[PATCH v6 1/4] mm,hwpoison,hugetlb,memory_hotplug: hotremove memory section with hwpoisoned hugepage

[Naoya Horiguchi]

From: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>

HWPoisoned page is not supposed to be accessed once marked, but currently
such accesses can happen during memory hotremove because do_migrate_range()
can be called before dissolve_free_huge_pages() is called.

Clear HPageMigratable for hwpoisoned hugepages to prevent them from being
migrated.  This should be done in hugetlb_lock to avoid race against
isolate_hugetlb().

get_hwpoison_huge_page() needs to have a flag to show it's called from
unpoison to take refcount of hwpoisoned hugepages, so add it.

Reported-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Signed-off-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
---
ChangeLog v3 -> v6:
- introduce migratable_cleared to remember that HPageMigratable is
  cleared in error handling.  It's needed to cancel when an error event
  is filtered by hwpoison_filter(). (Thanks to Miaohe)

ChangeLog v2 -> v3
- move to the approach of clearing HPageMigratable instead of shifting
  dissolve_free_huge_pages.
---
 include/linux/hugetlb.h | 10 ++++++----
 include/linux/mm.h      |  6 ++++--
 mm/hugetlb.c            |  9 +++++----
 mm/memory-failure.c     | 21 +++++++++++++++++----
 4 files changed, 32 insertions(+), 14 deletions(-)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 32d45e96a894..19b99ff7fea0 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -183,8 +183,9 @@ bool hugetlb_reserve_pages(struct inode *inode, long from, long to,
 long hugetlb_unreserve_pages(struct inode *inode, long start, long end,
 						long freed);
 int isolate_hugetlb(struct page *page, struct list_head *list);
-int get_hwpoison_huge_page(struct page *page, bool *hugetlb);
-int get_huge_page_for_hwpoison(unsigned long pfn, int flags);
+int get_hwpoison_huge_page(struct page *page, bool *hugetlb, bool unpoison);
+int get_huge_page_for_hwpoison(unsigned long pfn, int flags,
+				bool *migratable_cleared);
 void putback_active_hugepage(struct page *page);
 void move_hugetlb_state(struct page *oldpage, struct page *newpage, int reason);
 void free_huge_page(struct page *page);
@@ -391,12 +392,13 @@ static inline int isolate_hugetlb(struct page *page, struct list_head *list)
 	return -EBUSY;
 }
 
-static inline int get_hwpoison_huge_page(struct page *page, bool *hugetlb)
+static inline int get_hwpoison_huge_page(struct page *page, bool *hugetlb, bool unpoison)
 {
 	return 0;
 }
 
-static inline int get_huge_page_for_hwpoison(unsigned long pfn, int flags)
+static inline int get_huge_page_for_hwpoison(unsigned long pfn, int flags,
+					bool *migratable_cleared)
 {
 	return 0;
 }
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 8bbcccbc5565..3264bf993ad8 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3277,9 +3277,11 @@ extern void shake_page(struct page *p);
 extern atomic_long_t num_poisoned_pages __read_mostly;
 extern int soft_offline_page(unsigned long pfn, int flags);
 #ifdef CONFIG_MEMORY_FAILURE
-extern int __get_huge_page_for_hwpoison(unsigned long pfn, int flags);
+extern int __get_huge_page_for_hwpoison(unsigned long pfn, int flags,
+					bool *migratable_cleared);
 #else
-static inline int __get_huge_page_for_hwpoison(unsigned long pfn, int flags)
+static inline int __get_huge_page_for_hwpoison(unsigned long pfn, int flags,
+					bool *migratable_cleared)
 {
 	return 0;
 }
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 63fe47a0240a..0e482dfaf92e 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -7253,7 +7253,7 @@ int isolate_hugetlb(struct page *page, struct list_head *list)
 	return ret;
 }
 
-int get_hwpoison_huge_page(struct page *page, bool *hugetlb)
+int get_hwpoison_huge_page(struct page *page, bool *hugetlb, bool unpoison)
 {
 	int ret = 0;
 
@@ -7263,7 +7263,7 @@ int get_hwpoison_huge_page(struct page *page, bool *hugetlb)
 		*hugetlb = true;
 		if (HPageFreed(page))
 			ret = 0;
-		else if (HPageMigratable(page))
+		else if (HPageMigratable(page) || unpoison)
 			ret = get_page_unless_zero(page);
 		else
 			ret = -EBUSY;
@@ -7272,12 +7272,13 @@ int get_hwpoison_huge_page(struct page *page, bool *hugetlb)
 	return ret;
 }
 
-int get_huge_page_for_hwpoison(unsigned long pfn, int flags)
+int get_huge_page_for_hwpoison(unsigned long pfn, int flags,
+				bool *migratable_cleared)
 {
 	int ret;
 
 	spin_lock_irq(&hugetlb_lock);
-	ret = __get_huge_page_for_hwpoison(pfn, flags);
+	ret = __get_huge_page_for_hwpoison(pfn, flags, migratable_cleared);
 	spin_unlock_irq(&hugetlb_lock);
 	return ret;
 }
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 145bb561ddb3..d4fef56c0438 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1244,7 +1244,7 @@ static int __get_hwpoison_page(struct page *page, unsigned long flags)
 	int ret = 0;
 	bool hugetlb = false;
 
-	ret = get_hwpoison_huge_page(head, &hugetlb);
+	ret = get_hwpoison_huge_page(head, &hugetlb, false);
 	if (hugetlb)
 		return ret;
 
@@ -1334,7 +1334,7 @@ static int __get_unpoison_page(struct page *page)
 	int ret = 0;
 	bool hugetlb = false;
 
-	ret = get_hwpoison_huge_page(head, &hugetlb);
+	ret = get_hwpoison_huge_page(head, &hugetlb, true);
 	if (hugetlb)
 		return ret;
 
@@ -1785,7 +1785,8 @@ void hugetlb_clear_page_hwpoison(struct page *hpage)
  *   -EBUSY        - the hugepage is busy (try to retry)
  *   -EHWPOISON    - the hugepage is already hwpoisoned
  */
-int __get_huge_page_for_hwpoison(unsigned long pfn, int flags)
+int __get_huge_page_for_hwpoison(unsigned long pfn, int flags,
+				 bool *migratable_cleared)
 {
 	struct page *page = pfn_to_page(pfn);
 	struct page *head = compound_head(page);
@@ -1815,6 +1816,15 @@ int __get_huge_page_for_hwpoison(unsigned long pfn, int flags)
 		goto out;
 	}
 
+	/*
+	 * Clearing HPageMigratable for hwpoisoned hugepages to prevent them
+	 * from being migrated by memory hotremove.
+	 */
+	if (count_increased) {
+		*migratable_cleared = true;
+		ClearHPageMigratable(head);
+	}
+
 	return ret;
 out:
 	if (count_increased)
@@ -1834,10 +1844,11 @@ static int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb
 	struct page *p = pfn_to_page(pfn);
 	struct page *head;
 	unsigned long page_flags;
+	bool migratable_cleared = false;
 
 	*hugetlb = 1;
 retry:
-	res = get_huge_page_for_hwpoison(pfn, flags);
+	res = get_huge_page_for_hwpoison(pfn, flags, &migratable_cleared);
 	if (res == 2) { /* fallback to normal page handling */
 		*hugetlb = 0;
 		return 0;
@@ -1862,6 +1873,8 @@ static int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb
 
 	if (hwpoison_filter(p)) {
 		hugetlb_clear_page_hwpoison(head);
+		if (migratable_cleared)
+			SetHPageMigratable(head);
 		unlock_page(head);
 		if (res == 1)
 			put_page(head);
-- 
2.25.1