diff --git a/include/linux/idr.h b/include/linux/idr.h
index 95a82cf2ed02..86b38df6e121 100644
--- a/include/linux/idr.h
+++ b/include/linux/idr.h
@@ -18,6 +18,7 @@
 
 struct idr {
 	struct radix_tree_root	idr_rt;
+	unsigned int		idr_base;
 	unsigned int		idr_next;
 };
 
@@ -30,12 +31,20 @@ struct idr {
 /* Set the IDR flag and the IDR_FREE tag */
 #define IDR_RT_MARKER		((__force gfp_t)(3 << __GFP_BITS_SHIFT))
 
-#define IDR_INIT							\
-{									\
-	.idr_rt = RADIX_TREE_INIT(IDR_RT_MARKER)			\
+#define IDR_INIT_BASE(base) {						\
+	.idr_rt = RADIX_TREE_INIT(IDR_RT_MARKER),			\
+	.idr_base = (base),						\
+	.idr_next = 0,							\
 }
 #define DEFINE_IDR(name)	struct idr name = IDR_INIT
 
+/**
+ * IDR_INIT() - Initialise an IDR.
+ *
+ * A freshly-initialised IDR contains no IDs.
+ */
+#define IDR_INIT	IDR_INIT_BASE(0)
+
 /**
  * idr_get_cursor - Return the current position of the cyclic allocator
  * @idr: idr handle
@@ -81,10 +90,12 @@ static inline void idr_set_cursor(struct idr *idr, unsigned int val)
 
 void idr_preload(gfp_t gfp_mask);
 
-int idr_alloc(struct idr *, void *, int start, int end, gfp_t);
-int __must_check idr_alloc_u32(struct idr *, void *ptr, u32 *nextid,
+int idr_alloc(struct idr *, void *ptr, int start, int end, gfp_t);
+int __must_check idr_alloc_u32(struct idr *, void *ptr, u32 *id,
 				unsigned long max, gfp_t);
-int idr_alloc_cyclic(struct idr *, void *entry, int start, int end, gfp_t);
+int idr_alloc_cyclic(struct idr *, void *ptr, int start, int end, gfp_t);
+void *idr_remove(struct idr *, unsigned long id);
+void *idr_find(const struct idr *, unsigned long id);
 int idr_for_each(const struct idr *,
 		 int (*fn)(int id, void *p, void *data), void *data);
 void *idr_get_next(struct idr *, int *nextid);
@@ -92,17 +103,33 @@ void *idr_get_next_ul(struct idr *, unsigned long *nextid);
 void *idr_replace(struct idr *, void *, unsigned long id);
 void idr_destroy(struct idr *);
 
-static inline void *idr_remove(struct idr *idr, unsigned long id)
-{
-	return radix_tree_delete_item(&idr->idr_rt, id, NULL);
-}
-
-static inline void idr_init(struct idr *idr)
+/**
+ * idr_init_base() - Initialise an IDR.
+ * @idr: IDR handle.
+ * @base: The base value for the IDR.
+ *
+ * This variation of idr_init() creates an IDR which will allocate IDs
+ * starting at %base.
+ */
+static inline void idr_init_base(struct idr *idr, int base)
 {
 	INIT_RADIX_TREE(&idr->idr_rt, IDR_RT_MARKER);
+	idr->idr_base = base;
 	idr->idr_next = 0;
 }
 
+/**
+ * idr_init() - Initialise an IDR.
+ * @idr: IDR handle.
+ *
+ * Initialise a dynamically allocated IDR.  To initialise a
+ * statically allocated IDR, use DEFINE_IDR().
+ */
+static inline void idr_init(struct idr *idr)
+{
+	idr_init_base(idr, 0);
+}
+
 static inline bool idr_is_empty(const struct idr *idr)
 {
 	return radix_tree_empty(&idr->idr_rt) &&
@@ -120,25 +147,6 @@ static inline void idr_preload_end(void)
 	preempt_enable();
 }
 
-/**
- * idr_find() - Return pointer for given ID.
- * @idr: IDR handle.
- * @id: Pointer ID.
- *
- * Looks up the pointer associated with this ID.  A %NULL pointer may
- * indicate that @id is not allocated or that the %NULL pointer was
- * associated with this ID.
- *
- * This function can be called under rcu_read_lock(), given that the leaf
- * pointers lifetimes are correctly managed.
- *
- * Return: The pointer associated with this ID.
- */
-static inline void *idr_find(const struct idr *idr, unsigned long id)
-{
-	return radix_tree_lookup(&idr->idr_rt, id);
-}
-
 /**
  * idr_for_each_entry() - Iterate over an IDR's elements of a given type.
  * @idr: IDR handle.
diff --git a/lib/idr.c b/lib/idr.c
index b47055efceb0..c98d77fcf393 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -36,18 +36,21 @@ int idr_alloc_u32(struct idr *idr, void *ptr, u32 *nextid,
 {
 	struct radix_tree_iter iter;
 	void __rcu **slot;
+	int base = idr->idr_base;
+	int id = *nextid;
 
 	if (WARN_ON_ONCE(radix_tree_is_internal_node(ptr)))
 		return -EINVAL;
 	if (WARN_ON_ONCE(!(idr->idr_rt.gfp_mask & ROOT_IS_IDR)))
 		idr->idr_rt.gfp_mask |= IDR_RT_MARKER;
 
-	radix_tree_iter_init(&iter, *nextid);
-	slot = idr_get_free(&idr->idr_rt, &iter, gfp, max);
+	id = (id < base) ? 0 : id - base;
+	radix_tree_iter_init(&iter, id);
+	slot = idr_get_free(&idr->idr_rt, &iter, gfp, max - base);
 	if (IS_ERR(slot))
 		return PTR_ERR(slot);
 
-	*nextid = iter.index;
+	*nextid = iter.index + base;
 	/* there is a memory barrier inside radix_tree_iter_replace() */
 	radix_tree_iter_replace(&idr->idr_rt, &iter, slot, ptr);
 	radix_tree_iter_tag_clear(&idr->idr_rt, &iter, IDR_FREE);
@@ -135,6 +138,46 @@ int idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end, gfp_t gfp)
 }
 EXPORT_SYMBOL(idr_alloc_cyclic);
 
+/**
+ * idr_remove() - Remove an ID from the IDR.
+ * @idr: IDR handle.
+ * @id: Pointer ID.
+ *
+ * Removes this ID from the IDR.  If the ID was not previously in the IDR,
+ * this function returns %NULL.
+ *
+ * Since this function modifies the IDR, the caller should provide their
+ * own locking to ensure that concurrent modification of the same IDR is
+ * not possible.
+ *
+ * Return: The pointer formerly associated with this ID.
+ */
+void *idr_remove(struct idr *idr, unsigned long id)
+{
+	return radix_tree_delete_item(&idr->idr_rt, id - idr->idr_base, NULL);
+}
+EXPORT_SYMBOL_GPL(idr_remove);
+
+/**
+ * idr_find() - Return pointer for given ID.
+ * @idr: IDR handle.
+ * @id: Pointer ID.
+ *
+ * Looks up the pointer associated with this ID.  A %NULL pointer may
+ * indicate that @id is not allocated or that the %NULL pointer was
+ * associated with this ID.
+ *
+ * This function can be called under rcu_read_lock(), given that the leaf
+ * pointers lifetimes are correctly managed.
+ *
+ * Return: The pointer associated with this ID.
+ */
+void *idr_find(const struct idr *idr, unsigned long id)
+{
+	return radix_tree_lookup(&idr->idr_rt, id - idr->idr_base);
+}
+EXPORT_SYMBOL_GPL(idr_find);
+
 /**
  * idr_for_each() - Iterate through all stored pointers.
  * @idr: IDR handle.
@@ -157,13 +200,14 @@ int idr_for_each(const struct idr *idr,
 {
 	struct radix_tree_iter iter;
 	void __rcu **slot;
+	int base = idr->idr_base;
 
 	radix_tree_for_each_slot(slot, &idr->idr_rt, &iter, 0) {
 		int ret;
 
 		if (WARN_ON_ONCE(iter.index > INT_MAX))
 			break;
-		ret = fn(iter.index, rcu_dereference_raw(*slot), data);
+		ret = fn(iter.index + base, rcu_dereference_raw(*slot), data);
 		if (ret)
 			return ret;
 	}
@@ -186,15 +230,19 @@ void *idr_get_next(struct idr *idr, int *nextid)
 {
 	struct radix_tree_iter iter;
 	void __rcu **slot;
+	int base = idr->idr_base;
+	int id = *nextid;
 
-	slot = radix_tree_iter_find(&idr->idr_rt, &iter, *nextid);
+	id = (id < base) ? 0 : id - base;
+	slot = radix_tree_iter_find(&idr->idr_rt, &iter, id);
 	if (!slot)
 		return NULL;
+	id = iter.index + base;
 
-	if (WARN_ON_ONCE(iter.index > INT_MAX))
+	if (WARN_ON_ONCE(id > INT_MAX))
 		return NULL;
 
-	*nextid = iter.index;
+	*nextid = id;
 	return rcu_dereference_raw(*slot);
 }
 EXPORT_SYMBOL(idr_get_next);
@@ -213,12 +261,15 @@ void *idr_get_next_ul(struct idr *idr, unsigned long *nextid)
 {
 	struct radix_tree_iter iter;
 	void __rcu **slot;
+	unsigned long base = idr->idr_base;
+	unsigned long id = *nextid;
 
-	slot = radix_tree_iter_find(&idr->idr_rt, &iter, *nextid);
+	id = (id < base) ? 0 : id - base;
+	slot = radix_tree_iter_find(&idr->idr_rt, &iter, id);
 	if (!slot)
 		return NULL;
 
-	*nextid = iter.index;
+	*nextid = iter.index + base;
 	return rcu_dereference_raw(*slot);
 }
 EXPORT_SYMBOL(idr_get_next_ul);
@@ -245,6 +296,7 @@ void *idr_replace(struct idr *idr, void *ptr, unsigned long id)
 
 	if (WARN_ON_ONCE(radix_tree_is_internal_node(ptr)))
 		return ERR_PTR(-EINVAL);
+	id -= idr->idr_base;
 
 	entry = __radix_tree_lookup(&idr->idr_rt, id, &node, &slot);
 	if (!slot || radix_tree_tag_get(&idr->idr_rt, id, IDR_FREE))
diff --git a/tools/testing/radix-tree/idr-test.c b/tools/testing/radix-tree/idr-test.c
index 36437ade429c..44ef9eba5a7a 100644
--- a/tools/testing/radix-tree/idr-test.c
+++ b/tools/testing/radix-tree/idr-test.c
@@ -153,11 +153,12 @@ void idr_nowait_test(void)
 	idr_destroy(&idr);
 }
 
-void idr_get_next_test(void)
+void idr_get_next_test(int base)
 {
 	unsigned long i;
 	int nextid;
 	DEFINE_IDR(idr);
+	idr_init_base(&idr, base);
 
 	int indices[] = {4, 7, 9, 15, 65, 128, 1000, 99999, 0};
 
@@ -244,7 +245,9 @@ void idr_checks(void)
 	idr_alloc_test();
 	idr_null_test();
 	idr_nowait_test();
-	idr_get_next_test();
+	idr_get_next_test(0);
+	idr_get_next_test(1);
+	idr_get_next_test(4);
 }
 
 /*