doc,test: minor improvements to O_DSYNC

PR-URL: nodejs#15547
Refs: nodejs#15451
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

doc/api/fs.md

@@ -2867,12 +2867,13 @@ The following constants are meant for use with `fs.open()`.
   </tr>
   <tr>
     <td><code>O_SYNC</code></td>
-    <td>Flag indicating that the file is opened for synchronous I/O.</td>
+    <td>Flag indicating that the file is opened for synchronized I/O with write
+    operations waiting for file integrity.</td>
   </tr>
   <tr>
     <td><code>O_DSYNC</code></td>
-    <td>Flag indicating that the file is opened for synchronous I/O
-    with write operations waiting for data integrity.</td>
+    <td>Flag indicating that the file is opened for synchronized I/O with write
+    operations waiting for data integrity.</td>
   </tr>
   <tr>
     <td><code>O_SYMLINK</code></td>

test/parallel/test-fs-open-flags.js

@@ -79,12 +79,10 @@ assert.throws(
   /^Error: Unknown file open flag: null$/
 );
 
-if (common.isLinux === true) {
+if (common.isLinux) {
   const file = `${__dirname}/../fixtures/a.js`;
 
-  fs.open(file, O_DSYNC, common.mustCall(function(err, fd) {
-    assert.ifError(err);
-  }));
+  fs.open(file, O_DSYNC, common.mustCall(assert.ifError));
 }
 
 function escapeRegExp(string) {