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Date: Tue, 23 Dec 2014 02:45:51 -0800
From: Christoph Hellwig <hch@infradead.org>
To: Dongsu Park <dongsu.park@profitbricks.com>
Cc: linux-kernel@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
        Kent Overstreet <kmo@daterainc.com>, Ming Lin <mlin@minggr.net>,
        Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: [RFC PATCH 08/17] block: refactor __bio_copy_iov()
Message-ID: <20141223104551.GC27600@infradead.org>
References: <cover.1419241597.git.dongsu.park@profitbricks.com>
 <0b6ba533a64aec98e8447bfd30c6622d0729d12e.1419241597.git.dongsu.park@profitbricks.com>
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>  static int __bio_copy_iov(struct bio *bio, const struct iov_iter *iter,
> +			  int to_iov)
>  {
> +	int i;
>  	struct bio_vec *bvec;
>  	struct iov_iter iov_iter = *iter;

Why not pass the iov_iter by value?

>  	bio_for_each_segment_all(bvec, bio, i) {
> +		ssize_t ret;
> +
> +		if (to_iov == WRITE)
> +			ret = copy_page_to_iter(bvec->bv_page,
> +						bvec->bv_offset,
> +						bvec->bv_len,
> +						&iov_iter);
> +		else
> +			ret = copy_page_from_iter(bvec->bv_page,
> +						  bvec->bv_offset,
> +						  bvec->bv_len,
> +						  &iov_iter);
> +
> +		if (!iov_iter_count(&iov_iter))
> +			break;
>  
> +		if (ret < bvec->bv_len)
> +			return -EFAULT;
>  	}
>  
> +	return 0;

Seems like this should be split into two functions for the read
and write cases?