Re: [PATCH v7 06/15] iomap: Return error code from iomap_write_iter()

[Matthew Wilcox <willy@infradead.org>]

On Wed, Jun 01, 2022 at 02:01:32PM -0700, Stefan Roesch wrote:
> Change the signature of iomap_write_iter() to return an error code. In
> case we cannot allocate a page in iomap_write_begin(), we will not retry
> the memory alloction in iomap_write_begin().

loff_t can already represent an error code.  And it's already used like
that.

> @@ -829,7 +830,8 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
>  		length -= status;
>  	} while (iov_iter_count(i) && length);
>  
> -	return written ? written : status;
> +	*processed = written ? written : error;
> +	return error;

I think the change you really want is:

	if (status == -EAGAIN)
		return -EAGAIN;
	if (written)
		return written;
	return status;

> @@ -843,12 +845,15 @@ iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *i,
>  		.flags		= IOMAP_WRITE,
>  	};
>  	int ret;
> +	int error = 0;
>  
>  	if (iocb->ki_flags & IOCB_NOWAIT)
>  		iter.flags |= IOMAP_NOWAIT;
>  
> -	while ((ret = iomap_iter(&iter, ops)) > 0)
> -		iter.processed = iomap_write_iter(&iter, i);
> +	while ((ret = iomap_iter(&iter, ops)) > 0) {
> +		if (error != -EAGAIN)
> +			error = iomap_write_iter(&iter, i, &iter.processed);
> +	}

You don't need to change any of this.  Look at how iomap_iter_advance()
works.