linux-kernel - Re: [Resend][Patch v2] kexec: increase max of kexec segments and use dynamic allocation

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Date:	Fri, 13 Aug 2010 03:52:14 -0400
From:	Simon Horman <horms@...ge.net.au>
To:	Amerigo Wang <amwang@...hat.com>
Cc:	linux-kernel@...r.kernel.org, nhorman@...hat.com,
	kexec@...ts.infradead.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>, akpm@...ux-foundation.org,
	Vivek Goyal <vgoyal@...hat.com>,
	huang ying <huang.ying.caritas@...il.com>,
	ebiederm@...ssion.com
Subject: Re: [Resend][Patch v2] kexec: increase max of kexec segments and
 use dynamic allocation

On Fri, Aug 13, 2010 at 01:38:54AM -0400, Amerigo Wang wrote:
> 
> Currently KEXEC_SEGMENT_MAX is only 16 which is too small for machine with
> many memory ranges.  When hibernate on a machine with disjoint memory we do
> need one segment for each memory region. Increase this hard limit to 16K
> which is reasonably large.
> 
> And change ->segment from a static array to a dynamically allocated memory.

FWIW, this looks good to me.

Reviewed-by: Simon Horman <horms@...ge.net.au>

> 
> Cc: Neil Horman <nhorman@...hat.com>
> Cc: Vivek Goyal <vgoyal@...hat.com>
> Cc: huang ying <huang.ying.caritas@...il.com>
> Cc: Eric W. Biederman <ebiederm@...ssion.com>
> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> Cc: Paul Mackerras <paulus@...ba.org>
> Signed-off-by: WANG Cong <amwang@...hat.com>
> 
> ---
> 
> diff --git a/arch/powerpc/kernel/machine_kexec_64.c b/arch/powerpc/kernel/machine_kexec_64.c
> index 583af70..93f0542 100644
> --- a/arch/powerpc/kernel/machine_kexec_64.c
> +++ b/arch/powerpc/kernel/machine_kexec_64.c
> @@ -134,10 +134,7 @@ static void copy_segments(unsigned long ind)
>  void kexec_copy_flush(struct kimage *image)
>  {
>  	long i, nr_segments = image->nr_segments;
> -	struct  kexec_segment ranges[KEXEC_SEGMENT_MAX];
> -
> -	/* save the ranges on the stack to efficiently flush the icache */
> -	memcpy(ranges, image->segment, sizeof(ranges));
> +	struct  kexec_segment range;
>  
>  	/*
>  	 * After this call we may not use anything allocated in dynamic
> @@ -151,9 +148,11 @@ void kexec_copy_flush(struct kimage *image)
>  	 * we need to clear the icache for all dest pages sometime,
>  	 * including ones that were in place on the original copy
>  	 */
> -	for (i = 0; i < nr_segments; i++)
> -		flush_icache_range((unsigned long)__va(ranges[i].mem),
> -			(unsigned long)__va(ranges[i].mem + ranges[i].memsz));
> +	for (i = 0; i < nr_segments; i++) {
> +		memcpy(&range, &image->segment[i], sizeof(range));
> +		flush_icache_range((unsigned long)__va(range.mem),
> +			(unsigned long)__va(range.mem + range.memsz));
> +	}
>  }
>  
>  #ifdef CONFIG_SMP
> diff --git a/include/linux/kexec.h b/include/linux/kexec.h
> index 03e8e8d..ec783c1 100644
> --- a/include/linux/kexec.h
> +++ b/include/linux/kexec.h
> @@ -57,7 +57,7 @@ typedef unsigned long kimage_entry_t;
>  #define IND_DONE         0x4
>  #define IND_SOURCE       0x8
>  
> -#define KEXEC_SEGMENT_MAX 16
> +#define KEXEC_SEGMENT_MAX (1024*16)
>  struct kexec_segment {
>  	void __user *buf;
>  	size_t bufsz;
> @@ -86,7 +86,7 @@ struct kimage {
>  	struct page *swap_page;
>  
>  	unsigned long nr_segments;
> -	struct kexec_segment segment[KEXEC_SEGMENT_MAX];
> +	struct kexec_segment *segment;
>  
>  	struct list_head control_pages;
>  	struct list_head dest_pages;
> diff --git a/kernel/kexec.c b/kernel/kexec.c
> index c0613f7..22ff794 100644
> --- a/kernel/kexec.c
> +++ b/kernel/kexec.c
> @@ -131,6 +131,11 @@ static int do_kimage_alloc(struct kimage **rimage, unsigned long entry,
>  	if (!image)
>  		goto out;
>  
> +	image->segment = kzalloc(nr_segments * sizeof(struct kexec_segment),
> +				 GFP_KERNEL);
> +	if (!image->segment)
> +		goto out;
> +
>  	image->head = 0;
>  	image->entry = &image->head;
>  	image->last_entry = &image->head;
> @@ -218,8 +223,10 @@ static int do_kimage_alloc(struct kimage **rimage, unsigned long entry,
>  out:
>  	if (result == 0)
>  		*rimage = image;
> -	else
> +	else if (image) {
> +		kfree(image->segment);
>  		kfree(image);
> +	}
>  
>  	return result;
>  
> @@ -263,8 +270,10 @@ static int kimage_normal_alloc(struct kimage **rimage, unsigned long entry,
>   out:
>  	if (result == 0)
>  		*rimage = image;
> -	else
> +	else if (image) {
> +		kfree(image->segment);
>  		kfree(image);
> +	}
>  
>  	return result;
>  }
> @@ -332,8 +341,10 @@ static int kimage_crash_alloc(struct kimage **rimage, unsigned long entry,
>  out:
>  	if (result == 0)
>  		*rimage = image;
> -	else
> +	else if (image) {
> +		kfree(image->segment);
>  		kfree(image);
> +	}
>  
>  	return result;
>  }
> @@ -658,6 +669,7 @@ static void kimage_free(struct kimage *image)
>  
>  	/* Free the kexec control pages... */
>  	kimage_free_page_list(&image->control_pages);
> +	kfree(image->segment);
>  	kfree(image);
>  }
>  
> --
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