Fix multivolume archive creation when volume length=record size.

* src/tar.c (decode_options): Do not allow volume length less
than record size.
* src/buffer.c (_gnu_flush_write): Compensate for the effect
of eventual flush_archive occurring in the middle of buffer
move.
Increment records_written only if _flush_write was able to write
something.
* tests/multiv06.at: New testcase.
* tests/Makefile.am, test/testsuite.at: Add tests/multiv06.at

src/buffer.c

@@ -1,7 +1,7 @@
 /* Buffer management for tar.
 
    Copyright (C) 1988, 1992, 1993, 1994, 1996, 1997, 1999, 2000, 2001,
-   2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
+   2003, 2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc.
 
    Written by John Gilmore, on 1985-08-25.
 
@@ -1599,13 +1599,15 @@ _gnu_flush_write (size_t buffer_level)
   char *copy_ptr;
   size_t copy_size;
   size_t bufsize;
-
+  tarlong wrt;
+  
   status = _flush_write ();
   if (status != record_size && !multi_volume_option)
     archive_write_error (status);
   else
     {
-      records_written++;
+      if (status)
+	records_written++; 
       bytes_written += status;
     }
 
@@ -1654,6 +1656,7 @@ _gnu_flush_write (size_t buffer_level)
   
   if (real_s_name)
     add_chunk_header ();
+  wrt = bytes_written;
   header = find_next_block ();
   bufsize = available_space_after (header);
   while (bufsize < copy_size)
@@ -1668,6 +1671,16 @@ _gnu_flush_write (size_t buffer_level)
   memcpy (header->buffer, copy_ptr, copy_size);
   memset (header->buffer + copy_size, 0, bufsize - copy_size);
   set_next_block_after (header + (copy_size - 1) / BLOCKSIZE);
+  if (multi_volume_option && wrt < bytes_written)
+    {
+      /* The value of bytes_written has changed while moving data;
+	 that means that flush_archive was executed at least once in
+	 between, and, as a consequence, copy_size bytes were not written
+	 to disk.  We need to update sizeleft variables to compensate for
+         that. */
+      save_sizeleft += copy_size;
+      multi_volume_sync ();
+    }
   find_next_block ();
 }
 

src/create.c

@@ -1041,7 +1041,7 @@ dump_regular_file (int fd, struct tar_stat_info *st)
   while (size_left > 0)
     {
       size_t bufsize, count;
-
+      
       mv_size_left (size_left);
 
       blk = find_next_block ();

src/tar.c

@@ -2324,6 +2324,9 @@ decode_options (int argc, char **argv)
   else if (utc_option)
     verbose_option = 2;
 
+  if (tape_length_option && tape_length_option < record_size)
+    USAGE_ERROR ((0, 0, _("Volume length cannot be less than record size")));
+  
   /* Forbid using -c with no input files whatsoever.  Check that `-f -',
      explicit or implied, is used correctly.  */