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Subject[PATCH 19/22] HWPOISON: detect free buddy pages explicitly
The free pages in the buddy system may well have no PG_buddy set.
Introduce is_free_buddy_page() for detecting them reliably.

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
mm/internal.h | 3 +++
mm/memory-failure.c | 24 +++++++++---------------
mm/page_alloc.c | 16 ++++++++++++++++
3 files changed, 28 insertions(+), 15 deletions(-)

--- sound-2.6.orig/mm/memory-failure.c
+++ sound-2.6/mm/memory-failure.c
@@ -324,15 +324,15 @@ struct hwpoison_control {
* Do nothing, try to be lucky and not touch this instead. For a few cases we
* could be more sophisticated.
*/
-static int me_kernel(struct hwpoison_control *hpc)
+static int me_slab(struct hwpoison_control *hpc)
{
return DELAYED;
}

/*
- * Already poisoned page.
+ * Reserved kernel page.
*/
-static int me_ignore(struct hwpoison_control *hpc)
+static int me_reserved(struct hwpoison_control *hpc)
{
return IGNORED;
}
@@ -347,14 +347,6 @@ static int me_unknown(struct hwpoison_co
}

/*
- * Free memory
- */
-static int me_free(struct hwpoison_control *hpc)
-{
- return DELAYED;
-}
-
-/*
* Clean (or cleaned) page cache page.
*/
static int me_pagecache_clean(struct hwpoison_control *hpc)
@@ -539,15 +531,14 @@ static struct page_state {
char *msg;
int (*action)(struct hwpoison_control *hpc);
} error_states[] = {
- { reserved, reserved, "reserved kernel", me_ignore },
- { buddy, buddy, "free kernel", me_free },
+ { reserved, reserved, "reserved kernel", me_reserved },

/*
* Could in theory check if slab page is free or if we can drop
* currently unused objects without touching them. But just
* treat it as standard kernel for now.
*/
- { slab, slab, "kernel slab", me_kernel },
+ { slab, slab, "kernel slab", me_slab },

#ifdef CONFIG_PAGEFLAGS_EXTENDED
{ head, head, "huge", me_huge_page },
@@ -756,7 +747,10 @@ void memory_failure(unsigned long pfn, i
* that may make page_freeze_refs()/page_unfreeze_refs() mismatch.
*/
if (!get_page_unless_zero(p)) {
- action_result(&hpc, "free or high order kernel", IGNORED);
+ if (is_free_buddy_page(p))
+ action_result(&hpc, "free buddy", DELAYED);
+ else
+ action_result(&hpc, "high order kernel", IGNORED);
return;
}

--- sound-2.6.orig/mm/internal.h
+++ sound-2.6/mm/internal.h
@@ -49,6 +49,9 @@ extern void putback_lru_page(struct page
extern unsigned long highest_memmap_pfn;
extern void __free_pages_bootmem(struct page *page, unsigned int order);
extern void prep_compound_page(struct page *page, unsigned long order);
+#ifdef CONFIG_MEMORY_FAILURE
+extern bool is_free_buddy_page(struct page *page);
+#endif


/*
--- sound-2.6.orig/mm/page_alloc.c
+++ sound-2.6/mm/page_alloc.c
@@ -4966,3 +4966,19 @@ __offline_isolated_pages(unsigned long s
spin_unlock_irqrestore(&zone->lock, flags);
}
#endif
+
+#ifdef CONFIG_MEMORY_FAILURE
+bool is_free_buddy_page(struct page *page)
+{
+ int pfn = page_to_pfn(page);
+ int order;
+
+ for (order = 0; order < MAX_ORDER; order++) {
+ struct page *page_head = page - (pfn & ((1 << order) - 1));
+
+ if (PageBuddy(page_head) && page_order(page_head) >= order)
+ return true;
+ }
+ return false;
+}
+#endif
--



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