Re: Stack trace with Samba VFS io_uring and large transfers

[Forza <forza@tnonline.net>]

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.

Thanks.