Re: [PATCH 08/25] memremap: validate the pagemap type passed to devm_memremap_pages

[Ira Weiny <ira.weiny@intel.com>]

On Wed, Jun 26, 2019 at 02:27:07PM +0200, Christoph Hellwig wrote:
> Most pgmap types are only supported when certain config options are
> enabled.  Check for a type that is valid for the current configuration
> before setting up the pagemap.  For this the usage of the 0 type for
> device dax gets replaced with an explicit MEMORY_DEVICE_DEVDAX type.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Reviewed-by: Ira Weiny <ira.weiny@intel.com>

> ---
>  drivers/dax/device.c     |  1 +
>  include/linux/memremap.h |  8 ++++++++
>  kernel/memremap.c        | 22 ++++++++++++++++++++++
>  3 files changed, 31 insertions(+)
> 
> diff --git a/drivers/dax/device.c b/drivers/dax/device.c
> index 8465d12fecba..79014baa782d 100644
> --- a/drivers/dax/device.c
> +++ b/drivers/dax/device.c
> @@ -468,6 +468,7 @@ int dev_dax_probe(struct device *dev)
>  	dev_dax->pgmap.ref = &dev_dax->ref;
>  	dev_dax->pgmap.kill = dev_dax_percpu_kill;
>  	dev_dax->pgmap.cleanup = dev_dax_percpu_exit;
> +	dev_dax->pgmap.type = MEMORY_DEVICE_DEVDAX;
>  	addr = devm_memremap_pages(dev, &dev_dax->pgmap);
>  	if (IS_ERR(addr))
>  		return PTR_ERR(addr);
> diff --git a/include/linux/memremap.h b/include/linux/memremap.h
> index 995c62c5a48b..0c86f2c5ac9c 100644
> --- a/include/linux/memremap.h
> +++ b/include/linux/memremap.h
> @@ -45,13 +45,21 @@ struct vmem_altmap {
>   * wakeup is used to coordinate physical address space management (ex:
>   * fs truncate/hole punch) vs pinned pages (ex: device dma).
>   *
> + * MEMORY_DEVICE_DEVDAX:
> + * Host memory that has similar access semantics as System RAM i.e. DMA
> + * coherent and supports page pinning. In contrast to
> + * MEMORY_DEVICE_FS_DAX, this memory is access via a device-dax
> + * character device.
> + *
>   * MEMORY_DEVICE_PCI_P2PDMA:
>   * Device memory residing in a PCI BAR intended for use with Peer-to-Peer
>   * transactions.
>   */
>  enum memory_type {
> +	/* 0 is reserved to catch uninitialized type fields */
>  	MEMORY_DEVICE_PRIVATE = 1,
>  	MEMORY_DEVICE_FS_DAX,
> +	MEMORY_DEVICE_DEVDAX,
>  	MEMORY_DEVICE_PCI_P2PDMA,
>  };
>  
> diff --git a/kernel/memremap.c b/kernel/memremap.c
> index 6e1970719dc2..abda62d1e5a3 100644
> --- a/kernel/memremap.c
> +++ b/kernel/memremap.c
> @@ -157,6 +157,28 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
>  	pgprot_t pgprot = PAGE_KERNEL;
>  	int error, nid, is_ram;
>  
> +	switch (pgmap->type) {
> +	case MEMORY_DEVICE_PRIVATE:
> +		if (!IS_ENABLED(CONFIG_DEVICE_PRIVATE)) {
> +			WARN(1, "Device private memory not supported\n");
> +			return ERR_PTR(-EINVAL);
> +		}
> +		break;
> +	case MEMORY_DEVICE_FS_DAX:
> +		if (!IS_ENABLED(CONFIG_ZONE_DEVICE) ||
> +		    IS_ENABLED(CONFIG_FS_DAX_LIMITED)) {
> +			WARN(1, "File system DAX not supported\n");
> +			return ERR_PTR(-EINVAL);
> +		}
> +		break;
> +	case MEMORY_DEVICE_DEVDAX:
> +	case MEMORY_DEVICE_PCI_P2PDMA:
> +		break;
> +	default:
> +		WARN(1, "Invalid pgmap type %d\n", pgmap->type);
> +		break;
> +	}
> +
>  	if (!pgmap->ref || !pgmap->kill || !pgmap->cleanup) {
>  		WARN(1, "Missing reference count teardown definition\n");
>  		return ERR_PTR(-EINVAL);
> -- 
> 2.20.1
> 
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