[Samba] io_uring cause data corruption

[Jeremy Allison]

On Sun, Apr 26, 2020 at 11:51:42AM +0200, A L via samba wrote:
> 
> * Connected from a Windows 10 computer over 1G ethernet.
> * Copy data using Windows Explorer and FastCopy(1) from the Samba share to a
> local disk.
> * Verify the sha-256 sum on the files.
> 
> From what I can see there is data corruption on many of the files. Sha-256
> does not match. I copied the same files many times and the data corruption
> occurs within minutes. The total data set is about 800GB.

Can you do checksums on file fragments so we can
discover at what offset (if non-zero) the corruption
occurs.