[Patch 2/4] dm: mempool backport

Joe Thornber
2003-12-09T12:37:48Z

Backport of mempool code.
--- diff/mm/Makefile 2002-08-05 14:57:44.000000000 +0100
+++ source/mm/Makefile 2003-12-09 10:34:55.000000000 +0000
@@ -9,12 +9,12 @@

O_TARGET := mm.o

-export-objs := shmem.o filemap.o memory.o page_alloc.o
+export-objs := shmem.o filemap.o memory.o page_alloc.o mempool.o

obj-y := memory.o mmap.o filemap.o mprotect.o mlock.o mremap.o \
vmalloc.o slab.o bootmem.o swap.o vmscan.o page_io.o \
page_alloc.o swap_state.o swapfile.o numa.o oom_kill.o \
- shmem.o
+ shmem.o mempool.o

obj-$(CONFIG_HIGHMEM) += highmem.o

--- diff/include/linux/mempool.h 1970-01-01 01:00:00.000000000 +0100
+++ source/include/linux/mempool.h 2003-12-09 10:34:55.000000000 +0000
@@ -0,0 +1,31 @@
+/*
+ * memory buffer pool support
+ */
+#ifndef _LINUX_MEMPOOL_H
+#define _LINUX_MEMPOOL_H
+
+#include <linux/list.h>
+#include <linux/wait.h>
+
+struct mempool_s;
+typedef struct mempool_s mempool_t;
+
+typedef void * (mempool_alloc_t)(int gfp_mask, void *pool_data);
+typedef void (mempool_free_t)(void *element, void *pool_data);
+
+extern mempool_t * mempool_create(int min_nr, mempool_alloc_t *alloc_fn,
+ mempool_free_t *free_fn, void *pool_data);
+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.
+ */
+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 1970-01-01 01:00:00.000000000 +0100
+++ source/mm/mempool.c 2003-12-09 10:34:55.000000000 +0000
@@ -0,0 +1,299 @@
+/*
+ * linux/mm/mempool.c
+ *
+ * memory buffer pool support. Such pools are mostly used
+ * for guaranteed, deadlock-free memory allocations during
+ * extreme VM load.
+ *
+ * started by Ingo Molnar, Copyright (C) 2001
+ */
+
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/mempool.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
+ * @min_nr: the minimum number of elements guaranteed to be
+ * allocated for this pool.
+ * @alloc_fn: user-defined element-allocation function.
+ * @free_fn: user-defined element-freeing function.
+ * @pool_data: optional private data available to the user-defined functions.
+ *
+ * this function creates and allocates a guaranteed size, preallocated
+ * 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.
+ */
+mempool_t * mempool_create(int min_nr, mempool_alloc_t *alloc_fn,
+ mempool_free_t *free_fn, void *pool_data)
+{
+ mempool_t *pool;
+
+ 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_waitqueue_head(&pool->wait);
+ pool->alloc = alloc_fn;
+ pool->free = free_fn;
+
+ /*
+ * First pre-allocate the guaranteed number of buffers.
+ */
+ while (pool->curr_nr < pool->min_nr) {
+ void *element;
+
+ element = pool->alloc(GFP_KERNEL, pool->pool_data);
+ if (unlikely(!element)) {
+ free_pool(pool);
+ return NULL;
+ }
+ add_element(pool, element);
+ }
+ return pool;
+}
+
+/**
+ * mempool_resize - resize an existing memory pool
+ * @pool: pointer to the memory pool which was allocated via
+ * mempool_create().
+ * @new_min_nr: the new minimum number of elements guaranteed to be
+ * allocated for this pool.
+ * @gfp_mask: the usual allocation bitmask.
+ *
+ * This function shrinks/grows the pool. In the case of growing,
+ * it cannot be guaranteed that the pool will be grown to the new
+ * size immediately, but new mempool_free() calls will refill it.
+ *
+ * Note, the caller must guarantee that no mempool_destroy is called
+ * while this function is running. mempool_alloc() & mempool_free()
+ * might be called (eg. from IRQ contexts) while this function executes.
+ */
+int mempool_resize(mempool_t *pool, int new_min_nr, int gfp_mask)
+{
+ void *element;
+ void **new_elements;
+ unsigned long flags;
+
+ BUG_ON(new_min_nr <= 0);
+
+ spin_lock_irqsave(&pool->lock, flags);
+ if (new_min_nr < pool->min_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);
+ }
+ pool->min_nr = new_min_nr;
+ goto out_unlock;
+ }
+ spin_unlock_irqrestore(&pool->lock, flags);
+
+ /* 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)
+ 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;
+}
+
+/**
+ * mempool_destroy - deallocate a memory pool
+ * @pool: pointer to the memory pool which was allocated via
+ * mempool_create().
+ *
+ * this function only sleeps if the free_fn() function sleeps. The caller
+ * 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)
+{
+ if (pool->curr_nr != pool->min_nr)
+ BUG(); /* There were outstanding elements */
+ free_pool(pool);
+}
+
+/**
+ * mempool_alloc - allocate an element from a specific memory pool
+ * @pool: pointer to the memory pool which was allocated via
+ * mempool_create().
+ * @gfp_mask: the usual allocation bitmask.
+ *
+ * this function only sleeps if the alloc_fn function sleeps or
+ * returns NULL. Note that due to preallocation, this function
+ * *never* fails when called from process contexts. (it might
+ * fail if called from an IRQ context.)
+ */
+void * mempool_alloc(mempool_t *pool, int gfp_mask)
+{
+ void *element;
+ unsigned long flags;
+ int curr_nr;
+ DECLARE_WAITQUEUE(wait, current);
+ int gfp_nowait = gfp_mask & ~(__GFP_WAIT | __GFP_IO);
+
+repeat_alloc:
+ element = pool->alloc(gfp_nowait, pool->pool_data);
+ if (likely(element != NULL))
+ return element;
+
+ /*
+ * If the pool is less than 50% full then try harder
+ * to allocate an element:
+ */
+ if ((gfp_mask != gfp_nowait) && (pool->curr_nr <= pool->min_nr/2)) {
+ element = pool->alloc(gfp_mask, pool->pool_data);
+ if (likely(element != NULL))
+ return element;
+ }
+
+ /*
+ * Kick the VM at this point.
+ */
+ wakeup_bdflush();
+
+ spin_lock_irqsave(&pool->lock, flags);
+ if (likely(pool->curr_nr)) {
+ element = remove_element(pool);
+ spin_unlock_irqrestore(&pool->lock, flags);
+ return element;
+ }
+ spin_unlock_irqrestore(&pool->lock, flags);
+
+ /* We must not sleep in the GFP_ATOMIC case */
+ if (gfp_mask == gfp_nowait)
+ return NULL;
+
+ run_task_queue(&tq_disk);
+
+ add_wait_queue_exclusive(&pool->wait, &wait);
+ set_task_state(current, TASK_UNINTERRUPTIBLE);
+
+ spin_lock_irqsave(&pool->lock, flags);
+ curr_nr = pool->curr_nr;
+ spin_unlock_irqrestore(&pool->lock, flags);
+
+ if (!curr_nr)
+ schedule();
+
+ current->state = TASK_RUNNING;
+ remove_wait_queue(&pool->wait, &wait);
+
+ goto repeat_alloc;
+}
+
+/**
+ * mempool_free - return an element to the pool.
+ * @element: pool element pointer.
+ * @pool: pointer to the memory pool which was allocated via
+ * mempool_create().
+ *
+ * this function only sleeps if the free_fn() function sleeps.
+ */
+void mempool_free(void *element, mempool_t *pool)
+{
+ unsigned long flags;
+
+ if (pool->curr_nr < pool->min_nr) {
+ spin_lock_irqsave(&pool->lock, flags);
+ if (pool->curr_nr < pool->min_nr) {
+ add_element(pool, element);
+ spin_unlock_irqrestore(&pool->lock, flags);
+ wake_up(&pool->wait);
+ return;
+ }
+ spin_unlock_irqrestore(&pool->lock, flags);
+ }
+ pool->free(element, pool->pool_data);
+}
+
+/*
+ * A commonly used alloc and free fn.
+ */
+void *mempool_alloc_slab(int gfp_mask, void *pool_data)
+{
+ kmem_cache_t *mem = (kmem_cache_t *) pool_data;
+ return kmem_cache_alloc(mem, gfp_mask);
+}
+
+void mempool_free_slab(void *element, void *pool_data)
+{
+ kmem_cache_t *mem = (kmem_cache_t *) pool_data;
+ kmem_cache_free(mem, element);
+}
+
+
+EXPORT_SYMBOL(mempool_create);
+EXPORT_SYMBOL(mempool_resize);
+EXPORT_SYMBOL(mempool_destroy);
+EXPORT_SYMBOL(mempool_alloc);
+EXPORT_SYMBOL(mempool_free);
+EXPORT_SYMBOL(mempool_alloc_slab);
+EXPORT_SYMBOL(mempool_free_slab);