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>

diff --git a/Documentation/admin-guide/kdump/vmcoreinfo.rst b/Documentation/admin-guide/kdump/vmcoreinfo.rst
index c18d94fa64704820abd32ba39c8dee0025e2f187..baa1c355741d15a8692a048b0d6565c94baf3ca8 100644 (file)
--- a/Documentation/admin-guide/kdump/vmcoreinfo.rst
+++ b/Documentation/admin-guide/kdump/vmcoreinfo.rst
@@ -325,8 +325,8 @@ NR_FREE_PAGES
 On linux-2.6.21 or later, the number of free pages is in
 vm_stat[NR_FREE_PAGES]. Used to get the number of free pages.
 
-PG_lru|PG_private|PG_swapcache|PG_swapbacked|PG_slab|PG_hwpoision|PG_head_mask
-------------------------------------------------------------------------------
+PG_lru|PG_private|PG_swapcache|PG_swapbacked|PG_slab|PG_hwpoision|PG_head_mask|PG_hugetlb
+-----------------------------------------------------------------------------------------
 
 Page attributes. These flags are used to filter various unnecessary for
 dumping pages.
@@ -338,12 +338,6 @@ More page attributes. These flags are used to filter various unnecessary for
 dumping pages.
 
 
-HUGETLB_PAGE_DTOR
------------------
-
-The HUGETLB_PAGE_DTOR flag denotes hugetlbfs pages. Makedumpfile
-excludes these pages.
-
 x86_64
 ======
 

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 0955b6b13fd0f04700eb286d6e17f2cba60f6ea7..e241f5ee4dc4c4638d08943c91f5cd4dd5be1955 100644 (file)
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1240,11 +1240,7 @@ void folio_copy(struct folio *dst, struct folio *src);
 unsigned long nr_free_buffer_pages(void);
 
 enum compound_dtor_id {
-       NULL_COMPOUND_DTOR,
        COMPOUND_PAGE_DTOR,
-#ifdef CONFIG_HUGETLB_PAGE
-       HUGETLB_PAGE_DTOR,
-#endif
        TRANSHUGE_PAGE_DTOR,
        NR_COMPOUND_DTORS,
 };

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 9218028caf337e1fa9bc23a0b52019b943f1972a..e9e7cc45352d43072b771447a8042a5b4cd9ccb8 100644 (file)
--- 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)
 /**

diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 90ce1dfd591c3c4b41650f92f81a69e9e787becb..dd5f87047d068c36fffc882b8f8b75771fcb8258 100644 (file)
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -490,7 +490,7 @@ static int __init crash_save_vmcoreinfo_init(void)
 #define PAGE_BUDDY_MAPCOUNT_VALUE      (~PG_buddy)
        VMCOREINFO_NUMBER(PAGE_BUDDY_MAPCOUNT_VALUE);
 #ifdef CONFIG_HUGETLB_PAGE
-       VMCOREINFO_NUMBER(HUGETLB_PAGE_DTOR);
+       VMCOREINFO_NUMBER(PG_hugetlb);
 #define PAGE_OFFLINE_MAPCOUNT_VALUE    (~PG_offline)
        VMCOREINFO_NUMBER(PAGE_OFFLINE_MAPCOUNT_VALUE);
 #endif

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 6a3c80026ab3cdaf8382a2125685b852c7653062..a82c3104337e8848ec59da1c33132ac210826af7 100644 (file)
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1585,25 +1585,7 @@ static inline void __clear_hugetlb_destructor(struct hstate *h,
 {
        lockdep_assert_held(&hugetlb_lock);
 
-       /*
-        * Very subtle
-        *
-        * For non-gigantic pages set the destructor to the normal compound
-        * page dtor.  This is needed in case someone takes an additional
-        * temporary ref to the page, and freeing is delayed until they drop
-        * their reference.
-        *
-        * For gigantic pages set the destructor to the null dtor.  This
-        * destructor will never be called.  Before freeing the gigantic
-        * page destroy_compound_gigantic_folio will turn the folio into a
-        * simple group of pages.  After this the destructor does not
-        * apply.
-        *
-        */
-       if (hstate_is_gigantic(h))
-               folio_set_compound_dtor(folio, NULL_COMPOUND_DTOR);
-       else
-               folio_set_compound_dtor(folio, COMPOUND_PAGE_DTOR);
+       folio_clear_hugetlb(folio);
 }
 
 /*
@@ -1690,7 +1672,7 @@ static void add_hugetlb_folio(struct hstate *h, struct folio *folio,
                h->surplus_huge_pages_node[nid]++;
        }
 
-       folio_set_compound_dtor(folio, HUGETLB_PAGE_DTOR);
+       folio_set_hugetlb(folio);
        folio_change_private(folio, NULL);
        /*
         * We have to set hugetlb_vmemmap_optimized again as above
@@ -1814,9 +1796,8 @@ static void free_hpage_workfn(struct work_struct *work)
                /*
                 * The VM_BUG_ON_FOLIO(!folio_test_hugetlb(folio), folio) in
                 * folio_hstate() is going to trigger because a previous call to
-                * remove_hugetlb_folio() will call folio_set_compound_dtor
-                * (folio, NULL_COMPOUND_DTOR), so do not use folio_hstate()
-                * directly.
+                * remove_hugetlb_folio() will clear the hugetlb bit, so do
+                * not use folio_hstate() directly.
                 */
                h = size_to_hstate(page_size(page));
 
@@ -1955,7 +1936,7 @@ static void __prep_new_hugetlb_folio(struct hstate *h, struct folio *folio)
 {
        hugetlb_vmemmap_optimize(h, &folio->page);
        INIT_LIST_HEAD(&folio->lru);
-       folio_set_compound_dtor(folio, HUGETLB_PAGE_DTOR);
+       folio_set_hugetlb(folio);
        hugetlb_set_folio_subpool(folio, NULL);
        set_hugetlb_cgroup(folio, NULL);
        set_hugetlb_cgroup_rsvd(folio, NULL);
@@ -2070,28 +2051,10 @@ int PageHuge(struct page *page)
        if (!PageCompound(page))
                return 0;
        folio = page_folio(page);
-       return folio->_folio_dtor == HUGETLB_PAGE_DTOR;
+       return folio_test_hugetlb(folio);
 }
 EXPORT_SYMBOL_GPL(PageHuge);
 
-/**
- * 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.
- */
-bool folio_test_hugetlb(struct folio *folio)
-{
-       if (!folio_test_large(folio))
-               return false;
-
-       return folio->_folio_dtor == HUGETLB_PAGE_DTOR;
-}
-EXPORT_SYMBOL_GPL(folio_test_hugetlb);
-
 /*
  * Find and lock address space (mapping) in write mode.
  *

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 31fec31be31efe522493ad52056055374fbef94b..d96dc6a3077a6d96b2ddb9e76412c4ae87d1f80a 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1112,7 +1112,7 @@ static __always_inline bool free_pages_prepare(struct page *page,
                VM_BUG_ON_PAGE(compound && compound_order(page) != order, page);
 
                if (compound)
-                       ClearPageHasHWPoisoned(page);
+                       page[1].flags &= ~PAGE_FLAGS_SECOND;
                for (i = 1; i < (1 << order); i++) {
                        if (compound)
                                bad += free_tail_page_prepare(page, page + i);