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

From: Milton Miller <[email-masked]>
Date: Thu, 26 May 2011 06:18:46 -0500

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 <[email-masked]>
> Cc: Benjamin Herrenschmidt <[email-masked]>
> 
> ---
>  * 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