On Thu, 18 Apr 2019, J. Bruce Fields wrote: > On Thu, Apr 18, 2019 at 09:24:00AM -0400, Scott Mayhew wrote: > > While trying to track down some issues involving large numbers of > > delegations being recalled/revoked, I caught the server setting > > SEQ4_STATUS_CB_PATH_DOWN while the client was actively responding to > > CB_RECALLs. It turns out that the client had already done a > > TEST_STATEID and FREE_STATEID for a delegation being recalled by the > > time it received the CB_RECALL. > > That's interesting, thanks! > > This exception seems awfully narrow, though. > > If we get back any NFS-level error at all, then I think the callback > channel is working (am I wrong?) Correct, if the client replies with either NFS4ERR_DELAY or NFS4ERR_BAD_STATEID, the server will retry 1 time (see dl_retries). After that, we fall thru and nfsd4_cb_recall_done() returns -1 which causes the SEQ4_STATUS_CB_PATH_DOWN flag to be set. > and telling the client to set up a new > one is probably not going to help. The best we can do is probably just > give up That's what the patch is essentially doing. Or are you saying don't even bother with the checks but still return 1 so we don't set the SEQ4_STATUS_CB_PATH_DOWN flag? > and let the client deal with the ensuing > RECALLABLE_STATE_REVOKED flag. The client's already dealing with the RECALLABLE_STATE_REVOKED flag, that's why it sent a TEST_STATEID and FREE_STATEID before it got this particular CB_RECALL. The idea behind the patch is to not give the state manager on the client additional work by setting CB_PATH_DOWN when the callback channel is clearly working... -Scott > > --b. > > > > > Signed-off-by: Scott Mayhew <smayhew@xxxxxxxxxx> > > --- > > fs/nfsd/nfs4state.c | 8 ++++++++ > > 1 file changed, 8 insertions(+) > > > > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c > > index 6a45fb00c5fc..e88e429133a8 100644 > > --- a/fs/nfsd/nfs4state.c > > +++ b/fs/nfsd/nfs4state.c > > @@ -3958,6 +3958,14 @@ static int nfsd4_cb_recall_done(struct nfsd4_callback *cb, > > rpc_delay(task, 2 * HZ); > > return 0; > > } > > + /* > > + * Race: client may have done a FREE_STATEID before > > + * receiving the CB_RECALL. > > + */ > > + if (dp->dl_stid.sc_type == NFS4_REVOKED_DELEG_STID && > > + refcount_read(&dp->dl_stid.sc_count) == 1 && > > + list_empty(&dp->dl_recall_lru)) > > + return 1; > > /*FALLTHRU*/ > > default: > > return -1; > > -- > > 2.17.2
