linux-kernel - Re: [PATCH][next] io_uring: Remove logically dead code in io

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Date:   Mon, 4 May 2020 18:52:17 +0300
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Jens Axboe <axboe@...nel.dk>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Alexander Viro <viro@...iv.linux.org.uk>
Cc:     io-uring@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] io_uring: Remove logically dead code in io_splice

On 04/05/2020 18:25, Jens Axboe wrote:
> 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@...eddedor.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:

Oh, right, it will ignore O_NONBLOCK and be resubmitted, as going through
io_wq_submit_work(). I need to be more attentive.


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

-- 
Pavel Begunkov