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Re: [PATCH] Implement the mlock2 function
On 27/11/2017 14:43, Florian Weimer wrote:
> On 11/27/2017 05:35 PM, Adhemerval Zanella wrote:
>>
>>
>> On 27/11/2017 14:07, Florian Weimer wrote:
>>> On 11/27/2017 02:11 PM, Adhemerval Zanella wrote:
>>>> This is a reasonable approach and I am ok with this patch with the
>>>> INLINE_SYSCALL_CALL change. I wonder if it is worth to add a similar
>>>> change to p{read,write}v2 to return ENOSUP in the case of ENOSYS.
>>>
>>> My copy of the manual page says that EINVAL is used there as well.
>>>
>>> Thanks,
>>> Florian
>>
>> Indeed manpages [1] states that EINVAL is returned, but our documentation
>> states otherwise:
>>
>> manual/llio.texi
>>
>> 1286 @item EOPNOTSUPP
>> 1287
>> 1288 @c The default sysdeps/posix code will return it for any flags value
>> 1289 @c different than 0.
>> 1290 An unsupported @var{flags} was used.
>>
>> Also, "tst-preadvwritev" on a 4.13.0-17-generic indeed generates Linux
>> EOPNOTSUPP (ENOSUP):
>>
>> [pid 7896] preadv2(3, <unfinished ...>
>> [pid 7895] <... rt_sigaction resumed> {sa_handler=SIG_DFL, sa_mask=[], sa_flags=0}, 8) = 0
>> [pid 7896] <... preadv2 resumed> [{iov_base=0x7ffca77846d0, iov_len=32}], 1, 0, 0x10 /* RWF_??? */) = -1 EOPNOTSUPP (Operation not supported)
>> [pid 7895] wait4(7896, <unfinished ...>
>> [pid 7896] pwritev2(3, [{iov_base="\0\0\0\0\0\0\0\0\241H\363?\244\177\0\0@Gx\247\374\177\0\0\0\0\0\0\0\0\0\0", iov_len=32}], 1, 0, 0x10 /* RWF_??? */) = -1 EOPNOTSUPP (Operation not supported)
>>
>> So I think it would be worth to change p{read,write}v2 on GLIBC to
>> return EINVAL for invalid flags. I will prepare a patch.
>>
>> [1] http://man7.org/linux/man-pages/man2/preadv2.2.html
>
> Typo? Shouldn't we match the kernel behavior, so fail with EOPNOTSUPP?
Not for ENOSYS. And I though about following manpages definition, but
thinking twice I agree following the kernel would be better. I still
think it will be a small improvement to handle ENOSYS as ENOSUP as you
did for mlock2 and EINVAL.
Michael, I think you should update manpages with the correct errno
for invalid flags.
>
> (I double-checked, and for mlock2, the kernel does return EINVAL.)
>
> Thanks,
> Florian