+/*
+ * Calculate and dget next entry in the subdirs list under root.
+ */
+static struct dentry *get_next_positive_subdir(struct dentry *prev,
+ struct dentry *root)
+{
+ struct autofs_sb_info *sbi = autofs4_sbi(root->d_sb);
+ struct list_head *next;
+ struct dentry *p, *q;
+
+ spin_lock(&sbi->lookup_lock);
+
+ if (prev == NULL) {
+ spin_lock(&root->d_lock);
+ prev = dget_dlock(root);
+ next = prev->d_subdirs.next;
+ p = prev;
+ goto start;
+ }
+
+ p = prev;
+ spin_lock(&p->d_lock);
+again:
+ next = p->d_u.d_child.next;
+start:
+ if (next == &root->d_subdirs) {
+ spin_unlock(&p->d_lock);
+ spin_unlock(&sbi->lookup_lock);
+ dput(prev);
+ return NULL;
+ }
+
+ q = list_entry(next, struct dentry, d_u.d_child);
+
+ spin_lock_nested(&q->d_lock, DENTRY_D_LOCK_NESTED);
+ /* Negative dentry - try next */
+ if (!simple_positive(q)) {
+ spin_unlock(&p->d_lock);
+ p = q;
+ goto again;
+ }
+ dget_dlock(q);
+ spin_unlock(&q->d_lock);
+ spin_unlock(&p->d_lock);
+ spin_unlock(&sbi->lookup_lock);
+
+ dput(prev);
+
+ return q;
+}
+