Re: [PATCH 3/5] block: don't allow multiple bio_iov_iter_get_pages calls per bio

[Ming Lei <ming.lei@redhat.com>]

On Thu, Apr 11, 2019 at 08:23:29AM +0200, Christoph Hellwig wrote:
> No caller uses bio_iov_iter_get_pages multiple times on a given bio,
> and that funtionality isn't all that useful.  Removing it will make
> some future changes a little easier and also simplifies the function
> a bit.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
> ---
>  block/bio.c | 15 ++++++---------
>  1 file changed, 6 insertions(+), 9 deletions(-)
> 
> diff --git a/block/bio.c b/block/bio.c
> index ad346082a971..c2a389b1509a 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -958,7 +958,10 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
>  int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
>  {
>  	const bool is_bvec = iov_iter_is_bvec(iter);
> -	unsigned short orig_vcnt = bio->bi_vcnt;
> +	int ret;
> +
> +	if (WARN_ON_ONCE(bio->bi_vcnt))
> +		return -EINVAL;
>  
>  	/*
>  	 * If this is a BVEC iter, then the pages are kernel pages. Don't
> @@ -968,19 +971,13 @@ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
>  		bio_set_flag(bio, BIO_NO_PAGE_REF);
>  
>  	do {
> -		int ret;
> -
>  		if (is_bvec)
>  			ret = __bio_iov_bvec_add_pages(bio, iter);
>  		else
>  			ret = __bio_iov_iter_get_pages(bio, iter);
> +	} while (!ret && iov_iter_count(iter) && !bio_full(bio));
>  
> -		if (unlikely(ret))
> -			return bio->bi_vcnt > orig_vcnt ? 0 : ret;
> -
> -	} while (iov_iter_count(iter) && !bio_full(bio));
> -
> -	return 0;
> +	return bio->bi_vcnt ? 0 : ret;
>  }
>  
>  static void submit_bio_wait_endio(struct bio *bio)
> -- 
> 2.20.1
> 

Reviewed-by: Ming Lei <ming.lei@redhat.com>

-- 
Ming