HWPOISON: avoid grabbing the page count multiple times during madvise injection

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>

2 files changed, 4 insertions, 5 deletions

diff --git a/mm/madvise.c b/mm/madvise.c
index 35b1479b7c9d..18970aec0d2f 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -238,7 +238,6 @@ static int madvise_hwpoison(unsigned long start, unsigned long end)
                        page_to_pfn(p), start);
                 /* Ignore return value for now */
                 __memory_failure(page_to_pfn(p), 0, 1);
-                put_page(p);
         }
         return ret;
 }
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 275f4e2df8ac..4253e14fa709 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -627,7 +627,7 @@ static void action_result(unsigned long pfn, char *msg, int result)
 }
 
 static int page_action(struct page_state *ps, struct page *p,
-                        unsigned long pfn, int ref)
+                        unsigned long pfn)
 {
         int result;
         int count;
@@ -635,7 +635,7 @@ static int page_action(struct page_state *ps, struct page *p,
         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",
@@ -773,7 +773,7 @@ int __memory_failure(unsigned long pfn, int trapno, int ref)
          * 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;
         }
@@ -821,7 +821,7 @@ int __memory_failure(unsigned long pfn, int trapno, int ref)
         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;
                 }
         }