysfs_dirent,
                                                    s_sibling);
-                                if (!next->s_element)
+                                if (!next->s_type)
                                         continue;
 
                                 name = next->s_name;
@@ -671,7 +667,7 @@ static loff_t sysfs_dir_lseek(struct file * file, loff_t offset, int origin)
                                 struct sysfs_dirent *next;
                                 next = list_entry(p, struct sysfs_dirent,
                                                    s_sibling);
-                                if (next->s_element)
+                                if (next->s_type)
                                         n--;
                                 p = p->next;
                         }
@@ -738,9 +734,10 @@ struct dentry *sysfs_create_shadow_dir(struct kobject *kobj)
         if (!shadow)
                 goto nomem;
 
-        sd = sysfs_new_dirent("_SHADOW_", kobj, inode->i_mode, SYSFS_DIR);
+        sd = sysfs_new_dirent("_SHADOW_", inode->i_mode, SYSFS_DIR);
         if (!sd)
                 goto nomem;
+        sd->s_elem.dir.kobj = kobj;
         /* point to parent_sd but don't attach to it */
         sd->s_parent = sysfs_get(parent_sd);
         sysfs_attach_dirent(sd, NULL, shadow);
diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index 8240b1687dd0..04f6b0ebc889 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -88,7 +88,6 @@ remove_from_collection(struct sysfs_buffer *buffer, struct inode *node)
 static int fill_read_buffer(struct dentry * dentry, struct sysfs_buffer * buffer)
 {
         struct sysfs_dirent * sd = dentry->d_fsdata;
-        struct attribute * attr = to_attr(dentry);
         struct kobject * kobj = to_kobj(dentry->d_parent);
         struct sysfs_ops * ops = buffer->ops;
         int ret = 0;
@@ -100,7 +99,7 @@ static int fill_read_buffer(struct dentry * dentry, struct sysfs_buffer * buffer
                 return -ENOMEM;
 
         buffer->event = atomic_read(&sd->s_event);
-        count = ops->show(kobj,attr,buffer->page);
+        count = ops->show(kobj, sd->s_elem.attr.attr, buffer->page);
         BUG_ON(count > (ssize_t)PAGE_SIZE);
         if (count >= 0) {
                 buffer->needs_read_fill = 0;
@@ -199,11 +198,11 @@ fill_write_buffer(struct sysfs_buffer * buffer, const char __user * buf, size_t
 static int 
 flush_write_buffer(struct dentry * dentry, struct sysfs_buffer * buffer, size_t count)
 {
-        struct attribute * attr = to_attr(dentry);
+        struct sysfs_dirent *attr_sd = dentry->d_fsdata;
         struct kobject * kobj = to_kobj(dentry->d_parent);
         struct sysfs_ops * ops = buffer->ops;
 
-        return ops->store(kobj,attr,buffer->page,count);
+        return ops->store(kobj, attr_sd->s_elem.attr.attr, buffer->page, count);
 }
 
 
@@ -248,7 +247,8 @@ out:
 static int sysfs_open_file(struct inode *inode, struct file *file)
 {
         struct kobject *kobj = sysfs_get_kobject(file->f_path.dentry->d_parent);
-        struct attribute * attr = to_attr(file->f_path.dentry);
+        struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
+        struct attribute *attr = attr_sd->s_elem.attr.attr;
         struct sysfs_buffer_collection *set;
         struct sysfs_buffer * buffer;
         struct sysfs_ops * ops = NULL;
@@ -341,15 +341,15 @@ static int sysfs_open_file(struct inode *inode, struct file *file)
 static int sysfs_release(struct inode * inode, struct file * filp)
 {
         struct kobject * kobj = to_kobj(filp->f_path.dentry->d_parent);
-        struct attribute * attr = to_attr(filp->f_path.dentry);
-        struct module * owner = attr->owner;
+        struct sysfs_dirent *attr_sd = filp->f_path.dentry->d_fsdata;
+        struct attribute *attr = attr_sd->s_elem.attr.attr;
         struct sysfs_buffer * buffer = filp->private_data;
 
         if (buffer)
                 remove_from_collection(buffer, inode);
         kobject_put(kobj);
         /* After this point, attr should not be accessed. */
-        module_put(owner);
+        module_put(attr->owner);
 
         if (buffer) {
                 if (buffer->page)
@@ -454,11 +454,12 @@ int sysfs_add_file(struct dentry * dir, const struct attribute * attr, int type)
                 goto out_unlock;
         }
 
-        sd = sysfs_new_dirent(attr->name, (void *)attr, mode, type);
+        sd = sysfs_new_dirent(attr->name, mode, type);
         if (!sd) {
                 error = -ENOMEM;
                 goto out_unlock;
         }
+        sd->s_elem.attr.attr = (void *)attr;
         sysfs_attach_dirent(sd, parent_sd, NULL);
 
  out_unlock:
diff --git a/fs/sysfs/inode.c b/fs/sysfs/inode.c
index 5c605b0003a8..617d10cea07d 100644
--- a/fs/sysfs/inode.c
+++ b/fs/sysfs/inode.c
@@ -272,7 +272,7 @@ int sysfs_hash_and_remove(struct dentry * dir, const char * name)
         parent_sd = dir->d_fsdata;
         mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_PARENT);
         list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
-                if (!sd->s_element)
+                if (!sd->s_type)
                         continue;
                 if (!strcmp(sd->s_name, name)) {
                         list_del_init(&sd->s_sibling);
diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c
index 31c1fc67f604..8f6d8b1b211f 100644
--- a/fs/sysfs/mount.c
+++ b/fs/sysfs/mount.c
@@ -31,7 +31,6 @@ static struct sysfs_dirent sysfs_root = {
         .s_count        = ATOMIC_INIT(1),
         .s_sibling      = LIST_HEAD_INIT(sysfs_root.s_sibling),
         .s_children     = LIST_HEAD_INIT(sysfs_root.s_children),
-        .s_element      = NULL,
         .s_type         = SYSFS_ROOT,
         .s_iattr        = NULL,
         .s_ino          = 1,
diff --git a/fs/sysfs/symlink.c b/fs/sysfs/symlink.c
index c72820450e7c..27df635b786a 100644
--- a/fs/sysfs/symlink.c
+++ b/fs/sysfs/symlink.c
@@ -48,30 +48,15 @@ static void fill_object_path(struct kobject * kobj, char * buffer, int length)
 static int sysfs_add_link(struct dentry * parent, const char * name, struct kobject * target)
 {
         struct sysfs_dirent * parent_sd = parent->d_fsdata;
-        struct sysfs_symlink * sl;
         struct sysfs_dirent * sd;
-        int error;
 
-        error = -ENOMEM;
-        sl = kzalloc(sizeof(*sl), GFP_KERNEL);
-        if (!sl)
-                goto err_out;
-
-        sl->target_kobj = kobject_get(target);
-
-        sd = sysfs_new_dirent(name, sl, S_IFLNK|S_IRWXUGO, SYSFS_KOBJ_LINK);
+        sd = sysfs_new_dirent(name, S_IFLNK|S_IRWXUGO, SYSFS_KOBJ_LINK);
         if (!sd)
-                goto err_out;
-        sysfs_attach_dirent(sd, parent_sd, NULL);
+                return -ENOMEM;
 
+        sd->s_elem.symlink.target_kobj = kobject_get(target);
+        sysfs_attach_dirent(sd, parent_sd, NULL);
         return 0;
-
- err_out:
-        if (sl) {
-                kobject_put(sl->target_kobj);
-                kfree(sl);
-        }
-        return error;
 }
 
 /**
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);