cifs: return the more nuanced writeback error on close()

As filemap_check_errors() only report -EIO or -ENOSPC, we return more nuanced
writeback error -(file->f_mapping->wb_err & MAX_ERRNO).

  filemap_write_and_wait
    filemap_write_and_wait_range
      filemap_check_errors
        -ENOSPC or -EIO
  filemap_check_wb_err
    errseq_check
      return -(file->f_mapping->wb_err & MAX_ERRNO)
Signed-off-by: ChenXiaoSong <chenxiaosong2@huawei.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/file.c

@@ -2777,8 +2777,11 @@ int cifs_flush(struct file *file, fl_owner_t id)
 		rc = filemap_write_and_wait(inode->i_mapping);
 
 	cifs_dbg(FYI, "Flush inode %p file %p rc %d\n", inode, file, rc);
-	if (rc)
+	if (rc) {
+		/* get more nuanced writeback errors */
+		rc = filemap_check_wb_err(file->f_mapping, 0);
 		trace_cifs_flush_err(inode->i_ino, rc);
+	}
 	return rc;
 }