/* * We special-case the C-O-W ZERO_PAGE, because it's such * a common occurrence (no need to read the page to know * that it's zero - better for the cache and memory subsystem). */ static inline void copy_cow_page(struct page * from, struct page * to, unsigned long address) { if (from == ZERO_PAGE(address)) { clear_user_highpage(to, address); return; } copy_user_highpage(to, from, address); }
static int remap_copy_page(struct page *to, struct page *from) { #ifdef CONFIG_REALTEK_PREVENT_DC_ALIAS copy_user_highpage(to, from, 0); #else copy_highpage(to, from); #endif return 0; }
static void copy_huge_page(struct page *dst, struct page *src, unsigned long addr, struct vm_area_struct *vma) { int i; might_sleep(); for (i = 0; i < HPAGE_SIZE/PAGE_SIZE; i++) { cond_resched(); copy_user_highpage(dst + i, src + i, addr + i*PAGE_SIZE, vma); } }
/* * do_no_page() tries to create a new page mapping. It aggressively * tries to share with existing pages, but makes a separate copy if * the "write_access" parameter is true in order to avoid the next * page fault. * * As this is called only for pages that do not currently exist, we * do not need to flush old virtual caches or the TLB. * * This is called with the MM semaphore held and the page table * spinlock held. Exit with the spinlock released. */ static int do_no_page(struct mm_struct * mm, struct vm_area_struct * vma, unsigned long address, int write_access, pte_t *page_table) { struct page * new_page; pte_t entry; if (!vma->vm_ops || !vma->vm_ops->nopage) return do_anonymous_page(mm, vma, page_table, write_access, address); spin_unlock(&mm->page_table_lock); new_page = vma->vm_ops->nopage(vma, address & PAGE_MASK, 0); if (new_page == NULL) /* no page was available -- SIGBUS */ return 0; if (new_page == NOPAGE_OOM) return -1; /* * Should we do an early C-O-W break? */ if (write_access && !(vma->vm_flags & VM_SHARED)) { struct page * page = alloc_page(GFP_HIGHUSER); if (!page) { page_cache_release(new_page); return -1; } copy_user_highpage(page, new_page, address); page_cache_release(new_page); lru_cache_add(page); new_page = page; } spin_lock(&mm->page_table_lock); /* * This silly early PAGE_DIRTY setting removes a race * due to the bad i386 page protection. But it's valid * for other architectures too. * * Note that if write_access is true, we either now have * an exclusive copy of the page, or this is a shared mapping, * so we can make it writable and dirty to avoid having to * handle that later. */ /* Only go through if we didn't race with anybody else... */ if (pte_none(*page_table)) { ++mm->rss; flush_page_to_ram(new_page); flush_icache_page(vma, new_page); entry = mk_pte(new_page, vma->vm_page_prot); if (write_access) entry = pte_mkwrite(pte_mkdirty(entry)); set_pte(page_table, entry); } else { /* One of our sibling threads was faster, back out. */ page_cache_release(new_page); spin_unlock(&mm->page_table_lock); return 1; } /* no need to invalidate: a not-present page shouldn't be cached */ update_mmu_cache(vma, address, entry); spin_unlock(&mm->page_table_lock); return 2; /* Major fault */ }