[Samba] File Locking on Samba & Terminal Server 2008R2
Nick Couchman
Nick.Couchman at seakr.com
Tue Jan 7 13:48:02 MST 2014
>
>> We have a document management system (DMS) where all of our documents are
> stored and users have either an HTTP interface or a .NET application (that
> uses HTTP) to download the files from the DMS to the system for viewing. The
> DMS allows us to specify what directory these are saved to - for various
> reasons we're saving them to a Samba server. The Samba server (3.6.18 on
> Solaris) has a per-user share defined:
>>
>> [doc_checkout]
>> path = /storage/doc_checkout/%U
>> comment = IFS Shared Document Checkout Space
>> force create mode = 0200
>> read only = No
>> inherit permissions = yes
>> inherit acls = yes
>> wide links = yes
>> map archive = no
>> map readonly = no
>> vfs objects = zfsacl
>> nfs4:mode = special
>> nfs4:acedup = merge
>> zfsacl:acesort = dontcare
>> preexec = /storage/doc_checkout/mkdoc.sh %U
>> postexec = /storage/doc_checkout/cleandoc.sh %U
>> veto files = /mkdoc.sh/cleandoc.sh/*.lnk/autorun.inf/
>> csc policy = disable
>> guest ok = no
>>
>> In certain situations, multiple users on the same terminal server try to
> view (or check out to edit) the same document from the DMS. Let's say the
> document is document1.doc, and usera and userb are the two users trying to
> open the document. usera downloads document1.doc, which goes to filesystem
> as /storage/doc_checkout/usera/document1.doc, but is opened on the file
> server as \\server\doc_checkout\document1.doc. userb downloads the same
> document, which goes to the filesystem as
> /storage/doc_checkout/userb/document1.doc, but is opened on the file server
> as \\server\doc_checkout\document1.doc. In this scenario, one or the other
> of the users (whomever opened it second/third/etc.) will get an error that
> "file document1.doc is already in use by usera." I'm guessing that, because
> terminal server aggregates the users under a single connection, and because
> Samba has a single PID opened, and either the document name or the SMB file
> path (\\server\doc_checkout\document1.doc) is th
>> e same, Samba or Windows (or both) believe that the file is already locked
> even though, at the filesystem level, the files are completely different and
> should have different locks.
>>
>> This scenario looked very similar to ones described several years ago that
> were fixed by using the "MultiUserEnabled" registry tweak in Windows, which
> is what I've been trying to chase down, but apparently does not exist in the
> most recent versions of Windows. I suppose I ought to try giving up on the
> fancy per-user share and just have \\server\doc_checkout point to
> /storage/doc_checkout, and then have the application use the username to
> figure out the rest of the path, but it isn't quite as simple or elegant to
> implement that way, from the application perspective.
>
> smbd uses the dev_t/ino_t pair as an index
> into our file sharing/locking databases.
>
> Are /storage/doc_checkout/usera/document1.doc
> and /storage/doc_checkout/userb/document1.doc
> actually the same file on the file system ?
No, they are not the same on the filesystem - they are different inodes.
>
> If not then I'm at a loss as to how they
> can conflict at all, unless you're getting
> a locking/sharing violation from the Windows
> client redirector.
That wouldn't surprise me too much.
>
> Do you ever see an error message coming back
> from Samba in the wireshark trace ?
>
I hadn't gone that deep (packet captures) in dealing with this, yet...I'll add it to my list of things to try and see what happens.
-Nick
--------
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