+struct nfs_referral_count {
+ struct list_head list;
+ const struct task_struct *task;
+ unsigned int referral_count;
+};
+
+static LIST_HEAD(nfs_referral_count_list);
+static DEFINE_SPINLOCK(nfs_referral_count_list_lock);
+
+static struct nfs_referral_count *nfs_find_referral_count(void)
+{
+ struct nfs_referral_count *p;
+
+ list_for_each_entry(p, &nfs_referral_count_list, list) {
+ if (p->task == current)
+ return p;
+ }
+ return NULL;
+}
+
+#define NFS_MAX_NESTED_REFERRALS 2
+
+static int nfs_referral_loop_protect(void)
+{
+ struct nfs_referral_count *p, *new;
+ int ret = -ENOMEM;
+
+ new = kmalloc(sizeof(*new), GFP_KERNEL);
+ if (!new)
+ goto out;
+ new->task = current;
+ new->referral_count = 1;
+
+ ret = 0;
+ spin_lock(&nfs_referral_count_list_lock);
+ p = nfs_find_referral_count();
+ if (p != NULL) {
+ if (p->referral_count >= NFS_MAX_NESTED_REFERRALS)
+ ret = -ELOOP;
+ else
+ p->referral_count++;
+ } else {
+ list_add(&new->list, &nfs_referral_count_list);
+ new = NULL;
+ }
+ spin_unlock(&nfs_referral_count_list_lock);
+ kfree(new);
+out:
+ return ret;
+}
+
+static void nfs_referral_loop_unprotect(void)
+{
+ struct nfs_referral_count *p;
+
+ spin_lock(&nfs_referral_count_list_lock);
+ p = nfs_find_referral_count();
+ p->referral_count--;
+ if (p->referral_count == 0)
+ list_del(&p->list);
+ else
+ p = NULL;
+ spin_unlock(&nfs_referral_count_list_lock);
+ kfree(p);
+}
+