Tidy up ld preload hacks

tests/acceptance/ld_preload.rb

@@ -0,0 +1,36 @@
+require 'tempfile'
+
+# LdPreload is a little wrapper for using LD_PRELOAD when testing flexnbd
+module LdPreload
+  # This takes an object name, sets up a temporary log file, whose name is
+  # recorded in the environment as OUTPUT_obj_name, where obj_name is the
+  # name of the preload module to build and load.
+  def with_ld_preload(obj_name)
+    @ld_preload_logs ||= {}
+    flunk 'Can only load a preload module once!' if @ld_preload_logs[obj_name]
+
+    system("make -C ld_preloads/ #{obj_name}.o > /dev/null") ||
+      flunk("Failed to build object #{obj_name}")
+    orig_env = ENV['LD_PRELOAD']
+    ENV['LD_PRELOAD'] = [orig_env, File.expand_path("./ld_preloads/#{obj_name}.o")].compact.join(' ')
+
+    # Open the log, and stick it in a hash
+    @ld_preload_logs[obj_name] = Tempfile.new(obj_name)
+    ENV['OUTPUT_' + obj_name] = @ld_preload_logs[obj_name].path
+
+    yield
+  ensure
+    if @ld_preload_logs[obj_name]
+      @ld_preload_logs[obj_name].close
+      @ld_preload_logs.delete(obj_name)
+    end
+    ENV['LD_PRELOAD'] = orig_env
+  end
+
+  def read_ld_preload_log(obj_name)
+    lines = []
+    lines << @ld_preload_logs[obj_name].readline.chomp until
+      @ld_preload_logs[obj_name].eof?
+    lines
+  end
+end

tests/acceptance/ld_preloads/msync_logger.c

@@ -22,7 +22,7 @@ int msync(void *addr, size_t length, int flags) {
   
   retval = real_msync(addr, length, flags);
   
-  fn = getenv("MSYNC_CATCHER_OUTPUT");
+  fn = getenv("OUTPUT_msync_logger");
   if ( fn != NULL ) {
     fd = fopen(fn,"a");
     fprintf(fd,"msync:%d:%i:%i:%i\n", addr, length, flags, retval);

tests/acceptance/test_serve_mode.rb

@@ -1,9 +1,11 @@
 require 'test/unit'
 require 'environment'
 require 'flexnbd/fake_source'
-require 'tempfile'
+require 'ld_preload'
 
 class TestServeMode < Test::Unit::TestCase
+  include LdPreload
+
   def setup
     super
     @b = "\xFF".b
@@ -12,7 +14,6 @@ class TestServeMode < Test::Unit::TestCase
 
   def teardown
     @env.cleanup
-    teardown_msync_catcher
     super
   end
 
@@ -39,33 +40,10 @@ class TestServeMode < Test::Unit::TestCase
     end
   end
 
-  def setup_msync_catcher
-    `make -C ld_preloads/ msync_catcher.o`
-    omit 'LD_PRELOAD library not found' unless
-      File.exist?('ld_preloads/msync_catcher.o')
-
-    @msync_catcher = Tempfile.new('msync')
-    ENV['MSYNC_CATCHER_OUTPUT'] = @msync_catcher.path
-
-    @ld_preload_orig = ENV['LD_PRELOAD']
-    ENV['LD_PRELOAD'] = 'ld_preloads/msync_catcher.o'
+  def parse_msync_logs
+    read_ld_preload_log('msync_logger').map do |l|
+      l.split(':').map { |i| i =~ /^\d+$/ ? i.to_i : i }
     end
-
-  def parse_msync_output
-    op = []
-    until @msync_catcher.eof?
-      op << @msync_catcher.readline.chomp.split(':').map do |e|
-        e =~ /^\d+$/ ? e.to_i : e
-      end
-    end
-    op
-  end
-
-  def teardown_msync_catcher
-    @msync_catcher.close if @msync_catcher
-
-    ENV.delete 'MSYNC_CATCHER_OUTPUT'
-    ENV['LD_PRELOAD'] = @ld_preload_orig
   end
 
   def test_bad_request_magic_receives_error_response
@@ -160,22 +138,24 @@ class TestServeMode < Test::Unit::TestCase
   end
 
   def test_flush_is_accepted
-    setup_msync_catcher
+    with_ld_preload('msync_logger') do
       connect_to_server do |client|
         client.flush
         rsp = client.read_response
         assert_equal FlexNBD::REPLY_MAGIC, rsp[:magic]
         assert_equal 0, rsp[:error]
       end
-    op = parse_msync_output
+      op = parse_msync_logs
       assert_equal 1, op.count, 'Only one msync expected'
       assert_equal @env.blocksize, op.first[2], 'msync length wrong'
       assert_equal 6, op.first[3], 'msync called with incorrect flags'
     end
+  end
 
   def test_write_with_fua_is_accepted
-    setup_msync_catcher
+    with_ld_preload('msync_logger') do
       page_size = Integer(`getconf PAGESIZE`)
+
       @env.blocksize = page_size * 10
       connect_to_server do |client|
         # Write somewhere in the third page
@@ -185,8 +165,8 @@ class TestServeMode < Test::Unit::TestCase
         assert_equal FlexNBD::REPLY_MAGIC, rsp[:magic]
         assert_equal 0, rsp[:error]
       end
+      op = parse_msync_logs
 
-    op = parse_msync_output
       assert_equal 1, op.count, 'Only one msync expected'
 
       # Should be 100 + 33, as we've started writing 100 bytes into a page, for
@@ -194,6 +174,7 @@ class TestServeMode < Test::Unit::TestCase
       assert_equal 133, op.first[2], 'msync length wrong'
       assert_equal 6, op.first[3], 'msync called with incorrect flags'
     end
+  end
 
   def test_odd_size_discs_are_truncated_to_nearest_512
     # This should get rounded down to 1024