[PATCH 08/14] sysfs: make sysfs_dirent->s_element a union

[Tejun Heo <htejun@gmail.com>]

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>
---
 fs/sysfs/bin.c     |   18 +++++++++++-------
 fs/sysfs/dir.c     |   40 ++++++++++++++++++----------------------
 fs/sysfs/file.c    |   19 ++++++++++---------
 fs/sysfs/inode.c   |    2 +-
 fs/sysfs/mount.c   |    1 -
 fs/sysfs/symlink.c |   23 ++++-------------------
 fs/sysfs/sysfs.h   |   47 +++++++++++++++++++++++++++--------------------
 7 files changed, 71 insertions(+), 79 deletions(-)

diff --git a/fs/sysfs/bin.c b/fs/sysfs/bin.c
index 8273dd6..0f0027b 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 26c3088..d70ead5 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -21,11 +21,10 @@ 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);
 
@@ -39,11 +38,8 @@ 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);
@@ -70,8 +66,7 @@ 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;
@@ -94,7 +89,6 @@ 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;
 
@@ -129,7 +123,7 @@ 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
@@ -184,9 +178,10 @@ 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);
@@ -259,10 +254,10 @@ 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;
         }
 
@@ -367,7 +362,7 @@ 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);
@@ -499,7 +494,7 @@ 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);
@@ -563,7 +558,7 @@ 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;
@@ -611,7 +606,7 @@ 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;
 			}
@@ -678,9 +673,10 @@ 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 62ab272..a6c72c6 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -89,7 +89,6 @@ 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;
@@ -101,7 +100,7 @@ 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;
@@ -229,11 +228,11 @@ 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);
 }
 
 
@@ -278,7 +277,8 @@ 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;
@@ -371,15 +371,15 @@ 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)
@@ -484,11 +484,12 @@ 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 4960be8..2581bfa 100644
--- a/fs/sysfs/inode.c
+++ b/fs/sysfs/inode.c
@@ -255,7 +255,7 @@ 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 141f7b1..0defb3a 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,
 };
diff --git a/fs/sysfs/symlink.c b/fs/sysfs/symlink.c
index c728204..27df635 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 ac5fd2a..c1965b9 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;
 	struct dentry		* s_dentry;
@@ -22,8 +45,8 @@ extern int sysfs_create(struct dentry *, int mode, int (*init)(struct inode *));
 extern struct kobject *sysfs_get_kobject(struct dentry *dentry);
 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);
@@ -46,10 +69,6 @@ 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;
@@ -69,19 +88,7 @@ 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 sysfs_dirent * sysfs_get(struct sysfs_dirent * sd)
-- 
1.5.0.3