[PATCH 03/13] Fix ridr_pre_get()

From: Nadia . Derbey
Date: Fri Apr 11 2008 - 12:21:19 EST


[PATCH 03/13]

This patch only fixes the ridr_pre_get() portion of ridr.c, to introduce a
per-cpu pool of preloaded ridr layer structures, and define the
ridr_pre_get[_end]() routines.

Signed-off-by: Nadia Derbey <Nadia.Derbey@xxxxxxxx>

---
include/linux/ridr.h | 7 ++++++-
lib/ridr.c | 50 ++++++++++++++++++++++++++++++++++++--------------
2 files changed, 42 insertions(+), 15 deletions(-)

Index: linux-2.6.25-rc8-mm1/include/linux/ridr.h
===================================================================
--- linux-2.6.25-rc8-mm1.orig/include/linux/ridr.h 2008-04-11 17:34:35.000000000 +0200
+++ linux-2.6.25-rc8-mm1/include/linux/ridr.h 2008-04-11 17:41:20.000000000 +0200
@@ -61,10 +61,15 @@ do { \
*/

void *ridr_find(struct ridr *idp, int id);
-int ridr_pre_get(struct ridr *idp, gfp_t gfp_mask);
+int ridr_pre_get(gfp_t gfp_mask);
int ridr_get_new(struct ridr *idp, void *ptr, int *id);
void ridr_remove(struct ridr *idp, int id);

void __init ridr_init_cache(void);

+static inline void ridr_pre_get_end(void)
+{
+ preempt_enable();
+}
+
#endif /* _RIDR_H_ */
Index: linux-2.6.25-rc8-mm1/lib/ridr.c
===================================================================
--- linux-2.6.25-rc8-mm1.orig/lib/ridr.c 2008-04-11 17:30:28.000000000 +0200
+++ linux-2.6.25-rc8-mm1/lib/ridr.c 2008-04-11 17:40:13.000000000 +0200
@@ -13,6 +13,15 @@

static struct kmem_cache *ridr_layer_cache;

+/*
+ * Per-cpu pool of preloaded layers
+ */
+struct ridr_preget {
+ int nr;
+ struct ridr_layer *layers[MAX_LEVEL];
+};
+DEFINE_PER_CPU(struct ridr_preget, ridr_pregets) = { 0, };
+
static struct ridr_layer *alloc_layer(struct ridr *idp)
{
struct ridr_layer *p;
@@ -75,23 +84,36 @@ static void ridr_mark_full(struct ridr_l
* @idp: ridr handle
* @gfp_mask: memory allocation flags
*
- * This function should be called prior to locking and calling the
- * following function. It preallocates enough memory to satisfy
- * the worst possible allocation.
+ * Load up this CPU's ridr_layer buffer with sufficient objects to
+ * ensure that the addition of a single element in the tree cannot fail.
*
- * If the system is REALLY out of memory this function returns 0,
- * otherwise 1.
+ * If the system is REALLY out of memory this function returns 0, with
+ * preemption enabled.
+ * Otherwise 1, with preemption disabled.
*/
-int ridr_pre_get(struct ridr *idp, gfp_t gfp_mask)
+int ridr_pre_get(gfp_t gfp_mask)
{
- while (idp->id_free_cnt < IDR_FREE_MAX) {
- struct ridr_layer *new;
- new = kmem_cache_alloc(ridr_layer_cache, gfp_mask);
- if (new == NULL)
- return (0);
- free_layer(idp, new);
- }
- return 1;
+ struct ridr_preget *idp;
+ struct ridr_layer *layer;
+ int ret = 0;
+
+ preempt_disable();
+ idp = &__get_cpu_var(ridr_pregets);
+ while (idp->nr < ARRAY_SIZE(idp->layers)) {
+ preempt_enable();
+ layer = kmem_cache_alloc(ridr_layer_cache, gfp_mask);
+ if (layer == NULL)
+ goto out;
+ preempt_disable();
+ idp = &__get_cpu_var(ridr_pregets);
+ if (idp->nr < ARRAY_SIZE(idp->layers))
+ idp->layers[idp->nr++] = layer;
+ else
+ kmem_cache_free(ridr_layer_cache, layer);
+ }
+ ret = 1;
+out:
+ return ret;
}
EXPORT_SYMBOL(ridr_pre_get);


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