The patch titled
Subject: mm, hwpoison, hugetlb: support saving mechanism of raw error pages
has been added to the -mm mm-unstable branch. Its filename is
mm-hwpoison-hugetlb-support-saving-mechanism-of-raw-error-pages.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-hwpoison-hugetlb-support-saving-mechanism-of-raw-error-pages.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Subject: mm, hwpoison, hugetlb: support saving mechanism of raw error pages
Date: Thu, 14 Jul 2022 13:24:15 +0900
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.
Link: https://lkml.kernel.org/r/20220714042420.1847125-4-naoya.horiguchi@xxxxxxxxx
Signed-off-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Reviewed-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Liu Shixin <liushixin2@xxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Yang Shi <shy828301@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/hugetlb.h | 17 ++++++-
mm/hugetlb.c | 23 +++++----
mm/memory-failure.c | 89 ++++++++++++++++++++++++++++++++++++--
3 files changed, 116 insertions(+), 13 deletions(-)
--- a/include/linux/hugetlb.h~mm-hwpoison-hugetlb-support-saving-mechanism-of-raw-error-pages
+++ a/include/linux/hugetlb.h
@@ -43,6 +43,9 @@ enum {
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,
};
@@ -551,7 +554,7 @@ generic_hugetlb_get_unmapped_area(struct
* 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.
@@ -561,6 +564,8 @@ generic_hugetlb_get_unmapped_area(struct
* 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,
@@ -568,6 +573,7 @@ enum hugetlb_page_flags {
HPG_temporary,
HPG_freed,
HPG_vmemmap_optimized,
+ HPG_raw_hwp_unreliable,
__NR_HPAGEFLAGS,
};
@@ -614,6 +620,7 @@ HPAGEFLAG(Migratable, migratable)
HPAGEFLAG(Temporary, temporary)
HPAGEFLAG(Freed, freed)
HPAGEFLAG(VmemmapOptimized, vmemmap_optimized)
+HPAGEFLAG(RawHwpUnreliable, raw_hwp_unreliable)
#ifdef CONFIG_HUGETLB_PAGE
@@ -796,6 +803,14 @@ extern int dissolve_free_huge_page(struc
extern int dissolve_free_huge_pages(unsigned long start_pfn,
unsigned long end_pfn);
+#ifdef CONFIG_MEMORY_FAILURE
+extern void hugetlb_clear_page_hwpoison(struct page *hpage);
+#else
+static inline void hugetlb_clear_page_hwpoison(struct page *hpage)
+{
+}
+#endif
+
#ifdef CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION
#ifndef arch_hugetlb_migration_supported
static inline bool arch_hugetlb_migration_supported(struct hstate *h)
--- a/mm/hugetlb.c~mm-hwpoison-hugetlb-support-saving-mechanism-of-raw-error-pages
+++ a/mm/hugetlb.c
@@ -1535,6 +1535,13 @@ static void __update_and_free_page(struc
if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
return;
+ /*
+ * If we don't know which subpages are hwpoisoned, we can't free
+ * the hugepage, so it's leaked intentionally.
+ */
+ if (HPageRawHwpUnreliable(page))
+ return;
+
if (hugetlb_vmemmap_restore(h, page)) {
spin_lock_irq(&hugetlb_lock);
/*
@@ -1547,6 +1554,13 @@ static void __update_and_free_page(struc
return;
}
+ /*
+ * 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);
+
for (i = 0; i < pages_per_huge_page(h);
i++, subpage = mem_map_next(subpage, page, i)) {
subpage->flags &= ~(1 << PG_locked | 1 << PG_error |
@@ -2109,15 +2123,6 @@ retry:
*/
rc = hugetlb_vmemmap_restore(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);
--- a/mm/memory-failure.c~mm-hwpoison-hugetlb-support-saving-mechanism-of-raw-error-pages
+++ a/mm/memory-failure.c
@@ -1664,6 +1664,90 @@ unlock:
EXPORT_SYMBOL_GPL(mf_dax_kill_procs);
#endif /* CONFIG_FS_DAX */
+#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 void __free_raw_hwp_pages(struct page *hpage)
+{
+ struct llist_head *head;
+ struct llist_node *t, *tnode;
+
+ 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);
+}
+
+static 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 = TestSetPageHWPoison(hpage) ? -EHWPOISON : 0;
+
+ /*
+ * 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;
+ }
+
+ raw_hwp = kmalloc(sizeof(struct raw_hwp_page), GFP_ATOMIC);
+ if (raw_hwp) {
+ raw_hwp->page = page;
+ llist_add(&raw_hwp->node, head);
+ /* the first error event will be counted in action_result(). */
+ if (ret)
+ num_poisoned_pages_inc();
+ } 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);
+ /*
+ * Once HPageRawHwpUnreliable is set, raw_hwp_page is not
+ * used any more, so free it.
+ */
+ __free_raw_hwp_pages(hpage);
+ }
+ return ret;
+}
+
+void hugetlb_clear_page_hwpoison(struct page *hpage)
+{
+ if (HPageRawHwpUnreliable(hpage))
+ return;
+ ClearPageHWPoison(hpage);
+ __free_raw_hwp_pages(hpage);
+}
+
/*
* Called from hugetlb code with hugetlb_lock held.
*
@@ -1698,7 +1782,7 @@ int __get_huge_page_for_hwpoison(unsigne
goto out;
}
- if (TestSetPageHWPoison(head)) {
+ if (hugetlb_set_page_hwpoison(head, page)) {
ret = -EHWPOISON;
goto out;
}
@@ -1710,7 +1794,6 @@ out:
return ret;
}
-#ifdef CONFIG_HUGETLB_PAGE
/*
* Taking refcount of hugetlb pages needs extra care about race conditions
* with basic operations like hugepage allocation/free/demotion.
@@ -1751,7 +1834,7 @@ retry:
lock_page(head);
if (hwpoison_filter(p)) {
- ClearPageHWPoison(head);
+ hugetlb_clear_page_hwpoison(head);
res = -EOPNOTSUPP;
goto out;
}
_
Patches currently in -mm which might be from naoya.horiguchi@xxxxxxx are
mm-hugetlb-separate-path-for-hwpoison-entry-in-copy_hugetlb_page_range.patch
mm-hugetlb-check-gigantic_page_runtime_supported-in-return_unused_surplus_pages.patch
mm-hugetlb-make-pud_huge-and-follow_huge_pud-aware-of-non-present-pud-entry.patch
mm-hwpoison-hugetlb-support-saving-mechanism-of-raw-error-pages.patch
mm-hwpoison-make-unpoison-aware-of-raw-error-info-in-hwpoisoned-hugepage.patch
mm-hwpoison-set-pg_hwpoison-for-busy-hugetlb-pages.patch
mm-hwpoison-make-__page_handle_poison-returns-int.patch
mm-hwpoison-skip-raw-hwpoison-page-in-freeing-1gb-hugepage.patch
mm-hwpoison-enable-memory-error-handling-on-1gb-hugepage.patch
