journald: fix space limits reporting

Reporting of the free space was bogus, since the remaining space
was compared with the maximum allowed, instead of the current
use being compared with the maximum allowed. Simplify and fix
by reporting limits directly at the point where they are calculated.

Also, assign a UUID to the message.

man/journald.conf.xml

@@ -237,7 +237,17 @@
                                 while the former apply if persistent
                                 logging is enabled and the system is
                                 fully booted
-                                up. <varname>SystemMaxUse=</varname>
+                                up. <command>journalctl</command> and
+                                <command>systemd-journald</command>
+                                ignore all files with names not ending
+                                with <literal>.journal</literal> or
+                                <literal>.journal~</literal>, so only
+                                such files, located in the appropriate
+                                directories, are taken into account
+                                when calculating current disk usage.
+                                </para>
+
+                                <para><varname>SystemMaxUse=</varname>
                                 and <varname>RuntimeMaxUse=</varname>
                                 control how much disk space the
                                 journal may use up at
@@ -271,11 +281,11 @@
                                 values in bytes or use K, M, G, T, P,
                                 E as units for the specified sizes
                                 (equal to 1024, 1024²,... bytes).
-                                Note that size limits are
+                                Note that size limits are enforced
-                                enforced synchronously to journal
+                                synchronously when journal files
-                                files as they are extended, and need
+                                are extended, and no explicit
-                                no explicit rotation step triggered by
+                                rotation step triggered by
-                                time.</para></listitem>
+                                time is needed.</para></listitem>
                         </varlistentry>
 
                         <varlistentry>

src/journal/journald-server.c

@@ -89,21 +89,22 @@ static const char* const split_mode_table[] = {
 DEFINE_STRING_TABLE_LOOKUP(split_mode, SplitMode);
 DEFINE_CONFIG_PARSE_ENUM(config_parse_split_mode, split_mode, SplitMode, "Failed to parse split mode setting");
 
-static uint64_t available_space(Server *s) {
+static uint64_t available_space(Server *s, bool verbose) {
         char ids[33];
         _cleanup_free_ char *p = NULL;
-        const char *f;
         sd_id128_t machine;
         struct statvfs ss;
-        uint64_t sum = 0, avail = 0, ss_avail = 0;
+        uint64_t sum = 0, ss_avail = 0, avail = 0;
         int r;
         _cleanup_closedir_ DIR *d = NULL;
         usec_t ts;
+        const char *f;
         JournalMetrics *m;
 
         ts = now(CLOCK_MONOTONIC);
 
-        if (s->cached_available_space_timestamp + RECHECK_AVAILABLE_SPACE_USEC > ts)
+        if (s->cached_available_space_timestamp + RECHECK_AVAILABLE_SPACE_USEC > ts
+            && !verbose)
                 return s->cached_available_space;
 
         r = sd_id128_get_machine(&machine);
@@ -156,19 +157,27 @@ static uint64_t available_space(Server *s) {
                 sum += (uint64_t) st.st_blocks * 512UL;
         }
 
-        avail = sum >= m->max_use ? 0 : m->max_use - sum;
-
         ss_avail = ss.f_bsize * ss.f_bavail;
+        avail = ss_avail > m->keep_free ? ss_avail - m->keep_free : 0;
 
-        ss_avail = ss_avail < m->keep_free ? 0 : ss_avail - m->keep_free;
+        s->cached_available_space = MIN(m->max_use, avail) > sum ? MIN(m->max_use, avail) - sum : 0;
-
-        if (ss_avail < avail)
-                avail = ss_avail;
-
-        s->cached_available_space = avail;
         s->cached_available_space_timestamp = ts;
 
-        return avail;
+        if (verbose) {
+                char    fb1[FORMAT_BYTES_MAX], fb2[FORMAT_BYTES_MAX], fb3[FORMAT_BYTES_MAX],
+                        fb4[FORMAT_BYTES_MAX], fb5[FORMAT_BYTES_MAX];
+
+                server_driver_message(s, SD_MESSAGE_JOURNAL_USAGE,
+                                      "%s journal is using %s (max %s, leaving %s of free %s, current limit %s).",
+                                      s->system_journal ? "Permanent" : "Runtime",
+                                      format_bytes(fb1, sizeof(fb1), sum),
+                                      format_bytes(fb2, sizeof(fb2), m->max_use),
+                                      format_bytes(fb3, sizeof(fb3), m->keep_free),
+                                      format_bytes(fb4, sizeof(fb4), ss_avail),
+                                      format_bytes(fb5, sizeof(fb5), MIN(m->max_use, avail)));
+        }
+
+        return s->cached_available_space;
 }
 
 static void server_read_file_gid(Server *s) {
@@ -853,7 +862,7 @@ void server_dispatch_message(
         }
 
         rl = journal_rate_limit_test(s->rate_limit, path,
-                                     priority & LOG_PRIMASK, available_space(s));
+                                     priority & LOG_PRIMASK, available_space(s, false));
 
         if (rl == 0)
                 return;
@@ -899,29 +908,14 @@ static int system_journal_open(Server *s) {
                 fn = strappenda(fn, "/system.journal");
                 r = journal_file_open_reliably(fn, O_RDWR|O_CREAT, 0640, s->compress, s->seal, &s->system_metrics, s->mmap, NULL, &s->system_journal);
 
-                if (r >= 0) {
+                if (r >= 0)
-                        char fb[FORMAT_BYTES_MAX];
-                        uint64_t avail;
-
                         server_fix_perms(s, s->system_journal, 0);
-
-                        server_driver_message(s, SD_ID128_NULL, "Allowing system journal files to grow to %s.",
-                                              format_bytes(fb, sizeof(fb), s->system_metrics.max_use));
-
-                        avail = available_space(s);
-
-                        if (s->system_metrics.max_use > avail)
-                               server_driver_message(s, SD_ID128_NULL, "Journal size currently limited to %s due to SystemKeepFree.",
-                                                     format_bytes(fb, sizeof(fb), avail));
-
         } else if (r < 0) {
-
                 if (r != -ENOENT && r != -EROFS)
                         log_warning("Failed to open system journal: %s", strerror(-r));
 
                 r = 0;
         }
-        }
 
         if (!s->runtime_journal &&
             (s->storage != STORAGE_NONE)) {
@@ -961,22 +955,12 @@ static int system_journal_open(Server *s) {
                         }
                 }
 
-                if (s->runtime_journal) {
+                if (s->runtime_journal)
-                        char fb[FORMAT_BYTES_MAX];
-                        uint64_t avail;
-
                         server_fix_perms(s, s->runtime_journal, 0);
-                        server_driver_message(s, SD_ID128_NULL, "Allowing runtime journal files to grow to %s.",
-                                              format_bytes(fb, sizeof(fb), s->runtime_metrics.max_use));
-
-                        avail = available_space(s);
-
-                        if (s->system_metrics.max_use > avail)
-                               server_driver_message(s, SD_ID128_NULL, "Journal size currently limited to %s due to RuntimeKeepFree.",
-                                                     format_bytes(fb, sizeof(fb), avail));
-                }
         }
 
+        available_space(s, true);
+
         return r;
 }
 

src/systemd/sd-messages.h

@@ -39,6 +39,7 @@ extern "C" {
 #define SD_MESSAGE_JOURNAL_STOP     SD_ID128_MAKE(d9,3f,b3,c9,c2,4d,45,1a,97,ce,a6,15,ce,59,c0,0b)
 #define SD_MESSAGE_JOURNAL_DROPPED  SD_ID128_MAKE(a5,96,d6,fe,7b,fa,49,94,82,8e,72,30,9e,95,d6,1e)
 #define SD_MESSAGE_JOURNAL_MISSED   SD_ID128_MAKE(e9,bf,28,e6,e8,34,48,1b,b6,f4,8f,54,8a,d1,36,06)
+#define SD_MESSAGE_JOURNAL_USAGE    SD_ID128_MAKE(ec,38,7f,57,7b,84,4b,8f,a9,48,f3,3c,ad,9a,75,e6)
 
 #define SD_MESSAGE_COREDUMP         SD_ID128_MAKE(fc,2e,22,bc,6e,e6,47,b6,b9,07,29,ab,34,a2,50,b1)