CTDB internals

[Volker Lendecke]

On Fri, Nov 02, 2012 at 02:44:45AM -0500, Christopher R. Hertel wrote:
> On 11/02/2012 02:29 AM, Volker Lendecke wrote:
> > On Fri, Nov 02, 2012 at 02:18:36AM -0500, Christopher R. Hertel wrote:
> >> Ah...
> >>
> >> No, it's *both*.  I just found the notes I need in smb.conf.  If I
> >> understand correctly, the byte-range locks are stored in brlock.tdb but are
> >> also made using fcntl byte-range locking.
> >>
> >> The only questions for me, then, are to know how byte range locks are
> >> enforced by Samba and whether or not I'm miles off in my understanding here.
> > 
> > Before every read and write we check if an fcntl lock is
> > set. Racy, but the best we can do.
> 
> What information is actually stored in brlock.tdb, and how is it used when
> it's checked?  Is it a short-cut?

In brlock.tdb the SMB style byte range locks are stored.
They are checked first. The locking code also mirrors the
locks as fcntl locks if possible. The fcntl check before r/w
are done to respect local process and NFS client locks as
mandatory for SMB.

Volker

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