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Subject[PATCH 05/24] HWPOISON: avoid grabbing page for two times
If page is double referenced in madvise_hwpoison() and __memory_failure(),
remove_mapping() will fail because it expects page_count=2. Fix it by
not grabbing extra page count in __memory_failure().

CC: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
mm/madvise.c | 1 -
mm/memory-failure.c | 8 ++++----
2 files changed, 4 insertions(+), 5 deletions(-)
--- linux-mm.orig/mm/madvise.c 2009-11-02 11:12:02.000000000 +0800
+++ linux-mm/mm/madvise.c 2009-11-02 12:31:52.000000000 +0800
@@ -238,7 +238,6 @@ static int madvise_hwpoison(unsigned lon
page_to_pfn(p), start);
/* Ignore return value for now */
__memory_failure(page_to_pfn(p), 0, 1);
- put_page(p);
}
return ret;
}
--- linux-mm.orig/mm/memory-failure.c 2009-11-02 12:31:49.000000000 +0800
+++ linux-mm/mm/memory-failure.c 2009-11-02 13:53:41.000000000 +0800
@@ -607,7 +607,7 @@ static void action_result(unsigned long
}

static int page_action(struct page_state *ps, struct page *p,
- unsigned long pfn, int ref)
+ unsigned long pfn)
{
int result;
int count;
@@ -615,7 +615,7 @@ static int page_action(struct page_state
result = ps->action(p, pfn);
action_result(pfn, ps->msg, result);

- count = page_count(p) - 1 - ref;
+ count = page_count(p) - 1;
if (count != 0)
printk(KERN_ERR
"MCE %#lx: %s page still referenced by %d users\n",
@@ -753,7 +753,7 @@ int __memory_failure(unsigned long pfn,
* In fact it's dangerous to directly bump up page count from 0,
* that may make page_freeze_refs()/page_unfreeze_refs() mismatch.
*/
- if (!get_page_unless_zero(compound_head(p))) {
+ if (!ref && !get_page_unless_zero(compound_head(p))) {
action_result(pfn, "free or high order kernel", IGNORED);
return PageBuddy(compound_head(p)) ? 0 : -EBUSY;
}
@@ -801,7 +801,7 @@ int __memory_failure(unsigned long pfn,
res = -EBUSY;
for (ps = error_states;; ps++) {
if (((p->flags | lru_flag)& ps->mask) == ps->res) {
- res = page_action(ps, p, pfn, ref);
+ res = page_action(ps, p, pfn);
break;
}
}



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