[PATCH 06/12] sparc: add pte_free_defer() for pgtables sharing page

Hugh Dickins
2023-05-29T06:21:44Z

Add sparc-specific pte_free_defer(), to call pte_free() via call_rcu().
pte_free_defer() will be called inside khugepaged's retract_page_tables()
loop, where allocating extra memory cannot be relied upon. This precedes
the generic version to avoid build breakage from incompatible pgtable_t.

Signed-off-by: Hugh Dickins <hughd@google.com>
---
arch/sparc/include/asm/pgalloc_64.h | 4 ++++
arch/sparc/mm/init_64.c | 16 ++++++++++++++++
2 files changed, 20 insertions(+)

diff --git a/arch/sparc/include/asm/pgalloc_64.h b/arch/sparc/include/asm/pgalloc_64.h
index 7b5561d17ab1..caa7632be4c2 100644
--- a/arch/sparc/include/asm/pgalloc_64.h
+++ b/arch/sparc/include/asm/pgalloc_64.h
@@ -65,6 +65,10 @@ pgtable_t pte_alloc_one(struct mm_struct *mm);
void pte_free_kernel(struct mm_struct *mm, pte_t *pte);
void pte_free(struct mm_struct *mm, pgtable_t ptepage);

+/* arch use pte_free_defer() implementation in arch/sparc/mm/init_64.c */
+#define pte_free_defer pte_free_defer
+void pte_free_defer(struct mm_struct *mm, pgtable_t pgtable);
+
#define pmd_populate_kernel(MM, PMD, PTE) pmd_set(MM, PMD, PTE)
#define pmd_populate(MM, PMD, PTE) pmd_set(MM, PMD, PTE)

diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c
index 04f9db0c3111..b7c6aa085ef6 100644
--- a/arch/sparc/mm/init_64.c
+++ b/arch/sparc/mm/init_64.c
@@ -2930,6 +2930,22 @@ void pgtable_free(void *table, bool is_page)
}

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+static void pte_free_now(struct rcu_head *head)
+{
+ struct page *page;
+
+ page = container_of(head, struct page, rcu_head);
+ __pte_free((pgtable_t)page_to_virt(page));
+}
+
+void pte_free_defer(struct mm_struct *mm, pgtable_t pgtable)
+{
+ struct page *page;
+
+ page = virt_to_page(pgtable);
+ call_rcu(&page->rcu_head, pte_free_now);
+}
+
void update_mmu_cache_pmd(struct vm_area_struct *vma, unsigned long addr,
pmd_t *pmd)
{
--
2.35.3