HWPOISON: abort on failed unmap

Don't try to isolate a still mapped page. Otherwise we will hit the
BUG_ON(page_mapped(page)) in __remove_from_page_cache().

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

1 files changed, 15 insertions, 5 deletions

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 3338c443272c..b62287db87af 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -655,7 +655,7 @@ static int page_action(struct page_state *ps, struct page *p,
  * Do all that is necessary to remove user space mappings. Unmap
  * the pages and send SIGBUS to the processes if the data was dirty.
  */
-static void hwpoison_user_mappings(struct page *p, unsigned long pfn,
+static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
                                   int trapno)
 {
         enum ttu_flags ttu = TTU_UNMAP | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
@@ -665,15 +665,18 @@ static void hwpoison_user_mappings(struct page *p, unsigned long pfn,
         int i;
         int kill = 1;
 
-        if (PageReserved(p) || PageCompound(p) || PageSlab(p) || PageKsm(p))
-                return;
+        if (PageReserved(p) || PageSlab(p))
+                return SWAP_SUCCESS;
 
         /*
          * This check implies we don't kill processes if their pages
          * are in the swap cache early. Those are always late kills.
          */
         if (!page_mapped(p))
-                return;
+                return SWAP_SUCCESS;
+
+        if (PageCompound(p) || PageKsm(p))
+                return SWAP_FAIL;
 
         if (PageSwapCache(p)) {
                 printk(KERN_ERR
@@ -735,6 +738,8 @@ static void hwpoison_user_mappings(struct page *p, unsigned long pfn,
          */
         kill_procs_ao(&tokill, !!PageDirty(p), trapno,
                       ret != SWAP_SUCCESS, pfn);
+
+        return ret;
 }
 
 int __memory_failure(unsigned long pfn, int trapno, int flags)
@@ -807,8 +812,13 @@ int __memory_failure(unsigned long pfn, int trapno, int flags)
 
         /*
          * Now take care of user space mappings.
+         * Abort on fail: __remove_from_page_cache() assumes unmapped page.
          */
-        hwpoison_user_mappings(p, pfn, trapno);
+        if (hwpoison_user_mappings(p, pfn, trapno) != SWAP_SUCCESS) {
+                printk(KERN_ERR "MCE %#lx: cannot unmap page, give up\n", pfn);
+                res = -EBUSY;
+                goto out;
+        }
 
         /*
          * Torn down by someone else?