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

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Date:	Tue, 5 Feb 2013 23:39:44 +0800
From:	majianpeng <majianpeng@...il.com>
To:	"Jens Axboe" <axboe@...nel.dk>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: Re: For the condition "file->f_mode", when it failed, it should return EACCES rather than EBADF.

>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