Implementing SMB_VFS_FCNTL in Samba

[Anoop C S]

On Thu, 2019-10-03 at 18:43 +0530, Anoop C S via samba-technical wrote:
> On Sun, 2019-09-29 at 08:26 +0530, Anoop C S via samba-technical
> wrote:
> > On Thu, 2019-09-26 at 00:09 +0530, Anoop C S via samba-technical
> > wrote:
> > > On Mon, 2019-09-23 at 08:31 -0700, Jeremy Allison via samba-
> > > technical
> > > wrote:
> > > > On Mon, Sep 23, 2019 at 02:51:24PM +0530, Anoop C S wrote:
> > > > > Hi all,
> > > > > 
> > > > > I am attaching a patch as an attempt to implement
> > > > > SMB_VFS_FCNTL(for
> > > > > a
> > > > > background see 
> > > > > https://bugzilla.samba.org/show_bug.cgi?id=14060
> > > > > ).
> > > > > But I
> > > > > have the following question.
> > > > > 
> > > > > int fcntl(int fd, int cmd, ... /* arg */ );
> > > > > 
> > > > > As per man page, fcntl(2) system call can accept a third
> > > > > optional
> > > > > argument. If present it can be of type int, struct flock *,
> > > > > struct
> > > > > f_owner_ex * or uint64_t *. Our current SMB_VFS_LOCK and
> > > > > SMB_VFS_GETLOCK takes care of "Advisory record locking" and
> > > > > "Open
> > > > > file
> > > > > description locks" commands which requires third argument of
> > > > > type
> > > > > struct flock *. Other important fact here to notice is that
> > > > > in
> > > > > most
> > > > > cases the required third argument type is int. The patch I
> > > > > have
> > > > > prepared right now assumes third argument type to be int. 
> > > > > 
> > > > > So should we rename the call to something else(keeping third
> > > > > argument
> > > > > as int) or change the implementation to consider optional
> > > > > third
> > > > > argument as variable?
> > > > 
> > > > I think we need a varargs argument here like the real fcntl
> > > > definition.
> > > 
> > > Please find the attached patch in the above suggested direction.
> > > For
> > > now it is compile tested only. I will respond back afterwards
> > > with
> > > some basic testing results.
> > 
> > An unexpected crash(during runtime) had to be resolved and Gitlab
> > CI
> > pipeline revealed some missing changes. Attaching the patch
> > set(near-
> > to-final) which successfully completed the following pipeline:
> > 
> > https://gitlab.com/samba-team/devel/samba/pipelines/85180275
> > 
> > Few recent fcntl() cmd flags needs to be conditionally checked
> > inside
> > vfs_default which should be the only missing here.
> 
> OK. This should be it. I hope attached patch covers the missing part
> where recent fcntl() commands are detected during configure. A
> pipeline
> has been completed successfully for the attached patches.
> 
> https://gitlab.com/samba-team/devel/samba/pipelines/86263033
> 
> Reviews are appreciated.

Please ignore the previous version which had a typo in checking
HAVE_XX_XX inside vfs_default. Attaching the patches after correction.
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