[PATCH] ttm_get_pages() will OOPS with highmem allocation

[Thomas Hellstrom]

On 11/13/2012 07:31 PM, Jonathan Morton wrote:
> Reposting from this kernel bug:
> https://bugzilla.kernel.org/show_bug.cgi?id=50241
>
> I've tested the patch and it solves a highly repeatable OOPS with the
> CedarView driver that I'm porting.
>
>
> >From 3552913d3a1c2d3c4ce158e91dc18cd12b522cb2 Mon Sep 17 00:00:00 2001
> From: Yakui Zhao <yakui.zhao at intel.com>
> Date: Tue, 7 Feb 2012 15:33:13 -0500
> Subject: [PATCH] Clear the ttm page allocated from high memory zone correctly
>
> The TTM page can be allocated from high memory. In such case it is
> wrong to use the page_address(page) as the virtual address for the high memory
> page.
>
> Signed-off-by: Zhao Yakui <yakui.zhao at intel.com>
> ---
>   drivers/gpu/drm/ttm/ttm_page_alloc.c |    5 ++++-
>   1 files changed, 4 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_page_alloc.c b/drivers/gpu/drm/ttm/ttm_page_alloc.c
> index d948575..df976d9 100644
> --- a/drivers/gpu/drm/ttm/ttm_page_alloc.c
> +++ b/drivers/gpu/drm/ttm/ttm_page_alloc.c
> @@ -708,7 +708,10 @@ int ttm_get_pages(struct list_head *pages, int flags,
>   	/* clear the pages coming from the pool if requested */
>   	if (flags & TTM_PAGE_FLAG_ZERO_ALLOC) {
>   		list_for_each_entry(p, pages, lru) {
> -			clear_page(page_address(p));
> +			if (PageHighMem(p))
> +				clear_highpage(p);
> +			else
> +				clear_page(page_address(p));
>   		}
>   	}
>   

This is a pretty bad bug. I think the only reason it hasn't been hit 
more often is that TTM_PAGE_FLAG_ZERO_ALLOC may not be used that often.
Please resend this patch with

Cc: stable at vger.kernel.org
Reviewed-by: Thomas Hellstrom <thellstrom at vmware.com>

Thanks,
Thomas