idr: Fix idr_get_next_ul race with idr_remove

Commit 5c089fd0 ("idr: Fix idr_get_next race with idr_remove")
neglected to fix idr_get_next_ul().  As far as I can tell, nobody's
actually using this interface under the RCU read lock, but fix it now
before anybody decides to use it.

Fixes: 5c089fd0 ("idr: Fix idr_get_next race with idr_remove")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

lib/idr.c

@@ -215,7 +215,7 @@ int idr_for_each(const struct idr *idr,
 EXPORT_SYMBOL(idr_for_each);
 
 /**
- * idr_get_next() - Find next populated entry.
+ * idr_get_next_ul() - Find next populated entry.
  * @idr: IDR handle.
  * @nextid: Pointer to an ID.
  *
@@ -224,7 +224,7 @@ EXPORT_SYMBOL(idr_for_each);
  * to the ID of the found value.  To use in a loop, the value pointed to by
  * nextid must be incremented by the user.
  */
-void *idr_get_next(struct idr *idr, int *nextid)
+void *idr_get_next_ul(struct idr *idr, unsigned long *nextid)
 {
 	struct radix_tree_iter iter;
 	void __rcu **slot;
@@ -245,18 +245,14 @@ void *idr_get_next(struct idr *idr, int *nextid)
 	}
 	if (!slot)
 		return NULL;
-	id = iter.index + base;
-
-	if (WARN_ON_ONCE(id > INT_MAX))
-		return NULL;
 
-	*nextid = id;
+	*nextid = iter.index + base;
 	return entry;
 }
-EXPORT_SYMBOL(idr_get_next);
+EXPORT_SYMBOL(idr_get_next_ul);
 
 /**
- * idr_get_next_ul() - Find next populated entry.
+ * idr_get_next() - Find next populated entry.
  * @idr: IDR handle.
  * @nextid: Pointer to an ID.
  *
@@ -265,22 +261,17 @@ EXPORT_SYMBOL(idr_get_next);
  * to the ID of the found value.  To use in a loop, the value pointed to by
  * nextid must be incremented by the user.
  */
-void *idr_get_next_ul(struct idr *idr, unsigned long *nextid)
+void *idr_get_next(struct idr *idr, int *nextid)
 {
-	struct radix_tree_iter iter;
-	void __rcu **slot;
-	unsigned long base = idr->idr_base;
 	unsigned long id = *nextid;
+	void *entry = idr_get_next_ul(idr, &id);
 
-	id = (id < base) ? 0 : id - base;
-	slot = radix_tree_iter_find(&idr->idr_rt, &iter, id);
-	if (!slot)
+	if (WARN_ON_ONCE(id > INT_MAX))
 		return NULL;
-
-	*nextid = iter.index + base;
-	return rcu_dereference_raw(*slot);
+	*nextid = id;
+	return entry;
 }
-EXPORT_SYMBOL(idr_get_next_ul);
+EXPORT_SYMBOL(idr_get_next);
 
 /**
  * idr_replace() - replace pointer for given ID.