mount: make sure we unmount tmpfs mounts before we deactivate swaps (#7076)

In the past we introduced this property just for tmp.mount. However on
todays systems usually there are many more tmpfs mounts. Most notably
mounts backing XDG_RUNTIME_DIR for each user.

Let's generalize what we already have for tmp.mount and implement the
ordering After=swap.target for all tmpfs based mounts.

src/core/dbus-mount.c

@@ -88,20 +88,12 @@ static int property_get_type(
                 sd_bus_error *error) {
 
         Mount *m = userdata;
-        const char *d;
 
         assert(bus);
         assert(reply);
         assert(m);
 
-        if (m->from_proc_self_mountinfo && m->parameters_proc_self_mountinfo.fstype)
-                d = m->parameters_proc_self_mountinfo.fstype;
-        else if (m->from_fragment && m->parameters_fragment.fstype)
-                d = m->parameters_fragment.fstype;
-        else
-                d = "";
-
-        return sd_bus_message_append(reply, "s", d);
+        return sd_bus_message_append(reply, "s", mount_get_fstype(m));
 }
 
 static BUS_DEFINE_PROPERTY_GET_ENUM(property_get_result, mount_result, MountResult);

src/core/mount.c

@@ -156,6 +156,21 @@ static bool needs_quota(const MountParameters *p) {
                                  "usrquota\0" "grpquota\0" "quota\0" "usrjquota\0" "grpjquota\0");
 }
 
+const char *mount_get_fstype(const Mount *m) {
+        const char *type = NULL;
+
+        assert(m);
+
+        if (m->from_proc_self_mountinfo && m->parameters_proc_self_mountinfo.fstype)
+                type = m->parameters_proc_self_mountinfo.fstype;
+        else if (m->from_fragment && m->parameters_fragment.fstype)
+                type = m->parameters_fragment.fstype;
+        else
+                type = "";
+
+        return type;
+}
+
 static void mount_init(Unit *u) {
         Mount *m = MOUNT(u);
 
@@ -267,6 +282,7 @@ _pure_ static MountParameters* get_mount_parameters(Mount *m) {
 
 static int mount_add_mount_links(Mount *m) {
         _cleanup_free_ char *parent = NULL;
+        const char *fstype;
         MountParameters *pm;
         Unit *other;
         Iterator i;
@@ -324,6 +340,14 @@ static int mount_add_mount_links(Mount *m) {
                 }
         }
 
+        /* If this is a tmpfs mount then we have to unmount it before we try to deactivate swaps */
+        fstype = mount_get_fstype(m);
+        if (streq(fstype, "tmpfs")) {
+                r = unit_add_dependency_by_name(UNIT(m), UNIT_AFTER, SPECIAL_SWAP_TARGET, NULL, true);
+                if (r < 0)
+                        return r;
+        }
+
         return 0;
 }
 

src/core/mount.h

@@ -110,3 +110,5 @@ MountExecCommand mount_exec_command_from_string(const char *s) _pure_;
 
 const char* mount_result_to_string(MountResult i) _const_;
 MountResult mount_result_from_string(const char *s) _pure_;
+
+const char *mount_get_fstype(const Mount *m);

units/tmp.mount

@@ -13,7 +13,6 @@ ConditionPathIsSymbolicLink=!/tmp
 DefaultDependencies=no
 Conflicts=umount.target
 Before=local-fs.target umount.target
-After=swap.target
 
 [Mount]
 What=tmpfs