syslogd: Unify unlink/truncate + unlock log-rotation logic

Always unlink + reopen, rather than sometimes using ftruncate();
using a single code-path reduces the opportunity for either
mistakes or duplicate code.

Signed-off-by: Joshua Judson Rosen <jrosen@harvestai.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 11 insertions, 19 deletions

diff --git a/sysklogd/syslogd.c b/sysklogd/syslogd.c
index d77fc9475..f75851085 100644
--- a/sysklogd/syslogd.c
+++ b/sysklogd/syslogd.c
@@ -648,32 +648,24 @@ static void log_locally(time_t now, char *msg, logFile_t *log_file)
                         }
                         /* newFile == "f.0" now */
                         rename(log_file->path, newFile);
-                        /* Incredibly, if F and F.0 are hardlinks, POSIX
-                         * _demands_ that rename returns 0 but does not
-                         * remove F!!!
-                         * (hardlinked F/F.0 pair was observed after
-                         * power failure during rename()).
-                         * Ensure old file is gone:
-                         */
-                        unlink(log_file->path);
-#ifdef SYSLOGD_WRLOCK
-                        fl.l_type = F_UNLCK;
-                        fcntl(log_file->fd, F_SETLKW, &fl);
-#endif
-                        close(log_file->fd);
-                        goto reopen;
                 }
 
-                /* We don't get here unless G.logFileRotate == 0;
-                 * in which case don't bother unlinking and reopening,
-                 * just truncate and reset size to match:
+                /* We may or may not have just renamed the file away;
+                 * if we didn't rename because we aren't keeping any backlog,
+                 * then it's time to clobber the file. If we did rename it...,
+                 * incredibly, if F and F.0 are hardlinks, POSIX _demands_
+                 * that rename returns 0 but does not remove F!!!
+                 * (hardlinked F/F.0 pair was observed after
+                 * power failure during rename()).
+                 * So ensure old file is gone in any case:
                  */
-                ftruncate(log_file->fd, 0);
-                log_file->size = 0;
+                unlink(log_file->path);
 #ifdef SYSLOGD_WRLOCK
                 fl.l_type = F_UNLCK;
                 fcntl(log_file->fd, F_SETLKW, &fl);
 #endif
+                close(log_file->fd);
+                goto reopen;
         }
         log_file->size +=
 #endif