linux-kernel - Re: [PATCH 1/1] NVMe: Do not take nsid while a passthrough IO command is being issued via a block device file descriptor

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Date:	Sun, 25 Jan 2015 06:59:00 -0800
From:	Christoph Hellwig <hch@...radead.org>
To:	Yan Liu <yan@...estorage.com>
Cc:	Matthew Wilcox <willy@...ux.intel.com>,
	linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] NVMe: Do not take nsid while a passthrough IO
 command is being issued via a block device file descriptor

On Fri, Jan 23, 2015 at 03:57:06PM -0800, Yan Liu wrote:
> When a passthrough IO command is issued with a specific block device file descriptor. It should be applied at
> the namespace which is associated with that block device file descriptor. This patch makes such passthrough
> command ignore nsid in nvme_passthru_cmd structure. Instead it takes the namespace ID asscoiated with the
> block device descriptor.

This looks good to me.  If Keith can point to a use case for magic or
hidden nsids we'll have to find a bypass for them, but this certainly
is the right short term fix:

Reviewed-by: Christoph Hellwig <hch@....de>

>  {
>  	struct nvme_dev *dev = f->private_data;
>  	struct nvme_ns *ns;
> +	int ret;
>  
>  	switch (cmd) {
>  	case NVME_IOCTL_ADMIN_CMD:
>  		return nvme_user_cmd(dev, NULL, (void __user *)arg);
>  	case NVME_IOCTL_IO_CMD:
> -		if (list_empty(&dev->namespaces))
> -			return -ENOTTY;
> -		ns = list_first_entry(&dev->namespaces, struct nvme_ns, list);
> +		ret = nvme_namespace_sel(dev, &ns, (void __user *)arg);
> +		if (ret)
> +			return ret;
>  		return nvme_user_cmd(dev, ns, (void __user *)arg);
>  	default:

This function would benefit from a local variable ala:

	void __user *argp = (void __user *)arg;

but that might be done in a follow up patch, or postponed for now.
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