On 2015/6/2 7:01, Jaegeuk Kim wrote:
> 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.
>
Ext4 do a check in the function do_blockdev_direct_IO:
if (align & blocksize_mask) {
if (bdev)
blkbits = blksize_bits(bdev_logical_block_size(bdev));
blocksize_mask = (1 << blkbits) - 1;
if (align & blocksize_mask)
goto out;
}
It will return -EINVAL if the alignment is not satisfied.
In f2fs, it do the check by check_direct_IO() before blockdev_direct_IO().
The difference between the two methods is whether turn dwrite with non-aligned
offset and size into buffered write. I am not very clear which one is better!
Thanks,
He
>>
>> 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
>
> .
>
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