[PATCH] NVMe: fix type warning on 32-bit

[keith.busch@intel.com (Keith Busch)]

On Tue, 19 May 2015, Arnd Bergmann wrote:
> A recent change to the ioctl handling caused a new harmless
> warning in the NVMe driver on all 32-bit machines:
>
> drivers/block/nvme-core.c: In function 'nvme_submit_io':
> drivers/block/nvme-core.c:1794:29: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
>
> In order to shup up that warning, this introduces a new
> temporary variable that uses a double cast to extract
> the pointer from an __u64 structure member.


Thanks for the fix.

Acked-by: Keith Busch <keith.busch at intel.com>

> Signed-off-by: Arnd Bergmann <arnd at arndb.de>
> Fixes: a67a95134ff ("NVMe: Meta data handling through submit io ioctl")
>
> diff --git a/drivers/block/nvme-core.c b/drivers/block/nvme-core.c
> index 85b8036deaa3..683dff272562 100644
> --- a/drivers/block/nvme-core.c
> +++ b/drivers/block/nvme-core.c
> @@ -1750,6 +1750,7 @@ static int nvme_submit_io(struct nvme_ns *ns, struct nvme_user_io __user *uio)
> 	struct nvme_iod *iod;
> 	dma_addr_t meta_dma = 0;
> 	void *meta = NULL;
> +	void __user *metadata;
>
> 	if (copy_from_user(&io, uio, sizeof(io)))
> 		return -EFAULT;
> @@ -1763,6 +1764,8 @@ static int nvme_submit_io(struct nvme_ns *ns, struct nvme_user_io __user *uio)
> 		meta_len = 0;
> 	}
>
> +	metadata = (void __user *)(unsigned long)io.metadata;
> +
> 	write = io.opcode & 1;
>
> 	switch (io.opcode) {
> @@ -1786,13 +1789,13 @@ static int nvme_submit_io(struct nvme_ns *ns, struct nvme_user_io __user *uio)
> 	if (meta_len) {
> 		meta = dma_alloc_coherent(&dev->pci_dev->dev, meta_len,
> 						&meta_dma, GFP_KERNEL);
> +
> 		if (!meta) {
> 			status = -ENOMEM;
> 			goto unmap;
> 		}
> 		if (write) {
> -			if (copy_from_user(meta, (void __user *)io.metadata,
> -								meta_len)) {
> +			if (copy_from_user(meta, metadata, meta_len)) {
> 				status = -EFAULT;
> 				goto unmap;
> 			}
> @@ -1819,8 +1822,7 @@ static int nvme_submit_io(struct nvme_ns *ns, struct nvme_user_io __user *uio)
> 	nvme_free_iod(dev, iod);
> 	if (meta) {
> 		if (status == NVME_SC_SUCCESS && !write) {
> -			if (copy_to_user((void __user *)io.metadata, meta,
> -								meta_len))
> +			if (copy_to_user(metadata, meta, meta_len))
> 				status = -EFAULT;
> 		}
> 		dma_free_coherent(&dev->pci_dev->dev, meta_len, meta, meta_dma);
>
>