[PATCH 10/10] mm,hwpoison: Use hugetlb_replace_page to replace free hugetlb pages

[Oscar Salvador]

When soft offlining a free hugtlb, try first to allocate a new hugetlb
to the pool and pass the old state to the new one by move_hugetlb_state().
Either we succeed or not, we dissolve the poisoned hugetlb page.

Worst-scenario case is that we cannot allocate a new fresh hugetlb page
as a replacement.

Signed-off-by: Oscar Salvador <osalvador@xxxxxxx>
---
 mm/hugetlb.c        | 16 ++++++++++++++++
 mm/memory-failure.c | 34 ++++++++++++++++++++++++++++------
 2 files changed, 44 insertions(+), 6 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 139e1c05c9a1..d0844aec7531 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5154,3 +5154,19 @@ void move_hugetlb_state(struct page *oldpage, struct page *newpage, int reason)
 		spin_unlock(&hugetlb_lock);
 	}
 }
+
+#ifdef CONFIG_MEMORY_FAILURE
+int hugetlb_replace_page(struct page *page, int reason)
+{
+	int nid = page_to_nid(page);
+	struct hstate *h = page_hstate(page);
+	struct page *new_page;
+
+	new_page = alloc_huge_page_nodemask(h, nid, &node_states[N_MEMORY]);
+	if (!new_page)
+		return -ENOMEM;
+
+	move_hugetlb_state(page, new_page, reason);
+	return 0;
+}
+#endif
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 03f07015a106..fe73fe19c6e9 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -79,6 +79,7 @@ EXPORT_SYMBOL_GPL(hwpoison_filter_flags_mask);
 EXPORT_SYMBOL_GPL(hwpoison_filter_flags_value);
 
 extern bool take_page_off_buddy(struct page *page);
+extern int hugetlb_replace_page(struct page *page, int reason);
 
 static bool page_set_poison(struct page *page)
 {
@@ -1804,16 +1805,37 @@ static int soft_offline_in_use_page(struct page *page)
 	return __soft_offline_page(page);
 }
 
+static int soft_offline_free_huge_page(struct page *page)
+{
+	struct page *hpage = compound_head(page);
+
+	/*
+	 * Try to add a new hugetlb page to the pool
+	 */
+	if (hugetlb_replace_page(hpage, MR_MEMORY_FAILURE))
+		return -EBUSY;
+
+	/*
+	 * Remove old hugetlb from the pool
+	 */
+	if (!page_set_poison(hpage))
+		return -EBUSY;
+
+	return 0;
+}
+
 static int soft_offline_free_page(struct page *page)
 {
-	int rc = dissolve_free_huge_page(page);
+	int rc = -EBUSY;
 
-	if (!rc) {
-		if (take_page_off_buddy(page))
+	if (PageHuge(page))
+		rc = soft_offline_free_huge_page(page);
+	else
+		if (take_page_off_buddy(page)) {
 			page_set_poison(page);
-		else
-			rc = -EBUSY;
-	}
+			rc = 0;
+		}
+
 	return rc;
 }
 
-- 
2.12.3