dax: protect PTE modification on WP fault by radix tree entry lock

{

	struct file *file = vma->vm_file;

	struct address_space *mapping = file->f_mapping;

	void *entry;

	void *entry, **slot;

	pgoff_t index = vmf->pgoff;

	spin_lock_irq(&mapping->tree_lock);

	entry = get_unlocked_mapping_entry(mapping, index, NULL);

	if (!entry || !radix_tree_exceptional_entry(entry))

		goto out;

	radix_tree_tag_set(&mapping->page_tree, index, PAGECACHE_TAG_DIRTY);

	entry = get_unlocked_mapping_entry(mapping, index, &slot);

	if (!entry || !radix_tree_exceptional_entry(entry)) {

		if (entry)

			put_unlocked_mapping_entry(mapping, index, entry);

out:

		spin_unlock_irq(&mapping->tree_lock);

		return VM_FAULT_NOPAGE;

	}

	radix_tree_tag_set(&mapping->page_tree, index, PAGECACHE_TAG_DIRTY);

	entry = lock_slot(mapping, slot);

	spin_unlock_irq(&mapping->tree_lock);

	/*

	 * If we race with somebody updating the PTE and finish_mkwrite_fault()

	 * fails, we don't care. We need to return VM_FAULT_NOPAGE and retry

	 * the fault in either case.

	 */

	finish_mkwrite_fault(vmf);

	put_locked_mapping_entry(mapping, index, entry);

	return VM_FAULT_NOPAGE;

}

EXPORT_SYMBOL_GPL(dax_pfn_mkwrite);

static bool dax_range_is_aligned(struct block_device *bdev,

		pte_unmap_unlock(vmf->pte, vmf->ptl);

		vmf->flags |= FAULT_FLAG_MKWRITE;

		ret = vma->vm_ops->pfn_mkwrite(vma, vmf);

		if (ret & VM_FAULT_ERROR)

		if (ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE))

			return ret;

		return finish_mkwrite_fault(vmf);

	}