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Subject[PATCH] [6/31] HWPOISON: avoid grabbing the page count multiple times during madvise injection
Date

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

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().

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>

---
mm/madvise.c | 1 -
mm/memory-failure.c | 8 ++++----
2 files changed, 4 insertions(+), 5 deletions(-)
Index: linux/mm/madvise.c
===================================================================
--- linux.orig/mm/madvise.c
+++ linux/mm/madvise.c
@@ -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;
}
Index: linux/mm/memory-failure.c
===================================================================
--- linux.orig/mm/memory-failure.c
+++ linux/mm/memory-failure.c
@@ -629,7 +629,7 @@ 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;
@@ -637,7 +637,7 @@ 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",
@@ -775,7 +775,7 @@ 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;
}
@@ -823,7 +823,7 @@ 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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