Re: [PATCH 1/2] kexec: remove unnecessary unusable_pages

[ebiederm@xmission.com (Eric W. Biederman)]

zhongjiang <zhongjiang@huawei.com> writes:

> From: zhong jiang <zhongjiang@huawei.com>
>
> In general, kexec alloc pages from buddy system, it cannot exceed
> the physical address in the system.
>
> The patch just remove this unnecessary code, no functional change.

On 32bit systems with highmem support kexec can very easily receive a
page from the buddy allocator that can exceed 4GiB.  This doesn't show
up on 64bit systems as typically the memory limits are less than the
address space.  But this code is very necessary on some systems and
removing it is not ok.

Nacked-by: "Eric W. Biederman" <ebiederm@xmission.com>


>
> Signed-off-by: zhong jiang <zhongjiang@huawei.com>
> ---
>  include/linux/kexec.h |  1 -
>  kernel/kexec_core.c   | 13 -------------
>  2 files changed, 14 deletions(-)
>
> diff --git a/include/linux/kexec.h b/include/linux/kexec.h
> index e8acb2b..26e4917 100644
> --- a/include/linux/kexec.h
> +++ b/include/linux/kexec.h
> @@ -162,7 +162,6 @@ struct kimage {
>  
>  	struct list_head control_pages;
>  	struct list_head dest_pages;
> -	struct list_head unusable_pages;
>  
>  	/* Address of next control page to allocate for crash kernels. */
>  	unsigned long control_page;
> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> index 56b3ed0..448127d 100644
> --- a/kernel/kexec_core.c
> +++ b/kernel/kexec_core.c
> @@ -257,9 +257,6 @@ struct kimage *do_kimage_alloc_init(void)
>  	/* Initialize the list of destination pages */
>  	INIT_LIST_HEAD(&image->dest_pages);
>  
> -	/* Initialize the list of unusable pages */
> -	INIT_LIST_HEAD(&image->unusable_pages);
> -
>  	return image;
>  }
>  
> @@ -517,10 +514,6 @@ static void kimage_free_extra_pages(struct kimage *image)
>  {
>  	/* Walk through and free any extra destination pages I may have */
>  	kimage_free_page_list(&image->dest_pages);
> -
> -	/* Walk through and free any unusable pages I have cached */
> -	kimage_free_page_list(&image->unusable_pages);
> -
>  }
>  void kimage_terminate(struct kimage *image)
>  {
> @@ -647,12 +640,6 @@ static struct page *kimage_alloc_page(struct kimage *image,
>  		page = kimage_alloc_pages(gfp_mask, 0);
>  		if (!page)
>  			return NULL;
> -		/* If the page cannot be used file it away */
> -		if (page_to_pfn(page) >
> -				(KEXEC_SOURCE_MEMORY_LIMIT >> PAGE_SHIFT)) {
> -			list_add(&page->lru, &image->unusable_pages);
> -			continue;
> -		}
>  		addr = page_to_pfn(page) << PAGE_SHIFT;
>  
>  		/* If it is the destination page we want use it */

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