[PATCH] virtio_blk: don't blindly derefence req->rq_disk

[Christoph Hellwig <hch@lst.de>]

request->rq_disk is only set for FS requests or BLOCK_PC requests
originating from the generic block layer scsi ioctls.  It's not set
for requests origination from other soures or internal cache flush
commands implemented by the patch I'll send after this.

So instead of using it to get at the private data in do_virtblk_request
setup queue->queuedata and use it.


Signed-off-by: Christoph Hellwig <hch@lst.de>

Index: xfs/drivers/block/virtio_blk.c
===================================================================
--- xfs.orig/drivers/block/virtio_blk.c	2009-05-11 10:09:59.833784412 +0200
+++ xfs/drivers/block/virtio_blk.c	2009-05-11 10:33:31.099659254 +0200
@@ -153,12 +153,11 @@ static bool do_req(struct request_queue 
 
 static void do_virtblk_request(struct request_queue *q)
 {
-	struct virtio_blk *vblk = NULL;
+	struct virtio_blk *vblk = q->queuedata;
 	struct request *req;
 	unsigned int issued = 0;
 
 	while ((req = elv_next_request(q)) != NULL) {
-		vblk = req->rq_disk->private_data;
 		BUG_ON(req->nr_phys_segments + 2 > vblk->sg_elems);
 
 		/* If this request fails, stop queue and wait for something to
@@ -286,6 +285,7 @@ static int virtblk_probe(struct virtio_d
 		goto out_put_disk;
 	}
 
+	vblk->disk->queue->queuedata = vblk;
 	queue_flag_set_unlocked(QUEUE_FLAG_VIRT, vblk->disk->queue);
 
 	if (index < 26) {