linux-kernel - Re: [PATCH]i[next] io_uring: remove redundant check on force

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Date:   Tue, 5 May 2020 14:59:41 +0300
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Colin King <colin.king@...onical.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Jens Axboe <axboe@...nel.dk>, linux-fsdevel@...r.kernel.org,
        io-uring@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH]i[next] io_uring: remove redundant check on force_nonblock

On 05/05/2020 12:33, Colin King wrote:
> From: Colin Ian King <colin.king@...onical.com>
> 
> The check on force_nonblock is redundant as this is performed
> several statements earlier and also returns with -EAGAIN. Remove
> the redundant check.

It's kind of scary that such simple transformation is repeatedly done wrongly.
In short, because force_nonblock is always false there, the equivalent
transformation would be to delete it altogether.

Kudos to Jens for his thoroughness. See
https://lore.kernel.org/io-uring/529ea928-88a6-2cbe-ba8c-72b4c68cc7e8@kernel.dk/T/#u

> 
> Addresses-Coverity: ("Logicall dead code")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  fs/io_uring.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index e5dfbbd2aa34..4b1efb062f7f 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -2782,7 +2782,7 @@ static int io_splice(struct io_kiocb *req, bool force_nonblock)
>  	poff_in = (sp->off_in == -1) ? NULL : &sp->off_in;
>  	poff_out = (sp->off_out == -1) ? NULL : &sp->off_out;
>  	ret = do_splice(in, poff_in, out, poff_out, sp->len, flags);
> -	if (force_nonblock && ret == -EAGAIN)
> +	if (ret == -EAGAIN)
>  		return -EAGAIN;
>  
>  	io_put_file(req, in, (sp->flags & SPLICE_F_FD_IN_FIXED));
> 

-- 
Pavel Begunkov