[PATCH v3 0/9] mm, hwpoison: enable 1GB hugepage support (v3)

[PATCH v3 0/9] mm, hwpoison: enable 1GB hugepage support (v3)

[Naoya Horiguchi]

Here is v3 of "enabling memory error handling on 1GB hugepage" patchset.

I applied feedbacks for v2, thank you very much.  Overall design of the
patchset is unchanged. Please see individual patches for details about
changes.

Patch dependency:

- "mm/memory-failure: disable unpoison once hw error happens"
  (actually the conflict is not logical one, but adding MF_SIMULATED to
   mf_flags conflicts with patch 6/9.)

Previous versions:

- v1: https://lore.kernel.org/linux-mm/20220602050631.771414-1-naoya.horiguchi@linux.dev/T/#u
- v2: https://lore.kernel.org/linux-mm/20220623235153.2623702-1-naoya.horiguchi@linux.dev/T/#u

Thanks,
Naoya Horiguchi
---
Summary:

Naoya Horiguchi (9):
      mm/hugetlb: check gigantic_page_runtime_supported() in return_unused_surplus_pages()
      mm/hugetlb: separate path for hwpoison entry in copy_hugetlb_page_range()
      mm/hugetlb: make pud_huge() and follow_huge_pud() aware of non-present pud entry
      mm, hwpoison, hugetlb: support saving mechanism of raw error pages
      mm, hwpoison: make unpoison aware of raw error info in hwpoisoned hugepage
      mm, hwpoison: set PG_hwpoison for busy hugetlb pages
      mm, hwpoison: make __page_handle_poison returns int
      mm, hwpoison: skip raw hwpoison page in freeing 1GB hugepage
      mm, hwpoison: enable memory error handling on 1GB hugepage

 arch/x86/mm/hugetlbpage.c |   8 ++-
 include/linux/hugetlb.h   |  18 +++++-
 include/linux/mm.h        |   2 +-
 include/linux/swapops.h   |   9 +++
 include/ras/ras_event.h   |   1 -
 mm/hugetlb.c              |  99 ++++++++++++++++++++++---------
 mm/memory-failure.c       | 148 ++++++++++++++++++++++++++++++++++++----------
 7 files changed, 224 insertions(+), 61 deletions(-)

[PATCH v3 1/9] mm/hugetlb: check gigantic_page_runtime_supported() in return_unused_surplus_pages()

[Naoya Horiguchi]

From: Naoya Horiguchi <naoya.horiguchi@nec.com>

I found a weird state of 1GB hugepage pool, caused by the following
procedure:

  - run a process reserving all free 1GB hugepages,
  - shrink free 1GB hugepage pool to zero (i.e. writing 0 to
    /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages), then
  - kill the reserving process.

, then all the hugepages are free *and* surplus at the same time.

  $ cat /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages
  3
  $ cat /sys/kernel/mm/hugepages/hugepages-1048576kB/free_hugepages
  3
  $ cat /sys/kernel/mm/hugepages/hugepages-1048576kB/resv_hugepages
  0
  $ cat /sys/kernel/mm/hugepages/hugepages-1048576kB/surplus_hugepages
  3

This state is resolved by reserving and allocating the pages then
freeing them again, so this seems not to result in serious problem.
But it's a little surprising (shrinking pool suddenly fails).

This behavior is caused by hstate_is_gigantic() check in
return_unused_surplus_pages(). This was introduced so long ago in 2008
by commit aa888a74977a ("hugetlb: support larger than MAX_ORDER"), and
at that time the gigantic pages were not supposed to be allocated/freed
at run-time.  Now kernel can support runtime allocation/free, so let's
check gigantic_page_runtime_supported() together.

Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
---
v2 -> v3:
- Fixed typo in patch description,
- add !gigantic_page_runtime_supported() check instead of removing
  hstate_is_gigantic() check (suggested by Miaohe and Muchun)
- add a few more !gigantic_page_runtime_supported() check in
  set_max_huge_pages() (by Mike).
---
 mm/hugetlb.c | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index a57e1be41401..e67540dbbf88 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2432,8 +2432,7 @@ static void return_unused_surplus_pages(struct hstate *h,
 	/* Uncommit the reservation */
 	h->resv_huge_pages -= unused_resv_pages;
 
-	/* Cannot return gigantic pages currently */
-	if (hstate_is_gigantic(h))
+	if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
 		goto out;
 
 	/*
@@ -3318,7 +3317,8 @@ static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid,
 	 * the user tries to allocate gigantic pages but let the user free the
 	 * boottime allocated gigantic pages.
 	 */
-	if (hstate_is_gigantic(h) && !IS_ENABLED(CONFIG_CONTIG_ALLOC)) {
+	if (hstate_is_gigantic(h) && (!IS_ENABLED(CONFIG_CONTIG_ALLOC) ||
+				      !gigantic_page_runtime_supported())) {
 		if (count > persistent_huge_pages(h)) {
 			spin_unlock_irq(&hugetlb_lock);
 			mutex_unlock(&h->resize_lock);
@@ -3366,6 +3366,19 @@ static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid,
 			goto out;
 	}
 
+	/*
+	 * We can not decrease gigantic pool size if runtime modification
+	 * is not supported.
+	 */
+	if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported()) {
+		if (count < persistent_huge_pages(h)) {
+			spin_unlock_irq(&hugetlb_lock);
+			mutex_unlock(&h->resize_lock);
+			NODEMASK_FREE(node_alloc_noretry);
+			return -EINVAL;
+		}
+	}
+
 	/*
 	 * Decrease the pool size
 	 * First return free pages to the buddy allocator (being careful
-- 
2.25.1

[PATCH v3 2/9] mm/hugetlb: separate path for hwpoison entry in copy_hugetlb_page_range()

[Naoya Horiguchi]

From: Naoya Horiguchi <naoya.horiguchi@nec.com>

Originally copy_hugetlb_page_range() handles migration entries and hwpoisoned
entries in similar manner.  But recently the related code path has more code
for migration entries, and when is_writable_migration_entry() was converted
to !is_readable_migration_entry(), hwpoison entries on source processes got
to be unexpectedly updated (which is legitimate for migration entries, but
not for hwpoison entries).  This results in unexpected serious issues like
kernel panic when forking processes with hwpoison entries in pmd.

Separate the if branch into one for hwpoison entries and one for migration
entries.

Fixes: 6c287605fd56 ("mm: remember exclusively mapped anonymous pages with PG_anon_exclusive")
Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: <stable@vger.kernel.org> # 5.18
---
 mm/hugetlb.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index e67540dbbf88..03fdf342f5f2 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -4801,8 +4801,13 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
 			 * sharing with another vma.
 			 */
 			;
-		} else if (unlikely(is_hugetlb_entry_migration(entry) ||
-				    is_hugetlb_entry_hwpoisoned(entry))) {
+		} else if (unlikely(is_hugetlb_entry_hwpoisoned(entry))) {
+			bool uffd_wp = huge_pte_uffd_wp(entry);
+
+			if (!userfaultfd_wp(dst_vma) && uffd_wp)
+				entry = huge_pte_clear_uffd_wp(entry);
+			set_huge_swap_pte_at(dst, addr, dst_pte, entry, sz);
+		} else if (unlikely(is_hugetlb_entry_migration(entry))) {
 			swp_entry_t swp_entry = pte_to_swp_entry(entry);
 			bool uffd_wp = huge_pte_uffd_wp(entry);
 
-- 
2.25.1

[PATCH v3 3/9] mm/hugetlb: make pud_huge() and follow_huge_pud() aware of non-present pud entry

[Naoya Horiguchi]

From: Naoya Horiguchi <naoya.horiguchi@nec.com>

follow_pud_mask() does not support non-present pud entry now.  As long as
I tested on x86_64 server, follow_pud_mask() still simply returns
no_page_table() for non-present_pud_entry() due to pud_bad(), so no severe
user-visible effect should happen.  But generally we should call
follow_huge_pud() for non-present pud entry for 1GB hugetlb page.

Update pud_huge() and follow_huge_pud() to handle non-present pud entries.
The changes are similar to previous works for pud entries commit e66f17ff7177
("mm/hugetlb: take page table lock in follow_huge_pmd()") and commit
cbef8478bee5 ("mm/hugetlb: pmd_huge() returns true for non-present hugepage").

Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
---
v2 -> v3:
- fixed typos in subject and description,
- added comment on pud_huge(),
- added comment about fallback for hwpoisoned entry,
- updated initial check about FOLL_{PIN,GET} flags.
---
 arch/x86/mm/hugetlbpage.c |  8 +++++++-
 mm/hugetlb.c              | 32 ++++++++++++++++++++++++++++++--
 2 files changed, 37 insertions(+), 3 deletions(-)

diff --git a/arch/x86/mm/hugetlbpage.c b/arch/x86/mm/hugetlbpage.c
index a0d023cb4292..9c8193df0187 100644
--- a/arch/x86/mm/hugetlbpage.c
+++ b/arch/x86/mm/hugetlbpage.c
@@ -68,9 +68,15 @@ int pmd_huge(pmd_t pmd)
 		(pmd_val(pmd) & (_PAGE_PRESENT|_PAGE_PSE)) != _PAGE_PRESENT;
 }
 
+/*
+ * pud_huge() returns 1 if @pud is hugetlb related entry, that is normal
+ * hugetlb entry or non-present (migration or hwpoisoned) hugetlb entry.
+ * Otherwise, returns 0.
+ */
 int pud_huge(pud_t pud)
 {
-	return !!(pud_val(pud) & _PAGE_PSE);
+	return !pud_none(pud) &&
+		(pud_val(pud) & (_PAGE_PRESENT|_PAGE_PSE)) != _PAGE_PRESENT;
 }
 #endif
 
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 03fdf342f5f2..4c30f3fcfe50 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -6963,10 +6963,38 @@ struct page * __weak
 follow_huge_pud(struct mm_struct *mm, unsigned long address,
 		pud_t *pud, int flags)
 {
-	if (flags & (FOLL_GET | FOLL_PIN))
+	struct page *page = NULL;
+	spinlock_t *ptl;
+	pte_t pte;
+
+	if (WARN_ON_ONCE(flags & FOLL_PIN))
 		return NULL;
 
-	return pte_page(*(pte_t *)pud) + ((address & ~PUD_MASK) >> PAGE_SHIFT);
+retry:
+	ptl = huge_pte_lock(hstate_sizelog(PUD_SHIFT), mm, (pte_t *)pud);
+	if (!pud_huge(*pud))
+		goto out;
+	pte = huge_ptep_get((pte_t *)pud);
+	if (pte_present(pte)) {
+		page = pud_page(*pud) + ((address & ~PUD_MASK) >> PAGE_SHIFT);
+		if (WARN_ON_ONCE(!try_grab_page(page, flags))) {
+			page = NULL;
+			goto out;
+		}
+	} else {
+		if (is_hugetlb_entry_migration(pte)) {
+			spin_unlock(ptl);
+			__migration_entry_wait(mm, (pte_t *)pud, ptl);
+			goto retry;
+		}
+		/*
+		 * hwpoisoned entry is treated as no_page_table in
+		 * follow_page_mask().
+		 */
+	}
+out:
+	spin_unlock(ptl);
+	return page;
 }
 
 struct page * __weak
-- 
2.25.1

[PATCH v3 4/9] mm, hwpoison, hugetlb: support saving mechanism of raw error pages

[Naoya Horiguchi]

From: Naoya Horiguchi <naoya.horiguchi@nec.com>

When handling memory error on a hugetlb page, the error handler tries to
dissolve and turn it into 4kB pages.  If it's successfully dissolved,
PageHWPoison flag is moved to the raw error page, so that's all right.
However, dissolve sometimes fails, then the error page is left as
hwpoisoned hugepage. It's useful if we can retry to dissolve it to save
healthy pages, but that's not possible now because the information about
where the raw error pages is lost.

Use the private field of a few tail pages to keep that information.  The
code path of shrinking hugepage pool uses this info to try delayed dissolve.
In order to remember multiple errors in a hugepage, a singly-linked list
originated from SUBPAGE_INDEX_HWPOISON-th tail page is constructed.  Only
simple operations (adding an entry or clearing all) are required and the
list is assumed not to be very long, so this simple data structure should
be enough.

If we failed to save raw error info, the hwpoison hugepage has errors on
unknown subpage, then this new saving mechanism does not work any more,
so disable saving new raw error info and freeing hwpoison hugepages.

Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
---
v2 -> v3:
- remove duplicate "return ret" lines,
- use GFP_ATOMIC instead of GFP_KERNEL,
- introduce HPageRawHwpUnreliable pseudo flag (suggested by Muchun),
- hugetlb_clear_page_hwpoison removes raw_hwp_page list even if
  HPageRawHwpUnreliable is true, (by Miaohe)

v1 -> v2:
- support hwpoison hugepage with multiple errors,
- moved the new interface functions to mm/memory-failure.c,
- define additional subpage index SUBPAGE_INDEX_HWPOISON_UNRELIABLE,
- stop freeing/dissolving hwpoison hugepages with unreliable raw error info,
- drop hugetlb_clear_page_hwpoison() in dissolve_free_huge_page() because
  that's done in update_and_free_page(),
- move setting/clearing PG_hwpoison flag to the new interfaces,
- checking already hwpoisoned or not on a subpage basis.

ChangeLog since previous post on 4/27:
- fixed typo in patch description (by Miaohe)
- fixed config value in #ifdef statement (by Miaohe)
- added sentences about "multiple hwpoison pages" scenario in patch
  description

Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
---
 include/linux/hugetlb.h | 18 +++++++++-
 mm/hugetlb.c            | 39 ++++++++++----------
 mm/memory-failure.c     | 80 +++++++++++++++++++++++++++++++++++++++--
 3 files changed, 114 insertions(+), 23 deletions(-)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index e4cff27d1198..bd92a1e9a97b 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -42,6 +42,9 @@ enum {
 	SUBPAGE_INDEX_CGROUP,		/* reuse page->private */
 	SUBPAGE_INDEX_CGROUP_RSVD,	/* reuse page->private */
 	__MAX_CGROUP_SUBPAGE_INDEX = SUBPAGE_INDEX_CGROUP_RSVD,
+#endif
+#ifdef CONFIG_MEMORY_FAILURE
+	SUBPAGE_INDEX_HWPOISON,
 #endif
 	__NR_USED_SUBPAGE,
 };
@@ -550,7 +553,7 @@ generic_hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
  *	Synchronization:  Initially set after new page allocation with no
  *	locking.  When examined and modified during migration processing
  *	(isolate, migrate, putback) the hugetlb_lock is held.
- * HPG_temporary - - Set on a page that is temporarily allocated from the buddy
+ * HPG_temporary -- Set on a page that is temporarily allocated from the buddy
  *	allocator.  Typically used for migration target pages when no pages
  *	are available in the pool.  The hugetlb free page path will
  *	immediately free pages with this flag set to the buddy allocator.
@@ -560,6 +563,8 @@ generic_hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
  * HPG_freed - Set when page is on the free lists.
  *	Synchronization: hugetlb_lock held for examination and modification.
  * HPG_vmemmap_optimized - Set when the vmemmap pages of the page are freed.
+ * HPG_raw_hwp_unreliable - Set when the hugetlb page has a hwpoison sub-page
+ *     that is not tracked by raw_hwp_page list.
  */
 enum hugetlb_page_flags {
 	HPG_restore_reserve = 0,
@@ -567,6 +572,7 @@ enum hugetlb_page_flags {
 	HPG_temporary,
 	HPG_freed,
 	HPG_vmemmap_optimized,
+	HPG_raw_hwp_unreliable,
 	__NR_HPAGEFLAGS,
 };
 
@@ -613,6 +619,7 @@ HPAGEFLAG(Migratable, migratable)
 HPAGEFLAG(Temporary, temporary)
 HPAGEFLAG(Freed, freed)
 HPAGEFLAG(VmemmapOptimized, vmemmap_optimized)
+HPAGEFLAG(RawHwpUnreliable, raw_hwp_unreliable)
 
 #ifdef CONFIG_HUGETLB_PAGE
 
@@ -798,6 +805,15 @@ extern int dissolve_free_huge_page(struct page *page);
 extern int dissolve_free_huge_pages(unsigned long start_pfn,
 				    unsigned long end_pfn);
 
+#ifdef CONFIG_MEMORY_FAILURE
+extern int hugetlb_clear_page_hwpoison(struct page *hpage);
+#else
+static inline int hugetlb_clear_page_hwpoison(struct page *hpage)
+{
+	return 0;
+}
+#endif
+
 #ifdef CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION
 #ifndef arch_hugetlb_migration_supported
 static inline bool arch_hugetlb_migration_supported(struct hstate *h)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 4c30f3fcfe50..0937638fcb36 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1541,17 +1541,15 @@ static void __update_and_free_page(struct hstate *h, struct page *page)
 	if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
 		return;
 
-	if (hugetlb_vmemmap_alloc(h, page)) {
-		spin_lock_irq(&hugetlb_lock);
-		/*
-		 * If we cannot allocate vmemmap pages, just refuse to free the
-		 * page and put the page back on the hugetlb free list and treat
-		 * as a surplus page.
-		 */
-		add_hugetlb_page(h, page, true);
-		spin_unlock_irq(&hugetlb_lock);
-		return;
-	}
+	if (hugetlb_vmemmap_alloc(h, page))
+		goto fail;
+
+	/*
+	 * Move PageHWPoison flag from head page to the raw error pages,
+	 * which makes any healthy subpages reusable.
+	 */
+	if (unlikely(PageHWPoison(page) && hugetlb_clear_page_hwpoison(page)))
+		goto fail;
 
 	for (i = 0; i < pages_per_huge_page(h);
 	     i++, subpage = mem_map_next(subpage, page, i)) {
@@ -1572,6 +1570,16 @@ static void __update_and_free_page(struct hstate *h, struct page *page)
 	} else {
 		__free_pages(page, huge_page_order(h));
 	}
+	return;
+fail:
+	spin_lock_irq(&hugetlb_lock);
+	/*
+	 * If we cannot allocate vmemmap pages or cannot identify raw hwpoison
+	 * subpages reliably, just refuse to free the page and put the page
+	 * back on the hugetlb free list and treat as a surplus page.
+	 */
+	add_hugetlb_page(h, page, true);
+	spin_unlock_irq(&hugetlb_lock);
 }
 
 /*
@@ -2115,15 +2123,6 @@ int dissolve_free_huge_page(struct page *page)
 		 */
 		rc = hugetlb_vmemmap_alloc(h, head);
 		if (!rc) {
-			/*
-			 * 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);
-			}
 			update_and_free_page(h, head, false);
 		} else {
 			spin_lock_irq(&hugetlb_lock);
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index fb3feb1f363e..71414eb90a7a 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1499,6 +1499,82 @@ static int try_to_split_thp_page(struct page *page, const char *msg)
 }
 
 #ifdef CONFIG_HUGETLB_PAGE
+/*
+ * Struct raw_hwp_page represents information about "raw error page",
+ * constructing singly linked list originated from ->private field of
+ * SUBPAGE_INDEX_HWPOISON-th tail page.
+ */
+struct raw_hwp_page {
+	struct llist_node node;
+	struct page *page;
+};
+
+static inline struct llist_head *raw_hwp_list_head(struct page *hpage)
+{
+	return (struct llist_head *)&page_private(hpage + SUBPAGE_INDEX_HWPOISON);
+}
+
+static inline int hugetlb_set_page_hwpoison(struct page *hpage,
+					struct page *page)
+{
+	struct llist_head *head;
+	struct raw_hwp_page *raw_hwp;
+	struct llist_node *t, *tnode;
+	int ret;
+
+	/*
+	 * Once the hwpoison hugepage has lost reliable raw error info,
+	 * there is little meaning to keep additional error info precisely,
+	 * so skip to add additional raw error info.
+	 */
+	if (HPageRawHwpUnreliable(hpage))
+		return -EHWPOISON;
+	head = raw_hwp_list_head(hpage);
+	llist_for_each_safe(tnode, t, head->first) {
+		struct raw_hwp_page *p = container_of(tnode, struct raw_hwp_page, node);
+
+		if (p->page == page)
+			return -EHWPOISON;
+	}
+
+	ret = TestSetPageHWPoison(hpage) ? -EHWPOISON : 0;
+	/* the first error event will be counted in action_result(). */
+	if (ret)
+		num_poisoned_pages_inc();
+
+	raw_hwp = kmalloc(sizeof(struct raw_hwp_page), GFP_ATOMIC);
+	if (raw_hwp) {
+		raw_hwp->page = page;
+		llist_add(&raw_hwp->node, head);
+	} else {
+		/*
+		 * Failed to save raw error info.  We no longer trace all
+		 * hwpoisoned subpages, and we need refuse to free/dissolve
+		 * this hwpoisoned hugepage.
+		 */
+		SetHPageRawHwpUnreliable(hpage);
+	}
+	return ret;
+}
+
+inline int hugetlb_clear_page_hwpoison(struct page *hpage)
+{
+	struct llist_head *head;
+	struct llist_node *t, *tnode;
+
+	if (!HPageRawHwpUnreliable(hpage))
+		ClearPageHWPoison(hpage);
+	head = raw_hwp_list_head(hpage);
+	llist_for_each_safe(tnode, t, head->first) {
+		struct raw_hwp_page *p = container_of(tnode, struct raw_hwp_page, node);
+
+		SetPageHWPoison(p->page);
+		kfree(p);
+	}
+	llist_del_all(head);
+	return 0;
+}
+
 /*
  * Called from hugetlb code with hugetlb_lock held.
  *
@@ -1533,7 +1609,7 @@ int __get_huge_page_for_hwpoison(unsigned long pfn, int flags)
 		goto out;
 	}
 
-	if (TestSetPageHWPoison(head)) {
+	if (hugetlb_set_page_hwpoison(head, page)) {
 		ret = -EHWPOISON;
 		goto out;
 	}
@@ -1585,7 +1661,7 @@ static int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb
 	lock_page(head);
 
 	if (hwpoison_filter(p)) {
-		ClearPageHWPoison(head);
+		hugetlb_clear_page_hwpoison(head);
 		res = -EOPNOTSUPP;
 		goto out;
 	}
-- 
2.25.1

[PATCH v3 5/9] mm, hwpoison: make unpoison aware of raw error info in hwpoisoned hugepage

[Naoya Horiguchi]

From: Naoya Horiguchi <naoya.horiguchi@nec.com>

Raw error info list needs to be removed when hwpoisoned hugetlb is
unpoisoned.  And unpoison handler needs to know how many errors there
are in the target hugepage. So add them.

Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
---
 include/linux/swapops.h |  9 +++++++++
 mm/memory-failure.c     | 32 ++++++++++++++++++++++++++------
 2 files changed, 35 insertions(+), 6 deletions(-)

diff --git a/include/linux/swapops.h b/include/linux/swapops.h
index 9584c2e1c54a..ad62776ee99c 100644
--- a/include/linux/swapops.h
+++ b/include/linux/swapops.h
@@ -494,6 +494,11 @@ static inline void num_poisoned_pages_dec(void)
 	atomic_long_dec(&num_poisoned_pages);
 }
 
+static inline void num_poisoned_pages_sub(long i)
+{
+	atomic_long_sub(i, &num_poisoned_pages);
+}
+
 #else
 
 static inline swp_entry_t make_hwpoison_entry(struct page *page)
@@ -514,6 +519,10 @@ static inline struct page *hwpoison_entry_to_page(swp_entry_t entry)
 static inline void num_poisoned_pages_inc(void)
 {
 }
+
+static inline void num_poisoned_pages_sub(long i)
+{
+}
 #endif
 
 static inline int non_swap_entry(swp_entry_t entry)
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 71414eb90a7a..dc90bfadb1dd 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1557,22 +1557,33 @@ static inline int hugetlb_set_page_hwpoison(struct page *hpage,
 	return ret;
 }
 
-inline int hugetlb_clear_page_hwpoison(struct page *hpage)
+static inline long free_raw_hwp_pages(struct page *hpage, bool move_flag)
 {
 	struct llist_head *head;
 	struct llist_node *t, *tnode;
+	long count = 0;
 
-	if (!HPageRawHwpUnreliable(hpage))
-		ClearPageHWPoison(hpage);
 	head = raw_hwp_list_head(hpage);
 	llist_for_each_safe(tnode, t, head->first) {
 		struct raw_hwp_page *p = container_of(tnode, struct raw_hwp_page, node);
 
-		SetPageHWPoison(p->page);
+		if (move_flag)
+			SetPageHWPoison(p->page);
 		kfree(p);
+		count++;
 	}
 	llist_del_all(head);
-	return 0;
+	return count;
+}
+
+inline int hugetlb_clear_page_hwpoison(struct page *hpage)
+{
+	int ret = -EBUSY;
+
+	if (!HPageRawHwpUnreliable(hpage))
+		ret = !TestClearPageHWPoison(hpage);
+	free_raw_hwp_pages(hpage, true);
+	return ret;
 }
 
 /*
@@ -1714,6 +1725,10 @@ static inline int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *
 {
 	return 0;
 }
+
+static inline void free_raw_hwp_pages(struct page *hpage, bool move_flag)
+{
+}
 #endif
 
 static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
@@ -2173,6 +2188,7 @@ int unpoison_memory(unsigned long pfn)
 	struct page *p;
 	int ret = -EBUSY;
 	int freeit = 0;
+	long count = 1;
 	static DEFINE_RATELIMIT_STATE(unpoison_rs, DEFAULT_RATELIMIT_INTERVAL,
 					DEFAULT_RATELIMIT_BURST);
 
@@ -2220,6 +2236,8 @@ int unpoison_memory(unsigned long pfn)
 
 	ret = get_hwpoison_page(p, MF_UNPOISON);
 	if (!ret) {
+		if (PageHuge(p))
+			count = free_raw_hwp_pages(page, false);
 		ret = TestClearPageHWPoison(page) ? 0 : -EBUSY;
 	} else if (ret < 0) {
 		if (ret == -EHWPOISON) {
@@ -2228,6 +2246,8 @@ int unpoison_memory(unsigned long pfn)
 			unpoison_pr_info("Unpoison: failed to grab page %#lx\n",
 					 pfn, &unpoison_rs);
 	} else {
+		if (PageHuge(p))
+			count = free_raw_hwp_pages(page, false);
 		freeit = !!TestClearPageHWPoison(p);
 
 		put_page(page);
@@ -2240,7 +2260,7 @@ int unpoison_memory(unsigned long pfn)
 unlock_mutex:
 	mutex_unlock(&mf_mutex);
 	if (!ret || freeit) {
-		num_poisoned_pages_dec();
+		num_poisoned_pages_sub(count);
 		unpoison_pr_info("Unpoison: Software-unpoisoned page %#lx\n",
 				 page_to_pfn(p), &unpoison_rs);
 	}
-- 
2.25.1

[PATCH v3 6/9] mm, hwpoison: set PG_hwpoison for busy hugetlb pages

[Naoya Horiguchi]

From: Naoya Horiguchi <naoya.horiguchi@nec.com>

If memory_failure() fails to grab page refcount on a hugetlb page
because it's busy, it returns without setting PG_hwpoison on it.
This not only loses a chance of error containment, but breaks the rule
that action_result() should be called only when memory_failure() do
any of handling work (even if that's just setting PG_hwpoison).
This inconsistency could harm code maintainability.

So set PG_hwpoison and call hugetlb_set_page_hwpoison() for such a case.

Fixes: 405ce051236c ("mm/hwpoison: fix race between hugetlb free/demotion and memory_failure_hugetlb()")
Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
---
 include/linux/mm.h  | 1 +
 mm/memory-failure.c | 8 ++++----
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 4346e51484ba..044dc5a2e361 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3233,6 +3233,7 @@ enum mf_flags {
 	MF_SOFT_OFFLINE = 1 << 3,
 	MF_UNPOISON = 1 << 4,
 	MF_SW_SIMULATED = 1 << 5,
+	MF_NO_RETRY = 1 << 6,
 };
 extern int memory_failure(unsigned long pfn, int flags);
 extern void memory_failure_queue(unsigned long pfn, int flags);
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index dc90bfadb1dd..81e591cf8b4a 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1617,7 +1617,8 @@ int __get_huge_page_for_hwpoison(unsigned long pfn, int flags)
 			count_increased = true;
 	} else {
 		ret = -EBUSY;
-		goto out;
+		if (!(flags & MF_NO_RETRY))
+			goto out;
 	}
 
 	if (hugetlb_set_page_hwpoison(head, page)) {
@@ -1644,7 +1645,6 @@ 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 retry = true;
 
 	*hugetlb = 1;
 retry:
@@ -1660,8 +1660,8 @@ static int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb
 		}
 		return res;
 	} else if (res == -EBUSY) {
-		if (retry) {
-			retry = false;
+		if (!(flags & MF_NO_RETRY)) {
+			flags |= MF_NO_RETRY;
 			goto retry;
 		}
 		action_result(pfn, MF_MSG_UNKNOWN, MF_IGNORED);
-- 
2.25.1

[PATCH v3 7/9] mm, hwpoison: make __page_handle_poison returns int

[Naoya Horiguchi]

From: Naoya Horiguchi <naoya.horiguchi@nec.com>

__page_handle_poison() returns bool that shows whether
take_page_off_buddy() has passed or not now.  But we will want to
distinguish another case of "dissolve has passed but taking off failed"
by its return value. So change the type of the return value.
No functional change.

Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
---
v2 -> v3:
- move deleting "res = MF_FAILED" to the later patch. (by Miaohe)
---
 mm/memory-failure.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 81e591cf8b4a..6c7b9129eade 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -71,7 +71,13 @@ atomic_long_t num_poisoned_pages __read_mostly = ATOMIC_LONG_INIT(0);
 
 static bool hw_memory_failure __read_mostly = false;
 
-static bool __page_handle_poison(struct page *page)
+/*
+ * Return values:
+ *   1:   the page is dissolved (if needed) and taken off from buddy,
+ *   0:   the page is dissolved (if needed) and not taken off from buddy,
+ *   < 0: failed to dissolve.
+ */
+static int __page_handle_poison(struct page *page)
 {
 	int ret;
 
@@ -81,7 +87,7 @@ static bool __page_handle_poison(struct page *page)
 		ret = take_page_off_buddy(page);
 	zone_pcp_enable(page_zone(page));
 
-	return ret > 0;
+	return ret;
 }
 
 static bool page_handle_poison(struct page *page, bool hugepage_or_freepage, bool release)
@@ -91,7 +97,7 @@ static bool page_handle_poison(struct page *page, bool hugepage_or_freepage, boo
 		 * Doing this check for free pages is also fine since dissolve_free_huge_page
 		 * returns 0 for non-hugetlb pages as well.
 		 */
-		if (!__page_handle_poison(page))
+		if (__page_handle_poison(page) <= 0)
 			/*
 			 * We could fail to take off the target page from buddy
 			 * for example due to racy page allocation, but that's
@@ -1048,7 +1054,7 @@ static int me_huge_page(struct page_state *ps, struct page *p)
 		 * subpages.
 		 */
 		put_page(hpage);
-		if (__page_handle_poison(p)) {
+		if (__page_handle_poison(p) > 0) {
 			page_ref_inc(p);
 			res = MF_RECOVERED;
 		}
@@ -1684,7 +1690,7 @@ static int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb
 	if (res == 0) {
 		unlock_page(head);
 		res = MF_FAILED;
-		if (__page_handle_poison(p)) {
+		if (__page_handle_poison(p) > 0) {
 			page_ref_inc(p);
 			res = MF_RECOVERED;
 		}
-- 
2.25.1

[PATCH v3 8/9] mm, hwpoison: skip raw hwpoison page in freeing 1GB hugepage

[Naoya Horiguchi]

From: Naoya Horiguchi <naoya.horiguchi@nec.com>

Currently if memory_failure() (modified to remove blocking code with
subsequent patch) is called on a page in some 1GB hugepage, memory error
handling fails and the raw error page gets into leaked state.  The impact
is small in production systems (just leaked single 4kB page), but this
limits the testability because unpoison doesn't work for it.
We can no longer create 1GB hugepage on the 1GB physical address range
with such leaked pages, that's not useful when testing on small systems.

When a hwpoison page in a 1GB hugepage is handled, it's caught by the
PageHWPoison check in free_pages_prepare() because the 1GB hugepage is
broken down into raw error pages before coming to this point:

        if (unlikely(PageHWPoison(page)) && !order) {
                ...
                return false;
        }

Then, the page is not sent to buddy and the page refcount is left 0.

Originally this check is supposed to work when the error page is freed from
page_handle_poison() (that is called from soft-offline), but now we are
opening another path to call it, so the callers of __page_handle_poison()
need to handle the case by considering the return value 0 as success. Then
page refcount for hwpoison is properly incremented so unpoison works.

Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
---
v2 -> v3:
- remove "res = MF_FAILED" in try_memory_failure_hugetlb (by Miaohe)
---
 mm/memory-failure.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 6c7b9129eade..6a9b11807ee6 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1046,7 +1046,6 @@ static int me_huge_page(struct page_state *ps, struct page *p)
 		res = truncate_error_page(hpage, page_to_pfn(p), mapping);
 		unlock_page(hpage);
 	} else {
-		res = MF_FAILED;
 		unlock_page(hpage);
 		/*
 		 * migration entry prevents later access on error hugepage,
@@ -1054,9 +1053,11 @@ static int me_huge_page(struct page_state *ps, struct page *p)
 		 * subpages.
 		 */
 		put_page(hpage);
-		if (__page_handle_poison(p) > 0) {
+		if (__page_handle_poison(p) >= 0) {
 			page_ref_inc(p);
 			res = MF_RECOVERED;
+		} else {
+			res = MF_FAILED;
 		}
 	}
 
@@ -1689,10 +1690,11 @@ static int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb
 	 */
 	if (res == 0) {
 		unlock_page(head);
-		res = MF_FAILED;
-		if (__page_handle_poison(p) > 0) {
+		if (__page_handle_poison(p) >= 0) {
 			page_ref_inc(p);
 			res = MF_RECOVERED;
+		} else {
+			res = MF_FAILED;
 		}
 		action_result(pfn, MF_MSG_FREE_HUGE, res);
 		return res == MF_RECOVERED ? 0 : -EBUSY;
-- 
2.25.1

[PATCH v3 9/9] mm, hwpoison: enable memory error handling on 1GB hugepage

[Naoya Horiguchi]

From: Naoya Horiguchi <naoya.horiguchi@nec.com>

Now error handling code is prepared, so remove the blocking code and
enable memory error handling on 1GB hugepage.

Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
---
 include/linux/mm.h      |  1 -
 include/ras/ras_event.h |  1 -
 mm/memory-failure.c     | 16 ----------------
 3 files changed, 18 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 044dc5a2e361..9d7e9b5a4d1d 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3284,7 +3284,6 @@ enum mf_action_page_type {
 	MF_MSG_DIFFERENT_COMPOUND,
 	MF_MSG_HUGE,
 	MF_MSG_FREE_HUGE,
-	MF_MSG_NON_PMD_HUGE,
 	MF_MSG_UNMAP_FAILED,
 	MF_MSG_DIRTY_SWAPCACHE,
 	MF_MSG_CLEAN_SWAPCACHE,
diff --git a/include/ras/ras_event.h b/include/ras/ras_event.h
index d0337a41141c..cbd3ddd7c33d 100644
--- a/include/ras/ras_event.h
+++ b/include/ras/ras_event.h
@@ -360,7 +360,6 @@ TRACE_EVENT(aer_event,
 	EM ( MF_MSG_DIFFERENT_COMPOUND, "different compound page after locking" ) \
 	EM ( MF_MSG_HUGE, "huge page" )					\
 	EM ( MF_MSG_FREE_HUGE, "free huge page" )			\
-	EM ( MF_MSG_NON_PMD_HUGE, "non-pmd-sized huge page" )		\
 	EM ( MF_MSG_UNMAP_FAILED, "unmapping failed page" )		\
 	EM ( MF_MSG_DIRTY_SWAPCACHE, "dirty swapcache page" )		\
 	EM ( MF_MSG_CLEAN_SWAPCACHE, "clean swapcache page" )		\
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 6a9b11807ee6..6ee5cbe0cbab 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -728,7 +728,6 @@ static const char * const action_page_types[] = {
 	[MF_MSG_DIFFERENT_COMPOUND]	= "different compound page after locking",
 	[MF_MSG_HUGE]			= "huge page",
 	[MF_MSG_FREE_HUGE]		= "free huge page",
-	[MF_MSG_NON_PMD_HUGE]		= "non-pmd-sized huge page",
 	[MF_MSG_UNMAP_FAILED]		= "unmapping failed page",
 	[MF_MSG_DIRTY_SWAPCACHE]	= "dirty swapcache page",
 	[MF_MSG_CLEAN_SWAPCACHE]	= "clean swapcache page",
@@ -1702,21 +1701,6 @@ static int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb
 
 	page_flags = head->flags;
 
-	/*
-	 * TODO: hwpoison for pud-sized hugetlb doesn't work right now, so
-	 * simply disable it. In order to make it work properly, we need
-	 * make sure that:
-	 *  - conversion of a pud that maps an error hugetlb into hwpoison
-	 *    entry properly works, and
-	 *  - other mm code walking over page table is aware of pud-aligned
-	 *    hwpoison entries.
-	 */
-	if (huge_page_size(page_hstate(head)) > PMD_SIZE) {
-		action_result(pfn, MF_MSG_NON_PMD_HUGE, MF_IGNORED);
-		res = -EBUSY;
-		goto out;
-	}
-
 	if (!hwpoison_user_mappings(p, pfn, flags, head)) {
 		action_result(pfn, MF_MSG_UNMAP_FAILED, MF_IGNORED);
 		res = -EBUSY;
-- 
2.25.1