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Subject[PATCH] [11/16] HWPOISON: check and isolate corrupted free pages v2
Date

From: Wu Fengguang <fengguang.wu@intel.com>

If memory corruption hits the free buddy pages, we can safely ignore them.
No one will access them until page allocation time, then prep_new_page()
will automatically check and isolate PG_hwpoison page for us (for 0-order
allocation).

This patch expands prep_new_page() to check every component page in a high
order page allocation, in order to completely stop PG_hwpoison pages from
being recirculated.

Note that the common case -- only allocating a single page, doesn't
do any more work than before. Allocating > order 0 does a bit more work,
but that's relatively uncommon.
This simple implementation may drop some innocent neighbor pages, hopefully
it is not a big problem because the event should be rare enough.

This patch adds some runtime costs to high order page users.

[AK: Improved description]

v2: Andi Kleen:
Port to -mm code
Move check into separate function.
Don't dump stack in bad_pages for hwpoisoned pages.
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>

---
mm/page_alloc.c | 20 +++++++++++++++++++-
1 file changed, 19 insertions(+), 1 deletion(-)
Index: linux/mm/page_alloc.c
===================================================================
--- linux.orig/mm/page_alloc.c 2009-06-03 19:37:39.000000000 +0200
+++ linux/mm/page_alloc.c 2009-06-03 20:13:43.000000000 +0200
@@ -237,6 +237,12 @@
static unsigned long nr_shown;
static unsigned long nr_unshown;

+ /* Don't complain about poisoned pages */
+ if (PageHWPoison(page)) {
+ __ClearPageBuddy(page);
+ return;
+ }
+
/*
* Allow a burst of 60 reports, then keep quiet for that minute;
* or allow a steady drip of one report per second.
@@ -650,7 +656,7 @@
/*
* This page is about to be returned from the page allocator
*/
-static int prep_new_page(struct page *page, int order, gfp_t gfp_flags)
+static inline int check_new_page(struct page *page)
{
if (unlikely(page_mapcount(page) |
(page->mapping != NULL) |
@@ -659,6 +665,18 @@
bad_page(page);
return 1;
}
+ return 0;
+}
+
+static int prep_new_page(struct page *page, int order, gfp_t gfp_flags)
+{
+ int i;
+
+ for (i = 0; i < (1 << order); i++) {
+ struct page *p = page + i;
+ if (unlikely(check_new_page(p)))
+ return 1;
+ }

set_page_private(page, 0);
set_page_refcounted(page);

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