Re: [PATCH 02/24] x86: Make sure free_init_pages() free pages in boundary

[Johannes Weiner <hannes@cmpxchg.org>]

On Fri, Mar 26, 2010 at 03:21:32PM -0700, Yinghai Lu wrote:
> diff --git a/arch/x86/kernel/head32.c b/arch/x86/kernel/head32.c
> index adedeef..fe3d953 100644
> --- a/arch/x86/kernel/head32.c
> +++ b/arch/x86/kernel/head32.c
> @@ -47,6 +47,7 @@ void __init i386_start_kernel(void)
>  		u64 ramdisk_image = boot_params.hdr.ramdisk_image;
>  		u64 ramdisk_size  = boot_params.hdr.ramdisk_size;
>  		u64 ramdisk_end   = ramdisk_image + ramdisk_size;
> +		ramdisk_end = PFN_UP(ramdisk_end) << PAGE_SHIFT;

Why not PAGE_ALIGN()?

>  		reserve_early(ramdisk_image, ramdisk_end, "RAMDISK");
>  	}
>  #endif
> diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
> index b5a9896..fafba92 100644
> --- a/arch/x86/kernel/head64.c
> +++ b/arch/x86/kernel/head64.c
> @@ -106,6 +106,7 @@ void __init x86_64_start_reservations(char *real_mode_data)
>  		unsigned long ramdisk_image = boot_params.hdr.ramdisk_image;
>  		unsigned long ramdisk_size  = boot_params.hdr.ramdisk_size;
>  		unsigned long ramdisk_end   = ramdisk_image + ramdisk_size;
> +		ramdisk_end = PFN_UP(ramdisk_end) << PAGE_SHIFT;

Dito

>  		reserve_early(ramdisk_image, ramdisk_end, "RAMDISK");
>  	}
>  #endif
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index 5d7ba1a..2a1b9d4 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -317,57 +317,61 @@ static void __init relocate_initrd(void)
>  
>  	u64 ramdisk_image = boot_params.hdr.ramdisk_image;
>  	u64 ramdisk_size  = boot_params.hdr.ramdisk_size;
> +	u64 ramdisk_end   = ramdisk_image + ramdisk_size;
>  	u64 end_of_lowmem = max_low_pfn_mapped << PAGE_SHIFT;
> +	u64 image, size_aligned;
>  	u64 ramdisk_here;
>  	unsigned long slop, clen, mapaddr;
>  	char *p, *q;
>  
> +	ramdisk_end = PFN_UP(ramdisk_end) << PAGE_SHIFT;

Dito

> +	size_aligned = ramdisk_end - ramdisk_image;
> +
>  	/* We need to move the initrd down into lowmem */
> -	ramdisk_here = find_e820_area(0, end_of_lowmem, ramdisk_size,
> +	ramdisk_here = find_e820_area(0, end_of_lowmem, size_aligned,
>  					 PAGE_SIZE);
>  
>  	if (ramdisk_here == -1ULL)
>  		panic("Cannot find place for new RAMDISK of size %lld\n",
> -			 ramdisk_size);
> +			 size_aligned);
>  
>  	/* Note: this includes all the lowmem currently occupied by
>  	   the initrd, we rely on that fact to keep the data intact. */
> -	reserve_early(ramdisk_here, ramdisk_here + ramdisk_size,
> +	reserve_early(ramdisk_here, ramdisk_here + size_aligned,
>  			 "NEW RAMDISK");
>  	initrd_start = ramdisk_here + PAGE_OFFSET;
>  	initrd_end   = initrd_start + ramdisk_size;
>  	printk(KERN_INFO "Allocated new RAMDISK: %08llx - %08llx\n",
> -			 ramdisk_here, ramdisk_here + ramdisk_size);
> +			 ramdisk_here, ramdisk_here + size_aligned);
>  
>  	q = (char *)initrd_start;
>  
>  	/* Copy any lowmem portion of the initrd */
> -	if (ramdisk_image < end_of_lowmem) {
> -		clen = end_of_lowmem - ramdisk_image;
> -		p = (char *)__va(ramdisk_image);
> +	image = ramdisk_image;
> +	if (image < end_of_lowmem) {
> +		clen = end_of_lowmem - image;
> +		p = (char *)__va(image);
>  		memcpy(q, p, clen);
>  		q += clen;
> -		ramdisk_image += clen;
> -		ramdisk_size  -= clen;
> +		image += clen;
> +		size_aligned  -= clen;
>  	}
>  
>  	/* Copy the highmem portion of the initrd */
> -	while (ramdisk_size) {
> -		slop = ramdisk_image & ~PAGE_MASK;
> -		clen = ramdisk_size;
> +	while (size_aligned) {
> +		slop = image & ~PAGE_MASK;
> +		clen = size_aligned;
>  		if (clen > MAX_MAP_CHUNK-slop)
>  			clen = MAX_MAP_CHUNK-slop;
> -		mapaddr = ramdisk_image & PAGE_MASK;
> +		mapaddr = image & PAGE_MASK;
>  		p = early_memremap(mapaddr, clen+slop);
>  		memcpy(q, p+slop, clen);
>  		early_iounmap(p, clen+slop);
>  		q += clen;
> -		ramdisk_image += clen;
> -		ramdisk_size  -= clen;
> +		image += clen;
> +		size_aligned  -= clen;

Those appear to be a lot of spurious changes.  We don't need to
copy the alignment padding as well, so it only matters that the
arguments to find_e820_area() and reserve_early() are aligned, no?

>  	}
>  	/* high pages is not converted by early_res_to_bootmem */
> -	ramdisk_image = boot_params.hdr.ramdisk_image;
> -	ramdisk_size  = boot_params.hdr.ramdisk_size;
>  	printk(KERN_INFO "Move RAMDISK from %016llx - %016llx to"
>  		" %08llx - %08llx\n",
>  		ramdisk_image, ramdisk_image + ramdisk_size - 1,
> @@ -385,6 +389,8 @@ static void __init reserve_initrd(void)
>  	    !ramdisk_image || !ramdisk_size)
>  		return;		/* No initrd provided by bootloader */
>  
> +	ramdisk_end = PFN_UP(ramdisk_end) << PAGE_SHIFT;

Dito

> diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
> index e71c5cb..727d6b0 100644
> --- a/arch/x86/mm/init.c
> +++ b/arch/x86/mm/init.c
> @@ -332,6 +332,16 @@ int devmem_is_allowed(unsigned long pagenr)
>  void free_init_pages(char *what, unsigned long begin, unsigned long end)
>  {
>  	unsigned long addr = begin;
> +	unsigned long addr_aligned, end_aligned;
> +
> +	/* Make sure boundaries are page aligned */
> +	addr_aligned = PFN_UP(addr) << PAGE_SHIFT;
> +	end_aligned = PFN_DOWN(end) << PAGE_SHIFT;
> +
> +	if (WARN(addr_aligned != addr || end_aligned != end, "free_init_pages: range [%#lx, %#lx] is not aligned\n", addr, end)) {
> +		addr = addr_aligned;
> +		end = end_aligned;
> +	}

Maybe realign only for when it is not aligned?  So to keep the fixup
out of line.

I suppose WARN_ON() is enough as it will print a stack trace which
should be enough clue of what went wrong.

>  	if (addr >= end)
>  		return;
> @@ -376,6 +386,18 @@ void free_initmem(void)
>  #ifdef CONFIG_BLK_DEV_INITRD
>  void free_initrd_mem(unsigned long start, unsigned long end)
>  {
> -	free_init_pages("initrd memory", start, end);
> +	unsigned long end_aligned;
> +
> +	/*
> +	 * end could be not aligned, and We can not align that,
> +	 * decompresser could be confused by aligned initrd_end
> +	 * We already reserve the end partial page before in
> +	 *   - i386_start_kernel()
> +	 *   - x86_64_start_kernel()
> +	 *   - relocate_initrd()
> +	 * So here we can do PFN_UP() safely to get partial page to be freed
> +	 */
> +	end_aligned = PFN_UP(end) << PAGE_SHIFT;

PAGE_ALIGN()

> +	free_init_pages("initrd memory", start, end_aligned);
>  }
>  #endif