Re: [PATCH 2/2] zonefs: use zone-append for AIO as well

[Christoph Hellwig <hch@lst.de>]

On Mon, Jul 20, 2020 at 10:21:18PM +0900, Johannes Thumshirn wrote:
> On a successful completion, the position the data is written to is
> returned via AIO's res2 field to the calling application.

That is a major, and except for this changelog, undocumented ABI
change.  We had the whole discussion about reporting append results
in a few threads and the issues with that in io_uring.  So let's
have that discussion there and don't mix it up with how zonefs
writes data.  Without that a lot of the boilerplate code should
also go away.

> -	if (zi->i_ztype == ZONEFS_ZTYPE_SEQ &&
> -	    (ret > 0 || ret == -EIOCBQUEUED)) {
> +
> +	if (ret > 0 || ret == -EIOCBQUEUED) {
>  		if (ret > 0)
>  			count = ret;
>  		mutex_lock(&zi->i_truncate_mutex);

Don't we still need the ZONEFS_ZTYPE_SEQ after updating count, but
before updating i_wpoffset?  Also how is this related to the rest
of the patch?

> @@ -1580,6 +1666,11 @@ static int zonefs_fill_super(struct super_block *sb, void *data, int silent)
>  	if (!sb->s_root)
>  		goto cleanup;
>  
> +	sbi->s_dio_done_wq = alloc_workqueue("zonefs-dio/%s", WQ_MEM_RECLAIM,
> +					     0, sb->s_id);
> +	if (!sbi->s_dio_done_wq)
> +		goto cleanup;
> +

Can you reuse the sb->s_dio_done_wq pointer, and maybe even the helper
to initialize it?