HWPOISON: Add unpoisoning support

[net-next-2.6.git] / mm / memory-failure.c

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 5055b940df5f170f21b52ad7bb209d623722a081..ed6e91c87a5475a392d8d406b5d979a7a9b29654 100644 (file)
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -838,6 +838,16 @@ int __memory_failure(unsigned long pfn, int trapno, int flags)
         * and in many cases impossible, so we just avoid it here.
         */
        lock_page_nosync(p);
+
+       /*
+        * unpoison always clear PG_hwpoison inside page lock
+        */
+       if (!PageHWPoison(p)) {
+               action_result(pfn, "unpoisoned", IGNORED);
+               res = 0;
+               goto out;
+       }
+
        wait_on_page_writeback(p);
 
        /*
@@ -893,3 +903,61 @@ void memory_failure(unsigned long pfn, int trapno)
 {
        __memory_failure(pfn, trapno, 0);
 }
+
+/**
+ * unpoison_memory - Unpoison a previously poisoned page
+ * @pfn: Page number of the to be unpoisoned page
+ *
+ * Software-unpoison a page that has been poisoned by
+ * memory_failure() earlier.
+ *
+ * This is only done on the software-level, so it only works
+ * for linux injected failures, not real hardware failures
+ *
+ * Returns 0 for success, otherwise -errno.
+ */
+int unpoison_memory(unsigned long pfn)
+{
+       struct page *page;
+       struct page *p;
+       int freeit = 0;
+
+       if (!pfn_valid(pfn))
+               return -ENXIO;
+
+       p = pfn_to_page(pfn);
+       page = compound_head(p);
+
+       if (!PageHWPoison(p)) {
+               pr_debug("MCE: Page was already unpoisoned %#lx\n", pfn);
+               return 0;
+       }
+
+       if (!get_page_unless_zero(page)) {
+               if (TestClearPageHWPoison(p))
+                       atomic_long_dec(&mce_bad_pages);
+               pr_debug("MCE: Software-unpoisoned free page %#lx\n", pfn);
+               return 0;
+       }
+
+       lock_page_nosync(page);
+       /*
+        * This test is racy because PG_hwpoison is set outside of page lock.
+        * That's acceptable because that won't trigger kernel panic. Instead,
+        * the PG_hwpoison page will be caught and isolated on the entrance to
+        * the free buddy page pool.
+        */
+       if (TestClearPageHWPoison(p)) {
+               pr_debug("MCE: Software-unpoisoned page %#lx\n", pfn);
+               atomic_long_dec(&mce_bad_pages);
+               freeit = 1;
+       }
+       unlock_page(page);
+
+       put_page(page);
+       if (freeit)
+               put_page(page);
+
+       return 0;
+}
+EXPORT_SYMBOL(unpoison_memory);