[Samba] ceph is disabled even if explicitly asked to be enabled

[Anoop C S]

On Wed, 2024-07-31 at 08:36 +0300, Michael Tokarev via samba wrote:
> 31.07.2024 07:55, Anoop C S via samba wrote:
> > On Tue, 2024-07-30 at 21:12 +0300, Michael Tokarev via samba wrote:
> > > Hi!
> > > 
> > > Building current samba on debian bullseye with
> > > 
> > >     ./configure --enable-cephfs
> > > 
> > > results in the following output:
> > > 
> > > Checking for header cephfs/libcephfs.h              : yes
> > > Checking for library cephfs                         : yes
> > > Checking for ceph_statx in cephfs                   : ok
> > > Checking for ceph_openat in cephfs                  : not found
> > > Ceph support disabled due to --without-acl-support
> > >            or lack of ceph_statx/ceph_openat support
> > > ...
> > > 
> > > but despite --enable-cephfs option, ./configure succeeds and
> > > subsequent build succeeds too, just vfs/ceph.so etc aren't being
> > > produced.
> > > 
> > > This seems like (configure) bug.
> > 
> > I hope the description(and hyperlinked discussion) from
> > https://gitlab.com/samba-team/samba/-/merge_requests/3715 explains
> > the situation with upcoming v4.21 in detail. Basically we decided
> > to go with the mandate of requiring certain APIs from libcephfs.
> > Those APIs have been around since v17 and it is the least among the
> > non-EOL(not archived) versions of Ceph as
> > per https://docs.ceph.com/en/latest/releases/#ceph-releases-index .
> 
> The problem here is not requirement of a modern ceph - this is
> entirely okay.
> 
> The problem is that ceph is disabled by configure even if it is
> explicitly enabled by the command-line switch.  Configure should fail
> here instead of continuing, - *that* is the problem.

This is/was always the situation because building vfs_ceph is enabled
by default. Therefore an explicit '--enable-cephfs' doesn't end up as
an indication to fail the build in the absence of certain libcephfs
requirements. We had the following configure stage warning previously
for v4.20 which might have gone unnoticed:

...
Checking for ceph_mkdirat in cephfs       : not found 
Checking for ceph_openat in cephfs        : not found 
Checking for ceph_unlinkat in cephfs      : not found 
Checking for ceph_symlinkat in cephfs     : not found 
Checking for ceph_readlinkat in cephfs    : not found 
Checking for ceph_statxat in cephfs       : not found
Installed Ceph version support is at the verge of deprecation due to
the absence of some mandatory libcephfs APIs. This warning there shall
result in disabling the Ceph VFS module altogether with the next major
Samba version. It is highly recommended to update to a more
recent/active version of Ceph.
...

People will start noticing the difference now with upcoming v4.21 if
they do not have the minimum required Ceph version(libcephfs).

May be we could rethink on the current behaviour which silently disable
building the module when requirements are not met. But keep in mind
that this silent approach existed all this while if either libcephfs or
related dependencies(acl support) were not present during build
process. It is also an option to switch the default from 'True' to
'False' so that failing at configure stage is much more meaningful.


Thanks,
Anoop C S.