Merge tag 'mm-hotfixes-stable-2024-04-26-13-30' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull misc fixes from Andrew Morton:
 "11 hotfixes. 8 are cc:stable and the remaining 3 (nice ratio!) address
  post-6.8 issues or aren't considered suitable for backporting.

  All except one of these are for MM. I see no particular theme - it's
  singletons all over"

* tag 'mm-hotfixes-stable-2024-04-26-13-30' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm:
  mm/hugetlb: fix DEBUG_LOCKS_WARN_ON(1) when dissolve_free_hugetlb_folio()
  selftests: mm: protection_keys: save/restore nr_hugepages value from launch script
  stackdepot: respect __GFP_NOLOCKDEP allocation flag
  hugetlb: check for anon_vma prior to folio allocation
  mm: zswap: fix shrinker NULL crash with cgroup_disable=memory
  mm: turn folio_test_hugetlb into a PageType
  mm: support page_mapcount() on page_has_type() pages
  mm: create FOLIO_FLAG_FALSE and FOLIO_TYPE_OPS macros
  mm/hugetlb: fix missing hugetlb_lock for resv uncharge
  selftests: mm: fix unused and uninitialized variable warning
  selftests/harness: remove use of LINE_MAX

3 files changed, 88 insertions, 65 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 7b0ee64225de9..b6bdaa18b9e9d 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1223,14 +1223,16 @@ static inline void page_mapcount_reset(struct page *page)
  * a large folio, it includes the number of times this page is mapped
  * as part of that folio.
  *
- * The result is undefined for pages which cannot be mapped into userspace.
- * For example SLAB or special types of pages. See function page_has_type().
- * They use this field in struct page differently.
+ * Will report 0 for pages which cannot be mapped into userspace, eg
+ * slab, page tables and similar.
  */
 static inline int page_mapcount(struct page *page)
 {
 	int mapcount = atomic_read(&page->_mapcount) + 1;
 
+	/* Handle page_has_type() pages */
+	if (mapcount < 0)
+		mapcount = 0;
 	if (unlikely(PageCompound(page)))
 		mapcount += folio_entire_mapcount(page_folio(page));
 
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 652d77805e99d..4bf1c25fd1dc5 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -190,7 +190,6 @@ enum pageflags {
 
 	/* At least one page in this folio has the hwpoison flag set */
 	PG_has_hwpoisoned = PG_error,
-	PG_hugetlb = PG_active,
 	PG_large_rmappable = PG_workingset, /* anon or file-backed */
 };
 
@@ -458,30 +457,51 @@ static __always_inline int TestClearPage##uname(struct page *page)	\
 	TESTSETFLAG(uname, lname, policy)				\
 	TESTCLEARFLAG(uname, lname, policy)
 
+#define FOLIO_TEST_FLAG_FALSE(name)					\
+static inline bool folio_test_##name(const struct folio *folio)		\
+{ return false; }
+#define FOLIO_SET_FLAG_NOOP(name)					\
+static inline void folio_set_##name(struct folio *folio) { }
+#define FOLIO_CLEAR_FLAG_NOOP(name)					\
+static inline void folio_clear_##name(struct folio *folio) { }
+#define __FOLIO_SET_FLAG_NOOP(name)					\
+static inline void __folio_set_##name(struct folio *folio) { }
+#define __FOLIO_CLEAR_FLAG_NOOP(name)					\
+static inline void __folio_clear_##name(struct folio *folio) { }
+#define FOLIO_TEST_SET_FLAG_FALSE(name)					\
+static inline bool folio_test_set_##name(struct folio *folio)		\
+{ return false; }
+#define FOLIO_TEST_CLEAR_FLAG_FALSE(name)				\
+static inline bool folio_test_clear_##name(struct folio *folio)		\
+{ return false; }
+
+#define FOLIO_FLAG_FALSE(name)						\
+FOLIO_TEST_FLAG_FALSE(name)						\
+FOLIO_SET_FLAG_NOOP(name)						\
+FOLIO_CLEAR_FLAG_NOOP(name)
+
 #define TESTPAGEFLAG_FALSE(uname, lname)				\
-static inline bool folio_test_##lname(const struct folio *folio) { return false; } \
+FOLIO_TEST_FLAG_FALSE(lname)						\
 static inline int Page##uname(const struct page *page) { return 0; }
 
 #define SETPAGEFLAG_NOOP(uname, lname)					\
-static inline void folio_set_##lname(struct folio *folio) { }		\
+FOLIO_SET_FLAG_NOOP(lname)						\
 static inline void SetPage##uname(struct page *page) {  }
 
 #define CLEARPAGEFLAG_NOOP(uname, lname)				\
-static inline void folio_clear_##lname(struct folio *folio) { }		\
+FOLIO_CLEAR_FLAG_NOOP(lname)						\
 static inline void ClearPage##uname(struct page *page) {  }
 
 #define __CLEARPAGEFLAG_NOOP(uname, lname)				\
-static inline void __folio_clear_##lname(struct folio *folio) { }	\
+__FOLIO_CLEAR_FLAG_NOOP(lname)						\
 static inline void __ClearPage##uname(struct page *page) {  }
 
 #define TESTSETFLAG_FALSE(uname, lname)					\
-static inline bool folio_test_set_##lname(struct folio *folio)		\
-{ return 0; }								\
+FOLIO_TEST_SET_FLAG_FALSE(lname)					\
 static inline int TestSetPage##uname(struct page *page) { return 0; }
 
 #define TESTCLEARFLAG_FALSE(uname, lname)				\
-static inline bool folio_test_clear_##lname(struct folio *folio)	\
-{ return 0; }								\
+FOLIO_TEST_CLEAR_FLAG_FALSE(lname)					\
 static inline int TestClearPage##uname(struct page *page) { return 0; }
 
 #define PAGEFLAG_FALSE(uname, lname) TESTPAGEFLAG_FALSE(uname, lname)	\
@@ -855,29 +875,6 @@ TESTPAGEFLAG_FALSE(LargeRmappable, large_rmappable)
 
 #define PG_head_mask ((1UL << PG_head))
 
-#ifdef CONFIG_HUGETLB_PAGE
-int PageHuge(const struct page *page);
-SETPAGEFLAG(HugeTLB, hugetlb, PF_SECOND)
-CLEARPAGEFLAG(HugeTLB, hugetlb, PF_SECOND)
-
-/**
- * folio_test_hugetlb - Determine if the folio belongs to hugetlbfs
- * @folio: The folio to test.
- *
- * Context: Any context.  Caller should have a reference on the folio to
- * prevent it from being turned into a tail page.
- * Return: True for hugetlbfs folios, false for anon folios or folios
- * belonging to other filesystems.
- */
-static inline bool folio_test_hugetlb(const struct folio *folio)
-{
-	return folio_test_large(folio) &&
-		test_bit(PG_hugetlb, const_folio_flags(folio, 1));
-}
-#else
-TESTPAGEFLAG_FALSE(Huge, hugetlb)
-#endif
-
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 /*
  * PageHuge() only returns true for hugetlbfs pages, but not for
@@ -934,33 +931,22 @@ PAGEFLAG_FALSE(HasHWPoisoned, has_hwpoisoned)
 #endif
 
 /*
- * Check if a page is currently marked HWPoisoned. Note that this check is
- * best effort only and inherently racy: there is no way to synchronize with
- * failing hardware.
- */
-static inline bool is_page_hwpoison(struct page *page)
-{
-	if (PageHWPoison(page))
-		return true;
-	return PageHuge(page) && PageHWPoison(compound_head(page));
-}
-
-/*
  * For pages that are never mapped to userspace (and aren't PageSlab),
  * page_type may be used.  Because it is initialised to -1, we invert the
  * sense of the bit, so __SetPageFoo *clears* the bit used for PageFoo, and
  * __ClearPageFoo *sets* the bit used for PageFoo.  We reserve a few high and
- * low bits so that an underflow or overflow of page_mapcount() won't be
+ * low bits so that an underflow or overflow of _mapcount won't be
  * mistaken for a page type value.
  */
 
 #define PAGE_TYPE_BASE	0xf0000000
-/* Reserve		0x0000007f to catch underflows of page_mapcount */
+/* Reserve		0x0000007f to catch underflows of _mapcount */
 #define PAGE_MAPCOUNT_RESERVE	-128
 #define PG_buddy	0x00000080
 #define PG_offline	0x00000100
 #define PG_table	0x00000200
 #define PG_guard	0x00000400
+#define PG_hugetlb	0x00000800
 
 #define PageType(page, flag)						\
 	((page->page_type & (PAGE_TYPE_BASE | flag)) == PAGE_TYPE_BASE)
@@ -977,35 +963,38 @@ static inline int page_has_type(const struct page *page)
 	return page_type_has_type(page->page_type);
 }
 
+#define FOLIO_TYPE_OPS(lname, fname)					\
+static __always_inline bool folio_test_##fname(const struct folio *folio)\
+{									\
+	return folio_test_type(folio, PG_##lname);			\
+}									\
+static __always_inline void __folio_set_##fname(struct folio *folio)	\
+{									\
+	VM_BUG_ON_FOLIO(!folio_test_type(folio, 0), folio);		\
+	folio->page.page_type &= ~PG_##lname;				\
+}									\
+static __always_inline void __folio_clear_##fname(struct folio *folio)	\
+{									\
+	VM_BUG_ON_FOLIO(!folio_test_##fname(folio), folio);		\
+	folio->page.page_type |= PG_##lname;				\
+}
+
 #define PAGE_TYPE_OPS(uname, lname, fname)				\
+FOLIO_TYPE_OPS(lname, fname)						\
 static __always_inline int Page##uname(const struct page *page)		\
 {									\
 	return PageType(page, PG_##lname);				\
 }									\
-static __always_inline int folio_test_##fname(const struct folio *folio)\
-{									\
-	return folio_test_type(folio, PG_##lname);			\
-}									\
 static __always_inline void __SetPage##uname(struct page *page)		\
 {									\
 	VM_BUG_ON_PAGE(!PageType(page, 0), page);			\
 	page->page_type &= ~PG_##lname;					\
 }									\
-static __always_inline void __folio_set_##fname(struct folio *folio)	\
-{									\
-	VM_BUG_ON_FOLIO(!folio_test_type(folio, 0), folio);		\
-	folio->page.page_type &= ~PG_##lname;				\
-}									\
 static __always_inline void __ClearPage##uname(struct page *page)	\
 {									\
 	VM_BUG_ON_PAGE(!Page##uname(page), page);			\
 	page->page_type |= PG_##lname;					\
-}									\
-static __always_inline void __folio_clear_##fname(struct folio *folio)	\
-{									\
-	VM_BUG_ON_FOLIO(!folio_test_##fname(folio), folio);		\
-	folio->page.page_type |= PG_##lname;				\
-}									\
+}
 
 /*
  * PageBuddy() indicates that the page is free and in the buddy system
@@ -1052,6 +1041,37 @@ PAGE_TYPE_OPS(Table, table, pgtable)
  */
 PAGE_TYPE_OPS(Guard, guard, guard)
 
+#ifdef CONFIG_HUGETLB_PAGE
+FOLIO_TYPE_OPS(hugetlb, hugetlb)
+#else
+FOLIO_TEST_FLAG_FALSE(hugetlb)
+#endif
+
+/**
+ * PageHuge - Determine if the page belongs to hugetlbfs
+ * @page: The page to test.
+ *
+ * Context: Any context.
+ * Return: True for hugetlbfs pages, false for anon pages or pages
+ * belonging to other filesystems.
+ */
+static inline bool PageHuge(const struct page *page)
+{
+	return folio_test_hugetlb(page_folio(page));
+}
+
+/*
+ * Check if a page is currently marked HWPoisoned. Note that this check is
+ * best effort only and inherently racy: there is no way to synchronize with
+ * failing hardware.
+ */
+static inline bool is_page_hwpoison(struct page *page)
+{
+	if (PageHWPoison(page))
+		return true;
+	return PageHuge(page) && PageHWPoison(compound_head(page));
+}
+
 extern bool is_free_buddy_page(struct page *page);
 
 PAGEFLAG(Isolated, isolated, PF_ANY);
@@ -1118,7 +1138,7 @@ static __always_inline void __ClearPageAnonExclusive(struct page *page)
  */
 #define PAGE_FLAGS_SECOND						\
 	(0xffUL /* order */		| 1UL << PG_has_hwpoisoned |	\
-	 1UL << PG_hugetlb		| 1UL << PG_large_rmappable)
+	 1UL << PG_large_rmappable)
 
 #define PAGE_FLAGS_PRIVATE				\
 	(1UL << PG_private | 1UL << PG_private_2)
diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h
index d801409b33cfe..d55e53ac91bd2 100644
--- a/include/trace/events/mmflags.h
+++ b/include/trace/events/mmflags.h
@@ -135,6 +135,7 @@ IF_HAVE_PG_ARCH_X(arch_3)
 #define DEF_PAGETYPE_NAME(_name) { PG_##_name, __stringify(_name) }
 
 #define __def_pagetype_names						\
+	DEF_PAGETYPE_NAME(hugetlb),					\
 	DEF_PAGETYPE_NAME(offline),					\
 	DEF_PAGETYPE_NAME(guard),					\
 	DEF_PAGETYPE_NAME(table),					\