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Subject: Re: [PATCH][next] io_uring: Remove logically dead code in io_splice
To:     "Gustavo A. R. Silva" <gustavo@embeddedor.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Pavel Begunkov <asml.silence@gmail.com>
Cc:     io-uring@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20200504151912.GA22779@embeddedor>
From:   Jens Axboe <axboe@kernel.dk>
Message-ID: <b26c33c8-e636-edf6-3d43-7b3394850d7a@kernel.dk>
Date:   Mon, 4 May 2020 09:25:26 -0600
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On 5/4/20 9:19 AM, Gustavo A. R. Silva wrote:
> In case force_nonblock happens to be true, the function returns
> at:
> 
>  2779         if (force_nonblock)
>  2780                 return -EAGAIN;
> 
> before reaching this line of code. So, the null check on force_nonblock
> at 2785, is never actually being executed.
> 
> Addresses-Coverity-ID: 1492838 ("Logically dead code")
> Fixes: 2fb3e82284fc ("io_uring: punt splice async because of inode mutex")
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.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;

This isn't right, it should just remove the two lines completely. But
also see:

https://lore.kernel.org/io-uring/529ea928-88a6-2cbe-ba8c-72b4c68cc7e8@kernel.dk/T/#u

-- 
Jens Axboe