/** * __replace_page - replace page in vma by new page. * based on replace_page in mm/ksm.c * * @vma: vma that holds the pte pointing to page * @addr: address the old @page is mapped at * @page: the cowed page we are replacing by kpage * @kpage: the modified page we replace page by * * Returns 0 on success, -EFAULT on failure. */ static int __replace_page(struct vm_area_struct *vma, unsigned long addr, struct page *old_page, struct page *new_page) { struct mm_struct *mm = vma->vm_mm; spinlock_t *ptl; pte_t *ptep; int err; /* For mmu_notifiers */ const unsigned long mmun_start = addr; const unsigned long mmun_end = addr + PAGE_SIZE; struct mem_cgroup *memcg; err = mem_cgroup_try_charge(new_page, vma->vm_mm, GFP_KERNEL, &memcg, false); if (err) return err; /* For try_to_free_swap() and munlock_vma_page() below */ lock_page(old_page); mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); err = -EAGAIN; ptep = page_check_address(old_page, mm, addr, &ptl, 0); if (!ptep) { mem_cgroup_cancel_charge(new_page, memcg, false); goto unlock; } get_page(new_page); page_add_new_anon_rmap(new_page, vma, addr, false); mem_cgroup_commit_charge(new_page, memcg, false, false); lru_cache_add_active_or_unevictable(new_page, vma); if (!PageAnon(old_page)) { dec_mm_counter(mm, mm_counter_file(old_page)); inc_mm_counter(mm, MM_ANONPAGES); } flush_cache_page(vma, addr, pte_pfn(*ptep)); ptep_clear_flush_notify(vma, addr, ptep); set_pte_at_notify(mm, addr, ptep, mk_pte(new_page, vma->vm_page_prot)); page_remove_rmap(old_page, false); if (!page_mapped(old_page)) try_to_free_swap(old_page); pte_unmap_unlock(ptep, ptl); if (vma->vm_flags & VM_LOCKED) munlock_vma_page(old_page); put_page(old_page); err = 0; unlock: mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); unlock_page(old_page); return err; }
static ssize_t clear_refs_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos) { struct task_struct *task; char buffer[PROC_NUMBUF]; struct mm_struct *mm; struct vm_area_struct *vma; enum clear_refs_types type; int itype; int rv; memset(buffer, 0, sizeof(buffer)); if (count > sizeof(buffer) - 1) count = sizeof(buffer) - 1; if (copy_from_user(buffer, buf, count)) return -EFAULT; rv = kstrtoint(strstrip(buffer), 10, &itype); if (rv < 0) return rv; type = (enum clear_refs_types)itype; if (type < CLEAR_REFS_ALL || type >= CLEAR_REFS_LAST) return -EINVAL; if (type == CLEAR_REFS_SOFT_DIRTY) { soft_dirty_cleared = true; pr_warn_once("The pagemap bits 55-60 has changed their meaning!" " See the linux/Documentation/vm/pagemap.txt for " "details.\n"); } task = get_proc_task(file_inode(file)); if (!task) return -ESRCH; mm = get_task_mm(task); if (mm) { struct clear_refs_private cp = { .type = type, }; struct mm_walk clear_refs_walk = { .pmd_entry = clear_refs_pte_range, .test_walk = clear_refs_test_walk, .mm = mm, .private = &cp, }; if (type == CLEAR_REFS_MM_HIWATER_RSS) { /* * Writing 5 to /proc/pid/clear_refs resets the peak * resident set size to this mm's current rss value. */ down_write(&mm->mmap_sem); reset_mm_hiwater_rss(mm); up_write(&mm->mmap_sem); goto out_mm; } down_read(&mm->mmap_sem); if (type == CLEAR_REFS_SOFT_DIRTY) { for (vma = mm->mmap; vma; vma = vma->vm_next) { if (!(vma->vm_flags & VM_SOFTDIRTY)) continue; up_read(&mm->mmap_sem); down_write(&mm->mmap_sem); for (vma = mm->mmap; vma; vma = vma->vm_next) { vma->vm_flags &= ~VM_SOFTDIRTY; vma_set_page_prot(vma); } downgrade_write(&mm->mmap_sem); break; } mmu_notifier_invalidate_range_start(mm, 0, -1); } walk_page_range(0, ~0UL, &clear_refs_walk); if (type == CLEAR_REFS_SOFT_DIRTY) mmu_notifier_invalidate_range_end(mm, 0, -1); flush_tlb_mm(mm); up_read(&mm->mmap_sem); out_mm: mmput(mm); } put_task_struct(task); return count; }