qib_fs: fix (some) dcache abuses

* lookup_one_len() really wants i_mutex held on directory.
* leaks galore - just mount ipathfs, then
cd /sys/bus/pci/drivers/qib_ib; echo *:*:*.* >unbind
on a box with that card present and try to umount ipathfs...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

drivers/infiniband/hw/qib/qib_fs.c

@@ -456,13 +456,13 @@ static int remove_file(struct dentry *parent, char *name)
 
 	spin_lock(&tmp->d_lock);
 	if (!(d_unhashed(tmp) && tmp->d_inode)) {
-		dget_dlock(tmp);
 		__d_drop(tmp);
 		spin_unlock(&tmp->d_lock);
 		simple_unlink(parent->d_inode, tmp);
 	} else {
 		spin_unlock(&tmp->d_lock);
 	}
+	dput(tmp);
 
 	ret = 0;
 bail:
@@ -491,6 +491,7 @@ static int remove_device_files(struct super_block *sb,
 		goto bail;
 	}
 
+	mutex_lock(&dir->d_inode->i_mutex);
 	remove_file(dir, "counters");
 	remove_file(dir, "counter_names");
 	remove_file(dir, "portcounter_names");
@@ -505,8 +506,10 @@ static int remove_device_files(struct super_block *sb,
 		}
 	}
 	remove_file(dir, "flash");
-	d_delete(dir);
+	mutex_unlock(&dir->d_inode->i_mutex);
 	ret = simple_rmdir(root->d_inode, dir);
+	d_delete(dir);
+	dput(dir);
 
 bail:
 	mutex_unlock(&root->d_inode->i_mutex);