linux-kernel - Re: [PATCH v2] MIPS: Kernel crashes on boot with SPARSEMEM + HIGHMEM enabled

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Date:	Fri, 01 Apr 2011 09:56:56 -0700
From:	David Daney <ddaney@...iumnetworks.com>
To:	Kevin Cernekee <cernekee@...il.com>
CC:	Ralf Baechle <ralf@...ux-mips.org>,
	Michael Sundius <msundius@...co.com>,
	David VomLehn <dvomlehn@...co.com>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	Andy Whitcroft <apw@...dowen.org>,
	Jon Fraser <jfraser@...adcom.com>, linux-mips@...ux-mips.org,
	linux-kernel@...r.kernel.org, stable@...nel.org
Subject: Re: [PATCH v2] MIPS: Kernel crashes on boot with SPARSEMEM + HIGHMEM
 enabled

On 03/31/2011 05:27 PM, Kevin Cernekee wrote:
> From: Michael Sundius<msundius@...co.com>
>
> Fix 3 problems in the MIPS SPARSEMEM implementation:
>
> 1) mem_init() sets/clears PG_reserved on all pages in the HIGHMEM range
> without checking to see whether the page descriptor actually exists.
>
> 2) bootmem_init() never calls memory_present() on HIGHMEM pages, so
> page descriptors are never created for them if SPARSEMEM is enabled.
>
> 3) bootmem_init() calls memory_present() on lowmem pages before bootmem
> is fully set up.  This is bad because memory_present() can allocate
> bootmem in some circumstances (e.g. if SPARSEMEM_EXTREME ever got
> enabled).
>


I think this may do the same thing as my patch:

http://patchwork.linux-mips.org/patch/1988/

Although my patch had different motivations, and changes some other 
things around too.

David Daney


> Signed-off-by: Michael Sundius<msundius@...co.com>
> Signed-off-by: Kevin Cernekee<cernekee@...il.com>
> Cc: stable@...nel.org
> ---
>   arch/mips/kernel/setup.c |   18 +++++++++++++++++-
>   arch/mips/mm/init.c      |    3 +++
>   2 files changed, 20 insertions(+), 1 deletions(-)
>
> diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
> index 8ad1d56..1f9f902 100644
> --- a/arch/mips/kernel/setup.c
> +++ b/arch/mips/kernel/setup.c
> @@ -390,7 +390,6 @@ static void __init bootmem_init(void)
>
>   		/* Register lowmem ranges */
>   		free_bootmem(PFN_PHYS(start), size<<  PAGE_SHIFT);
> -		memory_present(0, start, end);
>   	}
>
>   	/*
> @@ -402,6 +401,23 @@ static void __init bootmem_init(void)
>   	 * Reserve initrd memory if needed.
>   	 */
>   	finalize_initrd();
> +
> +	/*
> +	 * Call memory_present() on all valid ranges, for SPARSEMEM.
> +	 * This must be done after setting up bootmem, since memory_present()
> +	 * may allocate bootmem.
> +	 */
> +	for (i = 0; i<  boot_mem_map.nr_map; i++) {
> +		unsigned long start, end;
> +
> +		if (boot_mem_map.map[i].type != BOOT_MEM_RAM)
> +			continue;
> +
> +		start = PFN_UP(boot_mem_map.map[i].addr);
> +		end   = PFN_DOWN(boot_mem_map.map[i].addr
> +				    + boot_mem_map.map[i].size);
> +		memory_present(0, start, end);
> +	}
>   }
>
>   #endif	/* CONFIG_SGI_IP27 */
> diff --git a/arch/mips/mm/init.c b/arch/mips/mm/init.c
> index 279599e..78a4cf2 100644
> --- a/arch/mips/mm/init.c
> +++ b/arch/mips/mm/init.c
> @@ -392,6 +392,9 @@ void __init mem_init(void)
>   	for (tmp = highstart_pfn; tmp<  highend_pfn; tmp++) {
>   		struct page *page = pfn_to_page(tmp);
>
> +		if (!pfn_valid(tmp))
> +			continue;
> +
>   		if (!page_is_ram(tmp)) {
>   			SetPageReserved(page);
>   			continue;

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