core/swap: only make configured units part of swap.target

We used to make all .swap units either RequiredBy=swap.target or
WantedBy=swap.target. But swap.target should be the "configured swap
units", either through /etc/fstab or non-generated .swap units. It
is surprising when systemd starts treating a swap device that was
possibly temporarily enabled as a hard dependency for other units.
So do not add dependencies with swap.target for units gleaned from
/proc/swaps.

Similarly, we added dependencies for all aliases of the device name,
which clutters up the dependency graph but does not seem to bring any
value, since the status of those following units is consistent with
the main one anyway.

This should be a fix for [1], and it seems the right thing to do
anyway.

[1] https://bugzilla.redhat.com/show_bug.cgi?id=1114786

1 files changed, 11 insertions, 9 deletions

diff --git a/src/core/swap.c b/src/core/swap.c
index ef90d0efde..b2ca048bcb 100644
--- a/src/core/swap.c
+++ b/src/core/swap.c
@@ -213,7 +213,7 @@ static int swap_add_device_links(Swap *s) {
 }
 
 static int swap_add_default_dependencies(Swap *s) {
-        bool nofail = false, noauto = false;
+        bool nofail, noauto;
         int r;
 
         assert(s);
@@ -228,23 +228,25 @@ static int swap_add_default_dependencies(Swap *s) {
         if (r < 0)
                 return r;
 
-        if (s->from_fragment) {
-                SwapParameters *p = &s->parameters_fragment;
+        if (!s->from_fragment)
+                /* The swap unit can either be for an alternative device name, in which
+                 * case we don't need to add the dependency on swap.target because this unit
+                 * is following a different unit which will have this dependency added,
+                 * or it can be derived from /proc/swaps, in which case it was started
+                 * manually, and should not become a dependency of swap.target. */
+                return 0;
 
-                nofail = p->nofail;
-                noauto = p->noauto;
-        }
+        nofail = s->parameters_fragment.nofail;
+        noauto = s->parameters_fragment.noauto;
 
         if (!noauto) {
                 if (nofail)
                         r = unit_add_dependency_by_name_inverse(UNIT(s), UNIT_WANTS, SPECIAL_SWAP_TARGET, NULL, true);
                 else
                         r = unit_add_two_dependencies_by_name_inverse(UNIT(s), UNIT_AFTER, UNIT_REQUIRES, SPECIAL_SWAP_TARGET, NULL, true);
-                if (r < 0)
-                        return r;
         }
 
-        return 0;
+        return r < 0 ? r : 0;
 }
 
 static int swap_verify(Swap *s) {