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, 14 insertions, 17 deletions

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);