fs: fix writeFile[Sync] for non-seekable files

Completely disables the use of positioned writes at
writeFile and writeFileSync, which allows it to work
with non-seekable files.

Fixes: nodejs/node#31926

lib/fs.js

@@ -1248,9 +1248,9 @@ function futimesSync(fd, atime, mtime) {
   handleErrorFromBinding(ctx);
 }
 
-function writeAll(fd, isUserFd, buffer, offset, length, position, callback) {
+function writeAll(fd, isUserFd, buffer, offset, length, callback) {
   // write(fd, buffer, offset, length, position, callback)
-  fs.write(fd, buffer, offset, length, position, (writeErr, written) => {
+  fs.write(fd, buffer, offset, length, null, (writeErr, written) => {
     if (writeErr) {
       if (isUserFd) {
         callback(writeErr);
@@ -1268,10 +1268,7 @@ function writeAll(fd, isUserFd, buffer, offset, length, position, callback) {
     } else {
       offset += written;
       length -= written;
-      if (position !== null) {
-        position += written;
-      }
-      writeAll(fd, isUserFd, buffer, offset, length, position, callback);
+      writeAll(fd, isUserFd, buffer, offset, length, callback);
     }
   });
 }
@@ -1288,7 +1285,7 @@ function writeFile(path, data, options, callback) {
 
   if (isFd(path)) {
     const isUserFd = true;
-    writeAll(path, isUserFd, data, 0, data.byteLength, null, callback);
+    writeAll(path, isUserFd, data, 0, data.byteLength, callback);
     return;
   }
 
@@ -1297,8 +1294,7 @@ function writeFile(path, data, options, callback) {
       callback(openErr);
     } else {
       const isUserFd = false;
-      const position = /a/.test(flag) ? null : 0;
-      writeAll(fd, isUserFd, data, 0, data.byteLength, position, callback);
+      writeAll(fd, isUserFd, data, 0, data.byteLength, callback);
     }
   });
 }
@@ -1318,15 +1314,11 @@ function writeFileSync(path, data, options) {
 
   let offset = 0;
   let length = data.byteLength;
-  let position = (/a/.test(flag) || isUserFd) ? null : 0;
   try {
     while (length > 0) {
-      const written = fs.writeSync(fd, data, offset, length, position);
+      const written = fs.writeSync(fd, data, offset, length);
       offset += written;
       length -= written;
-      if (position !== null) {
-        position += written;
-      }
     }
   } finally {
     if (!isUserFd) fs.closeSync(fd);