+ /*
+ * We share a lot of code with fs/dnotify. We also share
+ * the bit layout between inotify's IN_* and the fsnotify
+ * FS_*. This check ensures that only the inotify IN_*
+ * bits get passed in and set in watches/events.
+ */
+ if (unlikely(mask & ~ALL_INOTIFY_BITS))
+ return -EINVAL;
+ /*
+ * Require at least one valid bit set in the mask.
+ * Without _something_ set, we would have no events to
+ * watch for.
+ */