linux-kernel - Re: [PATCH v2 6/6] block: skip queue if NULL on blk_cleanup

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Date:   Mon, 19 Jul 2021 10:50:13 +0100
From:   Christoph Hellwig <hch@...radead.org>
To:     Luis Chamberlain <mcgrof@...nel.org>
Cc:     Christoph Hellwig <hch@...radead.org>, axboe@...nel.dk,
        hare@...e.de, bvanassche@....org, ming.lei@...hat.com,
        jack@...e.cz, osandov@...com, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 6/6] block: skip queue if NULL on blk_cleanup_queue()

On Thu, Jul 15, 2021 at 12:07:26PM -0700, Luis Chamberlain wrote:
> > For all drivers using blk_alloc_disk/blk_mq_alloc_disk there should
> > always be a queue.  The others ones aren't ready to handle errors
> > from add_disk yet in any way I think (and I plan to fix this up
> > ASAP).
> 
> Have an example in mind?

The only ones left are nvme, dasd and scsi.  NVMe is trivial (attached),
dasd needs a little more work, I need to send up a WIP to the
maintainers.  scsi is the real problem and will require a fair amount
of work.

---
diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 11779be42186..35da956acef6 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -3726,9 +3726,14 @@ static void nvme_alloc_ns(struct nvme_ctrl *ctrl, unsigned nsid,
 	if (!ns)
 		goto out_free_id;
 
-	ns->queue = blk_mq_init_queue(ctrl->tagset);
-	if (IS_ERR(ns->queue))
+	disk = blk_mq_alloc_disk(ctrl->tagset, ns);
+	if (IS_ERR(disk))
 		goto out_free_ns;
+	disk->fops = &nvme_bdev_ops;
+	disk->private_data = ns;
+
+	ns->disk = disk;
+	ns->queue = disk->queue;
 
 	if (ctrl->opts && ctrl->opts->data_digest)
 		blk_queue_flag_set(QUEUE_FLAG_STABLE_WRITES, ns->queue);
@@ -3737,20 +3742,12 @@ static void nvme_alloc_ns(struct nvme_ctrl *ctrl, unsigned nsid,
 	if (ctrl->ops->flags & NVME_F_PCI_P2PDMA)
 		blk_queue_flag_set(QUEUE_FLAG_PCI_P2PDMA, ns->queue);
 
-	ns->queue->queuedata = ns;
 	ns->ctrl = ctrl;
 	kref_init(&ns->kref);
 
 	if (nvme_init_ns_head(ns, nsid, ids, id->nmic & NVME_NS_NMIC_SHARED))
-		goto out_free_queue;
-
-	disk = alloc_disk_node(0, node);
-	if (!disk)
-		goto out_unlink_ns;
+		goto out_cleanup_disk;
 
-	disk->fops = &nvme_bdev_ops;
-	disk->private_data = ns;
-	disk->queue = ns->queue;
 	/*
 	 * Without the multipath code enabled, multiple controller per
 	 * subsystems are visible as devices and thus we cannot use the
@@ -3759,15 +3756,14 @@ static void nvme_alloc_ns(struct nvme_ctrl *ctrl, unsigned nsid,
 	if (!nvme_mpath_set_disk_name(ns, disk->disk_name, &disk->flags))
 		sprintf(disk->disk_name, "nvme%dn%d", ctrl->instance,
 			ns->head->instance);
-	ns->disk = disk;
 
 	if (nvme_update_ns_info(ns, id))
-		goto out_put_disk;
+		goto out_unlink_ns;
 
 	if ((ctrl->quirks & NVME_QUIRK_LIGHTNVM) && id->vs[0] == 0x1) {
 		if (nvme_nvm_register(ns, disk->disk_name, node)) {
 			dev_warn(ctrl->device, "LightNVM init failure\n");
-			goto out_put_disk;
+			goto out_unlink_ns;
 		}
 	}
 
@@ -3786,10 +3782,7 @@ static void nvme_alloc_ns(struct nvme_ctrl *ctrl, unsigned nsid,
 	kfree(id);
 
 	return;
- out_put_disk:
-	/* prevent double queue cleanup */
-	ns->disk->queue = NULL;
-	put_disk(ns->disk);
+
  out_unlink_ns:
 	mutex_lock(&ctrl->subsys->lock);
 	list_del_rcu(&ns->siblings);
@@ -3797,8 +3790,8 @@ static void nvme_alloc_ns(struct nvme_ctrl *ctrl, unsigned nsid,
 		list_del_init(&ns->head->entry);
 	mutex_unlock(&ctrl->subsys->lock);
 	nvme_put_ns_head(ns->head);
- out_free_queue:
-	blk_cleanup_queue(ns->queue);
+ out_cleanup_disk:
+	blk_cleanup_disk(disk);
  out_free_ns:
 	kfree(ns);
  out_free_id: