[PATCH 07/10]
This patch introduces the ridr_find() routine.
Signed-off-by: Nadia Derbey <Nadia.Derbey@bull.net>
---
include/linux/ridr.h | 17 +++++++++++++++++
lib/ridr.c | 34 ++++++++++++++++++++++++++++++++++
2 files changed, 51 insertions(+)
Index: linux-2.6.25-mm1/include/linux/ridr.h
===================================================================
--- linux-2.6.25-mm1.orig/include/linux/ridr.h 2008-04-29 14:16:09.000000000 +0200
+++ linux-2.6.25-mm1/include/linux/ridr.h 2008-04-29 14:31:43.000000000 +0200
@@ -40,9 +40,26 @@ struct ridr {
#define idr_to_ridr(p) container_of((p), struct ridr_layer, idr)
#define ridr_to_idr(p) (&((p)->idr))
+/**
+ * Ridr synchronization (see radix-tree.h)
+ *
+ * ridr_find() is able to be called locklessly, using RCU. The caller must
+ * ensure calls to this function are made within rcu_read_lock() regions.
+ * Other readers (lock-free or otherwise) and modifications may be running
+ * concurrently.
+ *
+ * It is still required that the caller manage the synchronization and
+ * lifetimes of the items. So if RCU lock-free lookups are used, typically
+ * this would mean that the items have their own locks, or are amenable to
+ * lock-free access; and that the items are freed by RCU (or only freed after
+ * having been deleted from the ridr tree *and* a synchronize_rcu() grace
+ * period).
+ */
+
/*
* This is what we export.
*/
+void *ridr_find(struct ridr *, int);
int ridr_pre_get(struct ridr *, gfp_t);
int ridr_get_new(struct ridr *, void *, int *);
int ridr_get_new_above(struct ridr *, void *, int, int *);
Index: linux-2.6.25-mm1/lib/ridr.c
===================================================================
--- linux-2.6.25-mm1.orig/lib/ridr.c 2008-04-29 14:17:05.000000000 +0200
+++ linux-2.6.25-mm1/lib/ridr.c 2008-04-29 14:32:26.000000000 +0200
@@ -259,6 +259,40 @@ int ridr_get_new(struct ridr *idp, void
}
EXPORT_SYMBOL(ridr_get_new);
+/**
+ * ridr_find - return pointer for given id
+ * @idp: ridr 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
+ * ridr_get_new().
+ *
+ * This function can be called under rcu_read_lock(), given that the leaf
+ * pointers lifetimes are correctly managed.
+ */
+void *ridr_find(struct ridr *idp, int id)
+{
+ int n;
+ struct ridr_layer *p;
+
+ n = idp->layers * IDR_BITS;
+ p = rcu_dereference(idp->top);
+
+ /* Mask off upper bits we don't use for the search. */
+ id &= MAX_ID_MASK;
+
+ if (id >= (1 << n))
+ return NULL;
+
+ while (n > 0 && p) {
+ n -= IDR_BITS;
+ p = rcu_dereference(p->idr.ary[(id >> n) & IDR_MASK]);
+ }
+ return((void *)p);
+}
+EXPORT_SYMBOL(ridr_find);
+
static void ridr_cache_ctor(struct kmem_cache *ridr_layer_cache,
void *ridr_layer)
{
--
--
