Re: Stack trace with Samba VFS io_uring and large transfers

[Jens Axboe <axboe@kernel.dk>]

On 7/24/21 1:51 PM, Forza wrote:
> 
> 
> On 2021-07-24 21:44, Jens Axboe wrote:
>> On 7/24/21 12:23 PM, Forza wrote:
>>> Hi!
>>>
>>> On 2021-07-24 19:04, Jens Axboe wrote:
>>>> I'll see if I can reproduce this. I'm assuming samba is using buffered
>>>> IO, and it looks like it's reading in chunks of 1MB. Hopefully it's
>>>> possible to reproduce without samba with a windows client, as I don't
>>>> have any of those. If synthetic reproducing fails, I can try samba
>>>> with a Linux client.
>>>
>>> I attached the logs from both a Windows 10 client and a Linux client
>>> (kernel 5.11.0).
>>>
>>> https://paste.tnonline.net/files/r4yebSzlGEVD_linux-client.txt
>>>
>>>     smbd_smb2_read: fnum 2641229669, file
>>> media/vm/libvirt/images/Mint_Cinnamon.img, length=4194304
>>> offset=736100352 read=4194304
>>> [2021/07/24 17:26:09.120779,  3]
>>> ../../source3/smbd/smb2_read.c:415(smb2_read_complete)
>>>     smbd_smb2_read: fnum 2641229669, file
>>> media/vm/libvirt/images/Mint_Cinnamon.img, length=4194304
>>> offset=740294656 read=4194304
>>> [2021/07/24 17:26:09.226593,  3]
>>> ../../source3/smbd/smb2_read.c:415(smb2_read_complete)
>>>     smbd_smb2_read: fnum 2641229669, file
>>> media/vm/libvirt/images/Mint_Cinnamon.img, length=4194304
>>> offset=748683264 read=4194304
>>
>> Thanks, this is useful. Before I try and reproduce it, what is the
>> filesystem that is hosting the samba mount?
>>
> 
> I am using Btrfs.
> 
> My testing was done by exporting the share with
> 
>    vfs objects = io_uring
>    vfs objects = btrfs, io_uring
> 
> Same results in both cases. Exporting with "vfs objects = btrfs" (no 
> io_uring) works as expected.

Seems to be specific to btrfs, I can reproduce it here. I'll dive in
and see what I can find.

-- 
Jens Axboe