[SMB3][PATCH] snapshots work from Linux!

[Jeremy Allison]

On Fri, Aug 10, 2018 at 02:38:31AM -0500, Steve French via samba-technical wrote:
>     mounting with the "snapshots=" mount parm allows a read-only
>     view of a previous version of a file system (see MS-SMB2
>     and "timewarp" tokens, section 2.2.13.2.6) based on the timestamp
>     passed in on the snapshots mount parm.
> 
>     Add processing to optionally send this create context.
> 
>     Example output:
> 
>     /mnt1 is mounted with "snapshots=..." and will see an earlier
>     version of the directory, with three fewer files than /mnt2
>     the current version of the directory.
> 
>     root at Ubuntu-17-Virtual-Machine:~/cifs-2.6# cat /proc/mounts | grep cifs
>     //172.22.149.186/public /mnt1 cifs
>     ro,relatime,vers=default,cache=strict,username=smfrench,uid=0,noforceuid,gid=0,noforcegid,addr=172.22.149.186,file_mode=0755,dir_mode=0755,soft,nounix,mapposix,rsize=1048576,wsize=1048576,echo_interval=60,snapshot=131748608570000000,actimeo=1
> 
>     //172.22.149.186/public /mnt2 cifs
>     rw,relatime,vers=default,cache=strict,username=smfrench,uid=0,noforceuid,gid=0,noforcegid,addr=172.22.149.186,file_mode=0755,dir_mode=0755,soft,nounix,mapposix,rsize=1048576,wsize=1048576,echo_interval=60,actimeo=1
> 
>     root at Ubuntu-17-Virtual-Machine:~/cifs-2.6# ls /mnt1
>     EmptyDir  newerdir
>     root at Ubuntu-17-Virtual-Machine:~/cifs-2.6# ls /mnt1/newerdir
> 
>     root at Ubuntu-17-Virtual-Machine:~/cifs-2.6# ls /mnt2
>     EmptyDir  file  newerdir  newestdir  timestamp-trace.cap
>     root at Ubuntu-17-Virtual-Machine:~/cifs-2.6# ls /mnt2/newerdir
>     new-file-not-in-snapshot
> 
>     Snapshots are extremely useful for comparing previous versions of
> files or directories,
>     and recovering from data corruptions or mistakes.
> 
> 
> See attached patch

Great work Steve ! Well done ! Great to see this available from
the Linux client.

Cheers,

	Jeremy.