Re: [RFC][PATCH 1/3] xip: no struct pages -- get_xip_mem

[Linus Torvalds <torvalds@linux-foundation.org>]

On Fri, 7 Mar 2008, Jared Hulbert wrote:
>
> [RFC][PATCH 1/3] xip: no struct pages -- get_xip_mem
> 
> Convert XIP to support non-struct page backed memory.
> The get_xip_page API is changed from a page based to an address/pfn based one.

Is there any way we could just re-use the same calling conventions as we 
already use for "vma->fault()"?

> +	int (*get_xip_mem)(struct address_space *, pgoff_t, int, void **,
> +			unsigned long *);

This really looks very close to 

	int (*fault)(struct vm_area_struct *vma, struct vm_fault *vmf);

and "struct vm_fault" returns either a kernel virtual address or a "struct 
page *" 

So would it be possible to just use the same calling convention, except 
passing a "struct address_space" instead of a "struct vm_area_struct"?

I realize that "struct vm_fault" doesn't have a pfn in it (if they don't 
do a "struct page", they are expected to fill in the PTE directly instead 
and return VM_FAULT_NOPAGE), but I wonder if it should.

The whole git_xip_page() issue really looks very similar to "fault in a 
page from an address space". It feels kind of wrong to have filesystems 
implement two functions for what seems to be the exact same issue.

			Linus

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