Backport r1883340:

Follow up to r1790200: fall back to fsync() if F_FULLFSYNC is not supported
by the file descriptor, filesystem or underlying device.

See, e.g.: vim/vim#4025


git-svn-id: https://svn.apache.org/repos/asf/apr/apr/branches/1.7.x@1883341 13f79535-47bb-0310-9956-ffa450edef68

file_io/unix/readwrite.c

@@ -373,6 +373,7 @@ APR_DECLARE(apr_status_t) apr_file_sync(apr_file_t *thefile)
 APR_DECLARE(apr_status_t) apr_file_datasync(apr_file_t *thefile)
 {
     apr_status_t rv = APR_SUCCESS;
+    int os_status = 0;
 
     file_lock(thefile);
 
@@ -386,12 +387,17 @@ APR_DECLARE(apr_status_t) apr_file_datasync(apr_file_t *thefile)
     }
 
 #ifdef HAVE_FDATASYNC
-    if (fdatasync(thefile->filedes)) {
+    os_status = fdatasync(thefile->filedes);
 #elif defined(F_FULLFSYNC)
-    if (fcntl(thefile->filedes, F_FULLFSYNC)) {
+    os_status = fcntl(thefile->filedes, F_FULLFSYNC);
+    if (os_status) {
+        /* Fall back to fsync() if the device doesn't support F_FULLFSYNC. */
+        os_status = fsync(thefile->filedes);
+    }
 #else
-    if (fsync(thefile->filedes)) {
+    os_status = fsync(thefile->filedes);
 #endif
+    if (os_status) {
         rv = apr_get_os_error();
     }
 

test/testfile.c

@@ -1219,6 +1219,41 @@ static void test_xthread(abts_case *tc, void *data)
     apr_file_close(f);
 }
 
+static void test_datasync_on_file(abts_case *tc, void *data)
+{
+    apr_status_t rv;
+    apr_file_t *f;
+    const char *fname = DIRNAME "/testtest_datasync.dat";
+    apr_size_t bytes_written;
+
+    apr_file_remove(fname, p);
+
+    rv = apr_file_open(&f, fname, APR_FOPEN_CREATE | APR_FOPEN_WRITE,
+                       APR_FPROT_OS_DEFAULT, p);
+    APR_ASSERT_SUCCESS(tc, "open test file for writing", rv);
+    rv = apr_file_write_full(f, "abcdef", 6, &bytes_written);
+    APR_ASSERT_SUCCESS(tc, "write to file", rv);
+    rv = apr_file_datasync(f);
+    APR_ASSERT_SUCCESS(tc, "sync file contents", rv);
+    apr_file_close(f);
+
+    apr_file_remove(fname, p);
+}
+
+static void test_datasync_on_stream(abts_case *tc, void *data)
+{
+    apr_status_t rv;
+    apr_file_t *f;
+    apr_size_t bytes_written;
+
+    rv = apr_file_open_stdout(&f, p);
+    APR_ASSERT_SUCCESS(tc, "open stdout", rv);
+    rv = apr_file_write_full(f, "abcdef\b\b\b\b\b\b\b", 12, &bytes_written);
+    APR_ASSERT_SUCCESS(tc, "write to stdout", rv);
+    rv = apr_file_datasync(f);
+    APR_ASSERT_SUCCESS(tc, "sync stdout", rv);
+}
+
 abts_suite *testfile(abts_suite *suite)
 {
     suite = ADD_SUITE(suite)
@@ -1263,6 +1298,8 @@ abts_suite *testfile(abts_suite *suite)
     abts_run_test(suite, test_fail_read_flush, NULL);
     abts_run_test(suite, test_buffer_set_get, NULL);
     abts_run_test(suite, test_xthread, NULL);
+    abts_run_test(suite, test_datasync_on_file, NULL);
+    abts_run_test(suite, test_datasync_on_stream, NULL);
 
     return suite;
 }