Re: [PATCH 1/4] rbd: allocate image requests with a slab allocator

[Josh Durgin]

It looks like the GFP flags used throughout request creation
could be cleanup up (there's a mix of ATOMIC, KERNEL, and NOIO).
I just noticed since this changes a GFP_ATOMIC to GFP_KERNEL.
Making them consistent can be a later patch though.

Reviewed-by: Josh Durgin <josh.dur...@inktank.com>

On 05/01/2013 02:35 PM, Alex Elder wrote:

Create a slab cache to manage rbd_img_request allocation.  Nothing
too fancy at this point--we'll still initialize everything at
allocation time (no constructor)

This is part of:
     http://tracker.ceph.com/issues/3926

Signed-off-by: Alex Elder <el...@inktank.com>
---
  drivers/block/rbd.c |   39 ++++++++++++++++++++++++++++++++++-----
  1 file changed, 34 insertions(+), 5 deletions(-)

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index a6e5fe3..005c397 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -40,6 +40,7 @@
  #include <linux/module.h>
  #include <linux/fs.h>
  #include <linux/blkdev.h>
+#include <linux/slab.h>

  #include "rbd_types.h"

@@ -344,6 +345,8 @@ static DEFINE_SPINLOCK(rbd_dev_list_lock);
  static LIST_HEAD(rbd_client_list);            /* clients */
  static DEFINE_SPINLOCK(rbd_client_list_lock);

+static struct kmem_cache       *rbd_img_request_cache;
+
  static int rbd_img_request_submit(struct rbd_img_request *img_request);

  static void rbd_dev_device_release(struct device *dev);
@@ -1821,7 +1824,7 @@ static struct rbd_img_request *rbd_img_request_create(
  {
        struct rbd_img_request *img_request;

-       img_request = kmalloc(sizeof (*img_request), GFP_ATOMIC);
+       img_request = kmem_cache_alloc(rbd_img_request_cache, GFP_KERNEL);
        if (!img_request)
                return NULL;

@@ -1884,7 +1887,7 @@ static void rbd_img_request_destroy(struct kref *kref)
        if (img_request_child_test(img_request))
                rbd_obj_request_put(img_request->obj_request);

-       kfree(img_request);
+       kmem_cache_free(rbd_img_request_cache, img_request);
  }

  static bool rbd_img_obj_end_request(struct rbd_obj_request *obj_request)
@@ -4992,6 +4995,26 @@ static void rbd_sysfs_cleanup(void)
        device_unregister(&rbd_root_dev);
  }

+static int rbd_slab_init(void)
+{
+       rbd_assert(!rbd_img_request_cache);
+       rbd_img_request_cache = kmem_cache_create("rbd_img_request",
+                                       sizeof (struct rbd_img_request),
+                                       __alignof__(struct rbd_img_request),
+                                       0, NULL);
+       if (rbd_img_request_cache)
+               return 0;
+
+       return -ENOMEM;
+}
+
+static void rbd_slab_exit(void)
+{
+       rbd_assert(rbd_img_request_cache);
+       kmem_cache_destroy(rbd_img_request_cache);
+       rbd_img_request_cache = NULL;
+}
+
  static int __init rbd_init(void)
  {
        int rc;
@@ -5001,16 +5024,22 @@ static int __init rbd_init(void)

                return -EINVAL;
        }
-       rc = rbd_sysfs_init();
+       rc = rbd_slab_init();
        if (rc)
                return rc;
-       pr_info("loaded " RBD_DRV_NAME_LONG "\n");
-       return 0;
+       rc = rbd_sysfs_init();
+       if (rc)
+               rbd_slab_exit();
+       else
+               pr_info("loaded " RBD_DRV_NAME_LONG "\n");
+
+       return rc;
  }

  static void __exit rbd_exit(void)
  {
        rbd_sysfs_cleanup();
+       rbd_slab_exit();
  }

  module_init(rbd_init);

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