ksym_tracer: Report error when failed to re-register hbp

When access type is changed, the hw break point will be
unregistered and then be registered again with new access
type. But the registration may fail, in this case, -errno
should be returned.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: "K.Prasad" <prasad@linux.vnet.ibm.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <4A52E314.7070004@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/trace/trace_ksym.c

@@ -302,13 +302,13 @@ static ssize_t ksym_trace_filter_write(struct file *file,
 				ret = count;
 				goto unlock_ret_path;
 			}
-		}
+		} else
+			ret = count;
 		ksym_filter_entry_count--;
 		hlist_del_rcu(&(entry->ksym_hlist));
 		synchronize_rcu();
 		kfree(entry->ksym_hbp);
 		kfree(entry);
-		ret = count;
 		goto err_ret;
 	} else {
 		/* Check for malformed request: (4) */