[Samba] io_uring cause data corruption

[Jeremy Allison]

On Sun, Apr 26, 2020 at 11:51:42AM +0200, A L via samba wrote:
> Hello,
> 
> Using Samba 4.12.1 with kernel 5.6.7 on Gentoo Linux, I wanted to test the
> new vfs_io_uring module.
> 
> * Stand-alone Samba server acting as NAS for home setup.
> * /media/usb-backup is a mounted read-only btrfs filesystem.
> * Samba share exported as:

Thanks SO MUCH for testing this !

Can you log this information as a bug
at bugzilla.samba.org so we can properly
track it ?

Cheers,

Jeremy.

> ===== smb.conf =====
> [global]
>     log level = 1
>     workgroup = WORKGROUP
>     netbios name = NAS
>     server string = Samba Server
>     server role = standalone server
>     hosts allow = 192.168.0. 127.
>     interfaces = lan
>     max protocol = SMB3_11
> 
>     log file = /var/log/samba/%I.log
>     max log size = 10240
> 
>     security = user
>     passdb backend = tdbsam
>     wins support = yes
>     dns proxy = yes
> 
> [usb-backup]
>     comment = USB Backup - Media files
>     path = /media/usb-backup
>     writeable = no
>     browseable = yes
>     read only = yes
>     create mask = 0664
>     directory mask = 0775
>     guest only = Yes
>     guest ok = Yes
>     force user = nasuser
>     force group = nas
>     vfs objects = btrfs, io_uring (also tried without the btrfs module)
> =====
> 
> * 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.
> 
> When I disable io_uring, no data corruptions occur. I verified this with
> multiple TBs of data transferred and no corruptions were detected.
> 
> Samba log files contain no errors, nor does dmesg. The Windows client detect
> no error when copying the files.
> 
> I'd really like to debug this problem and find the cause. io_uring seems to
> give a massive performance i/o boost.
> 
> * net-fs/samba-4.12.1
> * sys-devel/gcc-9.3.0
> * sys-libs/glibc-2.30-r8
> * sys-kernel/linux-headers-5.6
> * Linux-kernel-5.6.7-gentoo
> 
> Compile info:
> * CFLAGS="-O2 -march=native -pipe"
> * CPU: "AMD Athlon 3000G with Radeon Vega Graphics"
> 
> 
> -- 
> To unsubscribe from this list go to the following URL and read the
> instructions:  https://lists.samba.org/mailman/options/samba