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I think I've found a bug or regression in something when trying to mount
a remote samba share. Modified/Created times are not properly preserved
in newer versions of Ubuntu. Because of this, rsync thinks files are
different based on their modified times and keeps re-syncing them.

I have a NAS on my network, running samba.

I have two devices, a desktop and laptop. Both are running Ubuntu, and
set up the exact same way. The desktop is running ubuntu 20.04, the
laptop 22.04.

I have mounted the NAS on both devices the exact same way. I attempt to
copy a file (rsync) the exact same way. On the 20.04 desktop, this works
perfectly fine. On the 22.04 laptop, the modified times are not
preserved and set to the current time, preventing things like rsync -t
from working.

The only difference i can find is that between the two systems, the newer laptop 22.04 mount adds a few more options than the older system to the cifs mount options. These are added automatically without being specified explicitly (see the mount -v output below): 
* 'forceuid'/'forcegid' are changed to 'noforceuid'/'noforcegid
*  iocharset=utf8 added
*  serverino added

desktop:

$ lsb_release -rd
Description:    Ubuntu 20.04.5 LTS
Release:        20.04
$ apt-cache policy cifs-utils
cifs-utils:
  Installed: 2:6.9-1ubuntu0.2
  Candidate: 2:6.9-1ubuntu0.2
  Version table:
 *** 2:6.9-1ubuntu0.2 500
        500 http://us.archive.ubuntu.com/ubuntu focal-updates/main amd64 Packages
        500 http://security.ubuntu.com/ubuntu focal-security/main amd64 Packages
        100 /var/lib/dpkg/status
     2:6.9-1 500
        500 http://us.archive.ubuntu.com/ubuntu focal/main amd64 Packages
$ uname -a
Linux desktop 5.4.0-132-generic #148-Ubuntu SMP Mon Oct 17 16:02:06 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux
$ mount -v 
//nas/backup on /media/scratch type cifs (rw,relatime,vers=3.0,cache=strict,username=nas_rw,uid=1000,forceuid,gid=1000,forcegid,addr=192.168.1.10,file_mode=0664,dir_mode=0775,soft,nounix,mapposix,rsize=4194304,wsize=4194304,bsize=1048576,echo_interval=60,actimeo=1)


laptop:

$ lsb_release -rd
Description:    KDE neon 5.26
Release:        22.04
$ apt-cache policy cifs-utils
cifs-utils:
  Installed: 2:6.14-1ubuntu0.1
  Candidate: 2:6.14-1ubuntu0.1
  Version table:
 *** 2:6.14-1ubuntu0.1 500
        500 http://security.ubuntu.com/ubuntu jammy-security/main amd64 Packages
        500 http://archive.ubuntu.com/ubuntu jammy-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     2:6.14-1build1 500
        500 http://archive.ubuntu.com/ubuntu jammy/main amd64 Packages
$ uname -a
Linux laptop 5.15.0-60-generic #66-Ubuntu SMP Fri Jan 20 14:29:49 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux
$ mount -v
//nas/backup on /media/scratch type cifs (rw,relatime,vers=3.0,cache=strict,username=nas_rw,uid=1000,noforceuid,gid=1000,noforcegid,addr=192.168.1.10,file_mode=0664,dir_mode=0775,iocharset=utf8,soft,nounix,serverino,mapposix,rsize=4194304,wsize=4194304,bsize=1048576,echo_interval=60,actimeo=1)

the remote NAS is a synology appliance, running Samba version 4.10.18.
SMB version 3

Steps to reproduce:
1. Similar setup, 1 device running 20.04, another running 22.04, otherwise up to date.

2. mount the NAS on both devices the exact same way
$ sudo mount -t cifs -o vers=3.0,credentials=/etc/samba/smbcreds,iocharset=utf8,rw,uid=1000,gid=1000,dir_mode=0775,file_mode=0664 //nas/backup /media/scratch

3. on the 20.04 older desktop, create a test file and show the modify time
$ fallocate -l 1M test1.txt
$ stat test1.txt
  File: test1.txt
  Size: 1048576         Blocks: 2048       IO Block: 4096   regular file
Device: 801h/2049d      Inode: 13634663    Links: 1
Access: (0664/-rw-rw-r--)  Uid: ( 1000/desktop_user)   Gid: ( 1000/desktop_user)
Access: 2023-02-12 18:35:48.978743377 -0700
Modify: 2023-02-12 18:35:48.978743377 -0700
Change: 2023-02-12 18:35:48.978743377 -0700
 Birth: -

4. rsync the test file to the mount, stat the file and see the modify/change are preserved
$ rsync -avh test1.txt /media/scratch/
sending incremental file list
test1.txt

sent 1.05M bytes  received 35 bytes  2.10M bytes/sec
total size is 1.05M  speedup is 1.00
$ stat /media/scratch/test1.txt 
  File: /media/scratch/test1.txt
  Size: 1048576         Blocks: 2064       IO Block: 1048576 regular file
Device: 52h/82d Inode: 321811      Links: 1
Access: (0664/-rw-rw-r--)  Uid: ( 1000/desktop_user)   Gid: ( 1000/desktop_user)
Access: 2023-02-12 18:38:25.671230900 -0700
Modify: 2023-02-12 18:35:48.978743300 -0700
Change: 2023-02-12 18:35:48.978743300 -0700
 Birth: -

5. rsync again, notice the file is correctly skipped.
$ rsync -avh test1.txt /media/scratch/
sending incremental file list

sent 68 bytes  received 12 bytes  160.00 bytes/sec
total size is 1.05M  speedup is 13,107.20

6. repeat the same steps above on the newer 22.04 laptop, only this time notice that the modify/change are NOT preserved. rsync re-sends the file because modified time changed.
$ fallocate -l 1M test2.txt
$ stat test2.txt
  File: test2.txt
  Size: 1048576         Blocks: 2048       IO Block: 4096   regular file
Device: fd00h/64768d    Inode: 526622      Links: 1
Access: (0664/-rw-rw-r--)  Uid: ( 1000/  laptop_user)   Gid: ( 1000/  laptop_user)
Access: 2023-02-12 18:42:55.467521856 -0700
Modify: 2023-02-12 18:42:55.467521856 -0700
Change: 2023-02-12 18:42:55.467521856 -0700
 Birth: 2023-02-12 18:42:55.467521856 -0700
$ rsync -avh test2.txt /media/scratch/
sending incremental file list
test2.txt

sent 1.05M bytes  received 35 bytes  2.10M bytes/sec
total size is 1.05M  speedup is 1.00
$ stat /media/scratch/test2.txt 
  File: /media/scratch/test2.txt
  Size: 1048576         Blocks: 2064       IO Block: 1048576 regular file
Device: 54h/84d Inode: 565291      Links: 1
Access: (0664/-rw-rw-r--)  Uid: ( 1000/  laptop_user)   Gid: ( 1000/  laptop_user)
Access: 2023-02-12 18:43:24.265024500 -0700
Modify: 2023-02-12 18:43:24.265024500 -0700
Change: 2023-02-12 18:43:24.265024500 -0700
 Birth: 2023-02-12 18:43:24.248938600 -0700
$ rsync -avh test2.txt /media/scratch/
sending incremental file list
test2.txt

sent 1.05M bytes  received 35 bytes  2.10M bytes/sec
total size is 1.05M  speedup is 1.00
$ stat /media/scratch/test2.txt 
  File: /media/scratch/test2.txt
  Size: 1048576         Blocks: 2064       IO Block: 1048576 regular file
Device: 54h/84d Inode: 565292      Links: 1
Access: (0664/-rw-rw-r--)  Uid: ( 1000/  laptop_user)   Gid: ( 1000/  laptop_user)
Access: 2023-02-12 18:43:45.413195300 -0700
Modify: 2023-02-12 18:43:45.413195300 -0700
Change: 2023-02-12 18:43:45.413195300 -0700
 Birth: 2023-02-12 18:43:45.398091900 -0700


As best I can tell I am doing _everything_ EXACTLY the same way. Word for word. The remote system is the same device, same share, same directory. The only difference is the software version, and the extra options thrown in automatically when mounting a cifs share. I've tried to 'unspecify' those extra bits but it still happens.

I'd tag this to a proper package, but i'm not sure if this is cifs-
tools, or something else entirely.


The only thing I can find online that's possibly similar is this ask ubuntu thread:
https://askubuntu.com/questions/1426772/after-upgrade-from-ubuntu-20-to-ubuntu-22-rsync-copies-unchanged-files-and-chan
It sure looks like the same thing, but no solutions are presented.

** Affects: samba (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: bot-comment
-- 
cifs/samba mount not preserving file timestamps
https://bugs.launchpad.net/bugs/2007055
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