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, 10 insertions, 9 deletions

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: