From d81a1818d67860085fc7e73f0a48d9a2c588c7df Mon Sep 17 00:00:00 2001
From: Christian Schwarz <me@cschwarz.com>
Date: Sat, 7 Sep 2019 20:01:15 +0200
Subject: [PATCH] endpoint: Receiver: only create placeholders below root_fs

fixes #195
---
 endpoint/endpoint.go | 9 +++++++++
 zfs/placeholder.go   | 3 +++
 2 files changed, 12 insertions(+)

diff --git a/endpoint/endpoint.go b/endpoint/endpoint.go
index 389527e..9813f8b 100644
--- a/endpoint/endpoint.go
+++ b/endpoint/endpoint.go
@@ -380,6 +380,15 @@ func (s *Receiver) Receive(ctx context.Context, req *pdu.ReceiveReq, receive zfs
 			}
 
 			if !ph.FSExists {
+				if s.rootWithoutClientComponent.HasPrefix(v.Path) {
+					if v.Path.Length() == 1 {
+						visitErr = fmt.Errorf("pool %q not imported", v.Path.ToString())
+					} else {
+						visitErr = fmt.Errorf("root_fs %q does not exist", s.rootWithoutClientComponent.ToString())
+					}
+					getLogger(ctx).WithError(visitErr).Error("placeholders are only created automatically below root_fs")
+					return false
+				}
 				l := getLogger(ctx).WithField("placeholder_fs", v.Path)
 				l.Debug("create placeholder filesystem")
 				err := zfs.ZFSCreatePlaceholderFilesystem(v.Path)
diff --git a/zfs/placeholder.go b/zfs/placeholder.go
index 10caa17..1fc95f1 100644
--- a/zfs/placeholder.go
+++ b/zfs/placeholder.go
@@ -78,6 +78,9 @@ func ZFSGetFilesystemPlaceholderState(p *DatasetPath) (state *FilesystemPlacehol
 }
 
 func ZFSCreatePlaceholderFilesystem(p *DatasetPath) (err error) {
+	if p.Length() == 1 {
+		return fmt.Errorf("cannot create %q: pools cannot be created with zfs create", p.ToString())
+	}
 	cmd := exec.Command(ZFS_BINARY, "create",
 		"-o", fmt.Sprintf("%s=%s", PlaceholderPropertyName, placeholderPropertyOn),
 		"-o", "mountpoint=none",