Remove serverids_exist from parse_share_modes?

[Volker Lendecke]

Hi!

Under

https://git.samba.org/?p=vl/samba.git/.git;a=shortlog;h=refs/heads/wip

find a patchset that removes the serverids_exist check from
parse_share_modes. It replaces the central check by checks
when conflicts happen. Thus it removes the assumption that
the data from get_share_mode_lock & friends only contains
entries with live processes attached. In a normally
functioning server, this is certainly still the case because
everybody is supposed to clean up behind itself. The
different behavior shows when smbds crash hard.

There are two reasons for this change. For busy files (for
example a popular directory everybody watches with notify)
we are beating the serverid.tdb pretty hard by checking
every entry on every open and close possibly multiple times.
This is a penalty for well-functioning servers. In this
particular case those checks are not strictly required
anyway because no oplocks are granted that would need to be
revoked and no share mode locks will happen. So we could
live with stale entries. The second reason for this change
is a requirement from the implementation of durable file
handles. With DH we can not clean up all entries without
processes behind, this needs to be more fine-grained.

I have tried to catch all cases where we rely on proper
cleanup. The cleanup3 test plays some tricks with
locking.tdb, forcing smbd to excercise some of the new code.
Unfortunately we can't run this in make test because we have
no access to the server's locking.tdb from smbtorture, so we
have to rely on manual tests for this new functionality.

There's one downside so far: For crashing servers the code
leaves stale entries behind as long as they do not conflict
with other opens. I am not sure it is worth a regular
cleanup process which would put quite some load on the tdb
files whenever it is run on large and busy servers.

Comments?

Volker

-- 
SerNet GmbH, Bahnhofsallee 1b, 37081 Göttingen
phone: +49-551-370000-0, fax: +49-551-370000-9
AG Göttingen, HRB 2816, GF: Dr. Johannes Loxen
http://www.sernet.de, mailto:kontakt at sernet.de