Use explicit functions with args instead of work_structs for callbacks.

Signed-off-by: Christian Limpach <Christian.Limpach@cl.cam.ac.uk>

linux-2.6-xen-sparse/arch/xen/kernel/gnttab.c

@@ -69,11 +69,13 @@ get_free_entry(
 
 static void do_free_callbacks(void)
 {
-    struct gnttab_free_callback *callback = gnttab_free_callback_list;
+    struct gnttab_free_callback *callback = gnttab_free_callback_list, *next;
     gnttab_free_callback_list = NULL;
     while (callback) {
-	schedule_work(callback->work);
-	callback = callback->next;
+	next = callback->next;
+	callback->next = NULL;
+	callback->fn(callback->arg);
+	callback = next;
     }
 }
 
@@ -266,9 +268,12 @@ gnttab_release_grant_reference( grant_ref_t *private_head,
 
 void
 gnttab_request_free_callback(struct gnttab_free_callback *callback,
-			     struct work_struct *work)
+			     void (*fn)(void *), void *arg)
 {
-    callback->work = work;
+    if (callback->next)
+	return;
+    callback->fn = fn;
+    callback->arg = arg;
     callback->next = gnttab_free_callback_list;
     gnttab_free_callback_list = callback;
 }

linux-2.6-xen-sparse/drivers/xen/blkfront/blkfront.c

@@ -157,11 +157,16 @@ static void blkif_restart_queue(void *arg)
 {
 	struct blkfront_info *info = (struct blkfront_info *)arg;
 	spin_lock_irq(&blkif_io_lock);
-	info->callback.work = NULL;
 	kick_pending_request_queues(info);
 	spin_unlock_irq(&blkif_io_lock);
 }
 
+static void blkif_restart_queue_callback(void *arg)
+{
+	struct blkfront_info *info = (struct blkfront_info *)arg;
+	schedule_work(&info->work);
+}
+
 int blkif_open(struct inode *inode, struct file *filep)
 {
 	// struct gendisk *gd = inode->i_bdev->bd_disk;
@@ -239,10 +244,8 @@ static int blkif_queue_request(struct request *req)
 
     if (gnttab_alloc_grant_references(BLKIF_MAX_SEGMENTS_PER_REQUEST,
 				      &gref_head, &gref_terminal) < 0) {
-	    if (info->callback.work)
-		    return 1;
-	    INIT_WORK(&info->work, blkif_restart_queue, (void *)info);
-	    gnttab_request_free_callback(&info->callback, &info->work);
+	    gnttab_request_free_callback(&info->callback,
+					 blkif_restart_queue_callback, info);
 	    return 1;
     }
 
@@ -1242,6 +1245,7 @@ static int blkfront_probe(struct xenbus_device *dev,
 	info->vdevice = vdevice;
 	info->connected = BLKIF_STATE_DISCONNECTED;
 	info->mi = NULL;
+	INIT_WORK(&info->work, blkif_restart_queue, (void *)info);
 
 	/* Front end dir is a number, which is used as the id. */
 	info->handle = simple_strtoul(strrchr(dev->nodename,'/')+1, NULL, 0);

linux-2.6-xen-sparse/include/asm-xen/gnttab.h

@@ -25,7 +25,8 @@ struct work_struct;
 
 struct gnttab_free_callback {
     struct gnttab_free_callback *next;
-    struct work_struct *work;
+    void (*fn)(void *);
+    void *arg;
 };
 
 int
@@ -73,7 +74,7 @@ gnttab_release_grant_reference(
 
 void
 gnttab_request_free_callback(
-    struct gnttab_free_callback *callback, struct work_struct *work );
+    struct gnttab_free_callback *callback, void (*fn)(void *), void *arg);
 
 void
 gnttab_grant_foreign_access_ref(