Re: 2.6.25-rc2-mm1: WARNING at arch/x86/mm/ioremap.c:129

[Fabio Checconi]

> From: Ingo Molnar <mingo@xxxxxxx>
> Date: Mon, Mar 03, 2008 09:46:11AM +0100
>
...
> Subject: x86: warn about RAM pages in ioremap()
> From: Ingo Molnar <mingo@xxxxxxx>
> Date: Mon Mar 03 09:37:41 CET 2008
> 
> Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
> ---
>  arch/x86/mm/ioremap.c |    6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> Index: linux-x86.q/arch/x86/mm/ioremap.c
> ===================================================================
> --- linux-x86.q.orig/arch/x86/mm/ioremap.c
> +++ linux-x86.q/arch/x86/mm/ioremap.c
> @@ -149,9 +149,11 @@ static void __iomem *__ioremap(unsigned 
>  	for (pfn = phys_addr >> PAGE_SHIFT;
>  				(pfn << PAGE_SHIFT) < last_addr; pfn++) {
>  
> -		if (page_is_ram(pfn) && pfn_valid(pfn) &&
> -		    !PageReserved(pfn_to_page(pfn)))
> +		int is_ram = page_is_ram(pfn);
> +
> +		if (is_ram && pfn_valid(pfn) && !PageReserved(pfn_to_page(pfn)))
>  			return NULL;
> +		WARN_ON_ONCE(is_ram);
>  	}
>  
>  	switch (mode) {

In this way we can emit the warning even for pages that will not
be mapped, if asked for more than one page (e.g., one page triggers
the warning, one of the following triggers the return NULL condition,)
I don't think that would be useful, as the caller will notice the
error anyway.

I don't know if it's so important, but while we're at it, please
consider that, if last_addr % PAGE_SIZE == 0 the for loop exits
without checking the last pfn, that will be mapped.

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