[PATCH][next] io_uring: Remove logically dead code in io_splice

[PATCH][next] io_uring: Remove logically dead code in io_splice

[Gustavo A. R. Silva]

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;
 
 	io_put_file(req, in, (sp->flags & SPLICE_F_FD_IN_FIXED));
-- 
2.26.0

Re: [PATCH][next] io_uring: Remove logically dead code in io_splice

[Pavel Begunkov]

On 04/05/2020 18:19, 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")

It's not a bug, so 'Fixes' tag is IMHO misleading. Anyway,

Acked-by: Pavel Begunkov <asml.silence@gmail.com>

> 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;
>  
>  	io_put_file(req, in, (sp->flags & SPLICE_F_FD_IN_FIXED));
> 

-- 
Pavel Begunkov

Re: [PATCH][next] io_uring: Remove logically dead code in io_splice

[Jens Axboe]

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

Re: [PATCH][next] io_uring: Remove logically dead code in io_splice

[Pavel Begunkov]

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@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:

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

Re: [PATCH][next] io_uring: Remove logically dead code in io_splice

[Gustavo A. R. Silva]

On 5/4/20 10:25, Jens Axboe wrote:
>> 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
> 

Oh, I see now. Thanks for the feedback.

--
Gustavo