Update Linux to v5.4.2
Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/arch/powerpc/mm/pgtable-frag.c b/arch/powerpc/mm/pgtable-frag.c
new file mode 100644
index 0000000..ee4bd6d
--- /dev/null
+++ b/arch/powerpc/mm/pgtable-frag.c
@@ -0,0 +1,119 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Handling Page Tables through page fragments
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/gfp.h>
+#include <linux/mm.h>
+#include <linux/percpu.h>
+#include <linux/hardirq.h>
+#include <linux/hugetlb.h>
+#include <asm/pgalloc.h>
+#include <asm/tlbflush.h>
+#include <asm/tlb.h>
+
+void pte_frag_destroy(void *pte_frag)
+{
+ int count;
+ struct page *page;
+
+ page = virt_to_page(pte_frag);
+ /* drop all the pending references */
+ count = ((unsigned long)pte_frag & ~PAGE_MASK) >> PTE_FRAG_SIZE_SHIFT;
+ /* We allow PTE_FRAG_NR fragments from a PTE page */
+ if (atomic_sub_and_test(PTE_FRAG_NR - count, &page->pt_frag_refcount)) {
+ pgtable_pte_page_dtor(page);
+ __free_page(page);
+ }
+}
+
+static pte_t *get_pte_from_cache(struct mm_struct *mm)
+{
+ void *pte_frag, *ret;
+
+ if (PTE_FRAG_NR == 1)
+ return NULL;
+
+ spin_lock(&mm->page_table_lock);
+ ret = pte_frag_get(&mm->context);
+ if (ret) {
+ pte_frag = ret + PTE_FRAG_SIZE;
+ /*
+ * If we have taken up all the fragments mark PTE page NULL
+ */
+ if (((unsigned long)pte_frag & ~PAGE_MASK) == 0)
+ pte_frag = NULL;
+ pte_frag_set(&mm->context, pte_frag);
+ }
+ spin_unlock(&mm->page_table_lock);
+ return (pte_t *)ret;
+}
+
+static pte_t *__alloc_for_ptecache(struct mm_struct *mm, int kernel)
+{
+ void *ret = NULL;
+ struct page *page;
+
+ if (!kernel) {
+ page = alloc_page(PGALLOC_GFP | __GFP_ACCOUNT);
+ if (!page)
+ return NULL;
+ if (!pgtable_pte_page_ctor(page)) {
+ __free_page(page);
+ return NULL;
+ }
+ } else {
+ page = alloc_page(PGALLOC_GFP);
+ if (!page)
+ return NULL;
+ }
+
+ atomic_set(&page->pt_frag_refcount, 1);
+
+ ret = page_address(page);
+ /*
+ * if we support only one fragment just return the
+ * allocated page.
+ */
+ if (PTE_FRAG_NR == 1)
+ return ret;
+ spin_lock(&mm->page_table_lock);
+ /*
+ * If we find pgtable_page set, we return
+ * the allocated page with single fragement
+ * count.
+ */
+ if (likely(!pte_frag_get(&mm->context))) {
+ atomic_set(&page->pt_frag_refcount, PTE_FRAG_NR);
+ pte_frag_set(&mm->context, ret + PTE_FRAG_SIZE);
+ }
+ spin_unlock(&mm->page_table_lock);
+
+ return (pte_t *)ret;
+}
+
+pte_t *pte_fragment_alloc(struct mm_struct *mm, int kernel)
+{
+ pte_t *pte;
+
+ pte = get_pte_from_cache(mm);
+ if (pte)
+ return pte;
+
+ return __alloc_for_ptecache(mm, kernel);
+}
+
+void pte_fragment_free(unsigned long *table, int kernel)
+{
+ struct page *page = virt_to_page(table);
+
+ BUG_ON(atomic_read(&page->pt_frag_refcount) <= 0);
+ if (atomic_dec_and_test(&page->pt_frag_refcount)) {
+ if (!kernel)
+ pgtable_pte_page_dtor(page);
+ __free_page(page);
+ }
+}