[PATCH 08/17] idr: Add idr_alloc_u32 helper

[Matthew Wilcox <willy@infradead.org>]

From: Matthew Wilcox <mawilcox@microsoft.com>

All current users of idr_alloc_ext() actually want to allocate a u32 and
it's a little painful for them to use idr_alloc_ext().  This convenience
function makes it simple.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
---
 include/linux/idr.h | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/include/linux/idr.h b/include/linux/idr.h
index 12514ec0cd28..9b2fd6f408b2 100644
--- a/include/linux/idr.h
+++ b/include/linux/idr.h
@@ -139,6 +139,35 @@ void *idr_get_next_ext(struct idr *idr, unsigned long *nextid);
 void *idr_replace(struct idr *, void *, unsigned long id);
 void idr_destroy(struct idr *);
 
+/**
+ * idr_alloc_u32() - Allocate an ID.
+ * @idr: IDR handle.
+ * @ptr: Pointer to be associated with the new ID.
+ * @nextid: The new ID.
+ * @max: The maximum ID to allocate (inclusive).
+ * @gfp: Memory allocation flags.
+ *
+ * Allocates an unused ID in the range [*nextid, max] and updates the @nextid
+ * pointer with the newly assigned ID.  Returns -ENOSPC and does not modify
+ * @nextid if there are no unused IDs in the range.
+ *
+ * The caller should provide their own locking to ensure that two concurrent
+ * modifications to the IDR are not possible.  Read-only accesses to the
+ * IDR may be done under the RCU read lock or may exclude simultaneous
+ * writers.
+ *
+ * Return: 0 on success, -ENOMEM for memory allocation errors, -ENOSPC if
+ * there are no free IDs in the range.
+ */
+static inline int __must_check idr_alloc_u32(struct idr *idr, void *ptr,
+				u32 *nextid, unsigned long max, gfp_t gfp)
+{
+	unsigned long tmp = *nextid;
+	int ret = idr_alloc_ext(idr, ptr, &tmp, tmp, max + 1, gfp);
+	*nextid = tmp;
+	return ret;
+}
+
 static inline void *idr_remove(struct idr *idr, unsigned long id)
 {
 	return radix_tree_delete_item(&idr->idr_rt, id, NULL);
-- 
2.15.0