[PATCH] mm/memory_failure: reject unsupported non-folio compound page

[Zi Yan]

When !CONFIG_TRANSPARENT_HUGEPAGE, a non-folio compound page can appear in
a userspace mapping via either vm_insert_*() functions or
vm_operatios_struct->fault(). They are not folios, thus should not be
considered for folio operations like split. Change memory_failure() and
soft_offline_page() to reject these non-folio compound pages as
EOPNOTSUPP.

Add PageNonFolioCompound() helper function. This function is functionally
equivalent to folio_test_large() && !folio_test_large_rmappable(), but it
is supposed to be used on struct page. So open code it instead.

Fixes: 689b8986776c ("mm/memory-failure: improve large block size folio handling")
Reported-by: 是参差 <shicenci@xxxxxxxxx>
Closes: https://lore.kernel.org/all/PS1PPF7E1D7501F1E4F4441E7ECD056DEADAB98A@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
---
 include/linux/page-flags.h | 16 ++++++++++++++++
 mm/memory-failure.c        |  9 ++++++---
 2 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index f7a0e4af0c73..2fe8047f42a3 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -1102,6 +1102,22 @@ static inline bool folio_contain_hwpoisoned_page(struct folio *folio)
 
 bool is_free_buddy_page(const struct page *page);
 
+static inline bool PageNonFolioCompound(const struct page *page)
+{
+	if (PageCompound(page)) {
+		const struct page *head = compound_head(page);
+
+		/*
+		 * Without CONFIG_TRANSPARENT_HUGEPAGE, PG_large_rmappable
+		 * should not be set/used.
+		 */
+		return !IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) ||
+		       !test_bit(PG_large_rmappable, &head[1].flags.f);
+	}
+
+	return false;
+}
+
 #ifdef CONFIG_MIGRATION
 /*
  * This page is migratable through movable_ops (for selected typed pages
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index cf0d526e6d41..8b6b5950bb66 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -2440,9 +2440,12 @@ int memory_failure(unsigned long pfn, int flags)
 
 	folio = page_folio(p);
 
-	/* filter pages that are protected from hwpoison test by users */
+	/*
+	 * filter pages that are protected from hwpoison test by users or
+	 * unsupported non folio compound ones
+	 */
 	folio_lock(folio);
-	if (hwpoison_filter(p)) {
+	if (hwpoison_filter(p) || PageNonFolioCompound(p)) {
 		ClearPageHWPoison(p);
 		folio_unlock(folio);
 		folio_put(folio);
@@ -2945,7 +2948,7 @@ int soft_offline_page(unsigned long pfn, int flags)
 	ret = get_hwpoison_page(page, flags | MF_SOFT_OFFLINE);
 	put_online_mems();
 
-	if (hwpoison_filter(page)) {
+	if (hwpoison_filter(page) || PageNonFolioCompound(page)) {
 		if (ret > 0)
 			put_page(page);
 
-- 
2.51.0