[v7] powerpc: Force page alignment for initrd reserved memory

From: Dave Carroll <dcarroll@astekcorp.com>

When using 64K pages with a separate cpio rootfs, U-Boot will align
the rootfs on a 4K page boundary. When the memory is reserved, and
subsequent early memblock_alloc is called, it will allocate memory
between the 64K page alignment and reserved memory. When the reserved
memory is subsequently freed, it is done so by pages, causing the
early memblock_alloc requests to be re-used, which in my case, caused
the device-tree to be clobbered.

This patch forces the reserved memory for initrd to be kernel page
aligned, and will move the device tree if it overlaps with the range
extension of initrd. This patch will also consolidate the identical
function free_initrd_mem() from mm/init_32.c, init_64.c to mm/mem.c,
and adds the same range extension when freeing initrd.

Many thanks to Milton Miller for his input on this patch.

Signed-off-by: Dave Carroll <dcarroll@astekcorp.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>

---
 * The previous patch [v6] was the wrong copy, sorry ...
 
 arch/powerpc/kernel/prom.c |   21 ++++++++++++++++++---
 arch/powerpc/mm/init_32.c  |   15 ---------------
 arch/powerpc/mm/init_64.c  |   13 -------------
 arch/powerpc/mm/mem.c      |   19 +++++++++++++++++++
 4 files changed, 37 insertions(+), 31 deletions(-)

On Wed, 25 May 2011 about 20:32:42 -0600, Dave Carroll wrote:

> When using 64K pages with a separate cpio rootfs, U-Boot will align
> the rootfs on a 4K page boundary. When the memory is reserved, and
> subsequent early memblock_alloc is called, it will allocate memory
> between the 64K page alignment and reserved memory. When the reserved
> memory is subsequently freed, it is done so by pages, causing the
> early memblock_alloc requests to be re-used, which in my case, caused
> the device-tree to be clobbered.
> 
> This patch forces the reserved memory for initrd to be kernel page
> aligned, and will move the device tree if it overlaps with the range
> extension of initrd. This patch will also consolidate the identical
> function free_initrd_mem() from mm/init_32.c, init_64.c to mm/mem.c,
> and adds the same range extension when freeing initrd.
> 
> Many thanks to Milton Miller for his input on this patch.
> 

Thanks for the mailer update, it applied cleanly.

> Signed-off-by: Dave Carroll <dcarroll@astekcorp.com>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> 
> ---
>  * The previous patch [v6] was the wrong copy, sorry ...
>  
>  arch/powerpc/kernel/prom.c |   21 ++++++++++++++++++---
>  arch/powerpc/mm/init_32.c  |   15 ---------------
>  arch/powerpc/mm/init_64.c  |   13 -------------
>  arch/powerpc/mm/mem.c      |   19 +++++++++++++++++++
>  4 files changed, 37 insertions(+), 31 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
> index 48aeb55..86966a0 100644
> --- a/arch/powerpc/kernel/prom.c
> +++ b/arch/powerpc/kernel/prom.c
> @@ -81,12 +81,24 @@ static int __init early_parse_mem(char *p)
>  	return 0;
>  }
>  early_param("mem", early_parse_mem);
> +/**
> + * overlaps_initrd - check for overlap with page aligned extension of
> + * initrd.
> + */

1) Please place a blank line after the above early_param before
the comment block.

2) /** says it is kernel doc format, so you need to follow the rules.
The description should fit on one line (I might say: ... with the initrd,
page aligned.)  and you have to document the parameters.  (Or just make
it a simple comment block by removing the second *)

> +static inline int overlaps_initrd(unsigned long start, unsigned long size)
> +{
> +	if (!initrd_start)
> +		return 0;
>  
> +	return	(start + size) > _ALIGN_DOWN(initrd_start, PAGE_SIZE) &&
> +			start <= _ALIGN_UP(initrd_end, PAGE_SIZE);
> +}
>  /**

need a blank line after the function before this comment block too.

>   * move_device_tree - move tree to an unused area, if needed.
>   *
>   * The device tree may be allocated beyond our memory limit, or inside the
> - * crash kernel region for kdump. If so, move it out of the way.
> + * crash kernel region for kdump, or within the page aligned range of initrd.
> + * If so, move it out of the way.

of the initrd.

>   */
>  static void __init move_device_tree(void)
>  {
> @@ -99,7 +111,8 @@ static void __init move_device_tree(void)
>  	size = be32_to_cpu(initial_boot_params->totalsize);
>  
>  	if ((memory_limit && (start + size) > PHYSICAL_START + memory_limit) ||
> -			overlaps_crashkernel(start, size)) {
> +			overlaps_crashkernel(start, size) ||
> +			overlaps_initrd(start, size)) {
>  		p = __va(memblock_alloc(size, PAGE_SIZE));
>  		memcpy(p, initial_boot_params, size);
>  		initial_boot_params = (struct boot_param_header *)p;
> @@ -555,7 +568,9 @@ static void __init early_reserve_mem(void)
>  #ifdef CONFIG_BLK_DEV_INITRD
>  	/* then reserve the initrd, if any */
>  	if (initrd_start && (initrd_end > initrd_start))
> -		memblock_reserve(__pa(initrd_start), initrd_end - initrd_start);
> +		memblock_reserve(_ALIGN_DOWN(__pa(initrd_start), PAGE_SIZE),
> +			_ALIGN_UP(initrd_end, PAGE_SIZE) -
> +			_ALIGN_DOWN(initrd_start, PAGE_SIZE));
>  #endif /* CONFIG_BLK_DEV_INITRD */
>  
>  #ifdef CONFIG_PPC32
> diff --git a/arch/powerpc/mm/init_32.c b/arch/powerpc/mm/init_32.c
> index d65b591..5de0f25 100644
> --- a/arch/powerpc/mm/init_32.c
> +++ b/arch/powerpc/mm/init_32.c
> @@ -223,21 +223,6 @@ void free_initmem(void)
>  #undef FREESEC
>  }
>  
> -#ifdef CONFIG_BLK_DEV_INITRD
> -void free_initrd_mem(unsigned long start, unsigned long end)
> -{
> -	if (start < end)
> -		printk ("Freeing initrd memory: %ldk freed\n", (end - start) >> 10);
> -	for (; start < end; start += PAGE_SIZE) {
> -		ClearPageReserved(virt_to_page(start));
> -		init_page_count(virt_to_page(start));
> -		free_page(start);
> -		totalram_pages++;
> -	}
> -}
> -#endif
> -
> -
>  #ifdef CONFIG_8xx /* No 8xx specific .c file to put that in ... */
>  void setup_initial_memory_limit(phys_addr_t first_memblock_base,
>  				phys_addr_t first_memblock_size)
> diff --git a/arch/powerpc/mm/init_64.c b/arch/powerpc/mm/init_64.c
> index 6374b21..7591a97 100644
> --- a/arch/powerpc/mm/init_64.c
> +++ b/arch/powerpc/mm/init_64.c
> @@ -99,19 +99,6 @@ void free_initmem(void)
>  		((unsigned long)__init_end - (unsigned long)__init_begin) >> 10);
>  }
>  
> -#ifdef CONFIG_BLK_DEV_INITRD
> -void free_initrd_mem(unsigned long start, unsigned long end)
> -{
> -	if (start < end)
> -		printk ("Freeing initrd memory: %ldk freed\n", (end - start) >> 10);
> -	for (; start < end; start += PAGE_SIZE) {
> -		ClearPageReserved(virt_to_page(start));
> -		init_page_count(virt_to_page(start));
> -		free_page(start);
> -		totalram_pages++;
> -	}
> -}
> -#endif
>  
>  static void pgd_ctor(void *addr)
>  {
> diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
> index 57e545b..f60e44e 100644
> --- a/arch/powerpc/mm/mem.c
> +++ b/arch/powerpc/mm/mem.c
> @@ -160,6 +160,25 @@ walk_system_ram_range(unsigned long start_pfn, unsigned long nr_pages,
>  }
>  EXPORT_SYMBOL_GPL(walk_system_ram_range);
>  
> +#ifdef CONFIG_BLK_DEV_INITRD
> +void free_initrd_mem(unsigned long start, unsigned long end)
> +{
> +	if (start >= end)
> +		return;
> +
> +	start = _ALIGN_DOWN(start, PAGE_SIZE);
> +	end = _ALIGN_UP(end, PAGE_SIZE);
> +	printk(KERN_INFO "Freeing initrd memory: %ldk freed\n",
> +			(end - start) >> 10);

If you use pr_info then the above again fits on one line. 
(this is what triggered my formatting and whitespace review).

Although I would then add a blank line before the loop for readability.

> +	for (; start < end; start += PAGE_SIZE) {
> +		ClearPageReserved(virt_to_page(start));
> +		init_page_count(virt_to_page(start));
> +		free_page(start);
> +		totalram_pages++;
> +	}
> +}
> +#endif
> +

Nit: Looking at the whole file I would put this after mem_init
because that puts it next to the other code that sets page counts,
clears PageReerved, and hands pages to page_alloc.


>  /*
>   * Initialize the bootmem system and give it all the memory we
>   * have available.  If we are using highmem, we only put the
> -- 
> 1.7.4
> 

milton