On Fri, Apr 05, 2024 at 01:56:18PM -0400, Jeff Layton wrote: > Currently the CB_RECALL_ANY job takes a cl_rpc_users reference to the > client. While a callback job is technically an RPC that counter is > really more for client-driven RPCs, and this has the effect of > preventing the client from being unhashed until the callback completes. > > If nfsd decides to send a CB_RECALL_ANY just as the client reboots, we > can end up in a situation where the callback can't complete on the (now > dead) callback channel, but the new client can't connect because the old > client can't be unhashed. This usually manifests as a NFS4ERR_DELAY > return on the CREATE_SESSION operation. > > The job is only holding a reference to the client so it can clear a flag > in the after the RPC completes. Fix this by having CB_RECALL_ANY instead > hold a reference to the cl_nfsdfs.cl_ref. Typically we only take that > sort of reference when dealing with the nfsdfs info files, but it should > work appropriately here to ensure that the nfs4_client doesn't > disappear. > > Fixes: 44df6f439a17 ("NFSD: add delegation reaper to react to low memory condition") > Reported-by: Vladimir Benes <vbenes@xxxxxxxxxx> > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx> Applied to nfsd-fixes while waiting for review and testing. Thanks! > --- > Changes in v2: > - Clean up the changelog > - Add Fixes: tag > - Use kref_get instead of kref_get_unless_zero > --- > fs/nfsd/nfs4state.c | 7 ++----- > 1 file changed, 2 insertions(+), 5 deletions(-) > > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c > index 5fcd93f7cb8c..3cef81e196c6 100644 > --- a/fs/nfsd/nfs4state.c > +++ b/fs/nfsd/nfs4state.c > @@ -3042,12 +3042,9 @@ static void > nfsd4_cb_recall_any_release(struct nfsd4_callback *cb) > { > struct nfs4_client *clp = cb->cb_clp; > - struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id); > > - spin_lock(&nn->client_lock); > clear_bit(NFSD4_CLIENT_CB_RECALL_ANY, &clp->cl_flags); > - put_client_renew_locked(clp); > - spin_unlock(&nn->client_lock); > + drop_client(clp); > } > > static int > @@ -6616,7 +6613,7 @@ deleg_reaper(struct nfsd_net *nn) > list_add(&clp->cl_ra_cblist, &cblist); > > /* release in nfsd4_cb_recall_any_release */ > - atomic_inc(&clp->cl_rpc_users); > + kref_get(&clp->cl_nfsdfs.cl_ref); > set_bit(NFSD4_CLIENT_CB_RECALL_ANY, &clp->cl_flags); > clp->cl_ra_time = ktime_get_boottime_seconds(); > } > > --- > base-commit: 05258a0a69b3c5d2c003f818702c0a52b6fea861 > change-id: 20240405-rhel-31513-028ab6f14252 > > Best regards, > -- > Jeff Layton <jlayton@xxxxxxxxxx> > > -- Chuck Lever