+/*
+ * Check if we have a valid request.
+ * Returns
+ * 1 if the request should continue.
+ * In this case we can return an autofs_wait_queue entry if one is
+ * found or NULL to idicate a new wait needs to be created.
+ * 0 or a negative errno if the request shouldn't continue.
+ */
+static int validate_request(struct autofs_wait_queue **wait,
+ struct autofs_sb_info *sbi,
+ struct qstr *qstr,
+ struct dentry*dentry, enum autofs_notify notify)
+{
+ struct autofs_wait_queue *wq;
+ struct autofs_info *ino;
+
+ /* Wait in progress, continue; */
+ wq = autofs4_find_wait(sbi, qstr);
+ if (wq) {
+ *wait = wq;
+ return 1;
+ }
+
+ *wait = NULL;
+
+ /* If we don't yet have any info this is a new request */
+ ino = autofs4_dentry_ino(dentry);
+ if (!ino)
+ return 1;
+
+ /*
+ * If we've been asked to wait on an existing expire (NFY_NONE)
+ * but there is no wait in the queue ...
+ */
+ if (notify == NFY_NONE) {
+ /*
+ * Either we've betean the pending expire to post it's
+ * wait or it finished while we waited on the mutex.
+ * So we need to wait till either, the wait appears
+ * or the expire finishes.
+ */
+
+ while (ino->flags & AUTOFS_INF_EXPIRING) {
+ mutex_unlock(&sbi->wq_mutex);
+ schedule_timeout_interruptible(HZ/10);
+ if (mutex_lock_interruptible(&sbi->wq_mutex))
+ return -EINTR;
+
+ wq = autofs4_find_wait(sbi, qstr);
+ if (wq) {
+ *wait = wq;
+ return 1;
+ }
+ }
+
+ /*
+ * Not ideal but the status has already gone. Of the two
+ * cases where we wait on NFY_NONE neither depend on the
+ * return status of the wait.
+ */
+ return 0;
+ }
+
+ /*
+ * If we've been asked to trigger a mount and the request
+ * completed while we waited on the mutex ...
+ */
+ if (notify == NFY_MOUNT) {
+ /*
+ * If the dentry isn't hashed just go ahead and try the
+ * mount again with a new wait (not much else we can do).
+ */
+ if (!d_unhashed(dentry)) {
+ /*
+ * But if the dentry is hashed, that means that we
+ * got here through the revalidate path. Thus, we
+ * need to check if the dentry has been mounted
+ * while we waited on the wq_mutex. If it has,
+ * simply return success.
+ */
+ if (d_mountpoint(dentry))
+ return 0;
+ }
+ }
+
+ return 1;
+}
+