Re: [f2fs-dev] Dwrite with non-aligned offset and size

[Jaegeuk Kim <jaegeuk@kernel.org>]

On Mon, Jun 01, 2015 at 07:55:08PM +0800, He YunLei wrote:
> Hi Jaegeuk,
> 
> We run ltp testcase with f2fs and obtain a TFAIL in diotest4, the result in detail is
> as fallow:
> 
> dio04
> 
> <<<test_start>>>
> tag=dio04 stime=1432278894
> cmdline="diotest4"
> contacts=""
> analysis=exit
> <<<test_output>>>
> diotest4    1  TPASS  :  Negative Offset
> diotest4    2  TPASS  :  removed
> diotest4    3  TFAIL  :  diotest4.c:129: write allows odd count.returns 1: Success
> diotest4    4  TFAIL  :  diotest4.c:183: Odd count of read and write
> diotest4    5  TPASS  :  Read beyond the file size
> ......
> 
> the result of ext4 with same environment:
> 
> dio04
> 
> <<<test_start>>>
> tag=dio04 stime=1432259643
> cmdline="diotest4"
> contacts=""
> analysis=exit
> <<<test_output>>>
> diotest4    1  TPASS  :  Negative Offset
> diotest4    2  TPASS  :  removed
> diotest4    3  TPASS  :  Odd count of read and write
> diotest4    4  TPASS  :  Read beyond the file size
> ......
> 
> Does f2fs allow dwrite with non-aligned offset and size? I check the code and found
> dwrite with non-aligned offset and size will turn into buffered write. Whether it will
> have some impact on user layer applications?

It's not a big deal to return -EINVAL.
When I take a look at other filesystem behaviors, it seems there is no restriction.

> 
> I wrote a patch, not well tested, how do you think of it?

Returning the error number would be good to me.
Could you write and sumbit a complete one?

Thanks,

> 
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 9bedfa8..ba5d94c 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -2010,8 +2010,9 @@ static ssize_t f2fs_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
>         if (f2fs_encrypted_inode(inode) && S_ISREG(inode->i_mode))
>                 return 0;
> 
> -       if (check_direct_IO(inode, iter, offset))
> -               return 0;
> +       err = check_direct_IO(inode, iter, offset)
> +       if (err)
> +               return -EINVAL;
> 
>         trace_f2fs_direct_IO_enter(inode, offset, count, iov_iter_rw(iter));
> 
> I wish you and other developers in this list could help me in a correct way.
> 
> Thanks,
> He