Open Stack

On 2019/1/17 1:25, Dr. David Alan Gilbert wrote:
> * jiangyiwen (jiangyiwen at huawei.com) wrote:
>> On 2019/1/10 23:57, Vivek Goyal wrote:
>>> On Thu, Dec 27, 2018 at 10:57:21AM +0800, jiangyiwen wrote:
>>>
>>> [..]
>>>> what do I mean by "I filter O_DIRECT flag in libfuse-daemon"?
>>>>
>>>> I modify passthrough_ll.c code and ignore O_DIRECT flag when opening file,
>>>> then it return success. The codes as follows:
>>>> diff --git a/example/passthrough_ll.c b/example/passthrough_ll.c
>>>> index 3e37dbd..9edb5bb 100644
>>>> --- a/example/passthrough_ll.c
>>>> +++ b/example/passthrough_ll.c
>>>> @@ -1234,7 +1234,7 @@ static void lo_open(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi)
>>>>                 fi->flags &= ~O_APPEND;
>>>>
>>>>         sprintf(buf, "/proc/self/fd/%i", lo_fd(req, ino));
>>>> -       fd = open(buf, fi->flags & ~O_NOFOLLOW);
>>>> +       fd = open(buf, fi->flags & ~(O_NOFOLLOW | O_DIRECT));
>>>>         if (fd == -1)
>>>>                 return (void) fuse_reply_err(req, errno);
>>>
>>> Hi Yiwen,
>>>
>>> Ok, this issue is now fixed. We still do not ignore O_DIRECT flag on host.
>>> I think if file is opened with O_DIRECT in guest, then it makes sense to
>>> open with O_DIRECT on host as well.
>>>
>>> We were getting -EINVAL (-22) due to misaligned buffers. We were creating
>>> extra data copy in libfuse daemon and that copy created misalignment.
>>>
>>> David Gilbert has now fixed it. He has got rid of that extra copy and 
>>> that means if guest hands over aligned buffers, I/O should succeed. This
>>> should also result in some speed up on write path as one extra copy has
>>> been avoided.
>>>
>>> These fixes are still internal. David might push these externally soon.
>>>
>>> Thanks
>>> Vivek
>>>
>>> .
>>>
>>
>> Hi Vivek,
>>
>> Great, I am glad to test it if this patch is pushed.
> 
> Hi Yiwen,
>   That's now pushed to the 'dev' branch, here:
> 
> https://gitlab.com/virtio-fs/libfuse/commits/dev
> 
> it's only lightly tested and has a few rough edges, but seems to work!
> 
> Dave
> 
>> Thanks,
>> Yiwen.
>>
> --
> Dr. David Alan Gilbert / dgilbert at redhat.com / Manchester, UK
> 
> .
> 

Hi Dave,

Thanks, based on dev branch I tested basic direct-io ability and
it can work. That's great.

Thanks,
Yiwen.