idr: implement lookup hint

[linux-2.6-block.git] / include / linux / idr.h

diff --git a/include/linux/idr.h b/include/linux/idr.h
index 7b1c5c6f9a06b57fce0910677b5b374ccd51f5c5..a6f38b5c34e47d000f73483b6a8b3967a7c2f39e 100644 (file)
--- a/include/linux/idr.h
+++ b/include/linux/idr.h
@@ -37,6 +37,7 @@ struct idr_layer {
 };
 
 struct idr {
+       struct idr_layer __rcu  *hint;  /* the last layer allocated from */
        struct idr_layer __rcu  *top;
        struct idr_layer        *id_free;
        int                     layers; /* only valid w/o concurrent changes */
@@ -71,7 +72,7 @@ struct idr {
  * This is what we export.
  */
 
-void *idr_find(struct idr *idp, int id);
+void *idr_find_slowpath(struct idr *idp, int id);
 int idr_pre_get(struct idr *idp, gfp_t gfp_mask);
 int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id);
 void idr_preload(gfp_t gfp_mask);
@@ -96,6 +97,28 @@ static inline void idr_preload_end(void)
        preempt_enable();
 }
 
+/**
+ * idr_find - return pointer for given id
+ * @idp: idr handle
+ * @id: lookup key
+ *
+ * Return the pointer given the id it has been registered with.  A %NULL
+ * return indicates that @id is not valid or you passed %NULL in
+ * idr_get_new().
+ *
+ * This function can be called under rcu_read_lock(), given that the leaf
+ * pointers lifetimes are correctly managed.
+ */
+static inline void *idr_find(struct idr *idr, int id)
+{
+       struct idr_layer *hint = rcu_dereference_raw(idr->hint);
+
+       if (hint && (id & ~IDR_MASK) == hint->prefix)
+               return rcu_dereference_raw(hint->ary[id & IDR_MASK]);
+
+       return idr_find_slowpath(idr, id);
+}
+
 /**
  * idr_get_new - allocate new idr entry
  * @idp: idr handle