[PATCH] xen: fix scrub_page()

[Jeremy Fitzhardinge]

Impact: fix guest kernel crash with CONFIG_XEN_SCRUB_PAGES=y

Jens noticed that scrub_page() has a buggy unmap of the wrong
thing. (virtual address instead of page)

Linus pointed out that the whole scrub_page() code is an unnecessary
reimplementation of clear_highpage() to begin with.

Just use clear_highpage() rather than reimplementing it poorly.

Reported-by: Jens Axboe <jens.axboe@xxxxxxxxxx>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
 drivers/xen/balloon.c |    9 +--------
 1 files changed, 1 insertions(+), 8 deletions(-)

diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index a0fb5ea..526c191 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -122,14 +122,7 @@ static struct timer_list balloon_timer;
 static void scrub_page(struct page *page)
 {
 #ifdef CONFIG_XEN_SCRUB_PAGES
-	if (PageHighMem(page)) {
-		void *v = kmap(page);
-		clear_page(v);
-		kunmap(v);
-	} else {
-		void *v = page_address(page);
-		clear_page(v);
-	}
+	clear_highpage(page);
 #endif
 }
 

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