// 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); if (PageReserved(page)) return free_reserved_page(page); 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); } }