For the condition "file->f_mode", when it failed, it should return EACCES rather than EBADF.

For the condition "file->f_mode", when it failed, it should return EACCES rather than EBADF.

[majianpeng]

Hi all,
	When I wanted to do discard operations,but i set the  openflag was O_RDONLY,it returned a EBADF rather than EACCES or EPERM.
I searched the code and found:
>case BLKDISCARD:
>case BLKSECDISCARD: {
>		uint64_t range[2];

>		if (!(mode & FMODE_WRITE))
>			return -EBADF;
Initial i thought there was error.But i searched all code of kernel and found some places like this.

The description of EBADF is "Bad file numbe". There are some places where returned EBADF like,
>if (!f.file)
>		return -EBADF;

So i think for checking file->f_mode when failed, it should return EACCESS.


Jianpeng Ma
Thanks!

Re: For the condition "file->f_mode", when it failed, it should return EACCES rather than EBADF.

[Jens Axboe]

On Sun, Feb 03 2013, majianpeng wrote:
> Hi all,
> 	When I wanted to do discard operations,but i set the  openflag was O_RDONLY,it returned a EBADF rather than EACCES or EPERM.
> I searched the code and found:
> >case BLKDISCARD:
> >case BLKSECDISCARD: {
> >		uint64_t range[2];
> 
> >		if (!(mode & FMODE_WRITE))
> >			return -EBADF;
> Initial i thought there was error.But i searched all code of kernel and found some places like this.
> 
> The description of EBADF is "Bad file numbe". There are some places where returned EBADF like,
> >if (!f.file)
> >		return -EBADF;
> 
> So i think for checking file->f_mode when failed, it should return EACCESS.

But that would break the ABI at this point. I agree with you, though,
EBADF is not the right error for this case.

-- 
Jens Axboe

Re: Re: For the condition "file->f_mode", when it failed, it should return EACCES rather than EBADF.

[majianpeng]

>On Sun, Feb 03 2013, majianpeng wrote:
>> Hi all,
>> 	When I wanted to do discard operations,but i set the  openflag was O_RDONLY,it returned a EBADF rather than EACCES or EPERM.
>> I searched the code and found:
>> >case BLKDISCARD:
>> >case BLKSECDISCARD: {
>> >		uint64_t range[2];
>> 
>> >		if (!(mode & FMODE_WRITE))
>> >			return -EBADF;
>> Initial i thought there was error.But i searched all code of kernel and found some places like this.
>> 
>> The description of EBADF is "Bad file numbe". There are some places where returned EBADF like,
>> >if (!f.file)
>> >		return -EBADF;
>> 
>> So i think for checking file->f_mode when failed, it should return EACCESS.
>
>But that would break the ABI at this point. I agree with you, though,
>EBADF is not the right error for this case.
>
>-- 
>Jens Axboe
>
Sorry, can you explain in detail? Why can it break the ABI ?

Thanks!
Jianpeng Ma

Re: Re: For the condition "file->f_mode", when it failed, it should return EACCES rather than EBADF.

[Jens Axboe]

On Tue, Feb 05 2013, majianpeng wrote:
> >On Sun, Feb 03 2013, majianpeng wrote:
> >> Hi all,
> >> 	When I wanted to do discard operations,but i set the  openflag was O_RDONLY,it returned a EBADF rather than EACCES or EPERM.
> >> I searched the code and found:
> >> >case BLKDISCARD:
> >> >case BLKSECDISCARD: {
> >> >		uint64_t range[2];
> >> 
> >> >		if (!(mode & FMODE_WRITE))
> >> >			return -EBADF;
> >> Initial i thought there was error.But i searched all code of kernel and found some places like this.
> >> 
> >> The description of EBADF is "Bad file numbe". There are some places where returned EBADF like,
> >> >if (!f.file)
> >> >		return -EBADF;
> >> 
> >> So i think for checking file->f_mode when failed, it should return EACCESS.
> >
> >But that would break the ABI at this point. I agree with you, though,
> >EBADF is not the right error for this case.
> >
> >-- 
> >Jens Axboe
> >
> Sorry, can you explain in detail? Why can it break the ABI ?

Applications already depending on EBADF being returned for attempt to
discard on a file descriptor not opened for write. Granted it's a slim
possiblity, but it exists.

-- 
Jens Axboe