syslogd: stop doing open/fstat/lseek/close on _every_ write

(still doing it if more than a second passed in between).
Costs ~40 bytes.

1 files changed, 65 insertions, 52 deletions

diff --git a/sysklogd/syslogd.c b/sysklogd/syslogd.c
index f4644f218..7edce7a0a 100644
--- a/sysklogd/syslogd.c
+++ b/sysklogd/syslogd.c
@@ -29,6 +29,7 @@ static char *dev_log_name;
 
 /* Path for the file where all log messages are written */
 static const char *logFilePath = "/var/log/messages";
+static int logFD = -1;
 
 /* interval between marks in seconds */
 static int markInterval = 20 * 60;
@@ -41,9 +42,11 @@ static char localHostName[64];
 
 #if ENABLE_FEATURE_ROTATE_LOGFILE
 /* max size of message file before being rotated */
-static int logFileSize = 200 * 1024;
+static unsigned logFileSize = 200 * 1024;
 /* number of rotated message files */
-static int logFileRotate = 1;
+static unsigned logFileRotate = 1;
+static unsigned curFileSize;
+static smallint isRegular;
 #endif
 
 #if ENABLE_FEATURE_REMOTE_LOG
@@ -256,7 +259,10 @@ void log_to_shmem(const char *msg);
 /* Print a message to the log file. */
 static void log_locally(char *msg)
 {
-        int fd, len = strlen(msg);
+        static time_t last;
+
+        struct flock fl;
+        int len = strlen(msg);
 
 #if ENABLE_FEATURE_IPC_SYSLOG
         if ((option_mask32 & OPT_circularlog) && shbuf) {
@@ -264,62 +270,69 @@ static void log_locally(char *msg)
                 return;
         }
 #endif
-
- again:
-        fd = device_open(logFilePath, O_WRONLY | O_CREAT
+        if (logFD >= 0) {
+                time_t cur;
+                time(&cur);
+                if (last != cur) {
+                        last = cur; /* reopen log file every second */
+                        close(logFD);
+                        goto reopen;
+                }
+        } else {
+                struct stat statf;
+ reopen:
+                logFD = device_open(logFilePath, O_WRONLY | O_CREAT
                                         | O_NOCTTY | O_APPEND | O_NONBLOCK);
-        if (fd >= 0) {
-                struct flock fl;
+                if (logFD < 0) {
+                        /* cannot open logfile? - print to /dev/console then */
+                        int fd = device_open(_PATH_CONSOLE, O_WRONLY | O_NOCTTY | O_NONBLOCK);
+                        if (fd < 0)
+                                fd = 2; /* then stderr, dammit */
+                        full_write(fd, msg, len);
+                        if (fd != 2)
+                                close(fd);
+                        return;
+                }
+#if ENABLE_FEATURE_ROTATE_LOGFILE
+                isRegular = (fstat(logFD, &statf) == 0 && (statf.st_mode & S_IFREG));
+                /* bug (mostly harmless): can wrap around if file > 4gb */
+                curFileSize = statf.st_size;
+#endif
+        }
 
-                fl.l_whence = SEEK_SET;
-                fl.l_start = 0;
-                fl.l_len = 1;
-                fl.l_type = F_WRLCK;
-                fcntl(fd, F_SETLKW, &fl);
+        fl.l_whence = SEEK_SET;
+        fl.l_start = 0;
+        fl.l_len = 1;
+        fl.l_type = F_WRLCK;
+        fcntl(logFD, F_SETLKW, &fl);
 
 #if ENABLE_FEATURE_ROTATE_LOGFILE
-                if (logFileSize) {
-                        struct stat statf;
-                        int r = fstat(fd, &statf);
-                        if (!r && (statf.st_mode & S_IFREG)
-                         && (lseek(fd, 0, SEEK_END) > logFileSize)
-                        ) {
-                                if (logFileRotate) { /* always 0..99 */
-                                        int i = strlen(logFilePath) + 3 + 1;
-                                        char oldFile[i];
-                                        char newFile[i];
-                                        i = logFileRotate - 1;
-                                        /* rename: f.8 -> f.9; f.7 -> f.8; ... */
-                                        while (1) {
-                                                sprintf(newFile, "%s.%d", logFilePath, i);
-                                                if (i == 0) break;
-                                                sprintf(oldFile, "%s.%d", logFilePath, --i);
-                                                rename(oldFile, newFile);
-                                        }
-                                        /* newFile == "f.0" now */
-                                        rename(logFilePath, newFile);
-                                        fl.l_type = F_UNLCK;
-                                        fcntl(fd, F_SETLKW, &fl);
-                                        close(fd);
-                                        goto again;
-                                }
-                                ftruncate(fd, 0);
+        if (logFileSize && isRegular && curFileSize > logFileSize) {
+                if (logFileRotate) { /* always 0..99 */
+                        int i = strlen(logFilePath) + 3 + 1;
+                        char oldFile[i];
+                        char newFile[i];
+                        i = logFileRotate - 1;
+                        /* rename: f.8 -> f.9; f.7 -> f.8; ... */
+                        while (1) {
+                                sprintf(newFile, "%s.%d", logFilePath, i);
+                                if (i == 0) break;
+                                sprintf(oldFile, "%s.%d", logFilePath, --i);
+                                rename(oldFile, newFile);
                         }
+                        /* newFile == "f.0" now */
+                        rename(logFilePath, newFile);
+                        fl.l_type = F_UNLCK;
+                        fcntl(logFD, F_SETLKW, &fl);
+                        close(logFD);
+                        goto reopen;
                 }
-#endif
-                full_write(fd, msg, len);
-                fl.l_type = F_UNLCK;
-                fcntl(fd, F_SETLKW, &fl);
-                close(fd);
-        } else {
-                /* cannot open logfile? - print to /dev/console then */
-                fd = device_open(_PATH_CONSOLE, O_WRONLY | O_NOCTTY | O_NONBLOCK);
-                if (fd < 0)
-                        fd = 2; /* then stderr, dammit */
-                full_write(fd, msg, len);
-                if (fd != 2)
-                        close(fd);
+                ftruncate(logFD, 0);
         }
+#endif
+        curFileSize += full_write(logFD, msg, len);
+        fl.l_type = F_UNLCK;
+        fcntl(logFD, F_SETLKW, &fl);
 }
 
 static void parse_fac_prio_20(int pri, char *res20)