Re: [PATCH bpf v4 1/2] selftests/bpf: Add F_SETFL for fcntl in test_sockmap

[Martin KaFai Lau <martin.lau@linux.dev>]

On 4/17/24 1:14 AM, Geliang Tang wrote:
> Hi Martin,
> 
> On Thu, Apr 11, 2024 at 11:10:49AM -0700, Martin KaFai Lau wrote:
>> On 4/8/24 10:18 PM, Geliang Tang wrote:
>>> From: Geliang Tang <tanggeliang@kylinos.cn>
>>>
>>> Incorrect arguments are passed to fcntl() in test_sockmap.c when invoking
>>> it to set file status flags. If O_NONBLOCK is used as 2nd argument and
>>> passed into fcntl, -EINVAL will be returned (See do_fcntl() in fs/fcntl.c).
>>> The correct approach is to use F_SETFL as 2nd argument, and O_NONBLOCK as
>>> 3rd one.
>>>
>>> In nonblock mode, if EWOULDBLOCK is received, continue receiving, otherwise
>>> some subtests of test_sockmap fail.
>>>
>>> Fixes: 16962b2404ac ("bpf: sockmap, add selftests")
>>> Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
>>> Acked-by: Yonghong Song <yonghong.song@linux.dev>
>>> ---
>>>    tools/testing/selftests/bpf/test_sockmap.c | 5 ++++-
>>>    1 file changed, 4 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/tools/testing/selftests/bpf/test_sockmap.c b/tools/testing/selftests/bpf/test_sockmap.c
>>> index 024a0faafb3b..4feed253fca2 100644
>>> --- a/tools/testing/selftests/bpf/test_sockmap.c
>>> +++ b/tools/testing/selftests/bpf/test_sockmap.c
>>> @@ -603,7 +603,9 @@ static int msg_loop(int fd, int iov_count, int iov_length, int cnt,
>>>    		struct timeval timeout;
>>>    		fd_set w;
>>> -		fcntl(fd, fd_flags);
>>> +		if (fcntl(fd, F_SETFL, fd_flags))
>>> +			goto out_errno;
>>> +
>>>    		/* Account for pop bytes noting each iteration of apply will
>>>    		 * call msg_pop_data helper so we need to account for this
>>>    		 * by calculating the number of apply iterations. Note user
>>> @@ -678,6 +680,7 @@ static int msg_loop(int fd, int iov_count, int iov_length, int cnt,
>>>    					perror("recv failed()");
>>>    					goto out_errno;
>>>    				}
>>> +				continue;
>>
>>  From looking at it again, there is a select() earlier, so it should not hit
>> EWOULDBLOCK.
> 
> Can the patch in the attachment be accepted? It can work, but I'm not sure
> if it has changed the behavior of this test. Anyway, I would like to hear
> your opinion.

I don't know what is the correct expectation also. John and JakubS, can you take 
a look?