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>

1 files changed, 20 insertions, 3 deletions

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index d74be04ceeff..a72842aa3b53 100644
--- 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;