Added LD_PRELOAD library to monitor msync calls in testing

tests/acceptance/ld_preloads/Makefile

@@ -0,0 +1,13 @@
+
+SRC := $(wildcard *.c)
+OBJS := $(SRC:%.c=%.o)
+
+all: $(OBJS)
+
+clean:
+	$(RM) $(OBJS)
+
+%.o: %.c
+	gcc -shared -fPIC -ldl -o $@ $<
+
+.PHONY: all clean

tests/acceptance/ld_preloads/msync_catcher.c

@@ -0,0 +1,33 @@
+#define _GNU_SOURCE
+
+#include <dlfcn.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/mman.h>
+
+typedef int (*real_msync_t)(void *addr, size_t length, int flags);
+
+int real_msync(void *addr, size_t length, int flags) {
+  return ((real_msync_t)dlsym(RTLD_NEXT, "msync"))(addr, length, flags);
+}
+
+/*
+ * Noddy LD_PRELOAD wrapper to catch msync calls, and log them to a file.
+ */
+
+int msync(void *addr, size_t length, int flags) {
+  FILE *fd;
+  char *fn;
+  int retval;
+  
+  retval = real_msync(addr, length, flags);
+  
+  fn = getenv("MSYNC_CATCHER_OUTPUT");
+  if ( fn != NULL ) {
+    fd = fopen(fn,"a");
+    fprintf(fd,"msync:%d:%i:%i:%i\n", addr, length, flags, retval);
+    fclose(fd);
+  }
+
+  return retval;
+}

tests/acceptance/test_serve_mode.rb

@@ -1,6 +1,7 @@
 require 'test/unit'
 require 'environment'
 require 'flexnbd/fake_source'
+require 'tempfile'
 
 class TestServeMode < Test::Unit::TestCase
   def setup
@@ -11,6 +12,7 @@ class TestServeMode < Test::Unit::TestCase
 
   def teardown
     @env.cleanup
+    teardown_msync_catcher
     super
   end
 
@@ -37,6 +39,26 @@ class TestServeMode < Test::Unit::TestCase
     end
   end
 
+  def setup_msync_catcher
+    @msync_catcher = Tempfile.new('msync')
+    ENV['MSYNC_CATCHER_OUTPUT'] = @msync_catcher.path
+  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'
+  end
+
   def test_bad_request_magic_receives_error_response
     connect_to_server do |client|
       # replace REQUEST_MAGIC with all 0s to make it look bad
@@ -109,15 +131,21 @@ class TestServeMode < Test::Unit::TestCase
   end
 
   def test_flush_is_accepted
+    setup_msync_catcher
     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
+    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
 
   def test_write_with_fua_is_accepted
+    setup_msync_catcher
     page_size = Integer(`getconf PAGESIZE`)
     @env.blocksize = page_size * 10
     connect_to_server do |client|
@@ -127,13 +155,15 @@ class TestServeMode < Test::Unit::TestCase
       rsp = client.read_response
       assert_equal FlexNBD::REPLY_MAGIC, rsp[:magic]
       assert_equal 0, rsp[:error]
-      # TODO: test offset and length
-      # Should be rounded to the third page
-      # assert_equal(msync_offset, page_size *3)
-
-      # Should be 100 + 33, as we've started writing 100 bytes into a page, for
-      # 33 bytes
-      # assert_equal(msync_length, 133)
     end
+
+    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
+    # 33 bytes
+    assert_equal 133, op.first[2], 'msync length wrong'
+    assert_equal 6, op.first[3], 'msync called with incorrect flags'
   end
+
 end