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[PATCH v1 0/9] mm: hwpoison: fixlet for hugetlb migration

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  [PATCH v1 0/9] mm: hwpoison: fixlet for hugetlb migration Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> - 2017-06-01 10:20 +0200
    [PATCH v1 3/9] mm: hwpoison: change PageHWPoison behavior on hugetlb pages Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> - 2017-06-01 10:20 +0200
    [PATCH v1 4/9] mm: hugetlb: soft-offline: dissolve source hugepage after successful migration Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> - 2017-06-01 10:20 +0200

#1654913 — [PATCH v1 0/9] mm: hwpoison: fixlet for hugetlb migration

Hi everyone,

I wrote the patchset updating hwpoison/hugetlb code to address
the 2 reported issues.

One is madvise(MADV_HWPOISON) failure reported by Intel's lkp robot
(see http://lkml.kernel.org/r/20170417055948.GM31394@yexl-desktop.)
First half was already fixed in mainline, and another half about hugetlb
cases are solved in this series.

Another issue is "narrow-down error affected region into a single 4kB
page instead of a whole hugetlb page" issue, which was tried by Anshuman
(http://lkml.kernel.org/r/20170420110627.12307-1-khandual@linux.vnet.ibm.com)
and I updated it to apply it more widely.

Hopefully it helps people who are interested in hugetlb migration for
wider arch/setting.

Thanks,
Naoya Horiguchi
---
Summary:

Anshuman Khandual (1):
      mm: hugetlb: soft-offline: dissolve source hugepage after successful migration

Naoya Horiguchi (8):
      mm: hugetlb: prevent reuse of hwpoisoned free hugepages
      mm: hugetlb: return immediately for hugetlb page in __delete_from_page_cache()
      mm: hwpoison: change PageHWPoison behavior on hugetlb pages
      mm: soft-offline: dissolve free hugepage if soft-offlined
      mm: hwpoison: introduce memory_failure_hugetlb()
      mm: hwpoison: dissolve in-use hugepage in unrecoverable memory error
      mm: hugetlb: delete dequeue_hwpoisoned_huge_page()
      mm: hwpoison: introduce idenfity_page_state

 fs/hugetlbfs/inode.c    |  11 ++
 include/linux/hugetlb.h |   8 +-
 include/linux/swapops.h |   9 --
 mm/filemap.c            |   8 +-
 mm/hugetlb.c            |  47 ++-----
 mm/memory-failure.c     | 323 +++++++++++++++++++++++-------------------------
 mm/migrate.c            |   2 +
 7 files changed, 184 insertions(+), 224 deletions(-)

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#1654914 — [PATCH v1 3/9] mm: hwpoison: change PageHWPoison behavior on hugetlb pages

We'd like to narrow down the error region in memory error on hugetlb
pages.  However, currently we set PageHWPoison flags on all subpages
in the error hugepage and add # of subpages to num_hwpoison_pages,
which doesn't fit our purpose.

So this patch changes the behavior and we only set PageHWPoison on
the head page then increase num_hwpoison_pages only by 1. This is
a preparation for narrow-down part which comes in later patches.

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
---
 include/linux/swapops.h |  9 -----
 mm/memory-failure.c     | 87 ++++++++++++++-----------------------------------
 2 files changed, 24 insertions(+), 72 deletions(-)

diff --git v4.12-rc3/include/linux/swapops.h v4.12-rc3_patched/include/linux/swapops.h
index 5c3a5f3..c5ff7b2 100644
--- v4.12-rc3/include/linux/swapops.h
+++ v4.12-rc3_patched/include/linux/swapops.h
@@ -196,15 +196,6 @@ static inline void num_poisoned_pages_dec(void)
 	atomic_long_dec(&num_poisoned_pages);
 }
 
-static inline void num_poisoned_pages_add(long num)
-{
-	atomic_long_add(num, &num_poisoned_pages);
-}
-
-static inline void num_poisoned_pages_sub(long num)
-{
-	atomic_long_sub(num, &num_poisoned_pages);
-}
 #else
 
 static inline swp_entry_t make_hwpoison_entry(struct page *page)
diff --git v4.12-rc3/mm/memory-failure.c v4.12-rc3_patched/mm/memory-failure.c
index 6c1a7c9..aae620f 100644
--- v4.12-rc3/mm/memory-failure.c
+++ v4.12-rc3_patched/mm/memory-failure.c
@@ -1009,22 +1009,6 @@ static bool hwpoison_user_mappings(struct page *p, unsigned long pfn,
 	return unmap_success;
 }
 
-static void set_page_hwpoison_huge_page(struct page *hpage)
-{
-	int i;
-	int nr_pages = 1 << compound_order(hpage);
-	for (i = 0; i < nr_pages; i++)
-		SetPageHWPoison(hpage + i);
-}
-
-static void clear_page_hwpoison_huge_page(struct page *hpage)
-{
-	int i;
-	int nr_pages = 1 << compound_order(hpage);
-	for (i = 0; i < nr_pages; i++)
-		ClearPageHWPoison(hpage + i);
-}
-
 /**
  * memory_failure - Handle memory failure of a page.
  * @pfn: Page Number of the corrupted page
@@ -1050,7 +1034,6 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
 	struct page *hpage;
 	struct page *orig_head;
 	int res;
-	unsigned int nr_pages;
 	unsigned long page_flags;
 
 	if (!sysctl_memory_failure_recovery)
@@ -1064,24 +1047,23 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
 
 	p = pfn_to_page(pfn);
 	orig_head = hpage = compound_head(p);
+
+	/* tmporary check code, to be updated in later patches */
+	if (PageHuge(p)) {
+		if (TestSetPageHWPoison(hpage)) {
+			pr_err("Memory failure: %#lx: already hardware poisoned\n", pfn);
+			return 0;
+		}
+		goto tmp;
+	}
 	if (TestSetPageHWPoison(p)) {
 		pr_err("Memory failure: %#lx: already hardware poisoned\n",
 			pfn);
 		return 0;
 	}
 
-	/*
-	 * Currently errors on hugetlbfs pages are measured in hugepage units,
-	 * so nr_pages should be 1 << compound_order.  OTOH when errors are on
-	 * transparent hugepages, they are supposed to be split and error
-	 * measurement is done in normal page units.  So nr_pages should be one
-	 * in this case.
-	 */
-	if (PageHuge(p))
-		nr_pages = 1 << compound_order(hpage);
-	else /* normal page or thp */
-		nr_pages = 1;
-	num_poisoned_pages_add(nr_pages);
+tmp:
+	num_poisoned_pages_inc();
 
 	/*
 	 * We need/can do nothing about count=0 pages.
@@ -1109,12 +1091,11 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
 			if (PageHWPoison(hpage)) {
 				if ((hwpoison_filter(p) && TestClearPageHWPoison(p))
 				    || (p != hpage && TestSetPageHWPoison(hpage))) {
-					num_poisoned_pages_sub(nr_pages);
+					num_poisoned_pages_dec();
 					unlock_page(hpage);
 					return 0;
 				}
 			}
-			set_page_hwpoison_huge_page(hpage);
 			res = dequeue_hwpoisoned_huge_page(hpage);
 			action_result(pfn, MF_MSG_FREE_HUGE,
 				      res ? MF_IGNORED : MF_DELAYED);
@@ -1137,7 +1118,7 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
 				pr_err("Memory failure: %#lx: thp split failed\n",
 					pfn);
 			if (TestClearPageHWPoison(p))
-				num_poisoned_pages_sub(nr_pages);
+				num_poisoned_pages_dec();
 			put_hwpoison_page(p);
 			return -EBUSY;
 		}
@@ -1190,14 +1171,14 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
 	 */
 	if (!PageHWPoison(p)) {
 		pr_err("Memory failure: %#lx: just unpoisoned\n", pfn);
-		num_poisoned_pages_sub(nr_pages);
+		num_poisoned_pages_dec();
 		unlock_page(hpage);
 		put_hwpoison_page(hpage);
 		return 0;
 	}
 	if (hwpoison_filter(p)) {
 		if (TestClearPageHWPoison(p))
-			num_poisoned_pages_sub(nr_pages);
+			num_poisoned_pages_dec();
 		unlock_page(hpage);
 		put_hwpoison_page(hpage);
 		return 0;
@@ -1216,14 +1197,6 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
 		put_hwpoison_page(hpage);
 		return 0;
 	}
-	/*
-	 * Set PG_hwpoison on all pages in an error hugepage,
-	 * because containment is done in hugepage unit for now.
-	 * Since we have done TestSetPageHWPoison() for the head page with
-	 * page lock held, we can safely set PG_hwpoison bits on tail pages.
-	 */
-	if (PageHuge(p))
-		set_page_hwpoison_huge_page(hpage);
 
 	/*
 	 * It's very difficult to mess with pages currently under IO
@@ -1394,7 +1367,6 @@ int unpoison_memory(unsigned long pfn)
 	struct page *page;
 	struct page *p;
 	int freeit = 0;
-	unsigned int nr_pages;
 	static DEFINE_RATELIMIT_STATE(unpoison_rs, DEFAULT_RATELIMIT_INTERVAL,
 					DEFAULT_RATELIMIT_BURST);
 
@@ -1439,8 +1411,6 @@ int unpoison_memory(unsigned long pfn)
 		return 0;
 	}
 
-	nr_pages = 1 << compound_order(page);
-
 	if (!get_hwpoison_page(p)) {
 		/*
 		 * Since HWPoisoned hugepage should have non-zero refcount,
@@ -1470,10 +1440,8 @@ int unpoison_memory(unsigned long pfn)
 	if (TestClearPageHWPoison(page)) {
 		unpoison_pr_info("Unpoison: Software-unpoisoned page %#lx\n",
 				 pfn, &unpoison_rs);
-		num_poisoned_pages_sub(nr_pages);
+		num_poisoned_pages_dec();
 		freeit = 1;
-		if (PageHuge(page))
-			clear_page_hwpoison_huge_page(page);
 	}
 	unlock_page(page);
 
@@ -1604,14 +1572,10 @@ static int soft_offline_huge_page(struct page *page, int flags)
 			ret = -EIO;
 	} else {
 		/* overcommit hugetlb page will be freed to buddy */
-		if (PageHuge(page)) {
-			set_page_hwpoison_huge_page(hpage);
+		SetPageHWPoison(page);
+		if (PageHuge(page))
 			dequeue_hwpoisoned_huge_page(hpage);
-			num_poisoned_pages_add(1 << compound_order(hpage));
-		} else {
-			SetPageHWPoison(page);
-			num_poisoned_pages_inc();
-		}
+		num_poisoned_pages_inc();
 	}
 	return ret;
 }
@@ -1727,15 +1691,12 @@ static int soft_offline_in_use_page(struct page *page, int flags)
 
 static void soft_offline_free_page(struct page *page)
 {
-	if (PageHuge(page)) {
-		struct page *hpage = compound_head(page);
+	struct page *head = compound_head(page);
 
-		set_page_hwpoison_huge_page(hpage);
-		if (!dequeue_hwpoisoned_huge_page(hpage))
-			num_poisoned_pages_add(1 << compound_order(hpage));
-	} else {
-		if (!TestSetPageHWPoison(page))
-			num_poisoned_pages_inc();
+	if (!TestSetPageHWPoison(head)) {
+		num_poisoned_pages_inc();
+		if (PageHuge(head))
+			dequeue_hwpoisoned_huge_page(head);
 	}
 }
 
-- 
2.7.0

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#1654916 — [PATCH v1 4/9] mm: hugetlb: soft-offline: dissolve source hugepage after successful migration

From: Anshuman Khandual <khandual@linux.vnet.ibm.com>

Currently hugepage migrated by soft-offline (i.e. due to correctable
memory errors) is contained as a hugepage, which means many non-error
pages in it are unreusable, i.e. wasted.

This patch solves this issue by dissolving source hugepages into buddy.
As done in previous patch, PageHWPoison is set only on a head page of
the error hugepage. Then in dissoliving we move the PageHWPoison flag to
the raw error page so that all healthy subpages return back to buddy.

Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
---
 include/linux/hugetlb.h |  2 ++
 mm/hugetlb.c            | 10 +++++++++-
 mm/memory-failure.c     |  5 +----
 mm/migrate.c            |  2 ++
 4 files changed, 14 insertions(+), 5 deletions(-)

diff --git v4.12-rc3/include/linux/hugetlb.h v4.12-rc3_patched/include/linux/hugetlb.h
index b857fc8..89afe40 100644
--- v4.12-rc3/include/linux/hugetlb.h
+++ v4.12-rc3_patched/include/linux/hugetlb.h
@@ -461,6 +461,7 @@ static inline pgoff_t basepage_index(struct page *page)
 	return __basepage_index(page);
 }
 
+extern int dissolve_free_huge_page(struct page *page);
 extern int dissolve_free_huge_pages(unsigned long start_pfn,
 				    unsigned long end_pfn);
 static inline bool hugepage_migration_supported(struct hstate *h)
@@ -529,6 +530,7 @@ static inline pgoff_t basepage_index(struct page *page)
 {
 	return page->index;
 }
+#define dissolve_free_huge_page(p)	0
 #define dissolve_free_huge_pages(s, e)	0
 #define hugepage_migration_supported(h)	false
 
diff --git v4.12-rc3/mm/hugetlb.c v4.12-rc3_patched/mm/hugetlb.c
index 6d6c659..41c37ed 100644
--- v4.12-rc3/mm/hugetlb.c
+++ v4.12-rc3_patched/mm/hugetlb.c
@@ -1443,7 +1443,7 @@ static int free_pool_huge_page(struct hstate *h, nodemask_t *nodes_allowed,
  * number of free hugepages would be reduced below the number of reserved
  * hugepages.
  */
-static int dissolve_free_huge_page(struct page *page)
+int dissolve_free_huge_page(struct page *page)
 {
 	int rc = 0;
 
@@ -1456,6 +1456,14 @@ static int dissolve_free_huge_page(struct page *page)
 			rc = -EBUSY;
 			goto out;
 		}
+		/*
+		 * Move PageHWPoison flag from head page to the raw error page,
+		 * which makes any subpages rather than the error page reusable.
+		 */
+		if (PageHWPoison(head) && page != head) {
+			SetPageHWPoison(page);
+			ClearPageHWPoison(head);
+		}
 		list_del(&head->lru);
 		h->free_huge_pages--;
 		h->free_huge_pages_node[nid]--;
diff --git v4.12-rc3/mm/memory-failure.c v4.12-rc3_patched/mm/memory-failure.c
index aae620f..e03903f 100644
--- v4.12-rc3/mm/memory-failure.c
+++ v4.12-rc3_patched/mm/memory-failure.c
@@ -1571,11 +1571,8 @@ static int soft_offline_huge_page(struct page *page, int flags)
 		if (ret > 0)
 			ret = -EIO;
 	} else {
-		/* overcommit hugetlb page will be freed to buddy */
-		SetPageHWPoison(page);
 		if (PageHuge(page))
-			dequeue_hwpoisoned_huge_page(hpage);
-		num_poisoned_pages_inc();
+			dissolve_free_huge_page(page);
 	}
 	return ret;
 }
diff --git v4.12-rc3/mm/migrate.c v4.12-rc3_patched/mm/migrate.c
index 89a0a17..f0319db 100644
--- v4.12-rc3/mm/migrate.c
+++ v4.12-rc3_patched/mm/migrate.c
@@ -1251,6 +1251,8 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
 out:
 	if (rc != -EAGAIN)
 		putback_active_hugepage(hpage);
+	if (reason == MR_MEMORY_FAILURE && !test_set_page_hwpoison(hpage))
+		num_poisoned_pages_inc();
 
 	/*
 	 * If migration was not successful and there's a freeing callback, use
-- 
2.7.0

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