linux-kernel - Re: [PATCH 4/9 next] fs/io_uring Don't use the return value from import

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Message-ID: <20200921141456.GD24515@infradead.org>
Date:   Mon, 21 Sep 2020 15:14:56 +0100
From:   Christoph Hellwig <hch@...radead.org>
To:     David Laight <David.Laight@...lab.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "io-uring@...r.kernel.org" <io-uring@...r.kernel.org>,
        Jens Axboe <axboe@...nel.dk>,
        "David S. Miller" <davem@...emloft.net>,
        Al Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH 4/9 next] fs/io_uring Don't use the return value from
 import_iovec().

On Tue, Sep 15, 2020 at 02:55:20PM +0000, David Laight wrote:
> 
> This is the only code that relies on import_iovec() returning
> iter.count on success.
> This allows a better interface to import_iovec().

This looks generall sane, but a comment below:

> @@ -3123,7 +3123,7 @@ static int io_read(struct io_kiocb *req, bool force_nonblock,
>  	if (ret < 0)
>  		return ret;
>  	iov_count = iov_iter_count(iter);
> -	io_size = ret;
> +	io_size = iov_count;
>  	req->result = io_size;
>  	ret = 0;
>  
> @@ -3246,7 +3246,7 @@ static int io_write(struct io_kiocb *req, bool force_nonblock,
>  	if (ret < 0)
>  		return ret;
>  	iov_count = iov_iter_count(iter);
> -	io_size = ret;
> +	io_size = iov_count;
>  	req->result = io_size;

I tink the local iov_count variable can go away in both functions,
as io_size only changes after the last use of iov_count (io_read) or
not at all (io_write).