From 0a17bb5c343acd3d75df22499d0cf2fce458d140 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= <zbyszek@in.waw.pl>
Date: Tue, 18 Nov 2025 15:12:55 +0100
Subject: [PATCH] core: simplify requirements in unit_get_private_var_tmp() to
 just After=

As in the previous commit, checking for both requirements and ordering seems
unnecessary. In practical cases, the mount will be pulled in by the rest
of the transaction, so ordering is the part that matters. (The setup is
racy without the ordering.)  If we drop the second check, the admin can
just use After=tmp.mount to achieve the desired behaviour, without needing
to explicitly pull in the unit. This is easier to configure and more robust.

This changes the implementation introduced in
6156bec7a464815084fa5218fe782ea6cb20ad52.

Also actually describe the implemented behaviour in the man page.
---
 man/systemd.exec.xml |  8 +++++++-
 src/core/unit.c      | 12 ++----------
 2 files changed, 9 insertions(+), 11 deletions(-)

diff --git a/man/systemd.exec.xml b/man/systemd.exec.xml
index 3f06f564b3..e7d5e63c96 100644
--- a/man/systemd.exec.xml
+++ b/man/systemd.exec.xml
@@ -76,7 +76,13 @@
       <listitem><para>Units with <varname>PrivateTmp=disconnected</varname> automatically gain dependencies
       of type <varname>Wants=</varname> and <varname>After=</varname> on the mount required to access
       <filename>/var/</filename>, unless <varname>DefaultDependencies=no</varname> and/or
-      <varname>RootDirectory=/RootImage=</varname> are specified.</para></listitem>
+      <varname>RootDirectory=</varname>/<varname>RootImage=</varname> are specified. If
+      <varname>DefaultDependencies=no</varname> is specified, and a
+      <varname>RequiresMountsFor=/var/</varname>, <varname>WantsMountsFor=/var/</varname>,
+      <varname>After=var.mount</varname>, <varname>RootDirectory=</varname>/<varname>RootImage=</varname> are
+      not specified, the private mount on <filename>/tmp/</filename> is reused for
+      <filename>/var/tmp/</filename> by setting <varname>$TMPDIR</varname> appropriately.</para>
+      </listitem>
 
       <listitem><para>Units whose standard output or error output is connected to <option>journal</option> or
       <option>kmsg</option> (or their combinations with console output, see below) automatically acquire
diff --git a/src/core/unit.c b/src/core/unit.c
index dc158fb335..bb3430186c 100644
--- a/src/core/unit.c
+++ b/src/core/unit.c
@@ -4373,17 +4373,9 @@ static PrivateTmp unit_get_private_var_tmp(const Unit *u, const ExecContext *c)
                 if (hashmap_contains(u->mounts_for[t], "/var/"))
                         return PRIVATE_TMP_DISCONNECTED;
 
-        /* Check the same but for After= with Requires=/Requisite=/Wants= or friends. */
+        /* Check the same but for After=. */
         Unit *m = manager_get_unit(u->manager, "var.mount");
-        if (!m)
-                return PRIVATE_TMP_NO;
-
-        if (!unit_has_dependency(u, UNIT_ATOM_AFTER, m))
-                return PRIVATE_TMP_NO;
-
-        if (unit_has_dependency(u, UNIT_ATOM_PULL_IN_START, m) ||
-            unit_has_dependency(u, UNIT_ATOM_PULL_IN_VERIFY, m) ||
-            unit_has_dependency(u, UNIT_ATOM_PULL_IN_START_IGNORED, m))
+        if (m && unit_has_dependency(u, UNIT_ATOM_AFTER, m))
                 return PRIVATE_TMP_DISCONNECTED;
 
         return PRIVATE_TMP_NO;