Add the --unlink option to mirror

This deletes the local file before tearing down the mirror connection,
allowing us to avoid an ambiguous recovery situation.

tests/acceptance/environment.rb

@@ -73,6 +73,10 @@ class Environment
     @nbd1.mirror_unchecked( @nbd2.ip, @nbd2.port, nil, nil, 10 )
   end
 
+  def mirror12_unlink
+    @nbd1.mirror_unlink( @nbd2.ip, @nbd2.port, 2 )
+  end
+
 
   def writefile1(data)
     @file1 = FileWriter.new(@filename1, @blocksize).write(data)

tests/acceptance/flexnbd.rb

@@ -195,7 +195,7 @@ class FlexNBD
     end
   end
 
-  def initialize(bin, ip, port)
+  def initialize( bin, ip, port )
     @bin  = bin
     @do_debug = ENV['DEBUG']
     @debug = build_debug_opt
@@ -259,12 +259,29 @@ class FlexNBD
   end
 
 
-  def mirror_cmd(dest_ip, dest_port)
-    "#{@bin} mirror "\
-      "--addr #{dest_ip} "\
+  def base_mirror_opts( dest_ip, dest_port )
+    "--addr #{dest_ip} "\
       "--port #{dest_port} "\
       "--sock #{ctrl} "\
-      "#{@debug} "
+  end
+
+  def unlink_mirror_opts( dest_ip, dest_port )
+    "#{base_mirror_opts( dest_ip, dest_port )} "\
+      "--unlink "
+  end
+
+  def base_mirror_cmd( opts )
+    "#{@bin} mirror "\
+      "#{opts} "\
+      "#{@debug}"
+  end
+
+  def mirror_cmd(dest_ip, dest_port)
+    base_mirror_cmd( base_mirror_opts( dest_ip, dest_port ) )
+  end
+
+  def mirror_unlink_cmd( dest_ip, dest_port )
+    base_mirror_cmd( unlink_mirror_opts( dest_ip, dest_port ) )
   end
 
   def break_cmd
@@ -389,6 +406,14 @@ class FlexNBD
   end
 
 
+  def mirror_unlink( dest_ip, dest_port, timeout=nil )
+    cmd = mirror_unlink_cmd( dest_ip, dest_port )
+    debug( cmd )
+
+    maybe_timeout( cmd, timeout )
+  end
+
+
   def maybe_timeout(cmd, timeout=nil )
     stdout, stderr = "",""
     run = Proc.new do
@@ -417,6 +442,7 @@ class FlexNBD
   end
 
 
+
   def break(timeout=nil)
     cmd = break_cmd
     debug( cmd )

tests/acceptance/test_happy_path.rb

@@ -64,12 +64,17 @@ class TestHappyPath < Test::Unit::TestCase
   end
 
 
-  def test_mirror
+  def setup_to_mirror
     @env.writefile1( "f"*4 )
     @env.serve1
 
     @env.writefile2( "0"*4 )
     @env.listen2
+  end
+
+
+  def test_mirror
+    setup_to_mirror()
 
     @env.nbd1.can_die
     @env.nbd2.can_die(0)
@@ -78,11 +83,30 @@ class TestHappyPath < Test::Unit::TestCase
     @env.nbd1.join
     @env.nbd2.join
 
+    assert( File.file?( @env.filename1 ),
+           "The source file was incorrectly deleted")
     assert_equal(@env.file1.read_original( 0, @env.blocksize ),
                  @env.file2.read( 0, @env.blocksize ) )
   end
 
 
+  def test_mirror_unlink
+    setup_to_mirror()
+    assert File.file?( @env.filename1 )
+
+    stdout, stderr = @env.mirror12_unlink
+
+    assert_no_match( /unrecognized/, stderr )
+    @env.nbd1.can_die(0)
+    @env.nbd2.can_die(0)
+
+    Timeout.timeout(2) do @env.nbd1.join end
+
+    assert !File.file?( @env.filename1 )
+  end
+
+
+
   def test_write_to_high_block
     # Create a large file, then try to write to somewhere after the 2G boundary
     @env.truncate1 "4G"