Re: [PATCH 14/15] dax: associate mappings with inodes, and warn if dma collides with truncate

[Christoph Hellwig]

> +		struct {
> +			/*
> +			 * ZONE_DEVICE pages are never on an lru or handled by
> +			 * a slab allocator, this points to the hosting device
> +			 * page map.
> +			 */
> +			struct dev_pagemap *pgmap;
> +			/*
> +			 * inode association for MEMORY_DEVICE_FS_DAX page-idle
> +			 * callbacks. Note that we don't use ->mapping since
> +			 * that has hard coded page-cache assumptions in
> +			 * several paths.
> +			 */

What assumptions?  I'd much rather fix those up than having two fields
that have the same functionality.