move_to_close_lru() is currently called with ->st_mutex and .rp_mutex held. This can lead to a deadlock as move_to_close_lru() waits for sc_count to drop to 2, and some threads holding a reference might be waiting for either mutex. These references will never be dropped so sc_count will never reach 2. There can be no harm in dropping ->st_mutex to before move_to_close_lru() because the only place that takes the mutex is nfsd4_lock_ol_stateid(), and it quickly aborts if sc_type is NFS4_CLOSED_STID, which it will be before move_to_close_lru() is called. Similarly dropping .rp_mutex is safe after the state is closed and so no longer usable. Another way to look at this is that nothing significant happens between when nfsd4_close() now calls nfsd4_cstate_clear_replay(), and where nfsd4_proc_compound calls nfsd4_cstate_clear_replay() a little later. See also https://lore.kernel.org/lkml/4dd1fe21e11344e5969bb112e954affb@xxxxxx/T/ where this problem was raised but not successfully resolved. Signed-off-by: NeilBrown <neilb@xxxxxxx> --- Sorry - I posted v1 a little hastily. I need to drop rp_mutex as well to avoid the deadlock. This also is safe. fs/nfsd/nfs4state.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index 40415929e2ae..453714fbcd66 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -7055,7 +7055,7 @@ nfsd4_open_downgrade(struct svc_rqst *rqstp, return status; } -static void nfsd4_close_open_stateid(struct nfs4_ol_stateid *s) +static bool nfsd4_close_open_stateid(struct nfs4_ol_stateid *s) { struct nfs4_client *clp = s->st_stid.sc_client; bool unhashed; @@ -7072,11 +7072,11 @@ static void nfsd4_close_open_stateid(struct nfs4_ol_stateid *s) list_for_each_entry(stp, &reaplist, st_locks) nfs4_free_cpntf_statelist(clp->net, &stp->st_stid); free_ol_stateid_reaplist(&reaplist); + return false; } else { spin_unlock(&clp->cl_lock); free_ol_stateid_reaplist(&reaplist); - if (unhashed) - move_to_close_lru(s, clp->net); + return unhashed; } } @@ -7092,6 +7092,7 @@ nfsd4_close(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, struct nfs4_ol_stateid *stp; struct net *net = SVC_NET(rqstp); struct nfsd_net *nn = net_generic(net, nfsd_net_id); + bool need_move_to_close_list; dprintk("NFSD: nfsd4_close on file %pd\n", cstate->current_fh.fh_dentry); @@ -7114,8 +7115,11 @@ nfsd4_close(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, */ nfs4_inc_and_copy_stateid(&close->cl_stateid, &stp->st_stid); - nfsd4_close_open_stateid(stp); + need_move_to_close_list = nfsd4_close_open_stateid(stp); mutex_unlock(&stp->st_mutex); + nfsd4_cstate_clear_replay(cstate); + if (need_move_to_close_list) + move_to_close_lru(stp, net); /* v4.1+ suggests that we send a special stateid in here, since the * clients should just ignore this anyway. Since this is not useful -- 2.43.0
