[PATCH] pathname cleanups

Uri Simchoni uri at samba.org
Fri May 19 06:11:49 UTC 2017

On 05/19/2017 07:54 AM, Volker Lendecke via samba-technical wrote:
> On Thu, May 18, 2017 at 08:40:57PM -0700, Jeremy Allison via samba-technical wrote:
>> I'm getting ready to move the @GMT snapshot
>> name handling into struct smb_filename to
>> clean up a lot of the shadow_copy2 code.
> As you mention it: I've got a report from a customer that a certain
> access pattern does not work anymore: GPFS has the ability to show the
> .snapshots directory (the one where all the @GMT- subdirs show up) in
> all directories, with @GMT- subdirectories being relative to the
> current dir.
> For clients that do not understand the @GMT- logic or the timewarp
> token, essentially all non-windows clients, we need to be able to
> access previous versions through the subdir/.snapshots/@GMT-../subdir
> path. I think in the shadow_copy2 module we need to also preserve the
> non-stripped name and try with that also. Any other ideas?
> Thanks, Volker
Actually putting the timewarp timestamp into a separate field would
clean that nicely - if the timestamp is not assigned (zero?), then this
is a regular path and shadow_copy2 does not intervene. If it's assigned,
vfs_shadow_copy2 modifies the path. If we re-enter vfs_shadow_copy2, it
enters as a regular path. SMB2 becomes really clean that way.

With SMB1 clients, the @GMT comes as first path element, so the SMB1
server converts that into a timewarp element and strips it off the path
- that too supports regular clients which want to access
path/.snapshots/@GMT. Admittedly, this involves a bit of heuristics.
There's FLAGS2_REPARSE_PATH bit in FLAGS2 - Windows clients set it and
also Samba client since 4.6.x. The server can decide whether to be
strict about it or use the heuristic (currently smbd ignores this flag).


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