reiserfs: Safely acquire i_mutex from xattr_rmdir

Relax the reiserfs lock before taking the inode mutex from
xattr_rmdir() to avoid the usual reiserfs lock <-> inode mutex
bad dependency.

Signed-off-by: Frederic Weisbecker <[e-mail]>
Tested-by: Christian Kujau <[e-mail]>
Cc: Alexander Beregalov <[e-mail]>
Cc: Chris Mason <[e-mail]>
Cc: Ingo Molnar <[e-mail]>

fs/reiserfs/xattr.c

···
 	BUG_ON(!mutex_is_locked(&dir->i_mutex));
 	vfs_dq_init(dir);
 
-	mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_CHILD);
+	reiserfs_mutex_lock_nested_safe(&dentry->d_inode->i_mutex,
+					I_MUTEX_CHILD, dir->i_sb);
 	dentry_unhash(dentry);
 	error = dir->i_op->rmdir(dir, dentry);
 	if (!error)