linux-kernel - Re: [PATCH] Do not round per_cpu_ptr_to

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Date:	Fri, 16 Dec 2011 09:40:20 +0100
From:	Petr Tesarik <ptesarik@...e.cz>
To:	Tejun Heo <tj@...nel.org>
Cc:	linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>,
	Vivek Goyal <vgoyal@...hat.com>, surovegin@...gle.com,
	gthelen@...gle.com
Subject: Re: [PATCH] Do not round per_cpu_ptr_to_phys to page boundary

Ignore my patch. I can see, a patch has already been accepted.

I only replied too fast (before I read the rest of the thread).

Petr

Dne Pá 16. prosince 2011 09:04:23 Petr Tesarik napsal(a):
> The phys_addr_t per_cpu_ptr_to_phys() function ignores the offset within a
> page, whenever not using a simple translation using __pa().
> 
> Without this patch /sys/devices/system/cpu/cpu*/crash_notes shows incorrect
> values, which breaks kdump. Other things may also be broken.
> 
> Signed-off-by: Petr Tesarik <ptesarik@...e.cz>
> 
> diff --git a/mm/percpu.c b/mm/percpu.c
> index 3bb810a..1a1b5ac 100644
> --- a/mm/percpu.c
> +++ b/mm/percpu.c
> @@ -998,6 +998,7 @@ phys_addr_t per_cpu_ptr_to_phys(void *addr)
>  	bool in_first_chunk = false;
>  	unsigned long first_low, first_high;
>  	unsigned int cpu;
> +	phys_addr_t page_addr;
> 
>  	/*
>  	 * The following test on unit_low/high isn't strictly
> @@ -1023,9 +1024,10 @@ phys_addr_t per_cpu_ptr_to_phys(void *addr)
>  		if (!is_vmalloc_addr(addr))
>  			return __pa(addr);
>  		else
> -			return page_to_phys(vmalloc_to_page(addr));
> +			page_addr = page_to_phys(vmalloc_to_page(addr));
>  	} else
> -		return page_to_phys(pcpu_addr_to_page(addr));
> +		page_addr = page_to_phys(pcpu_addr_to_page(addr));
> +	return page_addr + offset_in_page(addr);
>  }
> 
>  /**
> 
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