units: introduce remote-fs-setup.target to pull in dependencies from remote mounts

This introduces remote-fs-setup.target independently of
remote-fs-pre.target. The former is only for pulling things in, the
latter only for ordering.

The new semantics:

remote-fs-setup.target: is pulled in automatically by all remote mounts.
Shall be used to pull in other units that want to run when at least one
remote mount is set up. Is not ordered against the actual mount units,
in order to allow activation of its dependencies even 'a posteriori',
i.e. when a mount is established outside of systemd and is only picked
up by it.

remote-fs-pre.target: needs to be pulled in automatically by the
implementing service, is otherwise not part of the initial transaction.
This is ordered before all remote mount units.

A service that wants to be pulled in and run before all remote mounts
should hence have:

a) WantedBy=remote-fs-setup.target -- so that it is pulled in

b) Wants=remote-fs-pre.target + Before=remote-fs-pre.target -- so that
   it is ordered before the mount point, normally.

1 files changed, 46 insertions, 4 deletions

diff --git a/man/systemd.special.xml b/man/systemd.special.xml
index 8a7242662d..18974477ea 100644
--- a/man/systemd.special.xml
+++ b/man/systemd.special.xml
@@ -79,6 +79,7 @@
                 <filename>reboot.target</filename>,
                 <filename>remote-fs.target</filename>,
                 <filename>remote-fs-pre.target</filename>,
+                <filename>remote-fs-setup.target</filename>,
                 <filename>rescue.target</filename>,
                 <filename>initrd-root-fs.target</filename>,
                 <filename>rpcbind.target</filename>,
@@ -565,11 +566,52 @@
                                 <listitem>
                                         <para>This target unit is
                                         automatically ordered before
-                                        all remote mount points marked
-                                        with <option>auto</option>
+                                        all remote mount point units
                                         (see above). It can be used to
-                                        execute certain units before
-                                        all remote mounts.</para>
+                                        run certain units before the
+                                        remote mounts are
+                                        established. Note that this
+                                        unit is generally not part of
+                                        the initial transaction,
+                                        unless the unit that wants to
+                                        be ordered before all remote
+                                        mounts pulls it in via a
+                                        <varname>Wants=</varname> type
+                                        dependency. If the unit wants
+                                        to be pulled in by the first
+                                        remote mount showing up it
+                                        should use
+                                        <filename>remote-fs-setup.target</filename>
+                                        (see below).</para>
+
+                                        <para>Again, this target unit
+                                        is <emphasis>not</emphasis>
+                                        suitable for pulling in other
+                                        units, it is only useful for
+                                        ordering.</para>
+                                </listitem>
+                        </varlistentry>
+                        <varlistentry>
+                                <term><filename>remote-fs-setup.target</filename></term>
+                                <listitem>
+                                        <para>This target unit is
+                                        automatically pulled in (by a
+                                        <varname>Wants=</varname> type
+                                        dependency) by all remote
+                                        mount points. It can be used
+                                        to run certain units when at
+                                        least one remote file system
+                                        is to be mounted. Note that
+                                        this target is not ordered
+                                        against the remote mounts, use
+                                        <filename>remote-fs-pre.target</filename>
+                                        for that.</para>
+
+                                        <para>Again, this target unit
+                                        is <emphasis>not</emphasis>
+                                        suitable for ordering, it is
+                                        only useful for pulling in
+                                        other units.</para>
                                 </listitem>
                         </varlistentry>
                         <varlistentry>