logging: support truncation of logfiles when opening

The virtlogd daemon currently opens all files for append, but
in some cases the user may wish to discard existing data. Define
a new flag to indicate that logfiles should be truncated when
opening.

src/logging/log_daemon_dispatch.c

@@ -50,13 +50,14 @@ virLogManagerProtocolDispatchDomainOpenLogFile(virNetServerPtr server ATTRIBUTE_
     int rv = -1;
     off_t offset;
     ino_t inode;
+    bool trunc = args->flags & VIR_LOG_MANAGER_PROTOCOL_DOMAIN_OPEN_LOG_FILE_TRUNCATE;
 
     if ((fd = virLogHandlerDomainOpenLogFile(virLogDaemonGetHandler(logDaemon),
                                              args->driver,
                                              (unsigned char *)args->dom.uuid,
                                              args->dom.name,
                                              args->path,
-                                             args->flags,
+                                             trunc,
                                              &inode, &offset)) < 0)
         goto cleanup;
 

src/logging/log_handler.c

@@ -357,7 +357,7 @@ virLogHandlerDomainOpenLogFile(virLogHandlerPtr handler,
                                const unsigned char *domuuid,
                                const char *domname,
                                const char *path,
-                               unsigned int flags,
+                               bool trunc,
                                ino_t *inode,
                                off_t *offset)
 {
@@ -365,8 +365,6 @@ virLogHandlerDomainOpenLogFile(virLogHandlerPtr handler,
     virLogHandlerLogFilePtr file = NULL;
     int pipefd[2] = { -1, -1 };
 
-    virCheckFlags(0, -1);
-
     virObjectLock(handler);
 
     handler->inhibitor(true, handler->opaque);
@@ -400,7 +398,7 @@ virLogHandlerDomainOpenLogFile(virLogHandlerPtr handler,
     if ((file->file = virRotatingFileWriterNew(path,
                                                DEFAULT_FILE_SIZE,
                                                DEFAULT_MAX_BACKUP,
-                                               false,
+                                               trunc,
                                                DEFAULT_MODE)) == NULL)
         goto error;
 

src/logging/log_handler.h

@@ -48,7 +48,7 @@ int virLogHandlerDomainOpenLogFile(virLogHandlerPtr handler,
                                    const unsigned char *domuuid,
                                    const char *domname,
                                    const char *path,
-                                   unsigned int flags,
+                                   bool trunc,
                                    ino_t *inode,
                                    off_t *offset);
 

src/logging/log_manager.h

@@ -26,6 +26,8 @@
 
 # include "internal.h"
 
+# include "logging/log_protocol.h"
+
 typedef struct _virLogManager virLogManager;
 typedef virLogManager *virLogManagerPtr;
 

src/logging/log_protocol.x

@@ -30,6 +30,10 @@ struct virLogManagerProtocolLogFilePosition {
 };
 typedef struct virLogManagerProtocolLogFilePosition virLogManagerProtocolLogFilePosition;
 
+enum virLogManagerProtocolDomainOpenLogFileFlags {
+    VIR_LOG_MANAGER_PROTOCOL_DOMAIN_OPEN_LOG_FILE_TRUNCATE = 1
+};
+
 /* Obtain a file handle suitable for writing to a
  * log file for a domain
  */