oom: make swap a soft requirement

3 files changed, 19 insertions, 6 deletions

diff --git a/src/oom/oomd-manager.c b/src/oom/oomd-manager.c
index e8ed6a5273..814fda51f3 100644
--- a/src/oom/oomd-manager.c
+++ b/src/oom/oomd-manager.c
@@ -6,6 +6,7 @@
 #include "cgroup-util.h"
 #include "fd-util.h"
 #include "fileio.h"
+#include "memory-util.h"
 #include "oomd-manager-bus.h"
 #include "oomd-manager.h"
 #include "path-util.h"
@@ -294,9 +295,12 @@ static int monitor_cgroup_contexts_handler(sd_event_source *s, uint64_t usec, vo
                 return log_error_errno(r, "Failed to update monitored memory pressure cgroup contexts");
 
         r = oomd_system_context_acquire("/proc/swaps", &m->system_context);
-        /* If there aren't units depending on swap actions, the only error we exit on is ENOMEM */
-        if (r == -ENOMEM || (r < 0 && !hashmap_isempty(m->monitored_swap_cgroup_contexts)))
+        /* If there aren't units depending on swap actions, the only error we exit on is ENOMEM.
+         * Allow ENOENT in the event that swap is disabled on the system. */
+        if (r == -ENOMEM || (r < 0 && r != -ENOENT && !hashmap_isempty(m->monitored_swap_cgroup_contexts)))
                 return log_error_errno(r, "Failed to acquire system context");
+        else if (r == -ENOENT)
+                zero(m->system_context);
 
         /* If we're still recovering from a kill, don't try to kill again yet */
         if (m->post_action_delay_start > 0) {
diff --git a/src/oom/oomd.c b/src/oom/oomd.c
index 1b0f8ff6c4..1fbcf41492 100644
--- a/src/oom/oomd.c
+++ b/src/oom/oomd.c
@@ -142,10 +142,8 @@ static int run(int argc, char *argv[]) {
                 return log_error_errno(r, "Failed to get SwapTotal from /proc/meminfo: %m");
 
         r = safe_atollu(swap, &s);
-        if (r < 0)
-                return log_error_errno(r, "Failed to parse SwapTotal from /proc/meminfo: %s: %m", swap);
-        if (s == 0)
-                return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), "Requires swap to operate");
+        if (r < 0 || s == 0)
+                log_warning("Swap is currently not detected; memory pressure usage will be degraded");
 
         if (!is_pressure_supported())
                 return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), "Pressure Stall Information (PSI) is not supported");
diff --git a/src/oom/test-oomd-util.c b/src/oom/test-oomd-util.c
index 8143408902..54fe2a03d1 100644
--- a/src/oom/test-oomd-util.c
+++ b/src/oom/test-oomd-util.c
@@ -159,6 +159,11 @@ static void test_oomd_system_context_acquire(void) {
         assert_se(ctx.swap_total == 0);
         assert_se(ctx.swap_used == 0);
 
+        assert_se(write_string_file(path, "Filename                                Type            Size    Used    Priority", WRITE_STRING_FILE_CREATE) == 0);
+        assert_se(oomd_system_context_acquire(path, &ctx) == 0);
+        assert_se(ctx.swap_total == 0);
+        assert_se(ctx.swap_used == 0);
+
         assert_se(write_string_file(path, "Filename                                Type            Size    Used    Priority\n"
                                           "/swapvol/swapfile                       file            18971644        0       -3\n"
                                           "/dev/vda2                               partition       1999868 993780  -2", WRITE_STRING_FILE_CREATE) == 0);
@@ -268,6 +273,12 @@ static void test_oomd_swap_free_below(void) {
                 .swap_used = 3310136 * 1024U,
         };
         assert_se(oomd_swap_free_below(&ctx, 20) == false);
+
+        ctx = (OomdSystemContext) {
+                .swap_total = 0,
+                .swap_used = 0,
+        };
+        assert_se(oomd_swap_free_below(&ctx, 20) == false);
 }
 
 static void test_oomd_sort_cgroups(void) {