systemctl: be more specific when emitting warning about rotated journal

See inline comment for disucssion.
Fixes #14281.

3 files changed, 22 insertions, 3 deletions

diff --git a/src/shared/journal-util.c b/src/shared/journal-util.c
index 2f672c2935..cb3762df43 100644
--- a/src/shared/journal-util.c
+++ b/src/shared/journal-util.c
@@ -80,6 +80,10 @@ static int access_check_var_log_journal(sd_journal *j, bool want_other_users) {
         return 1;
 }
 
+int journal_access_blocked(sd_journal *j) {
+        return hashmap_contains(j->errors, INT_TO_PTR(-EACCES));
+}
+
 int journal_access_check_and_warn(sd_journal *j, bool quiet, bool want_other_users) {
         Iterator it;
         void *code;
@@ -95,7 +99,7 @@ int journal_access_check_and_warn(sd_journal *j, bool quiet, bool want_other_use
                 return 0;
         }
 
-        if (hashmap_contains(j->errors, INT_TO_PTR(-EACCES))) {
+        if (journal_access_blocked(j)) {
                 if (!quiet)
                         (void) access_check_var_log_journal(j, want_other_users);
 
diff --git a/src/shared/journal-util.h b/src/shared/journal-util.h
index da86434a67..34ad1bfc8e 100644
--- a/src/shared/journal-util.h
+++ b/src/shared/journal-util.h
@@ -7,5 +7,5 @@
 #include "sd-journal.h"
 
 bool journal_field_valid(const char *p, size_t l, bool allow_protected);
-
+int journal_access_blocked(sd_journal *j);
 int journal_access_check_and_warn(sd_journal *j, bool quiet, bool want_other_users);
diff --git a/src/shared/logs-show.c b/src/shared/logs-show.c
index 605412aec5..b83f543ba8 100644
--- a/src/shared/logs-show.c
+++ b/src/shared/logs-show.c
@@ -20,6 +20,7 @@
 #include "id128-util.h"
 #include "io-util.h"
 #include "journal-internal.h"
+#include "journal-util.h"
 #include "json.h"
 #include "log.h"
 #include "logs-show.h"
@@ -1232,7 +1233,21 @@ int show_journal(
 
                         if (r > 0 && not_before < cutoff) {
                                 maybe_print_begin_newline(f, &flags);
-                                fprintf(f, "Warning: Journal has been rotated since unit was started. Log output is incomplete or unavailable.\n");
+
+                                /* If we logged *something* and no permission error happened, than we can
+                                 * reliably emit the warning about rotation. If we didn't log anything and
+                                 * access errors happened, emit hint about permissions. Otherwise, give a
+                                 * generic message, since we can't diagnose the issue. */
+
+                                bool noaccess = journal_access_blocked(j);
+
+                                if (line == 0 && noaccess)
+                                        fprintf(f, "Warning: some journal files were not opened due to insufficient permissions.");
+                                else if (!noaccess)
+                                        fprintf(f, "Warning: journal has been rotated since unit was started, output may be incomplete.\n");
+                                else
+                                        fprintf(f, "Warning: journal has been rotated since unit was started and some journal "
+                                                "files were not opened due to insufficient permissions, output may be incomplete.\n");
                         }
 
                         warn_cutoff = false;