Re: [RFC PATCH v3 07/10] ovl: implement overlayfs' ->write_inode operation

[Jan Kara <jack@suse.cz>]

On Sun 08-11-20 22:03:04, Chengguang Xu wrote:
> +static int ovl_write_inode(struct inode *inode,
> +			   struct writeback_control *wbc)
> +{
> +	struct ovl_fs *ofs = inode->i_sb->s_fs_info;
> +	struct inode *upper = ovl_inode_upper(inode);
> +	unsigned long iflag = 0;
> +	int ret = 0;
> +
> +	if (!upper)
> +		return 0;
> +
> +	if (!ovl_should_sync(ofs))
> +		return 0;
> +
> +	if (upper->i_sb->s_op->write_inode)
> +		ret = upper->i_sb->s_op->write_inode(inode, wbc);
> +
> +	iflag |= upper->i_state & I_DIRTY_ALL;
> +
> +	if (mapping_writably_mapped(upper->i_mapping) ||
> +	    mapping_tagged(upper->i_mapping, PAGECACHE_TAG_WRITEBACK))
> +		iflag |= I_DIRTY_PAGES;
> +
> +	if (iflag)
> +		ovl_mark_inode_dirty(inode);

I think you didn't incorporate feedback we were speaking about in the last
version of the series. May comment in [1] still applies - you can miss
inodes dirtied through mmap when you decide to clean the inode here. So
IMHO you need something like:

	if (inode_is_open_for_write(inode))
		ovl_mark_inode_dirty(inode);

here to keep inode dirty while it is open for write (and not based on upper
inode state which is unreliable).

								Honza

[1] https://lore.kernel.org/linux-fsdevel/20201105140332.GG32718@quack2.suse.cz/

> +
> +	return ret;
> +}
> +
>  static void ovl_evict_inode(struct inode *inode)
>  {
>  	struct ovl_fs *ofs = inode->i_sb->s_fs_info;
> @@ -411,6 +440,7 @@ static const struct super_operations ovl_super_operations = {
>  	.destroy_inode	= ovl_destroy_inode,
>  	.drop_inode	= generic_delete_inode,
>  	.evict_inode	= ovl_evict_inode,
> +	.write_inode	= ovl_write_inode,
>  	.put_super	= ovl_put_super,
>  	.sync_fs	= ovl_sync_fs,
>  	.statfs		= ovl_statfs,
> -- 
> 2.26.2
> 
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR