Re: [PATCH v2 1/7] splice: don't generate zero-len segement bvecs

From: Christoph Hellwig <hch@infradead.org>
To: Pavel Begunkov <asml.silence@gmail.com>
Cc: linux-block@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
	Christoph Hellwig <hch@infradead.org>,
	Matthew Wilcox <willy@infradead.org>,
	Ming Lei <ming.lei@redhat.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	"Darrick J . Wong" <darrick.wong@oracle.com>,
	"Martin K . Petersen" <martin.petersen@oracle.com>,
	Jonathan Corbet <corbet@lwn.net>,
	linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	io-uring@vger.kernel.org, linux-kernel@vger.kernel.org,
	target-devel@vger.kernel.org, linux-scsi@vger.kernel.org,
	linux-doc@vger.kernel.org
Subject: Re: [PATCH v2 1/7] splice: don't generate zero-len segement bvecs
Date: Mon, 4 Jan 2021 16:17:16 +0000	[thread overview]
Message-ID: <20210104161716.GA68600@infradead.org> (raw)
In-Reply-To: <ca14f80bf5156d83b38f543be2b9434a571474c9.1609461359.git.asml.silence@gmail.com>

On Sat, Jan 02, 2021 at 03:17:33PM +0000, Pavel Begunkov wrote:
> iter_file_splice_write() may spawn bvec segments with zero-length. In
> preparation for prohibiting them, filter out by hand at splice level.
> 
> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
> ---
>  fs/splice.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/splice.c b/fs/splice.c
> index 866d5c2367b2..7299330c3270 100644
> --- a/fs/splice.c
> +++ b/fs/splice.c
> @@ -644,7 +644,6 @@ iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
>  		ret = splice_from_pipe_next(pipe, &sd);
>  		if (ret <= 0)
>  			break;
> -

Spurious empty line removal..

> +			if (!this_len)
> +				continue;

Maybe throw in a comment on why we skip empty segments here?

Otherwise looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>