>
> +int shmem_mcopy_atomic_pte(struct mm_struct *dst_mm,
> + pmd_t *dst_pmd,
> + struct vm_area_struct *dst_vma,
> + unsigned long dst_addr,
> + unsigned long src_addr,
> + struct page **pagep)
> +{
> + struct inode *inode = file_inode(dst_vma->vm_file);
> + struct shmem_inode_info *info = SHMEM_I(inode);
> + struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
> + struct address_space *mapping = inode->i_mapping;
> + gfp_t gfp = mapping_gfp_mask(mapping);
> + pgoff_t pgoff = linear_page_index(dst_vma, dst_addr);
> + struct mem_cgroup *memcg;
> + spinlock_t *ptl;
> + void *page_kaddr;
> + struct page *page;
> + pte_t _dst_pte, *dst_pte;
> + int ret;
> +
> + if (!*pagep) {
> + ret = -ENOMEM;
> + if (shmem_acct_block(info->flags))
> + goto out;
> + if (sbinfo->max_blocks) {
> + if (percpu_counter_compare(&sbinfo->used_blocks,
> + sbinfo->max_blocks) >= 0)
> + goto out_unacct_blocks;
> + percpu_counter_inc(&sbinfo->used_blocks);
> + }
> +
> + page = shmem_alloc_page(gfp, info, pgoff);
> + if (!page)
> + goto out_dec_used_blocks;
> +
> + page_kaddr = kmap_atomic(page);
> + ret = copy_from_user(page_kaddr, (const void __user *)src_addr,
> + PAGE_SIZE);
> + kunmap_atomic(page_kaddr);
> +
> + /* fallback to copy_from_user outside mmap_sem */
> + if (unlikely(ret)) {
> + *pagep = page;
> + /* don't free the page */
> + return -EFAULT;
> + }
> + } else {
> + page = *pagep;
> + *pagep = NULL;
> + }
> +
> + _dst_pte = mk_pte(page, dst_vma->vm_page_prot);
> + if (dst_vma->vm_flags & VM_WRITE)
> + _dst_pte = pte_mkwrite(pte_mkdirty(_dst_pte));
> +
> + ret = -EEXIST;
> + dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
> + if (!pte_none(*dst_pte))
> + goto out_release_uncharge_unlock;
> +
> + __SetPageUptodate(page);
> +
> + ret = mem_cgroup_try_charge(page, dst_mm, gfp, &memcg,
> + false);
> + if (ret)
> + goto out_release_uncharge_unlock;
> + ret = radix_tree_maybe_preload(gfp & GFP_RECLAIM_MASK);
You have to load radix tree without &ptl held.
Hillf
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