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[dm-devel] [PATCH 2/6] dm raid45 target: introduce memory cache



This patch adds the dm-memcache memory cache module.

Heinz

 drivers/md/{dm-memcache.h.orig => dm-memcache.h} |   68 ++++++++++++++++++++++
 1 files changed, 68 insertions(+), 0 deletions(-)

diff --git a/drivers/md/dm-memcache.h.orig b/drivers/md/dm-memcache.h
index e69de29..87e4256 100644
--- a/drivers/md/dm-memcache.h.orig
+++ b/drivers/md/dm-memcache.h
@@ -0,0 +1,68 @@
+/*
+ * Copyright (C) 2006-2008 Red Hat, Inc. All rights reserved.
+ *
+ * Module Author: Heinz Mauelshagen <Mauelshagen RedHat com>
+ *
+ * Device-mapper memory object handling:
+ *
+ * o allocate/free total_pages in a per client page pool.
+ *
+ * o allocate/free memory objects with chunks (1..n) of
+ *   pages_per_chunk pages hanging off.
+ *
+ * This file is released under the GPL.
+ */
+
+#ifndef _DM_MEM_CACHE_H
+#define _DM_MEM_CACHE_H
+
+#define	DM_MEM_CACHE_H_VERSION	"0.1"
+
+#include "dm.h"
+#include <linux/dm-io.h>
+
+static inline struct page_list *pl_elem(struct page_list *pl, unsigned p)
+{
+	while (pl && p--)
+		pl = pl->next;
+
+	return pl;
+}
+
+struct dm_mem_cache_object {
+	struct page_list *pl; /* Dynamically allocated array */
+	void *private;	      /* Caller context reference */
+};
+
+struct dm_mem_cache_client;
+
+/*
+ * Create/destroy dm memory cache client resources.
+ *
+ * On creation, a number of @objects with @chunks of
+ * @pages_per_chunk pages will be allocated.
+ */
+struct dm_mem_cache_client *
+dm_mem_cache_client_create(unsigned objects, unsigned chunks,
+			   unsigned pages_per_chunk);
+void dm_mem_cache_client_destroy(struct dm_mem_cache_client *client);
+
+/*
+ * Grow/shrink a dm memory cache client resources
+ * by @objetcs amount of objects.
+ */
+int dm_mem_cache_grow(struct dm_mem_cache_client *client, unsigned objects);
+int dm_mem_cache_shrink(struct dm_mem_cache_client *client, unsigned objects);
+
+/*
+ * Allocate/free a memory object
+ *
+ * On allocation one object with an amount of chunks and
+ * an amount of pages per chunk will be returned on success.
+ */
+struct dm_mem_cache_object *
+dm_mem_cache_alloc(struct dm_mem_cache_client *client);
+void dm_mem_cache_free(struct dm_mem_cache_client *client,
+		       struct dm_mem_cache_object *object);
+
+#endif
 drivers/md/{dm-memcache.c.orig => dm-memcache.c} |  301 ++++++++++++++++++++++
 1 files changed, 301 insertions(+), 0 deletions(-)

diff --git a/drivers/md/dm-memcache.c.orig b/drivers/md/dm-memcache.c
index e69de29..4e3731c 100644
--- a/drivers/md/dm-memcache.c.orig
+++ b/drivers/md/dm-memcache.c
@@ -0,0 +1,301 @@
+/*
+ * Copyright (C) 2006-2008 Red Hat, Inc. All rights reserved.
+ *
+ * Module Author: Heinz Mauelshagen <heinzm redhat com>
+ *
+ * Device-mapper memory object handling:
+ *
+ * o allocate/free total_pages in a per client page pool.
+ *
+ * o allocate/free memory objects with chunks (1..n) of
+ *   pages_per_chunk pages hanging off.
+ *
+ * This file is released under the GPL.
+ */
+
+#define	DM_MEM_CACHE_VERSION	"0.2"
+
+#include "dm.h"
+#include "dm-memcache.h"
+#include <linux/dm-io.h>
+
+struct dm_mem_cache_client {
+	spinlock_t lock;
+	mempool_t *objs_pool;
+	struct page_list *free_list;
+	unsigned objects;
+	unsigned chunks;
+	unsigned pages_per_chunk;
+	unsigned free_pages;
+	unsigned total_pages;
+};
+
+/*
+ * Free pages and page_list elements of client.
+ */
+static void free_cache_pages(struct page_list *list)
+{
+	while (list) {
+		struct page_list *pl = list;
+
+		list = pl->next;
+		BUG_ON(!pl->page);
+		__free_page(pl->page);
+		kfree(pl);
+	}
+}
+
+/*
+ * Alloc number of pages and page_list elements as required by client.
+ */
+static struct page_list *alloc_cache_pages(unsigned pages)
+{
+	struct page_list *pl, *ret = NULL;
+	struct page *page;
+
+	while (pages--) {
+		page = alloc_page(GFP_NOIO);
+		if (!page)
+			goto err;
+
+		pl = kmalloc(sizeof(*pl), GFP_NOIO);
+		if (!pl) {
+			__free_page(page);
+			goto err;
+		}
+
+		pl->page = page;
+		pl->next = ret;
+		ret = pl;
+	}
+
+	return ret;
+
+err:
+	free_cache_pages(ret);
+	return NULL;
+}
+
+/*
+ * Allocate page_list elements from the pool to chunks of the memory object.
+ */
+static void alloc_chunks(struct dm_mem_cache_client *cl,
+			 struct dm_mem_cache_object *obj)
+{
+	unsigned chunks = cl->chunks;
+	unsigned long flags;
+
+	local_irq_save(flags);
+	local_irq_disable();
+	while (chunks--) {
+		unsigned p = cl->pages_per_chunk;
+
+		obj[chunks].pl = NULL;
+
+		while (p--) {
+			struct page_list *pl;
+
+			/* Take next element from free list */
+			spin_lock(&cl->lock);
+			pl = cl->free_list;
+			BUG_ON(!pl);
+			cl->free_list = pl->next;
+			spin_unlock(&cl->lock);
+
+			pl->next = obj[chunks].pl;
+			obj[chunks].pl = pl;
+		}
+	}
+
+	local_irq_restore(flags);
+}
+
+/*
+ * Free page_list elements putting them back onto free list
+ */
+static void free_chunks(struct dm_mem_cache_client *cl,
+			struct dm_mem_cache_object *obj)
+{
+	unsigned chunks = cl->chunks;
+	unsigned long flags;
+	struct page_list *next, *pl;
+
+	local_irq_save(flags);
+	local_irq_disable();
+	while (chunks--) {
+		for (pl = obj[chunks].pl; pl; pl = next) {
+			next = pl->next;
+
+			spin_lock(&cl->lock);
+			pl->next = cl->free_list;
+			cl->free_list = pl;
+			cl->free_pages++;
+			spin_unlock(&cl->lock);
+		}
+	}
+
+	local_irq_restore(flags);
+}
+
+/*
+ * Create/destroy dm memory cache client resources.
+ */
+struct dm_mem_cache_client *
+dm_mem_cache_client_create(unsigned objects, unsigned chunks,
+			   unsigned pages_per_chunk)
+{
+	unsigned total_pages = objects * chunks * pages_per_chunk;
+	struct dm_mem_cache_client *client;
+
+	BUG_ON(!total_pages);
+	client = kzalloc(sizeof(*client), GFP_KERNEL);
+	if (!client)
+		return ERR_PTR(-ENOMEM);
+
+	client->objs_pool = mempool_create_kmalloc_pool(objects,
+				chunks * sizeof(struct dm_mem_cache_object));
+	if (!client->objs_pool)
+		goto err;
+
+	client->free_list = alloc_cache_pages(total_pages);
+	if (!client->free_list)
+		goto err1;
+
+	spin_lock_init(&client->lock);
+	client->objects = objects;
+	client->chunks = chunks;
+	client->pages_per_chunk = pages_per_chunk;
+	client->free_pages = client->total_pages = total_pages;
+	return client;
+
+err1:
+	mempool_destroy(client->objs_pool);
+err:
+	kfree(client);
+	return ERR_PTR(-ENOMEM);
+}
+EXPORT_SYMBOL(dm_mem_cache_client_create);
+
+void dm_mem_cache_client_destroy(struct dm_mem_cache_client *cl)
+{
+	BUG_ON(cl->free_pages != cl->total_pages);
+	free_cache_pages(cl->free_list);
+	mempool_destroy(cl->objs_pool);
+	kfree(cl);
+}
+EXPORT_SYMBOL(dm_mem_cache_client_destroy);
+
+/*
+ * Grow a clients cache by an amount of pages.
+ *
+ * Don't call from interrupt context!
+ */
+int dm_mem_cache_grow(struct dm_mem_cache_client *cl, unsigned objects)
+{
+	unsigned pages = objects * cl->chunks * cl->pages_per_chunk;
+	struct page_list *pl, *last;
+
+	BUG_ON(!pages);
+	pl = alloc_cache_pages(pages);
+	if (!pl)
+		return -ENOMEM;
+
+	last = pl;
+	while (last->next)
+		last = last->next;
+
+	spin_lock_irq(&cl->lock);
+	last->next = cl->free_list;
+	cl->free_list = pl;
+	cl->free_pages += pages;
+	cl->total_pages += pages;
+	cl->objects++;
+	spin_unlock_irq(&cl->lock);
+
+	mempool_resize(cl->objs_pool, cl->objects, GFP_NOIO);
+	return 0;
+}
+EXPORT_SYMBOL(dm_mem_cache_grow);
+
+/* Shrink a clients cache by an amount of pages */
+int dm_mem_cache_shrink(struct dm_mem_cache_client *cl, unsigned objects)
+{
+	int r;
+	unsigned pages = objects * cl->chunks * cl->pages_per_chunk, p = pages;
+	unsigned long flags;
+	struct page_list *last = NULL, *pl, *pos;
+
+	BUG_ON(!pages);
+
+	spin_lock_irqsave(&cl->lock, flags);
+	pl = pos = cl->free_list;
+	while (p-- && pos->next) {
+		last = pos;
+		pos = pos->next;
+	}
+
+	if (++p)
+		r = -ENOMEM;
+	else {
+		r = 0;
+		cl->free_list = pos;
+		cl->free_pages -= pages;
+		cl->total_pages -= pages;
+		cl->objects--;
+		last->next = NULL;
+	}
+	spin_unlock_irqrestore(&cl->lock, flags);
+
+	if (!r) {
+		free_cache_pages(pl);
+		mempool_resize(cl->objs_pool, cl->objects, GFP_NOIO);
+	}
+
+	return r;
+}
+EXPORT_SYMBOL(dm_mem_cache_shrink);
+
+/*
+ * Allocate/free a memory object
+ *
+ * Can be called from interrupt context
+ */
+struct dm_mem_cache_object *dm_mem_cache_alloc(struct dm_mem_cache_client *cl)
+{
+	int r = 0;
+	unsigned pages = cl->chunks * cl->pages_per_chunk;
+	unsigned long flags;
+	struct dm_mem_cache_object *obj;
+
+	obj = mempool_alloc(cl->objs_pool, GFP_NOIO);
+	if (!obj)
+		return ERR_PTR(-ENOMEM);
+
+	spin_lock_irqsave(&cl->lock, flags);
+	if (pages > cl->free_pages)
+		r = -ENOMEM;
+	else
+		cl->free_pages -= pages;
+	spin_unlock_irqrestore(&cl->lock, flags);
+
+	if (r) {
+		mempool_free(obj, cl->objs_pool);
+		return ERR_PTR(r);
+	}
+
+	alloc_chunks(cl, obj);
+	return obj;
+}
+EXPORT_SYMBOL(dm_mem_cache_alloc);
+
+void dm_mem_cache_free(struct dm_mem_cache_client *cl,
+		       struct dm_mem_cache_object *obj)
+{
+	free_chunks(cl, obj);
+	mempool_free(obj, cl->objs_pool);
+}
+EXPORT_SYMBOL(dm_mem_cache_free);
+
+MODULE_DESCRIPTION(DM_NAME " dm memory cache");
+MODULE_AUTHOR("Heinz Mauelshagen <hjm redhat com>");
+MODULE_LICENSE("GPL");


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