Re: [PATCH RFC v3 0/5] un-deprecate nfsdcld

[Scott Mayhew <smayhew@redhat.com>]

On Thu, 28 Mar 2019, J. Bruce Fields wrote:

> Thanks!  It looks good to me on a first skim, but I probably won't get a
> proper look at it till next week.
> 
> You say "RFC"--are there still known issue that you're working on?

No, I just added RFC because of the new stuff I added for handling the
legacy records.  Plus I wasn't sure if you would have a problem with the
server not lifting the grace period early if there were legacy records.
I could do it if I moved some code out of nfs4recover.c but I chose not
to since it should really be a one-time thing and the original legacy
tracking didn't lift the grace period early anyway.

-Scott
> 
> --b.
> 
> On Tue, Mar 26, 2019 at 06:06:25PM -0400, Scott Mayhew wrote:
> > When nfsdcld was released, it was quickly deprecated in favor of the
> > nfsdcltrack usermodehelper, so as to not require another running daemon.
> > That prevents NFSv4 clients from reclaiming locks from nfsd's running in
> > containers, since neither nfsdcltrack nor the legacy client tracking
> > code work in containers.  These patches un-deprecate the use of nfsdcld
> > for NFSv4 client tracking.
> > 
> > These patches are intended to go alongside some nfs-utils patches that
> > introduce an enhancement that allows nfsd to "slurp" up the client
> > records during client tracking initialization and store them internally
> > in hash table.  This enables nfsd to check whether an NFSv4 client is
> > allowed to reclaim without having to do an upcall to nfsdcld.  It also
> > allows nfsd to decide to end the v4 grace period early if the number of
> > RECLAIM_COMPLETE operations it has received from "known" clients is
> > equal to the number of entries in the hash table.  It also allows nfsd
> > to skip the v4 grace period altogether if it knows there are no clients
> > allowed to reclaim.
> > 
> > There is a fallback to allow nfsd to continue to work with older nfsdcld
> > daemons in the event that any are out in the wild (unlikely).
> > Everything should work fine except nfsd will not be able to exit the
> > grace period early or skip the grace period altogether.
> > 
> > v3:
> > - nfs4_state_start_net() now calls nfsd4_end_grace() instead of
> >   open-coding it
> > - Removed some unnecessary initializations of nr_reclaim_complete
> > - Removed dec_reclaim_complete() altogether.  If we're calling
> >   expire_client() as a result of receiving a DESTROY_CLIENTID or
> >   SETCLIENTID_CONFIRM then we wouldn't want to decrement the count.  And
> >   laundromat thread never expires clients due to loss of lease until the
> >   grace period is over (the laundromat gets rescheduled by 1 second as
> >   long as clients are reclaiming during that 1 second, for up to 2x the
> >   original grace period in total).  So dec_reclaim_complete() is
> >   unnecessary.
> > - Changed the preference order of client tracking methods.  The new
> >   order is 1) new nfdscld, 2) old nfsdcld, 3) nfsdcltrack, 4) legacy
> >   v4recovery directory.
> > - Added some special handling of legacy records sent by nfsdcld in the
> >   GraceStart downcalls.  nfsdcld will do a one-time "upgrade" from old
> >   tracking methods.  No changes are needed to accomodate nfsdcltrack
> >   records, but legacy records will be prefixed with the string "hash:", 
> >   and in the event that we do have legacy records in the
> >   reclaim_str_hashtbl we may need to do a second lookup using the hash
> >   in the event that a lookup using the client name string fails.
> > 
> > v2:
> > - Addressed some coding style issues in nfsd4_create_clid_dir() &
> >   nfsd4_remove_clid_dir()
> > 
> > Scott Mayhew (5):
> >   nfsd: make nfs4_client_reclaim use an xdr_netobj instead of a fixed
> >     char array
> >   nfsd: un-deprecate nfsdcld
> >   nfsd: keep a tally of RECLAIM_COMPLETE operations when using nfsdcld
> >   nfsd: re-order client tracking method selection
> >   nfsd: handle legacy client tracking records sent by nfsdcld
> > 
> >  fs/nfsd/netns.h               |   3 +
> >  fs/nfsd/nfs4recover.c         | 436 +++++++++++++++++++++++++++++++---
> >  fs/nfsd/nfs4state.c           |  63 +++--
> >  fs/nfsd/nfsctl.c              |   1 +
> >  fs/nfsd/state.h               |   8 +-
> >  include/uapi/linux/nfsd/cld.h |   1 +
> >  6 files changed, 457 insertions(+), 55 deletions(-)
> > 
> > -- 
> > 2.17.2