http://lists.mysql.com/commits/59711

--- sql/sql_table.cc	2010-01-29 19:06:23.000000000 +0100
+++ sql/sql_table.cc.oden	2010-02-17 13:24:38.486094749 +0100
@@ -3903,15 +3903,43 @@ bool mysql_create_table_no_lock(THD *thd
   create_info->table_existed= 0;		// Mark that table is created
 
 #ifdef HAVE_READLINK
-  if (test_if_data_home_dir(create_info->data_file_name))
   {
-    my_error(ER_WRONG_ARGUMENTS, MYF(0), "DATA DIRECTORY");
-    goto unlock_and_end;
-  }
-  if (test_if_data_home_dir(create_info->index_file_name))
-  {
-    my_error(ER_WRONG_ARGUMENTS, MYF(0), "INDEX DIRECTORY");
-    goto unlock_and_end;
+    size_t dirlen;
+    char   dirpath[FN_REFLEN];
+
+    /*
+      data_file_name and index_file_name include the table name without
+      extension. Mostly this does not refer to an existing file. When
+      comparing data_file_name or index_file_name against the data
+      directory, we try to resolve all symbolic links. On some systems,
+      we use realpath(3) for the resolution. This returns ENOENT if the
+      resolved path does not refer to an existing file. my_realpath()
+      does then copy the requested path verbatim, without symlink
+      resolution. Thereafter the comparison can fail even if the
+      requested path is within the data directory. E.g. if symlinks to
+      another file system are used. To make realpath(3) return the
+      resolved path, we strip the table name and compare the directory
+      path only. If the directory doesn't exist either, table creation
+      will fail anyway.
+    */
+    if (create_info->data_file_name)
+    {
+      dirname_part(dirpath, create_info->data_file_name, &dirlen);
+      if (test_if_data_home_dir(dirpath))
+      {
+        my_error(ER_WRONG_ARGUMENTS, MYF(0), "DATA DIRECTORY");
+        goto unlock_and_end;
+      }
+    }
+    if (create_info->index_file_name)
+    {
+      dirname_part(dirpath, create_info->index_file_name, &dirlen);
+      if (test_if_data_home_dir(dirpath))
+      {
+        my_error(ER_WRONG_ARGUMENTS, MYF(0), "INDEX DIRECTORY");
+        goto unlock_and_end;
+      }
+    }
   }
 
 #ifdef WITH_PARTITION_STORAGE_ENGINE