volserver-dont-deal-poorly-with-fssync-blockage-20021016

The attached patch attempts to deal with the issue that the volserver
blocks if the fileserver's fssync interface isn't responsive by doing a
select (IOMGR_Select) before trying to read the server's response.

diff --git a/src/vol/fssync.c b/src/vol/fssync.c
index b911a16e36d227f05c241bb1df6128a417be7238..601bc5b71d2e31c62f42e94e49b69ca25b59192e 100644 (file)
--- a/src/vol/fssync.c
+++ b/src/vol/fssync.c
@@ -138,6 +138,10 @@ static void GetHandler(fd_set *fdsetp, int *maxfdp);
  */
 struct Lock FSYNC_handler_lock;
 
+/* this lock prevents a volume utility or volserver from having multiple FSYNC
+   requests active simultaneously */
+struct Lock FSYNC_client_lock;
+
 int FSYNC_clientInit(void)
 {
     struct sockaddr_in addr;
@@ -145,6 +149,7 @@ int FSYNC_clientInit(void)
     static backoff[] = {3,3,3,5,5,5,7,15,16,24,32,40,48,0};
     int *timeout = &backoff[0];
 
+    Lock_Init(&FSYNC_client_lock);
     for (;;) {
         FS_sd = getport(&addr);
        if (connect(FS_sd, (struct sockaddr *) &addr, sizeof(addr)) >= 0)
@@ -176,6 +181,7 @@ void FSYNC_clientFinis(void)
     close(FS_sd);
 #endif
     FS_sd = -1;
+    Lock_Destroy(&FSYNC_client_lock);
     Lock_Destroy(&FSYNC_handler_lock);
 }
 
@@ -184,6 +190,12 @@ int FSYNC_askfs(VolumeId volume, char *partName, int com, int reason)
     byte response;
     struct command command;
     int n;
+#ifndef AFS_NT40_ENV
+#ifndef AFS_PTHREAD_ENV
+    fd_set *fds;
+#endif
+    ObtainWriteLock(&FSYNC_client_lock);
+#endif
     command.volume = volume;
     command.command = com;
     command.reason = reason;
@@ -206,14 +218,28 @@ int FSYNC_askfs(VolumeId volume, char *partName, int com, int reason)
 #else
     if (write(FS_sd, &command, sizeof(command)) != sizeof(command)) {
        printf("FSYNC_askfs: write to file server failed\n");
+       ReleaseWriteLock(&FSYNC_client_lock);
        return FSYNC_DENIED;
     }
+#ifndef AFS_PTHREAD_ENV
+    fds=IOMGR_AllocFDSet();
+    if (fds) {
+       FD_SET(FS_sd, fds);
+       IOMGR_Select(FS_sd+1, fds, 0,0,0);
+       IOMGR_FreeFDSet(fds);
+       fds=0;
+    }
+#endif
     while ((n = read(FS_sd, &response, 1)) != 1) {
        if (n == 0 || errno != EINTR) {
            printf("FSYNC_askfs: No response from file server\n");
+           ReleaseWriteLock(&FSYNC_client_lock);
            return FSYNC_DENIED;
        }
     }
+#endif
+#ifndef AFS_NT40_ENV
+    ReleaseWriteLock(&FSYNC_client_lock);
 #endif
     if (response == 0) {
        printf("FSYNC_askfs: negative response from file server; volume %u, command %d\n", command.volume, command.command);