oomd: update system context when oomctl is invoked

Otherwise, oomctl shows 0 memory and swap usage when swap monitoring
is not enabled.
=======
$ oomctl
Dry Run: no
Swap Used Limit: 90.00%
Default Memory Pressure Limit: 60.00%
Default Memory Pressure Duration: 20s
System Context:
        Memory: Used: 0B Total: 0B
        Swap: Used: 0B Total: 0B
Swap Monitored CGroups:
Memory Pressure Monitored CGroups:
...
======

1 files changed, 7 insertions, 0 deletions

diff --git a/src/oom/oomd-manager.c b/src/oom/oomd-manager.c
index 5e25daadcb..6ff4d98c32 100644
--- a/src/oom/oomd-manager.c
+++ b/src/oom/oomd-manager.c
@@ -799,10 +799,17 @@ int manager_get_dump_string(Manager *m, char **ret) {
         _cleanup_(memstream_done) MemStream ms = {};
         OomdCGroupContext *c;
         FILE *f;
+        int r;
 
         assert(m);
         assert(ret);
 
+        /* Always reread memory/swap info here. Otherwise it may be outdated if swap monitoring is off.
+         * Let's make sure to always report up-to-date data. */
+        r = oomd_system_context_acquire("/proc/meminfo", &m->system_context);
+        if (r < 0)
+                log_debug_errno(r, "Failed to acquire system context, ignoring: %m");
+
         f = memstream_init(&ms);
         if (!f)
                 return -ENOMEM;