mm: remove HUGETLB_PAGE_DTOR

We can use a bit in page[1].flags to indicate that this folio belongs to
hugetlb instead of using a value in page[1].dtors.  That lets
folio_test_hugetlb() become an inline function like it should be.  We can
also get rid of NULL_COMPOUND_DTOR.

Link: https://lkml.kernel.org/r/20230816151201.3655946-8-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Yanteng Si <siyanteng@loongson.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 33 insertions, 10 deletions

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 9218028caf33..e9e7cc45352d 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -171,15 +171,6 @@ enum pageflags {
 	/* Remapped by swiotlb-xen. */
 	PG_xen_remapped = PG_owner_priv_1,
 
-#ifdef CONFIG_MEMORY_FAILURE
-	/*
-	 * Compound pages. Stored in first tail page's flags.
-	 * Indicates that at least one subpage is hwpoisoned in the
-	 * THP.
-	 */
-	PG_has_hwpoisoned = PG_error,
-#endif
-
 	/* non-lru isolated movable page */
 	PG_isolated = PG_reclaim,
 
@@ -190,6 +181,15 @@ enum pageflags {
 	/* For self-hosted memmap pages */
 	PG_vmemmap_self_hosted = PG_owner_priv_1,
 #endif
+
+	/*
+	 * Flags only valid for compound pages.  Stored in first tail page's
+	 * flags word.
+	 */
+
+	/* At least one page in this folio has the hwpoison flag set */
+	PG_has_hwpoisoned = PG_error,
+	PG_hugetlb = PG_active,
 };
 
 #define PAGEFLAGS_MASK		((1UL << NR_PAGEFLAGS) - 1)
@@ -812,7 +812,23 @@ static inline void ClearPageCompound(struct page *page)
 
 #ifdef CONFIG_HUGETLB_PAGE
 int PageHuge(struct page *page);
-bool folio_test_hugetlb(struct folio *folio);
+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(struct folio *folio)
+{
+	return folio_test_large(folio) &&
+		test_bit(PG_hugetlb, folio_flags(folio, 1));
+}
 #else
 TESTPAGEFLAG_FALSE(Huge, hugetlb)
 #endif
@@ -1056,6 +1072,13 @@ static __always_inline void __ClearPageAnonExclusive(struct page *page)
 #define PAGE_FLAGS_CHECK_AT_PREP	\
 	((PAGEFLAGS_MASK & ~__PG_HWPOISON) | LRU_GEN_MASK | LRU_REFS_MASK)
 
+/*
+ * Flags stored in the second page of a compound page.  They may overlap
+ * the CHECK_AT_FREE flags above, so need to be cleared.
+ */
+#define PAGE_FLAGS_SECOND						\
+	(1UL << PG_has_hwpoisoned	| 1UL << PG_hugetlb)
+
 #define PAGE_FLAGS_PRIVATE				\
 	(1UL << PG_private | 1UL << PG_private_2)
 /**