Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph...

[pandora-kernel.git] / include / linux / idr.h

diff --git a/include/linux/idr.h b/include/linux/idr.h
index 63aa542..a6f38b5 100644 (file)
--- a/include/linux/idr.h
+++ b/include/linux/idr.h
@@ -17,18 +17,18 @@
 #include <linux/init.h>
 #include <linux/rcupdate.h>
 
-#if BITS_PER_LONG == 32
-# define IDR_BITS 5
-#elif BITS_PER_LONG == 64
-# define IDR_BITS 6
-#else
-# error "BITS_PER_LONG is not 32 or 64"
-#endif
-
+/*
+ * We want shallower trees and thus more bits covered at each layer.  8
+ * bits gives us large enough first layer for most use cases and maximum
+ * tree depth of 4.  Each idr_layer is slightly larger than 2k on 64bit and
+ * 1k on 32bit.
+ */
+#define IDR_BITS 8
 #define IDR_SIZE (1 << IDR_BITS)
 #define IDR_MASK ((1 << IDR_BITS)-1)
 
 struct idr_layer {
+       int                     prefix; /* the ID prefix of this idr_layer */
        DECLARE_BITMAP(bitmap, IDR_SIZE); /* A zero bit means "space here" */
        struct idr_layer __rcu  *ary[1<<IDR_BITS];
        int                     count;  /* When zero, we can release it */
@@ -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