1 files changed, 90 insertions, 19 deletions

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 810328fe8adb..6a2b4b86b679 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1160,6 +1160,22 @@ static int page_action(struct page_state *ps, struct page *p,
 	return (result == MF_RECOVERED || result == MF_DELAYED) ? 0 : -EBUSY;
 }
 
+static inline bool PageHWPoisonTakenOff(struct page *page)
+{
+	return PageHWPoison(page) && page_private(page) == MAGIC_HWPOISON;
+}
+
+void SetPageHWPoisonTakenOff(struct page *page)
+{
+	set_page_private(page, MAGIC_HWPOISON);
+}
+
+void ClearPageHWPoisonTakenOff(struct page *page)
+{
+	if (PageHWPoison(page))
+		set_page_private(page, 0);
+}
+
 /*
  * Return true if a page type of a given page is supported by hwpoison
  * mechanism (while handling could fail), otherwise false.  This function
@@ -1262,6 +1278,27 @@ out:
 	return ret;
 }
 
+static int __get_unpoison_page(struct page *page)
+{
+	struct page *head = compound_head(page);
+	int ret = 0;
+	bool hugetlb = false;
+
+	ret = get_hwpoison_huge_page(head, &hugetlb);
+	if (hugetlb)
+		return ret;
+
+	/*
+	 * PageHWPoisonTakenOff pages are not only marked as PG_hwpoison,
+	 * but also isolated from buddy freelist, so need to identify the
+	 * state and have to cancel both operations to unpoison.
+	 */
+	if (PageHWPoisonTakenOff(page))
+		return -EHWPOISON;
+
+	return get_page_unless_zero(page) ? 1 : 0;
+}
+
 /**
  * get_hwpoison_page() - Get refcount for memory error handling
  * @p:		Raw error page (hit by memory error)
@@ -1278,18 +1315,26 @@ out:
  * extra care for the error page's state (as done in __get_hwpoison_page()),
  * and has some retry logic in get_any_page().
  *
+ * When called from unpoison_memory(), the caller should already ensure that
+ * the given page has PG_hwpoison. So it's never reused for other page
+ * allocations, and __get_unpoison_page() never races with them.
+ *
  * Return: 0 on failure,
  *         1 on success for in-use pages in a well-defined state,
  *         -EIO for pages on which we can not handle memory errors,
  *         -EBUSY when get_hwpoison_page() has raced with page lifecycle
- *         operations like allocation and free.
+ *         operations like allocation and free,
+ *         -EHWPOISON when the page is hwpoisoned and taken off from buddy.
  */
 static int get_hwpoison_page(struct page *p, unsigned long flags)
 {
 	int ret;
 
 	zone_pcp_disable(page_zone(p));
-	ret = get_any_page(p, flags);
+	if (flags & MF_UNPOISON)
+		ret = __get_unpoison_page(p);
+	else
+		ret = get_any_page(p, flags);
 	zone_pcp_enable(page_zone(p));
 
 	return ret;
@@ -1937,6 +1982,28 @@ core_initcall(memory_failure_init);
 		pr_info(fmt, pfn);			\
 })
 
+static inline int clear_page_hwpoison(struct ratelimit_state *rs, struct page *p)
+{
+	if (TestClearPageHWPoison(p)) {
+		unpoison_pr_info("Unpoison: Software-unpoisoned page %#lx\n",
+				 page_to_pfn(p), rs);
+		num_poisoned_pages_dec();
+		return 1;
+	}
+	return 0;
+}
+
+static inline int unpoison_taken_off_page(struct ratelimit_state *rs,
+					  struct page *p)
+{
+	if (put_page_back_buddy(p)) {
+		unpoison_pr_info("Unpoison: Software-unpoisoned page %#lx\n",
+				 page_to_pfn(p), rs);
+		return 0;
+	}
+	return -EBUSY;
+}
+
 /**
  * unpoison_memory - Unpoison a previously poisoned page
  * @pfn: Page number of the to be unpoisoned page
@@ -1953,9 +2020,7 @@ int unpoison_memory(unsigned long pfn)
 {
 	struct page *page;
 	struct page *p;
-	int freeit = 0;
-	int ret = 0;
-	unsigned long flags = 0;
+	int ret = -EBUSY;
 	static DEFINE_RATELIMIT_STATE(unpoison_rs, DEFAULT_RATELIMIT_INTERVAL,
 					DEFAULT_RATELIMIT_BURST);
 
@@ -1991,24 +2056,30 @@ int unpoison_memory(unsigned long pfn)
 		goto unlock_mutex;
 	}
 
-	if (!get_hwpoison_page(p, flags)) {
-		if (TestClearPageHWPoison(p))
-			num_poisoned_pages_dec();
-		unpoison_pr_info("Unpoison: Software-unpoisoned free page %#lx\n",
-				 pfn, &unpoison_rs);
+	if (PageSlab(page) || PageTable(page))
 		goto unlock_mutex;
-	}
 
-	if (TestClearPageHWPoison(page)) {
-		unpoison_pr_info("Unpoison: Software-unpoisoned page %#lx\n",
-				 pfn, &unpoison_rs);
-		num_poisoned_pages_dec();
-		freeit = 1;
-	}
+	ret = get_hwpoison_page(p, MF_UNPOISON);
+	if (!ret) {
+		if (clear_page_hwpoison(&unpoison_rs, page))
+			ret = 0;
+		else
+			ret = -EBUSY;
+	} else if (ret < 0) {
+		if (ret == -EHWPOISON) {
+			ret = unpoison_taken_off_page(&unpoison_rs, p);
+		} else
+			unpoison_pr_info("Unpoison: failed to grab page %#lx\n",
+					 pfn, &unpoison_rs);
+	} else {
+		int freeit = clear_page_hwpoison(&unpoison_rs, p);
 
-	put_page(page);
-	if (freeit && !(pfn == my_zero_pfn(0) && page_count(p) == 1))
 		put_page(page);
+		if (freeit && !(pfn == my_zero_pfn(0) && page_count(p) == 1)) {
+			put_page(page);
+			ret = 0;
+		}
+	}
 
 unlock_mutex:
 	mutex_unlock(&mf_mutex);