On Tue, 20 Jun 2023 00:51:19 -0700 (PDT)
Hugh Dickins <hughd@xxxxxxxxxx> wrote:
[...]
> @@ -407,6 +429,77 @@ void __tlb_remove_table(void *_table)
> __free_page(page);
> }
>
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> +static void pte_free_now0(struct rcu_head *head);
> +static void pte_free_now1(struct rcu_head *head);
> +
> +static void pte_free_pgste(struct rcu_head *head)
> +{
> + unsigned long *table;
> + struct page *page;
> +
> + page = container_of(head, struct page, rcu_head);
> + table = (unsigned long *)page_to_virt(page);
> + table = (unsigned long *)((unsigned long)table | 0x03U);
> + __tlb_remove_table(table);
> +}
> +
> +static void pte_free_half(struct rcu_head *head, unsigned int bit)
> +{
> + unsigned long *table;
> + struct page *page;
> + unsigned int mask;
> +
> + page = container_of(head, struct page, rcu_head);
> + mask = atomic_xor_bits(&page->_refcount, 0x04U << (bit + 24));
> +
> + table = (unsigned long *)page_to_virt(page);
> + table += bit * PTRS_PER_PTE;
> + table = (unsigned long *)((unsigned long)table | (0x01U << bit));
> + __tlb_remove_table(table);
> +
> + /* If pte_free_defer() of the other half came in, queue it now */
> + if (mask & 0x0CU)
> + call_rcu(&page->rcu_head, bit ? pte_free_now0 : pte_free_now1);
> +}
> +
> +static void pte_free_now0(struct rcu_head *head)
> +{
> + pte_free_half(head, 0);
> +}
> +
> +static void pte_free_now1(struct rcu_head *head)
> +{
> + pte_free_half(head, 1);
> +}
> +
> +void pte_free_defer(struct mm_struct *mm, pgtable_t pgtable)
> +{
> + unsigned int bit, mask;
> + struct page *page;
> +
> + page = virt_to_page(pgtable);
> + if (mm_alloc_pgste(mm)) {
> + call_rcu(&page->rcu_head, pte_free_pgste);
so is this now going to be used to free page tables
instead of page_table_free_rcu?
or will it be used instead of page_table_free?
this is actually quite important for KVM on s390
> + return;
> + }
> + bit = ((unsigned long)pgtable & ~PAGE_MASK) /
> + (PTRS_PER_PTE * sizeof(pte_t));
> +
> + spin_lock_bh(&mm_pgtable_list_lock);
> + mask = atomic_xor_bits(&page->_refcount, 0x15U << (bit + 24));
> + mask >>= 24;
> + /* Other half not allocated? Other half not already pending free? */
> + if ((mask & 0x03U) == 0x00U && (mask & 0x30U) != 0x30U)
> + list_del(&page->lru);
> + spin_unlock_bh(&mm_pgtable_list_lock);
> +
> + /* Do not relink on rcu_head if other half already linked on rcu_head */
> + if ((mask & 0x0CU) != 0x0CU)
> + call_rcu(&page->rcu_head, bit ? pte_free_now1 : pte_free_now0);
> +}
> +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
> +
> /*
> * Base infrastructure required to generate basic asces, region, segment,
> * and page tables that do not make use of enhanced features like EDAT1.
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index 306a3d1a0fa6..1667a1bdb8a8 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -146,7 +146,7 @@ struct page {
> pgtable_t pmd_huge_pte; /* protected by page->ptl */
> unsigned long _pt_pad_2; /* mapping */
> union {
> - struct mm_struct *pt_mm; /* x86 pgds only */
> + struct mm_struct *pt_mm; /* x86 pgd, s390 */
> atomic_t pt_frag_refcount; /* powerpc */
> };
> #if ALLOC_SPLIT_PTLOCKS
