Re: [PATCH] ttm_get_pages() will OOPS with highmem allocation

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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@xxxxxxxxx>
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@xxxxxxxxx>
---
  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@xxxxxxxxxxxxxxx
Reviewed-by: Thomas Hellstrom <thellstrom@xxxxxxxxxx>

Thanks,
Thomas


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