sysfs: Only take active references on attributes.

If we exclude directories and symlinks from the set of sysfs
dirents where we need active references we are left with
sysfs attributes (binary or not).

- Tweak sysfs_deactivate to only do something on attributes
- Move lockdep initialization into sysfs_file_add_mode to
  limit it to just attributes.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Acked-by: WANG Cong <xiyou.wangcong@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

fs/sysfs/dir.c

@@ -156,6 +156,10 @@ static void sysfs_deactivate(struct sysfs_dirent *sd)
 	int v;
 
 	BUG_ON(sd->s_sibling || !(sd->s_flags & SYSFS_FLAG_REMOVED));
+
+	if (!(sysfs_type(sd) & SYSFS_ACTIVE_REF))
+		return;
+
 	sd->s_sibling = (void *)&wait;
 
 	rwsem_acquire(&sd->dep_map, 0, 0, _RET_IP_);
@@ -315,7 +319,6 @@ struct sysfs_dirent *sysfs_new_dirent(const char *name, umode_t mode, int type)
 
 	atomic_set(&sd->s_count, 1);
 	atomic_set(&sd->s_active, 0);
-	sysfs_dirent_init_lockdep(sd);
 
 	sd->s_name = name;
 	sd->s_mode = mode;

fs/sysfs/file.c

@@ -509,6 +509,7 @@ int sysfs_add_file_mode(struct sysfs_dirent *dir_sd,
 	if (!sd)
 		return -ENOMEM;
 	sd->s_attr.attr = (void *)attr;
+	sysfs_dirent_init_lockdep(sd);
 
 	sysfs_addrm_start(&acxt, dir_sd);
 	rc = sysfs_add_one(&acxt, sd);

fs/sysfs/sysfs.h

@@ -79,6 +79,7 @@ struct sysfs_dirent {
 #define SYSFS_KOBJ_BIN_ATTR		0x0004
 #define SYSFS_KOBJ_LINK			0x0008
 #define SYSFS_COPY_NAME			(SYSFS_DIR | SYSFS_KOBJ_LINK)
+#define SYSFS_ACTIVE_REF		(SYSFS_KOBJ_ATTR | SYSFS_KOBJ_BIN_ATTR)
 
 #define SYSFS_FLAG_MASK			~SYSFS_TYPE_MASK
 #define SYSFS_FLAG_REMOVED		0x0200