From 952b355760c196ec014dd0b6878f85a11496e3da Mon Sep 17 00:00:00 2001
From: Mikulas Patocka <mpatocka@redhat.com>
Date: Thu, 10 Dec 2009 23:51:57 +0000
Subject: [PATCH] dm io: use slab for struct io

Allocate "struct io" from a slab.

This patch changes dm-io, so that "struct io" is allocated from a slab cache.
It used to be allocated with kmalloc. Allocating from a slab will be needed
for the next patch, because it requires a special alignment of "struct io"
and kmalloc cannot meet this alignment.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
---
 drivers/md/dm-io.c | 21 ++++++++++++++++++++-
 drivers/md/dm.c    |  2 ++
 drivers/md/dm.h    |  3 +++
 3 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/drivers/md/dm-io.c b/drivers/md/dm-io.c
index 3a2e6a2f8bdd..b0d264e684fd 100644
--- a/drivers/md/dm-io.c
+++ b/drivers/md/dm-io.c
@@ -5,6 +5,8 @@
  * This file is released under the GPL.
  */
 
+#include "dm.h"
+
 #include <linux/device-mapper.h>
 
 #include <linux/bio.h>
@@ -30,6 +32,8 @@ struct io {
 	void *context;
 };
 
+static struct kmem_cache *_dm_io_cache;
+
 /*
  * io contexts are only dynamically allocated for asynchronous
  * io.  Since async io is likely to be the majority of io we'll
@@ -53,7 +57,7 @@ struct dm_io_client *dm_io_client_create(unsigned num_pages)
 	if (!client)
 		return ERR_PTR(-ENOMEM);
 
-	client->pool = mempool_create_kmalloc_pool(ios, sizeof(struct io));
+	client->pool = mempool_create_slab_pool(ios, _dm_io_cache);
 	if (!client->pool)
 		goto bad;
 
@@ -472,3 +476,18 @@ int dm_io(struct dm_io_request *io_req, unsigned num_regions,
 			&dp, io_req->notify.fn, io_req->notify.context);
 }
 EXPORT_SYMBOL(dm_io);
+
+int __init dm_io_init(void)
+{
+	_dm_io_cache = KMEM_CACHE(io, 0);
+	if (!_dm_io_cache)
+		return -ENOMEM;
+
+	return 0;
+}
+
+void dm_io_exit(void)
+{
+	kmem_cache_destroy(_dm_io_cache);
+	_dm_io_cache = NULL;
+}
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 724efc63904d..473f0c3c0192 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -275,6 +275,7 @@ static int (*_inits[])(void) __initdata = {
 	dm_target_init,
 	dm_linear_init,
 	dm_stripe_init,
+	dm_io_init,
 	dm_kcopyd_init,
 	dm_interface_init,
 };
@@ -284,6 +285,7 @@ static void (*_exits[])(void) = {
 	dm_target_exit,
 	dm_linear_exit,
 	dm_stripe_exit,
+	dm_io_exit,
 	dm_kcopyd_exit,
 	dm_interface_exit,
 };
diff --git a/drivers/md/dm.h b/drivers/md/dm.h
index a7663eba17e2..4a95e8fa3607 100644
--- a/drivers/md/dm.h
+++ b/drivers/md/dm.h
@@ -118,6 +118,9 @@ int dm_lock_for_deletion(struct mapped_device *md);
 void dm_kobject_uevent(struct mapped_device *md, enum kobject_action action,
 		       unsigned cookie);
 
+int dm_io_init(void);
+void dm_io_exit(void);
+
 int dm_kcopyd_init(void);
 void dm_kcopyd_exit(void);