Mempool version by Christoph Hellwig that holds the free objects
in an array rather than a list. This prevents the objects getting
dirtied, eg, people maybe expecting them to come out of a slab with
a particular state.
--- diff/include/linux/mempool.h 2002-11-29 09:44:59.000000000 +0000
+++ source/include/linux/mempool.h 2002-11-29 09:45:30.000000000 +0000
@@ -13,24 +13,13 @@
typedef void * (mempool_alloc_t)(int gfp_mask, void *pool_data);
typedef void (mempool_free_t)(void *element, void *pool_data);
-struct mempool_s {
- spinlock_t lock;
- int min_nr, curr_nr;
- struct list_head elements;
-
- void *pool_data;
- mempool_alloc_t *alloc;
- mempool_free_t *free;
- wait_queue_head_t wait;
-};
extern mempool_t * mempool_create(int min_nr, mempool_alloc_t *alloc_fn,
mempool_free_t *free_fn, void *pool_data);
-extern void mempool_resize(mempool_t *pool, int new_min_nr, int gfp_mask);
+extern int mempool_resize(mempool_t *pool, int new_min_nr, int gfp_mask);
extern void mempool_destroy(mempool_t *pool);
extern void * mempool_alloc(mempool_t *pool, int gfp_mask);
extern void mempool_free(void *element, mempool_t *pool);
-
/*
* A mempool_alloc_t and mempool_free_t that get the memory from
* a slab that is passed in through pool_data.
@@ -38,4 +27,5 @@
void *mempool_alloc_slab(int gfp_mask, void *pool_data);
void mempool_free_slab(void *element, void *pool_data);
+
#endif /* _LINUX_MEMPOOL_H */
--- diff/mm/mempool.c 2002-11-29 09:44:59.000000000 +0000
+++ source/mm/mempool.c 2002-11-29 09:45:30.000000000 +0000
@@ -12,7 +12,40 @@
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/mempool.h>
-#include <linux/compiler.h>
+
+struct mempool_s {
+ spinlock_t lock;
+ int min_nr; /* nr of elements at *elements */
+ int curr_nr; /* Current nr of elements at *elements */
+ void **elements;
+
+ void *pool_data;
+ mempool_alloc_t *alloc;
+ mempool_free_t *free;
+ wait_queue_head_t wait;
+};
+
+static void add_element(mempool_t *pool, void *element)
+{
+ BUG_ON(pool->curr_nr >= pool->min_nr);
+ pool->elements[pool->curr_nr++] = element;
+}
+
+static void *remove_element(mempool_t *pool)
+{
+ BUG_ON(pool->curr_nr <= 0);
+ return pool->elements[--pool->curr_nr];
+}
+
+static void free_pool(mempool_t *pool)
+{
+ while (pool->curr_nr) {
+ void *element = remove_element(pool);
+ pool->free(element, pool->pool_data);
+ }
+ kfree(pool->elements);
+ kfree(pool);
+}
/**
* mempool_create - create a memory pool
@@ -26,24 +59,25 @@
* memory pool. The pool can be used from the mempool_alloc and mempool_free
* functions. This function might sleep. Both the alloc_fn() and the free_fn()
* functions might sleep - as long as the mempool_alloc function is not called
- * from IRQ contexts. The element allocated by alloc_fn() must be able to
- * hold a struct list_head. (8 bytes on x86.)
+ * from IRQ contexts.
*/
mempool_t * mempool_create(int min_nr, mempool_alloc_t *alloc_fn,
mempool_free_t *free_fn, void *pool_data)
{
mempool_t *pool;
- int i;
pool = kmalloc(sizeof(*pool), GFP_KERNEL);
if (!pool)
return NULL;
memset(pool, 0, sizeof(*pool));
-
+ pool->elements = kmalloc(min_nr * sizeof(void *), GFP_KERNEL);
+ if (!pool->elements) {
+ kfree(pool);
+ return NULL;
+ }
spin_lock_init(&pool->lock);
pool->min_nr = min_nr;
pool->pool_data = pool_data;
- INIT_LIST_HEAD(&pool->elements);
init_waitqueue_head(&pool->wait);
pool->alloc = alloc_fn;
pool->free = free_fn;
@@ -51,27 +85,15 @@
/*
* First pre-allocate the guaranteed number of buffers.
*/
- for (i = 0; i < min_nr; i++) {
+ while (pool->curr_nr < pool->min_nr) {
void *element;
- struct list_head *tmp;
- element = pool->alloc(GFP_KERNEL, pool->pool_data);
+ element = pool->alloc(GFP_KERNEL, pool->pool_data);
if (unlikely(!element)) {
- /*
- * Not enough memory - free the allocated ones
- * and return:
- */
- list_for_each(tmp, &pool->elements) {
- element = tmp;
- pool->free(element, pool->pool_data);
- }
- kfree(pool);
-
+ free_pool(pool);
return NULL;
}
- tmp = element;
- list_add(tmp, &pool->elements);
- pool->curr_nr++;
+ add_element(pool, element);
}
return pool;
}
@@ -92,53 +114,54 @@
* while this function is running. mempool_alloc() & mempool_free()
* might be called (eg. from IRQ contexts) while this function executes.
*/
-void mempool_resize(mempool_t *pool, int new_min_nr, int gfp_mask)
+int mempool_resize(mempool_t *pool, int new_min_nr, int gfp_mask)
{
- int delta;
void *element;
+ void **new_elements;
unsigned long flags;
- struct list_head *tmp;
- if (new_min_nr <= 0)
- BUG();
+ BUG_ON(new_min_nr <= 0);
spin_lock_irqsave(&pool->lock, flags);
if (new_min_nr < pool->min_nr) {
- pool->min_nr = new_min_nr;
- /*
- * Free possible excess elements.
- */
- while (pool->curr_nr > pool->min_nr) {
- tmp = pool->elements.next;
- if (tmp == &pool->elements)
- BUG();
- list_del(tmp);
- element = tmp;
- pool->curr_nr--;
+ while (pool->curr_nr > new_min_nr) {
+ element = remove_element(pool);
spin_unlock_irqrestore(&pool->lock, flags);
-
pool->free(element, pool->pool_data);
-
spin_lock_irqsave(&pool->lock, flags);
}
- spin_unlock_irqrestore(&pool->lock, flags);
- return;
+ pool->min_nr = new_min_nr;
+ goto out_unlock;
}
- delta = new_min_nr - pool->min_nr;
- pool->min_nr = new_min_nr;
spin_unlock_irqrestore(&pool->lock, flags);
- /*
- * We refill the pool up to the new treshold - but we dont
- * (cannot) guarantee that the refill succeeds.
- */
- while (delta) {
+ /* Grow the pool */
+ new_elements = kmalloc(new_min_nr * sizeof(*new_elements), gfp_mask);
+ if (!new_elements)
+ return -ENOMEM;
+
+ spin_lock_irqsave(&pool->lock, flags);
+ memcpy(new_elements, pool->elements,
+ pool->curr_nr * sizeof(*new_elements));
+ kfree(pool->elements);
+ pool->elements = new_elements;
+ pool->min_nr = new_min_nr;
+
+ while (pool->curr_nr < pool->min_nr) {
+ spin_unlock_irqrestore(&pool->lock, flags);
element = pool->alloc(gfp_mask, pool->pool_data);
if (!element)
- break;
- mempool_free(element, pool);
- delta--;
+ goto out;
+ spin_lock_irqsave(&pool->lock, flags);
+ if (pool->curr_nr < pool->min_nr)
+ add_element(pool, element);
+ else
+ kfree(element); /* Raced */
}
+out_unlock:
+ spin_unlock_irqrestore(&pool->lock, flags);
+out:
+ return 0;
}
/**
@@ -147,27 +170,14 @@
* mempool_create().
*
* this function only sleeps if the free_fn() function sleeps. The caller
- * has to guarantee that no mempool_alloc() nor mempool_free() happens in
- * this pool when calling this function.
+ * has to guarantee that all elements have been returned to the pool (ie:
+ * freed) prior to calling mempool_destroy().
*/
void mempool_destroy(mempool_t *pool)
{
- void *element;
- struct list_head *head, *tmp;
-
- if (!pool)
- return;
-
- head = &pool->elements;
- for (tmp = head->next; tmp != head; ) {
- element = tmp;
- tmp = tmp->next;
- pool->free(element, pool->pool_data);
- pool->curr_nr--;
- }
- if (pool->curr_nr)
- BUG();
- kfree(pool);
+ if (pool->curr_nr != pool->min_nr)
+ BUG(); /* There were outstanding elements */
+ free_pool(pool);
}
/**
@@ -185,7 +195,6 @@
{
void *element;
unsigned long flags;
- struct list_head *tmp;
int curr_nr;
DECLARE_WAITQUEUE(wait, current);
int gfp_nowait = gfp_mask & ~(__GFP_WAIT | __GFP_IO);
@@ -212,10 +221,7 @@
spin_lock_irqsave(&pool->lock, flags);
if (likely(pool->curr_nr)) {
- tmp = pool->elements.next;
- list_del(tmp);
- element = tmp;
- pool->curr_nr--;
+ element = remove_element(pool);
spin_unlock_irqrestore(&pool->lock, flags);
return element;
}
@@ -258,8 +264,7 @@
if (pool->curr_nr < pool->min_nr) {
spin_lock_irqsave(&pool->lock, flags);
if (pool->curr_nr < pool->min_nr) {
- list_add(element, &pool->elements);
- pool->curr_nr++;
+ add_element(pool, element);
spin_unlock_irqrestore(&pool->lock, flags);
wake_up(&pool->wait);
return;
@@ -292,4 +297,3 @@
EXPORT_SYMBOL(mempool_free);
EXPORT_SYMBOL(mempool_alloc_slab);
EXPORT_SYMBOL(mempool_free_slab);
-