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 d77fc94..f758510 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