rbd: allocate object requests with a slab allocator

Create a slab cache to manage rbd_obj_request allocation.  We aren't
using a constructor, and we'll zero-fill object request structures
when they're allocated.

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

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index d74be04..a72842a 100644 (file)
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -346,6 +346,7 @@ static LIST_HEAD(rbd_client_list);          /* clients */
 static DEFINE_SPINLOCK(rbd_client_list_lock);
 
 static struct kmem_cache       *rbd_img_request_cache;
+static struct kmem_cache       *rbd_obj_request_cache;
 
 static int rbd_img_request_submit(struct rbd_img_request *img_request);
 
@@ -1762,7 +1763,7 @@ static struct rbd_obj_request *rbd_obj_request_create(const char *object_name,
        if (!name)
                return NULL;
 
-       obj_request = kzalloc(sizeof (*obj_request), GFP_KERNEL);
+       obj_request = kmem_cache_zalloc(rbd_obj_request_cache, GFP_KERNEL);
        if (!obj_request) {
                kfree(name);
                return NULL;
@@ -1814,7 +1815,8 @@ static void rbd_obj_request_destroy(struct kref *kref)
        }
 
        kfree(obj_request->object_name);
-       kfree(obj_request);
+       obj_request->object_name = NULL;
+       kmem_cache_free(rbd_obj_request_cache, obj_request);
 }
 
 /*
@@ -5008,14 +5010,29 @@ static int rbd_slab_init(void)
                                        sizeof (struct rbd_img_request),
                                        __alignof__(struct rbd_img_request),
                                        0, NULL);
-       if (rbd_img_request_cache)
+       if (!rbd_img_request_cache)
+               return -ENOMEM;
+
+       rbd_assert(!rbd_obj_request_cache);
+       rbd_obj_request_cache = kmem_cache_create("rbd_obj_request",
+                                       sizeof (struct rbd_obj_request),
+                                       __alignof__(struct rbd_obj_request),
+                                       0, NULL);
+       if (rbd_obj_request_cache)
                return 0;
 
+       kmem_cache_destroy(rbd_img_request_cache);
+       rbd_img_request_cache = NULL;
+
        return -ENOMEM;
 }
 
 static void rbd_slab_exit(void)
 {
+       rbd_assert(rbd_obj_request_cache);
+       kmem_cache_destroy(rbd_obj_request_cache);
+       rbd_obj_request_cache = NULL;
+
        rbd_assert(rbd_img_request_cache);
        kmem_cache_destroy(rbd_img_request_cache);
        rbd_img_request_cache = NULL;