1 files changed, 27 insertions, 0 deletions

diff --git a/lib/idr.c b/lib/idr.c
index 322e2816f2fb..cca4b9302a71 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -495,6 +495,33 @@ int idr_alloc(struct idr *idr, void *ptr, int start, int end, gfp_t gfp_mask)
 }
 EXPORT_SYMBOL_GPL(idr_alloc);
 
+/**
+ * idr_alloc_cyclic - allocate new idr entry in a cyclical fashion
+ * @idr: the (initialized) idr
+ * @ptr: pointer to be associated with the new id
+ * @start: the minimum id (inclusive)
+ * @end: the maximum id (exclusive, <= 0 for max)
+ * @gfp_mask: memory allocation flags
+ *
+ * Essentially the same as idr_alloc, but prefers to allocate progressively
+ * higher ids if it can. If the "cur" counter wraps, then it will start again
+ * at the "start" end of the range and allocate one that has already been used.
+ */
+int idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end,
+                        gfp_t gfp_mask)
+{
+        int id;
+
+        id = idr_alloc(idr, ptr, max(start, idr->cur), end, gfp_mask);
+        if (id == -ENOSPC)
+                id = idr_alloc(idr, ptr, start, end, gfp_mask);
+
+        if (likely(id >= 0))
+                idr->cur = id + 1;
+        return id;
+}
+EXPORT_SYMBOL(idr_alloc_cyclic);
+
 static void idr_remove_warning(int id)
 {
         printk(KERN_WARNING